FC · E-5 BIB · Entry 9 of 32 · Publication

FIRE CONTROLMAN VOLUME 3--DIGITAL DATA SYSTEMS

NAVEDTRA 14100 · CHAPTER 1, 2, 5, 7, 8

CHAPTER 1

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TOPIC 1—COMPUTER FUNCTIONS AND TYPES The computers the Navy uses vary from mainframes to microcomputers. Regardless of the types of computers and their operational uses, their functions are basically the same. Depending on the type of computer and the operational use, the methods will vary. First, we discuss the functions of computers, the different ways computers handle data, and the methods they use to accomplish this. Then we discuss the functional operation of computers. COMPUTER FUNCTIONS All computers must be able to gather, process, store, disseminate, and display data. Gather Data All computers, no matter what their size, must gather data before they can process the data. The operational program will dictate how the data is gathered— manually, automatically, or a combination of both. Manually, an operator or technician will input the data to the computer. This can be done either directly or by a device external to the computer. The following are commonly used input devices: Keyboards Display consoles Data terminals Computer maintenance panels Storage devices (magnetic tape units, disk drive units, and paper tape units) As an example, an operator at a console will input data via the console to the computer and the computer will process the data for storage, dissemination, or display depending on the functions of the operational program. Data may be input from a console using pushbuttons, switches, toggles, or a combination of these. Automatically gathering data means the computer receives data from another system, subsystem, or equipment. The computer monitors for external requests through a series of programmed requests and acknowledges. The computer first sees the gathered data when it comes through the input section of the input/output section of the computer. Then depending on the operational program, the computer will either react immediately or store the data for future use. The following are examples of the sources from which computers gather the data automatically: Systems such as the fire control system Subsystems such as the combat direction system Data processing systems (another computer and conversion devices) Display systems via sensors (radar) Communication systems such as data links and local-area networks (LANs) Many computer systems are designed to gather data using a combination of both the manual and automatic methods. Process Data Processing data is the main function and the purpose of the computer. There are other systems, subsystems, and equipment that will work with the computer to help gather, store, disseminate, and display data; but processing the data is exclusively the computer’s function. The heart of the computer—the place where the data is processed in a computer-is called the central processing unit (CPU). Figure 1-1 shows the basic configuration of a digital computer. After the data is processed, it can be stored, disseminated, or displayed. Store Data The computer can store data either internally or externally. Internally, the computer uses memory Figure 1-1.—A basic functional composition of a digital computer. 1-2

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banks. These memory banks can hold instructions and both processed and unprocessed data. Memory access time and memory capacity are the other main factors that determine how powerful a computer is. Externally, computers can store data on magnetic disks (hard and floppy), magnetic tape, or paper tape. Disk drive units offer quicker access to the data than magnetic or paper tape units. On some systems, the disks can store more data than the internal memory of a computer. The amounts of each will depend on the design and requirements of the data system. Some systems internally store and process the data. Others depend heavily on the disks to hold and store the data, bringing the data into memory for processing, and then storing the results back onto disk. Disseminate Data After the computer has processed the data, it can send it to the I/O section or an I/O unit for immediate or future dissemination to various equipments. The data will exit the output section of the computer’s input/output section. It can be sent to an output device such as a printer, or to one of many storage devices such as a magnetic tape or disk unit. It can also be sent to a subsystem, such as a display system, via its associated equipment. Display Data Computer systems display two general types of data—data related to the mission of the system and status information related to operation of the system and hardware performance. The computer relies on peripheral equipment, such as printers and display units, to display the processed data—the mission related output of the operational program. Your interest in output generally relates to whether the data is sent properly by the computer and is displaying properly. In other words, you want to know the computer system is functioning properly. The content of the data is usually a secondary interest to you and a primary interest to the user/operator. The other type of data/information that can be displayed relates to the operation of the system. This includes operator information, system error messages, and indications of system problems. You will be particularly interested in this information. The maintenance panels and data terminals can display real-time data and provide you with current status of the operational program. For example, the maintenance panels of some computers have registers where the presence or absence of indicator lamps can indicate to the technician if the computer is communicating with a subsystem such as a display or communication subsystem. This is a very useful tool when you are performing maintenance, both preventive and corrective. Figure 1-2 is an example of a maintenance console panel. Notice the indicator lights for the I/O controller, I/O timing, Mode, Central Processor Register, and soon. These will provide you with status information. For example, you can monitor the I/O controller register to see if the computer is interfacing with a particular subsystem such as display or communications. Look to see if the indicator of that channel is illuminated (either flashing or constantly lit). Or, you could look at the contents of a particular register in the CPU by selecting that register while installing a patch to a program using an inspect and change procedure or utility. TYPES OF COMPUTERS In general terms, computers can be classified into three categories: mainframe computers minicomputers, and microcomputers. A computer’s power is determined by the technology it uses, NOT its physical size. Greater speed, greater capability and capacity to store information, and greater facility to accommodate additional peripheral (external) equipment will make one computer more powerful than another regardless of their overall physical sizes. We do not go into detail on each of the different types of computers. Rather, we identify examples of each and point out their physical and internal differences. This will prove valuable when you are maintaining them. Let’s take a look at the types of computers you will maintain in the Navy. Later in this manual, you will study the internal workings of computers-their basic functional operation. Mainframe Computers Mainframe computers are physically the largest computers you will maintain. Their ruggedness makes them better suited than microcomputers and minicomputers to handle the mechanical shock and vibration, salt spray, temperature and humidity found aboard Navy vessels. The mainframes you will maintain are general-purpose, digital data computers with multiprocessing capability. Mainframe computers are considered the heart of the afloat and ashore tactical and tactical support data systems. These mainframe computers are big, fast, multiprocessor computers with correspondingly large memories and multiple I/O channel capabilities. They process large volumes of data and require a lot of program flexibility. Their operational programs are 1-3

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Figure 1-2.—Examp1e of a maintenance console panel of a digital computer. complex, and as systems are updated, the programs and/or adapter unit with I/O connectors, heat must be revised to meet the new demands of the fleet. Operational programs for mainframe computers are supported by technical teams external to the command. Two examples of mainframes are the AN/UYK-7(V) and the AN/UYK-43(V) computers. They are general-purpose, militarized, digital data computers with large-scale memories, I/O capabilities, and multiprocessing capabilities that allow a number of CPUs to operate simultaneously in the same system. They interface with other mainframes and peripherals in the data processing subsystem, the display subsystem, and the communication subsystem. Training is obtained through formal C schools and is NEC producing. Figure 1-3 is an example of one of the Navy’s mainframe computers. Some physical features of mainframe computers are highlighted as follows: Large rugged frame or cabinet —Contains individual modules or units; central processor unit (CPU), memory modules, input/output controller 1-4 exchangers for each module or unit, power supply unit(s), and blower motors for cooling. Figure 1-3.—Examp1e of a mainframe computer.

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Operator console —Controls operation of the computer at the computer. This console/panel is usually located above the logic chassis but separate from the maintenance console/panel. It contains the controls and indicators necessary to initiate computer operations. You can turn on power to the system and load the operational program and start its execution. Remote console —Controls operation of the computer from a remote location. Performs the same functions as an operator console except it does not apply power to computer set. Maintenance console panel/display control unit (DCU) —Controls operation of the computer and is used to perform maintenance (preventive and corrective). Specific power requirements (frequency and voltage). Specific cooling requirements (air and/or liquid cooling). Minicomputers Minicomputers are mid-range computers. They are smaller in physical size than the large mainframes used for tactical and tactical support operations. ‘hey are also built for ruggedness. Minicomputers are capable of stand-alone or self-contained operation, or of being an embedded processor in a system or other type of digital device. Minicomputers are generally used in applications that don’t require the faster computational speeds or larger memory capacities available on mainframes. These computers also have program flexibility. Minicomputers receive external technical support for the operational programs they use. The programs for minicomputers are updated as specific jobs or applications are updated and revised. Some examples of minicomputers are the minis used as interface computers with communications or radar systems. Minis are also used as the host computers for the Shipboard Nontactical ADP Program (SNAP I, SNAP II, and SNAP III) Systems. Training for minicomputers is provided through formal A, C, and FTC schools and may be NEC producing. SNAP system training is an example of an NEC-producing school. Figure 1-4 is an illustration of a typical minicomputer. Some physical features of minicomputers are highlighted as follows: Figure 1-4.—Example of a minicomputer. 1-5

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Large to medium rugged frame or cabinet— Some frames or cabinets use a stationary or sliding chassis or assemblies or stationary racks or card cages that contain individual modules or printed circuit boards. The functional and support areas include a central processor unit (CPU), memory units, input/output controller boards for various peripherals, I/O connectors, power supply unit(s), and blower motors for cooling. (NOTE: Some minicomputer frames or cabinets also contain the peripheral—disk drive units, magnetic tape units, and paper tape units.) Control and Maintenance Panel (CMP) or computer control panel —Controls operation of the computer and is used to perform maintenance (preventive and corrective). Specific power requirements (frequency and voltage). Specific cooling requirements (air and/or liquid cooling). Microcomputers Microcomputers, personal computers (PCs), are small, lightweight, and portable. Some of them are more powerful than some of the older, larger mainframes and minicomputers. Microcomputers are unique in that the heart of the computer (the CPU) is contained on a single integrated chip (IC) and the entire computer system is contained on a handful of printed circuit boards located inside a small compact frame or cabinet. In some cases a complete microcomputer is located on a single chip; the CPU, co-processor, and memory. Some micros/PCs are high-speed, multi-user, multi-tasking units. Traditionally micros are used for word processing, database management, spreadsheets, graphics, desktop publishing, and other general office applications. Currently, micros and PCs are being used for tactical support systems, such as Naval Intelligence Processing Systems (NIPS) and Joint Operational Tactical System (JOTS). Micros and PCs can also be used as a SNAP system for shorebased operational commands, such as ASWOC. The operational programs for PCs used for a tactical support system are supported externally by technical teams. These operational programs are also updated as systems are added or replaced. Programs that are used for word processing, graphics, and soon are abundant and can be obtained through civilian vendors and software support teams such as Commander Naval Computer and Telecommunications Command (COMNAVCOMTELCOM). Training for micro- computers is obtained through formal A schools, civilian contractor schools, and OJT. Training for micros is not NEC producing. Figure 1-5 is an illustration of a typical microcomputer. The physical features of microcomputers are very different from mainframes and minis. The following is a brief description of a typical PC/desktop system. Small compact frame or cabinet —PCs are uni- que in that the frame or cabinet contains the majority of the components for a complete system. A typical PC frame or cabinet contains the following components: Backplane or motherboard for printed circuit boards A central processor unit (CPU) and memory printed circuit board(s) (pcb) (NOTE: In some cases the CPU and memory are located on the same pcb.) Input/output pcb Disk controller pcb Video controller pcb Data storage devices: Hard disk drive units, floppy disk drive units, and/or tape cassette units I/O connector: Parallel or serial communica- tions A small fan: No special cooling require- ments; the unit relies on ambient temperature of the room or space Power supply: No special requirements Display monitor —Display monitors are output devices for visual displays of data, and may have monochrome or color displays. Figure 1-5.—Examp1e of a microcomputer. 1-6

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Keyboard —Keyboards are input devices used to control operation of a computer. Printer —Printers are output devices for producing printed material. Modem —Modems are optional components used to communicate with mainframes, minicomputers, and microcomputers through existing phone lines. Mouse —Another optional component is a mouse. A mouse is an input device used to highlight text, move the cursor, and select commands and functions without using the keyboard. A mouse can be used in combination with a keyboard to control computer operations. TOPIC 2—FUNCTIONAL OPERATION OF COMPUTERS At the heart of every data system is a computer. All digital data made available on any system has been processed by the computer. The computer oversees the operation of any data system. Through a coordinated series of interrupts, requests, and acknowledges, the computer exchanges data with other computers, peripherals, and the subsystems required for that system. The signal flow between systems, subsystems, and equipment is all coordinated by the operational program of the computer(s). Exchange of signals between the systems, subsystems, and equipment is accomplished through a coordinated series of priorities where interrupts, requests, and acknowledges determine when the data will be exchanged. The type of data exchanged includes status signals, control signals, and data words. Interfacing between the computer(s) and other systems, subsystems, and equipment requires some type of cabling—standard shielded and unshielded cables, fiber-optic cables, and ribbon cables, and their associated connectors. Methods of interfacing include parallel and serial data transfers. OPERATIONAL USES OF COMPUTERS You may have the opportunity of maintaining three basic types of data systems: tactical, tactical support, and nontactical. all three rely on one or more computers to make rapid calculations and make information available. Tactical Systems A computer is the heart of the Combat Direction System (CDS)/Naval Tactical Data System (NTDS), which is a subsystem of the ship’s combat system. CDS/NTDS receives data from ship’s sensors and other ships using tactical data links. The CDS/NTDS consists of high-speed digital computers, peripherals, displays, communication links, and computer programs. The CDS/NTDS hardware is divided into three major equipment groups (subsystems) as follows: Data Processing Group Data Display Group Data Communications Group The data these subsystems generate and feed back to the data processing subsystem is stored, processed, and distributed by the operational program. The computer is part of the data processing group and coordinates the operations within CDS/NTDS and makes the information available to other major subsystems within combat systems: radar/IFF, weapons (guns, missiles, and underwater), electronic warfare, and navigation. The CDS/NTDS is a real-time system. The type of computer used in a tactical data system is a mainframe such as the AN/UYK-7(V) or AN/UYK43(V) computer. The number of computers used in a tactical data system depends on the class of ship and its configuration/setup. Figure 1-6 is a portion Figure 1-6.—Simplified block diagram of a tactical data system (CDS/NTDS). 1-7

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of a simplified block diagram of a typical CDS/NTDS in a tactical data system. Another example of a tactical data system is the Integrated Tactical Amphibious Warfare Data System (ITAWDS). Tactical Support Systems Tactical support platforms include a variety of systems. Unlike tactical data systems, tactical support systems generally use either mainframes or micros as their operational computers. Depending on the system, tactical support systems can use a single computer or a multiple computer configuration. The computers in tactical support systems also interface with other computers, peripherals, displays, communication links, and operational programs. Let’s look at three examples: ASW systems, JMCIS, and NIPS. ASW SYSTEMS. —ASW systems deal primarily with antisubmarine warfare. They provide active and passive search, detection, tracking, and classification operations necessary to engage and destroy subsurface or surface targets. They support ASW airborne systems. ASW systems include the Antisubmarine Warfare Operations Center (ASWOC) and Carrier- Antisubmarine Warfare Module (CV-ASWM) systems. These systems use a single computer as their central point of operation. The computers in these systems interface with the following subsystems or equipment within their subsystem: Command and Control Subsystem —Controls the data to and from this subsystem and other subsystems through the ADP Subsystem and Display Subsystem. Communication Subsystem —Allows com- munication between Maritime Patrol Aircraft (MPA) or Surface Units and/or ASWOCs, CV-ASWMs, and FHLTs. Communication is via secure voice or secure data networks. Fast Time Analysis System (FTAS) Subsystem (ASWOCs and CV-ASWMs only) —Analyzes acoustic and nonacoustic data provided by mission aircraft. JOINT MARITIME COMMAND INFORMA- TION SYSTEMS. —The Joint Maritime Command Information Systems (JMCIS) is an informational data system used to provide data to designated flagships. It is used to effectively conduct battle-management of the tactical situation. The JMCIS consists of a data processing subsystem and a video processing subsys- tem. The data processing subsystem includes desktop computers (DTWTAC-n 1 ) with single and dual monitors, printer plotters, and printers. The video processing subsystem includes high and low resolution monitors, large screen displays, and video switch. Communication between DTC/TAC-n in the data processing subsystem and video processing subsystem is accomplished via a Genser fiber-optic LAN. JMCIS gathers data from a variety of external links including OTCIXS, Flag communication, Fleet Broadcast, and Link 11 or Link 14. NAVAL INTELLIGENCE PROCESSING SYSTEM. —Naval Intelligence Processing System (NIPS) integrates up-to-the-minute tactical intelligence with national and fleet-produced database intelligence information. Data is gathered from the Naval Modular Automated Communication System (NAVMACS), Ocean Surveillance Product (OSP), Generic Front End Co-Processor (GFCP), Automatic Tracking Point (ATP), Fleet Imagery Support Terminal (FIST), video diskplayers, and optical disk recorders, and, in turn, is disseminated to GFCP, ATP, and Tactical Aviation Mission Planning System (TAMPS). The NIPS uses the DTC/TAC-n in a LAN configuration as its operational computers. The other hardware interfaces include hard drives, color printers, plotters, tape backup units, a camcorder, and light table. The NIPS uses both MS-DOS and the UNIX operating system to process and manage its mapping/imagery workstation and message handler workstation. Depending on the vessel, the NIPS can be a basic system, as on a multipurpose amphibious assault ship (LHD), or it can be a much larger system with multiple workstations and remotes, as on a carrier (CV). Naval Tactical Command Support Systems Naval Tactical Command Support Systems include those systems that handle data used for administrative purposes and office functions. They support organizational and intermediate-level maintenance, supply and financial management, and administrative applications. The types of computers generally used are minicomputers and microcomputers. Nontactical systems include the Shipboard Nontactical ADP Program (SNAP I, SNAP II, and SNAP III) Systems and PC. 1 n = configuration number. 1-8

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SNAP SYSTEMS. —The SNAP systems are used primarily to reduce the administrative workload associated with equipment maintenance, supply and financial management, and personnel administration. Because the SNAP systems differ in their subsystem configurations, we are only listing the equipment with which they are both capable of interfacing. Some SNAP systems communicate via modems and specialized interfacing techniques and hardware. SNAP computers interface with the following equipment: Disk drive units Magnetic tape drive units Keyboard/video display units (KVDTs Printers—High speed, display, line, and word processing Some SNAP systems use specialized com- munications hardware and interfacing methods. They use processors, adapters, and modems. PERSONAL COMPUTER/DESKTOP MICROCOMPUTER SYSTEMS. —Personal com- puter/desktop microcomputer systems (PC) software enables PC systems to perform word processing, database management, spreadsheets, graphics, and desktop publishing. For these functions, off-the- shelf software packages can be installed in each PC system. There are also many programming languages for programming the PC; they include BASIC, FORTRAN, COBOL, PASCAL, C, and many others. These languages allow you to design your own programs to perform functions exactly the way you want them. Figure 1-7 is a simplified block diagram of a PC system. A PC can interface with other hardware. The following are examples: Secondary storage units—hard disk drive units, floppy disk drive units, and/or tape cassette units Monitor—color or monochrome Printer Modem PCs can be operated as stand-alone systems or as remote units to a larger system. They can al SO be configured in local-area networks (LANs). With LANs, the PC can talk with other PCS and share data files, peripherals, and software. COMPUTER SYSTEMS CONFIGURATIONS AND SETUPS The computer system you are working with must be correctly configured/set up or it will be useless for operational purposes. You will need to be able to configure and set up the computer system for both operational purposes and for maintenance. You need to be aware of two things—the hardware and the software. Figure 1-7.—A simplified block diagram of a PC system. 1-9

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The type and number of computers that make up a system have a direct bearing on the configuration and setup of a system. Some systems require two or three computers connected in tandem. An example is a CDS/NTDS for a particular class of ship, which may use a three-bay/one-bay configuration for its CDS/NTDS. Others have only one computer. An example is a PC in an office setting. Hardware When configuring or setting up a computer system for operation or maintenance, check your computer’s technical, system operations, or combat systems technical operations manuals for the correct physical setup. Set up includes the following: Physical design Operator controls External controls PHYSICAL DESIGN. —The design of the computer system will predetermine how and where module units and printed circuit boards need to be inserted and where cables are to be connected. Once these items are correctly installed and connected, the next step is to ensure that all operator controls are in their correct positions. OPERATOR CONTROLS. —Computers can be controlled directly at the computer and in some cases remotely through panels/consoles. Mainframe and large minicomputers usually have controls for the computer at your fingertips. You can control the computer from several panels/consoles as follows: Maintenance panel/console Operator panel/console Remote panel/console (usually only mainframes for tactical systems have this capability) The types of controls these units most often use are discussed in more detail in chapter 3 of this manual. You can also control the computer’s mode of operation directly from the computer’s maintenance panel/console or operator’s panel/console. This feature is not available on all computers. Figure 1-8 shows a portion of a maintenance panel/console of a mainframe computer. For example, notice the mode select push-button indicator, jump switches, and stop switches. You can use the jump switches and/or stop switches when performing maintenance to set parameters for a diagnostic on the computer. EXTERNAL CONTROLS. —Some computers use external controls to configure and set up the computer to enable it to communicate with peripherals and other systems. These controls work in conjunction with the software. Unless these controls are configured and set up properly, the computer cannot perform its functions correctly. The controls maybe set through digital switchboards or computer switching and control panels. Figure 1-9 is an illustration of a computer switching and control panel used on a CDS/NTDS system. Notice the push-button indicator switches available. You can use these to control the configuration and data routing. Software Once you have the hardware of the computer physically configured and set up correctly, the correct software must be installed and correctly configured/set up. When we speak about configuring and setting up the software, we are referring to specifying the resources the software is to use-what peripherals the system has, what communications, how much memory, what options you want set as defaults, and so on. In this way the hardware and software can talk to each other. The software and hardware have to work hand-in-hand with each other. Depending on the type of computer and type of system application, the hardware and software have the ability to control and/or are dependent on each other. Perform the following procedures when working with software: Figure 1-8.—A portion of a maintenance panel/console of a mainframe computer. 1-10

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Figure 1-9.—Computer switching and control panel used on a CDS/NTDS system. Ensure you have the correct software for the type of system and type of computer Boot the computer Load the software via a peripheral device Initialize the system Monitor the computer for system operation and/or maintenance (tests—programmed and manual) Your involvement with the software is directly dependent on the type of computer. Generally speaking, the bigger the computer system, the less involved you will be with configuring and setting up the software. All computer systems have an operating system to control their operations. An operating system is a collection of many programs the computer uses to manage its own resources and operations. These programs control the execution of other programs. The operating system used will depend on the type of computer and the systems platform. To communicate with the operating system of any computer, you need to understand the operating system functions and the commands necessary to talk to it. This is also true of any applications software and utility programs you use. To communicate with any software, you need to know its functions and commands. For mainframe computers used in tactical and tactical support applications, the software is designed by an outside support activity. With these systems you do not have to perform any initial configuration or setup of the software before using it. This has already been done by the activity that writes the operational program for the system’s platform. The system operating commands you will use to talk to the computer to initialize and/or reconfigure the operational program are specific. Refer to your combat systems technical operations manuals (CSTOMs) or systems operations manuals (SOMs) for details. For some minicomputer systems, such as the ones used for the SNAP I and II systems, the software has also already been configured and set up. You simply boot and initialize the system. System operating 1-11

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commands for minicomputers are also specific. Refer to their system manuals and desktop guides for details. The operational software a microcomputer uses can be off-the-shelf software or it can be software designed by an outside support activity to meet the specific requirements of a platform or system. Before a microcomputer may be used, you must configure and set up the software. When configuring and setting up the software for a microcomputer, there are several things you must be aware of. The operating system must be customized to the hardware of the computer system. This can be accomplished by following the step-by-step procedures in the users/owners manual. You will use operating system commands to setup the software to execute the program exactly as you have specified. For example, you could specify to the operating system program to automatically load a word processing program when the computer is turned on. You may want a beeper to alert you to a given situation such as when certain error conditions occur. You can set this. When using applications software with your operating system, you must ensure that the application software is compatible with the operating system. The application software will also use commands to execute its functions. Refer to operating systems and application software users manuals for details. ONLINE AND OFFLINE MODES OF OPERATION Modes of operation are designed into the data systems and can be selected through hardware or software manipulation. Basically you can operate the computer either in an online or offline mode. What the computer can do in these modes depends on the type of computer and the software. Online When a computer is in the online mode of operation, it is performing operational functions. It is interfacing with other computers, peripherals, display systems, and communication systems to perform many tasks. And operationally, this means you must rely on the loaded software for the computer to perform its functions. The type of software the computer will use online will depend on the platform of the system (tactical, tactical support, and nontactical). A computer may perform the following types of operations in the online mode: Operational (includes application software) 1-12 Maintenance (only when the computer’s memory is large enough to accommodate the software can maintenance be performed while the operational program is still running) Offline In the offline mode of operation, a computer is limited to performing maintenance. The computer can be either powered or unpowered depending on the maintenance you are performing. When you take the computer offline, you remove the computer from controlling a whole system. The computer is limited to interfacing with only a single system, such as a display system or a peripheral system, to perform controlled tests or a diagnostic to test itself. In this mode some computers have the capability to not only operate in the run mode but other detailed steps such as instruction mode and sequence mode. These modes are quite useful for troubleshooting malfunctions that can’t be isolated using diagnostics or self-tests. Figure 1-10 shows the operating mode selections of a mainframe computer. In the offline mode, you can perform the following types of maintenance: Preventive maintenance —Testing the computer using program controlled tests and internal tests such as diagnostics and self-checks; and cleaning filters, heat exchangers, and so on. Corrective maintenance —Troubleshooting the computer using program controlled tests and manual tests to isolate faults; and repairing faults by replacing bad parts or using solder and solderless techniques. Figure 1-10.—The mode selections of a mainframe computer.

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BATTLE SHORT MODE OF OPERATION The battle short mode is used when it becomes necessary to run the computer continuously even though an overtemperature condition exists. The activation of a battle short switch will bypass overtemperature protection interlocks and power will be maintained to the computer for continued operation. An overtemperature condition is a result of a failed assembly or inadequate cooling. The requirement to run the computer continuously in an overtemperature condition usually only exists under battle conditions. Some computers are also equipped with a horn to warn an overtemperature condition exists. OPERATIONAL CAPABILITIES AND LIMITATIONS It is important to know the capabilities and limitations of the hardware and software of any system you maintain. It is equally important to know whether the system can operate at reduced capability and still accomplish its mission. Some systems are designed with more than one computer (CPU), sufficient memory, and enough peripheral devices to enable them to function even when some devices are down. The operational capabilities and limitations of a computer system can be controlled at the equipment through switchboards or control panels, or through commands to the software using an I/O device to talk to the computer. Figure 1-11 is an illustration of a digital fire control switchboard used on a CDS/NTDS to interconnect the computer to equipments and other major systems. To find out the capabilities and limitations of a computer system, refer to your system operating manuals (SOMs) or combat systems technical operations manuals (CSTOMs) for details. CDS/NTDS is an example of a system that uses a three-bay/one-bay computer configuration. This means it has four CPUs and can still meet its mission even if one of the CPUs is down. The term reduced capabilities means the computer system can perform its mission with fewer resources. Resources may be unavailable as a result of a casualty to a computer. If the memory of the computers allows it, you can take one of the computers offline to perform training. You can reduce the operational capability through the software using an I/O device to take the computer offline. This can be accomplished using operating system functions (commands). An example would be Figure 1-11.—A digital fire control switchboard used on a CDS/NTDS. 1-13

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a CDS/NTDS that normally uses a three-bay/one-bay computer configuration to operate at full capability. Because of a casualty to the one bay, that bay is dropped offline. The CDS/NTDS can still perform its basic mission, but the system is reduced because not all four computers are being used. Devices that are used to bring the computer to reduced capability are switchboards and computer control panels. The operational program (software) must also be reconfigured to reflect the hardware reconfiguration. This can be accomplished at an I/O device using operating system functions (commands). Again refer to the SOMs or CSTOMs for exact details of your system’s capabilities and limitations and the hardware and software required to reconfigure it. OPERATIONAL REQUIREMENTS OF COMPUTER SYSTEMS Effective operation of computer systems also depends on security and on controlling electromagnetic disturbances. You’ll need to pay particular attention to ADP security and electromagnetic interference (EMI). Lack of attention to these factors can seriously jeopardize the security and operation of a computer system. ADP Security The security of computers depends on administrative and physical controls. The administrative requirements (directives and instructions) will provide the policy and procedures to follow to meet the physical requirements. Let’s highlight some of the things you will handle on a regular basis that require protection to ensure the security of the computer system. Data and information —For tactical and tactical support systems, the data the computer handles and makes available is classified. (Includes COMSEC material for tactical data links). Passwords —Used with nontactical systems (SNAP) to ensure only authorized users gain access to the computer system. Operational programs on magnetic tape, disk, and disk packs—For tactical and tactical support systems, these programs and any revisions (program patches) are classified. For nontactical systems, the operational programs may be copyrighted and require protection to avoid misuse. 1-14 Safe combinations —For controlled spaces where computers are used. Computers —Computers must be safeguarded; they are an ADP asset. Be sure you know where the emergency destruction procedures for the computer system are. They should be readily available. For more detailed information on guidelines that will aid in the security of computers, refer to OPNAVINST 5239.1, Department of the Navy Security Program for Automatic Data Processing Systems and OPNAVINST 5510.1, Department of the Navy Information and Personnel Security Program Regulation. Electromagnetic Interference Electromagnetic interference (EMI) is an electromagnetic or electrostatic disturbance that causes electronic equipment to malfunction or to produce undesirable responses or conditions that do not meet the requirements of interference tests. You must be more aware of the problems EMI causes and the solutions required to resolve these problems. No magic is involved in reducing or eliminating EMI. Everyday common sense approaches to maintaining equipment will resolve many problems caused by EMI. TYPES OF EMI. —There are three types of EMI—natural, inherent, and manmade. Natural EMI. —Natural interference is caused by natural events, such as snowstorms, electrical storms, rain particles, and solar radiation. It can cause problems with rf data links between shore, ship, and air, but few problems with modem digital data equipment. Inherent EMI. —Inherent interference is noise within a piece of electronic equipment and is caused by thermal agitation or electrons flowing through circuit resistance. Manmade EMI. —Manmade EMI is produced by a number of different classes of electrical and electronic equipment. The equipment includes, but is not limited to, transmitters, welders, power lines, motors and generators, lighting, engines and igniters, and electrical controllers. A number of these devices can cause severe EMI, which can degrade the operation of shipboard and shorebased computer systems. EMI can be classified by its spectrum distribution. It can be either broadband or narrowband interference. These terms refer to the frequency spectrum the interference covers.

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Narrowband EMI consists of a single frequency or a narrowband of interference frequencies. Narrowband EMI usually has a minor effect on communications or electronic equipment. It can be tuned out or filtered out. Broadband EMI is not a discrete frequency. It occupies a relatively large part of the electromagnetic spectrum. It causes the majority of EMI problems in digital data equipment. It will be especially noticeable data on Link 11. CONTROL OF EMI. —EMI can be controlled or eliminated if some simple procedures are followed and good installation practices adhered to. Let’s look at control and reduction for shipboard and shorebased installations. Many of the problems are the same for both installations. Shipboard EMI Control. —Shipboard EMI control is greatly simplified for the typical digital data installation. Because of the ship’s steel hull and construction, a great deal of shielding and isolation are provided the typical shipboard computer room or digital equipment space. This blocks out the majority of broadband interference generated both internally and externally. Five major factors are considered in a shipboard computer and digital equipment installation. They are equipment location, equipment shielding, system and equipment grounds, interconnection cabling, and power source. Equipment location — Computers should be located in spaces that are free of sources of EMI. They should not be located in spaces that contain radars, radio transmitters, generators, or other rotating machinery. Equipment shielding —Digital computers should never be operated with drawers extended, cover plates removed, or doors open. Modem computers contain EMI-reducing gaskets and shields that enclose the equipment. Always reinstall cover plates with all the fasteners in place. If a cover plate or shield has to be removed in the course of corrective maintenance, ensure that the EMI reducing contacts or wire gaskets on the equipment opening are in good condition before the cover or shield is replaced. System and equipment grounds —System and equipment grounds are extremely important in digital computer installations. All cabinets should be grounded together on a common system ground bus. Each equipment cabinet is connected to the system ground by a heavy ground cable. The system ground is securely attached to the hull of the ship and provides a good ground reference for the system. Paint on ground straps or on the metal decks where the ground straps are mechanically attached will result in poor electrical connections. Interconnecting cables —All interconnecting cables used in a shipboard digital data system should be shielded cables. They should be assembled correctly according to installation drawings. The shield and connector shell should be electrically connected and properly secured at either end. The cables should never be run in the same cableways as cables carrying rf signals or high- power pulse cables. The shielding protects the data cables from EMI to a great extent. Power source —Power lines for digital computers can provide a transmission path for EMI from machinery spaces. The majority of input power passes through noise elimination filters as it enters computers. Unusual random problems in digital computers can sometimes be traced to defective line filters. Shorebased EMI Control. —Control of EMI at a shorebased installation requires the same consideration or the same factors as a shipboard system with two additions-site location and soil quality. Site location —Shorebased digital data equipment sites are sometimes built where the need dictates or where a convenient building is available. They are not always ideal sites. Sites built near a large industrial complex such as a shipyard repair facility (SRF) or a naval depot (NADEP) may be subjected to EMI. They also can cause power line fluctuations if the power source of the shore site and the SRF and NADEP are the same. Additional line filters and regulators for power lines may also be required to reduce EMI and provide line power within the limits prescribed by equipment manufacturers. Soil quality —At a shore installation, a system ground bus is usually attached to a grounding rod driven into the soil. If the soil is dry, sandy, rocky soil as found in the Southwestern United States and some places overseas, you will have a poor ground. A suspected system ground can be checked with an oscilloscope and 1:1 probe. Refer to Electromagnetic Compatibility, NAVELEX O967-LP-624-6010, for more information. DIRECTIVES. —Many directives provide guidelines to follow for avoiding or reducing the effects of EMI. The EIMB handbook entitled Electromagnetic Interference Reduction, NAVSHIPS 0967-LP-000-0150, includes topics of shipboard EMI 1-15

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tests and operating practices for EMI reduction. MIL-STD-1310 entitled Shipboard Bonding, Grounding, and Other Techniques for Electromagnetic Compatibility and Safety, is a military standard for the proper instruction of bonding straps and grounding cables. It is the reference for all shipboard electromagnetic capability (EMC) installations. It contains drawings that depict the proper shape of and lists materials required to construct bonding straps and grounding leads for shipboard electrical/electronics installation. The Naval Shore Electronics Criteria handbook, Electromagnetic Radiation Hazards, NAVSEA OP 3565 Volumes 1 and 2, (parts 1 and 2) (NAVELEX 0967-LP-624-6010) has information on the reduction of EMI at shorebased facilities. All facets of grounding, shielding, and equipment bonding are contained in this highly informative handbook. The Handbook of Shipboard Electromagnetic Shielding Practices, NAVSEA S9407-AB-HBK-010, provides specifications for cable spacing/shielding requirements and installation procedures that will minimize the effects of electromagnetic interference (EMI) on electronic equipment installed in naval vessels. It is intended for use by ship designers, planning engineers, personnel engaged in the installation of electronic equipment, overhaul and repair shipyards, tenders, and other repair and installation activities. SUMMARY—FUNDAMENTALS AND OPERATIONS OF COMPUTERS This chapter has introduced you to computer functions, types of computers (mainframe computers, minicomputers, and microcomputers), operational uses, modes of operation, capabilities and limitations, and operational requirements. The following information summarizes important points you should have learned: COMPUTER FUNCTIONS —Computers gather, process, store, disseminate, and display data. Data may be gathered manually or automatically or by a combination of both. Once processed, it can be stored either internally in memory banks or extemally on disk or tape. Data maybe disseminated and stored, or it may be sent to a display device. MAINFRAME COMPUTERS —Mainframe computers are large computers. Those used aboard Navy vessels are designed for ruggedness and are general-purpose, digital data computers with multiprocessing capability. They usually have operator and remote consoles and a maintenance panel/display control unit (DCU). They have specific power and cooling requirements. MINICOMPUTERS —Minicomputers are mid- range computers. They are capable of stand-alone (self-contained) operation, or they maybe an embedded processor in a system or other type of digital device. They usually have a control and maintenance panel (CMP) or computer control panel. Like the mainframe, they have a rugged frame when used aboard ship, and they have specific power and cooling requirements. MICROCOMPUTERS —Microcomputers (per- sonal computers) are small, lightweight computers. Their central processing unit is contained on a single integrated chip (IC) and the entire computer system is contained on a handful of printed circuit boards in a small compact frame or cabinet. FUNCTIONAL OPERATION OF COM- PUTERS —Computers exchange data with other computers, peripherals, and subsystems through a coordinated series of interrupts, requests, and acknowledges. The signal flow is coordinated by the operational program. INTERFACING —Interfacing between the computer and other systems, subsystems, and equipment includes cabling and associated connectors. Methods of interfacing include both parallel and serial data transfers. OPERATIONAL USES —Operational uses of computers include tactical and Naval Tactical Command Support Systems. COMPUTER SYSTEM CONFIGURA- TIONS —Each system must be configured for operation and maintenance. The hardware and software must be compatible and must be set up to work together. MODES OF OPERATION —Computer systems may be operated in online, offline, and battle short modes. Maintenance may be performed online if there is enough memory; otherwise it will be performed offline. Battle short mode is used when it is necessary to run the system continuously even though an overtemperature condition exists. OPERATIONAL SYSTEM REQUIRE- MENTS —The operational capabilities and limitations can be controlled at the equipment, or through switchboards, control panels, or commands to the software. Effective operation depends on adherence to 1-16

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ADP security requirements and reducing You will also need to be able to operate the computer electromagnetic interference. using maintenance and operator panels, display control Study the block diagrams and technical manuals units, and keyboards. You need to be familiar with and learn all you can about how the computer operates. operating the computer locally and remotely. 1-17

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CHAPTER 2 COMPUTER CONFIGURATIONS AND HARDWARE INTRODUCTION As a technician you must be able to recognize the different types of computers to maintain them. The functional units of any computer are consistent, no matter what type of computer you are maintaining. your main concern will be the architecture of the computers you maintain. Mainframe computers and minicomputers are usually housed in large- to medium-sized frames or cabinets suited for ruggedness. Microcomputers are housed in compact frames built more for their portability. If you can understand the architecture and general physical makeup, then you can maintain any type of computer. Technical manuals, owners’ manuals, desktop guides, and system operating manuals are all excellent sources of information that you can use to learn the configuration of a specific computer system and its physical makeup. After completing this chapter, you should be able to: Interpret the various types of diagrams and layouts used to specify unit configurations Describe the major hardware parts of a computer system Describe the unit connectors and cables of computer systems Describe the types of cooling systems used with computers TOPIC 1—COMPUTER CONFIGURATIONS/LAYOUTS To be an effective technician, you must be familiar with the computer—inside and out. You must be able to understand the hardware as well as each of the functional units by using technical documents. The computer’s technical manual will be your most reliable and effective source. Technical manuals usually start with a general description of the computer and become more detailed when discussing the hardware and each functiona.1 area of the computer. As a reminder, you must ensure you use the most current documentation when you perform maintenance on a computer. This is a MUST. In our discussion of the computer in this topic, we examine the computer from two aspects—the functional layout and the physical layout. Let’s begin by examining how computers are functionally configured. FUNCTIONAL BLOCK DIAGRAMS OF COMPUTERS A functional block diagram provides you with a general analysis of the principles of operation of the overall equipment, types of signals and their directional flow, and the major functional areas. Functional block diagrams can be of two types—the overall functional block diagram of the computer and the individual functional block diagrams of each functional unit. You can use both to gain a better understanding of the computer. 2-1

CHAPTER 2

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Overall Functional Block Diagrams Overall functional block diagrams will show the functional areas of the computer and the supporting functions, such as power, cooling, and control of the computer. They will also show the types of signals exchanged between the functional areas and the supporting functions and the direction of signal flow. Figure 2-1 is an example of an overall functional block diagram of a computer. Overall functional block diagrams are very useful when you perform corrective maintenance. After you have identified and elaborated on a problem, you can use the overall block diagram for the “listing of probable faulty functions.” This will help you in your next step in the troubleshooting process— “localizing the faulty function.” The overall functional block diagram can help you stay in the right area when troubleshooting. Individual Functional Block Diagrams Once an overall description has been presented, the technical manual will give a general description of each functional area separately. These will include the major functional areas (CPU, I/O, and memory); the supporting functional areas (power supply and any special cooling requirements); and control of the computer (maintenance console/panel or display control unit and remote console/panel). When each functional area is described individually, an accompanying functional block diagram of that area will follow. Individual functional block diagrams can help you in your troubleshooting once you have “localized the faulty function.” They provide a more detailed analysis of how that specific area of the computer operates. See figure 2-2 as an example of an individual functional block diagram of a CPU. FUNCTIONAL LAYOUTS OF COMPUTERS Functional layouts will show the major functional areas of the computer—CPU, I/O, and memory. Figure 2-3 is an example of an individual functional layout for a basic single cabinet configuration. Systems that use a multiple configuration with more than one computer will also be depicted using an Figure 2-1.—Example of an overall functional block diagram 2-2

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Figure 2-2.—Example of an individual functional block diagram of a CPU. Figure 2-3.—Example of an individual functional layout of a single cabinet configuration. 2-3

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overall functional layout. Figure 2-4 is an example of a functional layout of a multiconfiguration computer system. PHYSICAL LAYOUTS OF COMPUTERS Physical layouts provide you with a “picture” of the computer. They are designed to show what the computer looks like and where each assembly, module, or console (maintenance and operator) of the computer is located. Physical layouts do NOT depict detailed descriptions of signal flow. Let’s take a look at some of the ways computers are physically laid out. Overall Physical Layout of Computers Overall physical layouts will show you where each of the major parts of a single computer/computer set is located. The physical layouts and the terminology will vary with the type of computer and the manufacturer. The technical manual of each computer will provide you with the physical layout of that computer. Let’s take a look at four types of physical layouts—modular, chassis or assembly, cage or rack, and motherboard or backplane. MODULAR. —The functional areas of the computer are modularized. In other words, the functional areas only contain the hardware for the function specified. For example, the module designated as the CPU only contains the subassemblies or printed circuit boards for the CPU functions. Figure 2-5 is an example that depicts the physical layout of a single mainframe computer set. Notice the modular layout. Also keep in mind that data systems that employ a multiple configuration will depict the minimum physical layout configuration AND the frill physical layout configuration. CHASSIS OR ASSEMBLY. —Chassis or assemblies usually are door mounted or slide mounted. Computers that use chassis or assemblies may contain one or more chassis or assemblies for the whole system. For example, one chassis may be dedicated only for memory, one for the power supply, and a third chassis or assembly for the rest of the computer (the CPU and the I/O). One to several subassemblies or printed circuit boards (pcb’s) may comprise the CPU, I/O, or memory. Figure 2-6 is an illustration of a chassis used in a minicomputer. CARD CAGE OR RACK. —A card-cage or rack-designed computer will generally contain the major functional areas of a computer. The card cage or rack is usually centrally mounted in the overall computer chassis. The number of subassemblies or pcb’s contained in a card cage or rack can vary from just a few to many depending on the technology of the computer. One or more pcb’s may comprise a functional area. A card cage or rack is fixed in a single position; it does not slide out or swing open like a door. Figure 2-4.—Example of a functional layout of a multiconfiguration computer system. 2-4

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Figure 2-5.—Physica1 layout of a single mainframe computer set. Figure 2-6.—Example of a chassis used in a minicomputer. 2-5

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Figure 2-7.—Physica1 layout of a card cage or rack used in a minicomputer. Figure 2-7 is an example of a card cage or rack used in a minicomputer. BACKPLANE OR MOTHERBOARD.— Backplanes or motherboards are stationary and are generally located inside the computer’s chassis. In this arrangement, all the subassemblies or pcb’s needed to run the computer are contained on a single backplane or motherboard. The number of functional areas contained on a single subassembly or pcb may vary according to the technology of the computer. Computers that use a backplane or motherboard are compact. Figure 2-8 is an example of a backplane used in a microcomputer. Individual Physical Layouts of Computer Parts Using individual physical layouts, the technical manuals depict each part of the computer separately. By separating each major part of the computer, you can break down the computer from a whole unit to the Figure 2-8.—Example of a backplane used in a microcomputer. 2-6

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frame/cabinet to see how subassemblies or printed circuit boards are laid out in each assembly, chassis, or module. Check your computer’s technical manual for specific details. Examples of the parts of a computer that are depicted in individual physical layouts are the following: Maintenance and operator console/panel location and its identification of individual computer controls Display control unit location and identification of its individual controls Remote console/panel location and identifica- tion of its individual computer controls Mainframe or cabinet and its contents Assemblies or chassis and their contents Subassembly or printed circuit card locations and their component locations Figure 2-9 is an example of an individual physical layout of a module used in a mainframe computer. Notice how the contents of the module are physically laid out. For some computer units/parts, individual physical layouts are not provided in the technical manual. For example, a layout would not be provided for a power supply in a microcomputer that is sealed. You only need to determine that the power supply has a faulty output and turn the power supply in for a replacement. If you never have a reason or are never required to open a unit/part to repair it, there is no need to have an individual physical layout. We have discussed unit configurations, now let’s focus our attention on the hardware of a computer. We start with the frame/cabinet, some of the parts that are contained in a frame/cabinet, computer connectors, cables, and fmally computer cooling hardware. TOPIC 2—COMPUTER HARDWARE The hardware makeup of each computer will vary. Generally speaking, the type of computer and platform of the data system will dictate the physical makeup of the computer. Large computers tend to be more rugged and the modules or assemblies more tightly assembled than a microcomputer (PC), which is generally more adapted for portability and not for ruggedness. Let’s take a look at some of the hardware used in computers. Figure 2-9.—Example of an individual physical layout of a module used in a mainframe computer. We’ll start with the frame or cabinet and work our way down to the pcb’s, subassemblies, and the support hardware. COMPUTER FRAMES/CABINETS The frame or cabinet (often called the chassis) houses the computer. It holds or supports all the parts (the functional areas) of the computer. As you will see there are different designs based on the different types of computers and the types of systems on which they are used. These dictate the type of arrangement the frame or cabinet has. Inmost cases, the frame or cabinet also contains the support areas-the power supply module or unit and hardware for cooling. The frame or cabinet can provide limited protection for the computer against such hazards as shock, moisture, and EMI or RFI. As a general rule of thumb, except for PCs, all computers aboard ship are shock mounted to withstand the constant motion of the ship as well as sudden impact. For computers that are used ashore, the frame or cabinet is secured to the floor. The 2-7

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size of the frame or cabinet of a computer is a general indication of the type of computer and the type of data system the computer is used on. Consult your computer’s technical manual or owner’s manual for parts, tools, and test equipment needed in the maintenance of the computer. Let’s take a look at the designs or types of frames/cabinets—modular, chassis or assembly, cage or rack, and motherboard or backplane. Some computers use combinations of these designs. Modular-Designed Computer Frames/Cabinets A frame or cabinet of modular design uses the concept that a functional area maybe composed of one module or several modules. An example of several modules that comprise one functional area is memory. It may take four modules to make up one functional area, memory. Modular frames or cabinets contain the following: External connections for data, control, and I/O cables Modules with test blocks on some types of computers Module mounting slides and retaining hardware Module electrical connector receptacles and interconnecting wiring harness An operator’s control panel A blower unit and a system of air ducts allowing cooling air to circulate through all module heat exchangers Gaskets for electronic shielding, moisture protection, air ducting, and electrical connectors Filters for electronic shielding Each module is made up of subassemblies and/or pcb’s and a heat exchanger for air-to-air cooling. Modular-designed computers that are watercooled will have the necessary hardware fixtures for liquid cooling. A maintenance panel can be located up to 15 feet from the frame or cabinet that houses the functional areas or it may be affixed over the top of the frame or cabinet. In the modular setup, the power supply will be contained in a module just as the major functional areas are. Figure 2-10 is an illustration of a modular setup used in a large mainframe computer. The modular-designed frame or cabinet is the most rugged. Each module fits into a compartment. The modules slide into the compartments of the frame or cabinet and are secured with retaining hardware to prevent the module or assembly from sliding back out. At the rear of each compartment of the frame or cabinet for each module, there is an electrical connector receptacle for data and power. The receptacle is keyed so the module can only go in one way. You must secure the power when removing and replacing a module or to gain complete access to all the subassemblies or pcb’s inside a module. Each module contains all the electronic parts and circuitry that make up one functional area or a portion of a functional area. Examples of modules used in a modular design of a large mainframe computer are the CPU, I/O, memory, and power supply. The CPU usually consists of only one module, whereas the memory of a computer may require multiple modules to form the memory. Each module will consist of electronic subassemblies and/or printed circuit boards that are color coded for easy identification. The printed circuit boards will fit into keyed slots that are in close proximity to each other. In this way one module can hold over 200 pcb’s. The pcb’s are configured in rows. Check the computer’s technical manual for the chassis map of the pcb’s and other major subassemblies. Refer back to figure 2-9 for an illustration of a module with the cover removed. Other items found on a module are test blocks for maintenance, a time meter to monitor powered-on time, gaskets for electronic shielding, and a heat exchanger for cooling. The functional areas that are basic to most modularly designed computers include the following: Central processing unit (CPU) Input/Output controller (IOC) Input/Output adapter (IOA) Memory Power supply Chassis- or Assembly-Designed Computer Frames/Cabinets The design concept of computers that use the chassis or assembly arrangement is for the whole computer system to be located on one or more chassis or assemblies. Chassis- or assembly-designed computers are smaller than modular frame or cabinet housed computers, but they are also very rugged. 2-8

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Figure 2-10.—Examp1e of a modular-designed frame computer. The chassis- or assembly-designed computer contains the following: Chassis or assemblies Chassis or assembly mounting and retaining hardware Chassis or assembly electrical connector receptacles and interconnecting wiring harness External connections for data and power cables Printed circuit boards (pcb’s) An operator’s control or maintenance panel A blower unit with air filter and heat exchanger, which allows cooling air to circulate through all the chassis or assemblies inside the frame or cabinet Gaskets for electronic shielding, moisture protection, air ducting, and electrical connectors Filter unit for electronic shielding Test blocks for maintenance Time meter to monitor powered-on time Chassis or assemblies use the same basic concept as modules except they are not readily removable and usually contain more than one functional area of the computer. The functional areas are usually grouped together in blocks of two or more pcb’s. The subassemblies or pcb’s that make up a functional area are grouped together in a chassis or assembly rather than 2-9

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having a single module dedicated to one specific functional area. The chassis or assemblies can be mounted in one of several ways inside the computer’s frame or cabinet. These include brackets that permit the chassis or assembly to slide in and out of the frame or cabinet; doors that swing out from one side of the frame or cabinet; or a fixed chassis or assembly similar to a cage or rack inside the frame or cabinet. In some cases, a combination of two or more of these methods is used by a single computer. Chassis can slide out on mounting hardware, swing open like a door, or be fixed. Figure 2-11 is an illustration of a chassis or assembly-designed computer. The pcb’s inside a chassis or assembly are arranged in the same way as inside a module-in close proximity and configured in rows. Again refer to the computer’s technical manual for a chassis map that outlines the location of all parts of the computer. Each chassis or assembly contains subassemblies, pcb’s, and a power supply unit. Some computers use small brackets to secure the subassemblies or pcb’s inside each chassis or assembly. Each chassis or assembly is secured with retaining hardware. Check the computer technical manual to see if you can leave the power on while the assembly or chassis is extended or is being extended; it varies with the computer. This will affect the ability to extend subassemblies or pcb’s on an extender card with the power on. Support functions, such as power supplies and blower units, for chassis- or assembly-designed com- puters are usually located on a fixed chassis or assembly in the computer’s frame or cabinet. Chassis- or assembly-designed computers can also be water cooled. The functional areas that are basic to most chassis- or assembly-designed computers include the following: Central processing unit Input/output controller Input/output adapter Memory Power supply Cage- or Rack-Designed Computer Frames/Cabinets Computers that use cages or racks contain the following: A cage or rack Figure 2-11.—Example of a chassis- or assembly-designed computer. 2-10

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Subassembly or pcb mounting slides and retaining hardware Subassembly or pcb electrical connector receptacles and interconnecting wiring harness Printed circuit boards External connections for data and power cables An operator’s control or maintenance panel Power supply unit Blower unit Air falter In a cage or rack arrangement, only the functional areas of the computer are contained in the cage or rack. The cage or rack contains pcb’s that only house the major functional areas, such as CPU, memory, and I/O. Sometimes more than one functional area will be contained on a pcb. The pcb’s slide into slots inside the cage or rack. The connector receptacles for each subassembly or pcb are usually located at the rear of the cage or rack. The pcb’s are not always keyed, so you must exercise care when installing them. The pcb’s are secured in each slot by retaining hardware. The cage or rack is generally fixed and cannot be extended as a whole unit. The pcb’s can usually be accessed with power on, but power must be secured when you remove and replace a pcb. The pcb’s can be extended individually for rnaintenance. The other main parts of the computer, such as the power supply unit and cooling unit, are located in a different part of the frame or cabinet, not in the cage or rack with the pcb’s. Figure 2-12 is an illustration of a cage or rack setup. Motherboard- or Backplane-Designed Computer Framed/Cabinets Computers that use a motherboard or backplane design are built more for their portability and compactness. They are the least rugged. The frame or cabinet contains the following: A motherboard or backplane with the connector receptacles for each pcb, the keyboard, and in some types of micros: single inline memory modules (SIMMs), single inline packages (SIPS), and single inline pin packages (SIPPs) Wiring harness for the motherboard or backplane Pcb’s with the necessary I/O connectors External connections for the power cables Retaining hardware for the motherboard or backplane A power supply unit A small fan with an air filter for cooling A small speaker Figure 2-12.—Example of a cage- or rack-designed computer frame or cabinet 2-11

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Also contained in the frame or cabinet of the computer is the peripheral equipment-floppy and/or hard disk units. Computers that use motherboards or backplanes use a keyboard external to the frame or cabinet as their method to control the computer. With some micros, however, the keyboard is part of the cabinet assembly. The motherboard or backplane usually rests on the bottom of the frame or cabinet of the computer. The motherboard or backplane contains all the pcb’s for the whole computer, a keyboard connector, a battery backup circuit, and power supply status LEDs. A motherboard has IC chips included on the motherboard; a backplane does not. Each pcb contains one or more functional areas. Figure 2-13 is an illustration of a motherboard or backplane design used in a computer. It is easier to perform maintenance on computers with motherboards or backplanes than on modular- or chassis-designed computers because of their size and the easy accessibility to the interior of the computer. Extending pcb’s for maintenance is usually not necessary because everything can be readily accessed once the cover is removed; this includes maintenance with the power still applied. Remember, you must still exercise safety precautions when removing and installing any parts inside the frame or cabinet by securing power to the computer. Safety and Security Design Features of Computer Frames/Cabinets The frame or cabinet can provide limited protection for a computer by use of gaskets and filters. Gaskets and filters are not used on all types of computers, but they serve important safety and security functions on those where they are used. GASKETS. —Gaskets are used for two main purposes on computers. Gaskets provide moisture sealing protection and protection against interference (radio frequency interference [RFI] and electromagnetic interference [EMI]). The gaskets are usually located around the edges of an item to protect its contents or internal parts. For example, gaskets are used in heat exchangers for a module to protect the pcb’s inside the module from moisture and electronic interference. Gaskets are also used in electrical connectors inside a frame or cabinet to protect the connection from electronic interference. FILTERS. —There are two types of filters you will encounter. They are electronic (EMI and RFI) and environmental (foreign particles such as dust and dirt) filters. Both filters provide protection for the computer. The computer’s technical manual and/or the Planned Maintenance System (PMS) will provide you with the requirements for the maintenance of these two filter types. Figure 2-13.—Example of a motherboard- or backplane-designed computer. 2-12

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CAUTION DEVICES USED IN COMPUTERS ARE SENSITIVE TO ESD (ELEC- TROSTATIC DISCHARGE). ENSURE THAT YOU ARE FAMILIAR WITH THE COMPUTER’S SAFETY PRECAUTIONS THAT DEAL WITH ESD AND TAKE THE NECESSARY STEPS TO PROTECT THE COMPUTER. YOU CAN FIND THE REQUIREMENTS IN THE COM- PUTER’S TECHNICAL MANUALS. SUBASSEMBLIES USED IN COMPUTERS Subassemblies are electronic parts of the computer that are a portion or part of a functional area. A subassembly can contain pcb’s or just electronic parts. Two or more components combined into a unit will form a subassembly. Each subassembly can contain components, such as transistors, resistors, capacitors, and the like, and/or pcb’s to make one individual subassembly. We use a power supply module and a memory module of a large computer as our examples. A power supply module in a large computer usually has six or seven subassemblies. Each of these subassemblies contains transformers, transistors, diodes, resistors, capacitors, and the like. A memory module may need up to four memory stacks to make it complete. Each stack contains only the electronic components necessary to make it complete. Some of the items you will find in subassemblies of computers are as follows: Memory stacks of a memory unit Dc-to-dc converters in modules Dc switching regulators of a power supply KEYED SUBASSEMBLIES. —Subassemblies are keyed to assure that only the correct subassembly is inserted into a slot and that each subassembly is inserted properly (not backwards). The manufacturer will either cut a slot into the plug-in side of the pcb or put plastic sleeving on one or more of the connector pins. With the pin/plastic sleeving method, the connector receptacle must match the pin(s) with the sleeving to accommodate the pcb’s connector pin(s). The arrangement of the subassembly’s connector pins (plugs) can also act as a guide when you install the subassembly. MAINTENANCE OF SUBASSEMBLIES.— Subassembly units can be sealed or unsealed. With the sealed units, you cannot break them down any further for repair purposes. You’ll have to discard the sailed subassembly unit and replace it or turn it in for a new subassembly. A subassembly may or may not have test points for maintenance purposes. PRINTED CIRCUIT BOARDS USED IN COMPUTERS Printed circuit boards (pcb’s) makeup the majority of the computer’s functional areas. They vary in size from small pcb’s used in modular designs to large ones used in some cage-or rack-designed computers. Let’s take a look at the functions and physical characteristics of pcb’s. Functions of Printed Circuit Boards It doesn’t matter what type of computer we are talking about, the computer’s printed circuit boards process all the data the computer processes. The pcb’s contain the circuitry that electronically manipulates the data that enters and leaves the computer. The functional areas of the computer are contained on the pcb’s. Physical Characteristics of Printed Circuit Boards The physical characteristics of a pcb depend on the type of computer. Let's examine some general characteristics. SIZE AND NUMBER OF PRINTED CIRCUIT BOARDS. —The size and number of pcb’s vary from the computers that require many small pcb’s for one functional area of the computer, to the computers that need only a single medium to large pcb to handle one functional area. Take a computer’s CPU as an example. Larger militarized computers may use up to 200 small pcb’s to perform the functions of the CPU. Whereas a microcomputer needs only a single “chip” on a single pcb to perform the functions of the CPU; thus requiring less circuitry to perform the CPU functions. ARRANGEMENTS OF PRINTED CIRCUIT BOARDS. —Again the type of computer will dictate the arrangement of pcb’s. The computer’s technical manual will provide the information on how the pcb’s are arranged inside the computer’s frame or cabinet. Computers that are modular in design have all the pcb’s 2-13

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for a functional area located in one or more modules. In computers that use a chassis/assembly, cage/rack, or motherboard/backplane design, the functional areas are located on a single pcb or a group of pcb’s located in a single area. The pcb’s generally face in one direction whether they are used in a modular, chassis/assembly, cage/rack, or motherboard/backplane design. Some equipment provides card guides or brackets and locking or tiedown bars, so pcb’s will not suffer intermittent problems as a result of shock and vibrations. KEYED PRINTED CIRCUIT BOARDS.— Pcb’s are keyed to ensure that a different card type is not inserted into a slot or the correct pcb is not inserted backwards. The manufacturer will either cut a slot into the plug-in side of the pcb or put plastic sleeving on one or more of the connector pins (fig. 2-14, frame A). With the pin/plastic sleeving method, the connector receptacle must match the pin(s) with sleeving to accommodate the pcb’s connector pin(s) (plug [s])(fig. 2-14, frame B). COLOR-CODED PRINTED CIRCUIT BOARDS. —Pcb’s are identified by numbers. Some pcb’s in computers show the number(s) with color bands using the standard color code (also shown on fig. 2-14, frame B). With the color-code technique, you can check the card number. The color code is also very convenient when you are working with groups of cards that have the same card number. Refer to NEETS, Module 19, The Technician's Handbook, for the standard color code. MAINTENANCE FEATURES OF PRINTED CIRCUIT BOARDS. —Some pcb’s have indicators and test points that are very helpful when you perform maintenance. Figure 2-14.—Keyed pcb’s: A. Cut slots on a pcb; B. Plastic sleeving on pins. 2-14

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Maintenance Indicators or Diagnostic Light-Emitting Diodes (LEDs). —Maintenance indicators or LEDs provide you a readily visible indication to tell you when the equipment is operating normally and when it is operating abnormally. Refer to your computer’s technical manual or owner’s manual for their locations and operation. Test Points. —Test points are usually located on the outer edge of pcb’s. They can provide you with status or operational information with voltage levels and/or waveforms. Refer to the computer’s technical manuals for details. COMPUTER CONNECTORS AND CABLES Computers must have an organized way to exchange and route data and power signals internally and externally. Computers must have a place where the signals leave the computer externally and talk to other computers and/or other equipments, peripherals, displays systems, and/or communication systems. The computer’s technical manual or owner’s manual provides parts replacement information, recommended tools and test equipment, internal and external signal distribution, and I/O interface. The following documents also provide information useful in the maintenance of computer connections and cabling. They define the standards and specifications of the interface(s) that the computer uses as well as the standards and specifications of the actual repairs to the internal and external connectors and cables. MIL-STD-2000, Standard Requirements for Electrical and Electronic Assemblies —Provides associated standards and specifications that can be used when making solder repairs to connectors and their conductors. MIL-STD-2000 provides the standards for the actual solder terminations. MIL-STD-2036, General Requirements for Electronic Equipment Specifications —Provides a list of the standard external interfaces; parallel and serial interface formats and metallic and fiber optic cabling. The interfaces listed in MIL-STD-2036 define the requirements of each standard: mechanical, elec- trical, functional, procedural, and any other requirements that do not fall into any of the four listed categories. NEETS, Module 4, Introduction to Electrical Conductors, Wiring Techniques, and Schematic Reading —Provides information on conductor and cable (includes coaxial) architecture and characteristics, wiring and repair techniques, and signal interpretation and distribution. NEETS, Module 19, The Technician's Handbook —Provides connector and cable information; references, types and construction/description, gen- eral application data, identification, and insert arrangement. NEETS, Module 24, Introduction to Fiber Optic —Provides fiber optic theory and operation and connector and cable information. EIMB, Installation standards, NAVSEA 0967-LP-000-0110 —Provides connector and cable information; references, identification for interpretation and distribution, and installation and repair (includes MIL-STDs of specialized tools). Naval Shore Electronics Criteria, Installation Standards and Practices, 0280-LP-900-8000- Provides connector and cable information: references, identification for interpretation and distribution, and installation and repair (includes MIL-STDs of specialized tools). Miniature/Microminiature (2M) Electronic Repair Program, NAVSEA TE000-AAA-HBR 010/2M, Vol. 1; 020, Vol. 2; 030, Vol. 3 —Provide the same type of information as MIL-STD-2000 concerning solder repairs to a connectors and their conductors. Remember, when making repairs to the connectors and cables, use identical replacement parts or suitable substitutions. This is very important. Let’s start with the computer’s internal connectors, then external connectors, and finally the cables. Connector Architectures In electronics, connectors are designed to terminate pcb’s, conductors, and cables between electronic circuits within a system, between systems and subsystems and their power sources. Connectors interconnect circuits on circuit boards with backplanes/backpanels, motherboards, or wiring within a frame or cabinet of a computer (set). Connectors also terminate the cables interconnecting the external equipment and the computer. They come in many shapes and sizes. The interfaces listed in MIL-STD-2036 dictate the requirements needed for connectors. A connector consists of a connector 2-15

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receptacle (jack) and a connector plug (fig. 2-15). The receptacle can be located at the end of a cable or mounted stationary. The plug can be located at the end of pcb or cable. The actual connection (mating) of a connector consists of pcb card-edge, electrical pins (flat or round) and contacts, or soldered (wire to card-edge connector). Let’s examine the types of connectors. SINGLE-PIECE PCB OR CARD-EDGE CONNECTORS. —Single-piece pcb or card-edge connectors are used internally. They are the most widely used connectors for making connections from a pcb (plug) to a receptacle; cable, another pcb, or a larger item such as a backplane receptacle. Figure 2-16 shows a single-piece pcb or card-edge connector. Connection can also be made from the pcb edge to a wire (soldered). Terminations of conductor to receptacle include solder and solderless (wire wrap, crimping, pin removal and insertion, or Mass-Termination Insulation Displacement Connection (MTIDC) or Insulation Displacement connection (IDC). TWO-PIECE PLUG AND RECEPTACLE PCB CONNECTORS. —Two-piece plug and receptacle pcb connectors are used internally. Two-piece pcb connectors are basically the same as one-piece pcb connectors except the pcb is designed with a plug (male or female) on the card edge that plugs into a receptacle (male or female). Pins or contacts located on either receptacle or plug can be flat or round. See figure 2-17. No-piece connectors are preferred over one-piece because they provide more resistance to shock and vibration. Terminations of conductor to receptacle Figure 2-15.—A connector: a plug and a receptacle. 2-16 Figure 2-16.—Single-piece pcb or card-edge connector. include solder (2M or basic) or solderless (wire wrap, crimping, pin removal and insertion, or MTIDC or IDC [fig. 2-18]). RECTANGULAR MULTIPIN CON- NECTORS. —Rectangular plastic- or metal-shell receptacles and plugs can be used for internal and external connectors. They can be flat with a single row Figure 2-17.—Two-piece plug and receptacle pcb connector.

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Figure 2-18.—Insulation displacement connection (IDC). of conductors or have multiple rows of many conductors (fig. 2-19). Rectangular connectors can have over 100 pins or contacts. Contacts or pins located on either the receptacle or plug can be flat or round and can be male or female. Hardware is used to secure the connection to provide more stability against shock and vibration. Telephone jack connectors can be used to connect the conductor to a rectangular multipin connector. This is very useful in microcomputers; it makes it easy to disconnect and connect connectors. solderless (wire wrap, crimping, pin removal and insertion, MTIDC or IDC, and AMP TERMI- POINT). Terminations of conductor to plug include solder (2M and basic) and solderless (crimping, pin removal and insertion, and MTIDC or IDC). Combinations of termination are often used (fig. 2-20). For example, to secure a conductor to a connector receptacle pin or contact; it may be crimped or soldered, and then inserted into the connector receptacle. CIRCULAR OR CYLINDRICAL (SHELL) MULTIPLE-PIN CONNECTORS. —Circular plastic- or metal-shell receptacles and plugs can be used Externally, provisions can be made for shielding these connectors from EMI and RFI. Terminations of conductor to receptacle include solder (2M or basic) and Figure 2-19.—Rectangular multipin connectors. Figure 2-20.—Combination of various terminations. 2-17

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for internal and external connectors (fig. 2-21). Circular connectors can have over 100 pins or contacts. The contacts or pins located on either the receptacle or plug are usually round and can be male or female. Circular connectors can be secured to protect against shock and vibration with either complete or partially threaded shells (breech lock) or bayonet-style (pin and curved slot); neither kind requires internal or external screws for securing the mating parts. Externally, provisions can be made for shielding these connectors from EMI and RFI. Terminations of conductor to receptacle include solder (2M or basic) and solderless (wire wrap, crimping, pin removal and insertion, MTIDC or IDC, or AMP TERMI-POINT). Terminations of conductor to plug include solder (2M and basic) and solderless (crimping and pin removal and insertion). Combinations of termination are often used. Fiber optic connectors fall into the circular connector category. Refer to NEETS, Module 24, Introduction to Fiber Optics, for a discussion of the mating of fiberoptic connectors. COAXIAL CONNECTORS. —Coaxial con- nectors are designed for single, twin (twinax), and triple (triaxial) conductors (fig. 2-22). Refer to MIL-C-17 for connector specifications. Contacts or pins located on either the receptacle or plug are round and can be male or female. Coaxial connectors are secured bayonet-style (pin and curved slot) to protect against shock and vibration and for quick removal and replacement. Figure 2-21.—Circu1ar multipin connector. Figure 2-22.—Coaxial connector. Externally, provisions can be made for shielding these connectors from EMI and RFI. Terminations of conductor to receptacle include solder (2M or basic) and solderless (wire wrap, crimping, and pin removal and insertion). Terminations of conductor to plug include solder (2M and basic) and solderless (crimping, and pin removal and insertion). Combinations of termination are often used. COMPONENT CONNECTORS. —Although we may not think of it as a connector, a wire attached to a component’s lead also forms a connection. The most commonly used methods of securing a wire to a component’s lead are soldering and wire wrapping. For example, pushbutton indicators use wire wrap connections to secure a conductor(s) to its pin(s). Wire wrapping is often preferred because it is quick to remove and install, and it is strong. Also, you do not have to apply heat to the conductor. This prevents damage to the conductor’s insulation that can be caused by using a soldering iron. Internal Connectors Rather than have wires running everywhere inside the computer frame or cabinet and between the units, various methods are used to connect the conductors from point to point and to organize the conductors. Connectors are used inside the computer to interconnect the major individual units of the computer. Individual conductors are used to route each signal between the connectors of the major units and to 2-18

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provide power throughout the computer. For example, we want a signal to go from a CPU module or pcb to a memory module or pcb. A signal will leave the CPU at its plug, which is plugged into a connector receptacle. A conductor will route that signal from the CPU’s connector receptacle to the memory’s connector receptacle, where the signal will go from the connector plug to its destination inside a memory module or pcb. INTERNAL CONNECTOR RECEP- TACLES. —Internal connector receptacles receive the connector plug of an individual unit (module, subassembly, or pcb) or wiring harness. Connector receptacles can have male or female electrical contacts. The sizes and shapes of the electrical contacts vary. Figure 2-23.—Connector receptacle of a module for a pcb. Refer to your computer’s technical manual for details. Receptacle connectors are used in the following places: Frame or cabinet to receive a module or wiring harness Module to receive a subassembly or pcb Chassis or assembly to receive a subassembly or pcb Rack or cage to receive a pcb Motherboard or backplane to receive a pcb Examples of connector receptacles are illustrated in figures 2-23 and 2-24. Figure 2-23 shows the connector receptacles of a module for receiving pcb’s. Figure 2-24 illustrates the connector receptacles of a motherboard. INTERNAL CONNECTOR PLUGS.— Individual units and wiring harnesses will have a plug that connects into an internal connector receptacle. Again depending on the design, the plug can have male or female electrical contacts. The connector plugs on the following units will be plugged into connector receptacles: Module Subassembly Pcb Wiring harness Figure 2-24.—Connector receptacles of a motherboard. 2-19

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Remember that internal connector receptacles and plugs are keyed for each other; or in some cases, they will have guide pins. The receptacle and the plug must match to be connected properly. Pay attention to this because you can cause extensive damage if the connection is reversed or if you force the connection. Also, remember that connections should be made with the power secured to the computer. INTERNAL CONDUCTORS (WIRES). —The wires will take individual signals or mass data and route them for distribution throughout the computer. Signal names used by a computer can be found in the wire listings, computer prints, or the description of each pcb. Learn to interpret the computer’s wire listings and prints. This skill will prove invaluable when you have to trace signals from point to point when diagnostic testing does not prove conclusive in finding malfunctions. To find information on how to interpret signals and signal distribution, look in the computer’s technical manuals. The wires can be connected between two plugs, between two receptacles, between a receptacle and a plug or visa versa, or they can originate and terminate on the same receptacle, plug, or indicator/switch. They are used in every part of the computer and any type of computer. The following are some examples of where conductors are terminated: Wiring harness plugs Connector receptacles of a modular frame or cabinet Between a connector receptacle and a plug inside a module Connector receptacles inside a chassis-, assembly-, rack-, or cage-designed frame or cabinet Connector receptacles of a motherboard or backplane Indicators and switches throughout the computer External connector receptacles Conductors used internally in a computer are insulated with a plastic coating. Be careful when making repairs. If the repair calls for soldering, the fumes from heating the plastic coating can be toxic. Remember, conductors can originate and/or terminate from or to the same connector receptacle, indicator, or switch. Because wiring must be neatly organized, wire bundles in computers are used to route the conductors from point to point. The wire bundling method of organizing the wires is used for interconnections inside of a module, in a cage or rack, in a chassis or assembly, and inside a frame or cabinet. The wire bundles are secured by either lacing, spot tying, or self-clinching cable straps. The conductors are arranged in what is called a wiring harness. The wiring harness may include terminations. A wiring harness allows the wires to be neatly organized and uses the limited space more effectively. Figure 2-25 shows a wiring harness used inside a computer’s cabinet to secure the conductors in bundles. Notice how the wire bundles of the wiring harness are secured to keep the wiring neatly organized. Figure 2-26 is an example of a wiring harness connector (rectangular) assembly. Notice the plug and the connector pins (electrical contact). The plug is used to Figure 2-25.—Example of wire bundling inside a computer’s cabinet using a wiring harness. 2-20

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CAUTION Figure 2-26.—Wiring harness connector plug (rectangular) assembly. connect to an internal connector receptacle as part of the cabinet wiring harness. NOTE IF A CONDUCTOR MUST BE COMPLETELY OR PARTIALLY REPLACED, REPLACE IT WITH THE SAME GAUGE (AWG) AND TYPE OF CONDUCTOR. SEE THE TECHNICAL MANUAL FOR EXACT ORDERING AND REPLACEMENT INFORMATION. External Connectors The external connectors of a computer are designed to receive electrical power from power sources, send or receive data (input/output) to or from other computers or digital equipment, and to interconnect units of the same computer together. For example, the computer uses external connections to load operational programs and test programs that are stored externally on a magnetic tape unit. It also uses external connections to communicate with other computers or peripherals and/or other systems (display and/or communication). The computer’s prints, wire listings, owner’s manual, CSTOMs, SOMs, and/or systems doctrine or equivalent will provide the exact jack, channel or port, and pins assignments of where power and/or data enter or leave the computer. WHENEVER CONNECTIONS FOR POWER AND DATA ARE DIS- CONNECTED OR RECONNECTED, ENSURE THAT THE POWER TO THE COMPUTER AND THE POWER SOURCE HAVE BEEN SECURED AND THE PROPER TAG-OUT PROCEDURES HAVE BEEN FOLLOWED FOR SECURING THE POWER SOURCE. POWER REQUIREMENTS OF COM- PUTERS. —The power requirements for computers vary. The requirements depend on the type of computer and/or where the computer is used--on ship or ashore. Computers are designed to accept different combina- tions (voltage, frequency, and phase) of primary power. A couple of examples: for a large NTDS computer aboard ship, the requirement is 115 Vat, 400 Hz, 3 phase; whereas, a microcomputer computer ashore uses 115 Vat, 60 Hz, single phase. You need to know the primary power source for your computer system. Become very familiar with the location and operation of your computer’s power source. Know the exact location of power panels in your spaces and know which circuit breakers to secure for routine maintenance and emergency situations. We discuss computer power supplies in chapter 4. EXTERNAL CONNECTOR RECEP- TACLES. —External connector receptacles receive the plug of a cable (conductor). The cables carry power and data. External connector receptacles and their plugs come in all sizes and shapes. Like internal receptacles and plugs, they, too, are keyed or because of their physical shape, can only be mated one way. Power cables and cords are fairly standard. We, therefore concentrate our discussion on some of the I/O connections used for parallel and serial data transfers. The physical shape (architecture) of these connectors does not have anything to do with the standard or the format (parallel or serial) used for the data transferred. Some of the more common series of connectors used for parallel and serial data transfer include the following: Parallel —MIL-C-series—M28840, M38999, and M81511; Centronics Parallel; MTIDC or IDC; “D” series; and Nonstandard series 2-21

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Figure 2-27.—Example of a jack keyed for a connector plug. Serial —MIL-C-series—M28840 and M49142; MIL-C-series (fiber optics) M83522(ST) and M28876; ST 506 (fiber optics); “D” series; and Nonstandard series Figures 2-27 and 2-28 are examples of external I/O connections that computers may use. In figure 2-27, notice that the connector receptacle (jack) is keyed; this means that the connector plug of the cable must match Figure 2-28.—Examples of connector receptacle physical shapes.

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External connector receptacles vary in location on the computer; it depends on the type of computer. However, they are usually located on the top or the rear of the frame or cabinet. Take a microcomputer for example, the I/O jacks and all other connections are located in the rear of the microcomputer. Look at figure 2-29; you’ll notice the I/O jacks and other connections are located in the rear of the microcomputer’s frame or cabinet. Some of the more common I/O external connectors used for the parallel and serial input/output of data are shown in figure 2-30. Notice the shape of each connector receptacle; the connector plug can only be inserted in one way. Cable ArchitectureFigure 2-29.—Example of I/O jacks and other connections located on the rear of a microcomputer. A cable consists of two or more insulated conductors in a common jacket. Cables are used to receive electrical power from power sources, to send to make a connection. In figure 2-28, you’ll notice that the jacks are not keyed; but because of their shapes, the connector can only fit one way. data to (input) or receive data from (output) other Figure 2-30.—Examples of the different types of external connector receptacles used by computers. 2-23

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computers or digital equipment, and to interconnect units of the same computer together. We limit our discussion to I/O cables. The interfacing standards provide guidelines on the type and maximum cable length to be used for the I/O data cables. The number of conductors in each cable varies with type of computer. A cable can have from 2 to 120 conductors. The cable is grounded with a signal ground and/or to its common connector ground. If it has shielding, the shielding is also grounded to the connector (fig. 2-31). The cables must also be protected (shielded) from EMI and RFI. This is accomplished with a solid or braided covering of nonferrous conductive material, preferably copper. The cable is completely covered throughout its length. This insulated conductor or conductors provide high levels of RF attenuation to potential sources of compromising emanations (CE), such as RFI. This is not required for all cables; a shipboard environment and land-based operational sites, such as an ASWOC, are two examples of situations in which cables must be protected. We discuss some of the more common types of cables used for I/O transfer of data. They are flat, ribbon, twisted component, coaxial, and, fiber optic cables. FLAT CABLES. —Flat cables consist of multiconductors. They can have individually insulated round conductors (solid or stranded) or bare conductors sandwiched between layers of insulation. See figure 2-32 for an example. Flat cables can be terminated with single-piece pcb or card-edge connectors, two-piece plug and receptacle pcb connectors, rectangular multipin connectors, or IDCs. They can be used for parallel and serial transfer of data. They are used extensively with microcomputers. Figure 2-32.—Flat cable. RIBBON CABLES. —Ribbon cables are flat multiconductor cables with individual insulated conductors (usually solid) that can be easily separated. Figure 2-33 is an example of a ribbon cable. Ribbon cables are extremely flexible and can be bent around sharp turns. They can be terminated with single-piece pcb or card-edge connectors, two-piece plug and receptacle pcb connectors, rectangular multipin connectors, or IDCs. Ribbon cables can be used for parallel and serial data transfer. They are also used extensively with microcomputers. Figure 2-31.—Grounding a cable. 2-24 Figure 2-33.—Ribbon cable.

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Figure 2-34.—Twisted component or multiconductor cable. TWISTED COMPONENT OR MULTI- CONDUCTOR CABLES. —Twisted component cables consist of multi-insulated wires (solid or stranded), with up to 120 conductors. They can be single wires or twisted pairs. The cable is concentric in shape and the larger cables are usually semi-rigid to provide support and put less strain on the cable itself and its connector (fig. 2-34). Depending on the length of the cable, popular cable types for large main- frames and minis include 2U/2UW/LS2U or 2AU/2WAU/LS2AU. The construction and a description can be found in NEETS, Module 19, The Technician's Handbook. Twisted component cables can be terminated with rectangular multipin connectors or circular multipin connectors. They can be used for parallel and serial data transfer and in all types of computers. COAXIAL CABLES. —Coaxial cables are designed to transmit signals efficiently between 1 kHz and 4000 MHZ with minimum loss and little or no distortion. A coaxial cable is made of a central signal conductor covered with an insulating material (the dielectric core), which in turn, is covered by an outer tubular conductor (the return path). The cable is called coaxial because the conductors, usually two or three, are separated by the dielectric core. The inner core can be solid or stranded wire that is bare, timed, or silver coated. Coaxial cables always have an outer shielding; refer to MIL-C-17 for specifications. Commonly used coaxial cables include RG-12A, RG-58, and RG-59 for coaxial and TRF-8 and TRF-58 for triaxial. Coaxial component cables are terminated with circular multipin connectors. Coaxial cables are used for serial transfer of data. Figure 2-35 shows examples of two types of coaxial cable: single and triaxial. FIBER OPTIC CABLES. —Refer to NEETS, Module 24, Introduction to Fiber Optics, for a detailed discuss of the fiber optic cabling. Fiber optic cables are used for serial transfer of data. CAUTION CARE SHOULD ALWAYS BE EXERCISED WHEN HANDLING CABLES. SEVERE BENDING AND HANDLING OF THE CABLE BY ITS CONNECTOR CAN CAUSE DAMAGE. Figure 2-35.—Coaxia1 cable: A. Single; B. Triaxial. 2-25

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COMPUTER COOLING SYSTEMS The computer itself is the most critical piece of equipment in any data system. Because the contents of any computer generate a lot of heat, the computer must have a cooling system and it must be maintained at ALL times. The computer’s cooling system must be operating properly to ensure the computer will operate properly. The cooling system may be air cooled, liquid cooled, or a combination of air and liquid cooled. Remember, there are four methods of cooling—convection, forced air, air-to-air, and air-to-liquid. Examples of computer cooling systems are as follows: Heat sinks use convection cooling to dissipate heat in computer power supplies. Small box fans with a filter mounted in the rear of PC/desktop microcomputers use forced air cooling. Heat exchangers mounted on a module, the frame, or the-cabinet and air filters for blower units use air-to-air cooling. (Figure 2-36 is an example of a heat exchanger used on a large computer. Notice it is mounted on the side of a module.) Type III, Chilled Water/Distilled Water (CW/DW) Heat Exchanger with a CW/DW Heat Exchanger Standby is the liquid cooling system used for large water-cooled computers— primarily aboard ship. Learn how your computer is cooled, and who is responsible for the maintenance. Remember, of the four methods, shore stations use a combination of the first three—convection, forced air, and air-to-air methods of cooling. shipboard systems use a combination of all four methods—convection, forced air, air-to-air, and air-to-liquid. SUMMARY—COMPUTER CONFIGURATIONS AND HARDWARE In this chapter you have studied the various diagrams and layouts used to specify computer configurations and units, the major hardware parts of a computer system, the unit connections and cables, and the need for cooling systems. The following information highlights&e important points you should have learned. FUNCTIONAL BLOCK DIAGRAMS — Functional block diagrams provide you a detailed analysis of the principles of operation or the overall equipment, types of signals and their directional flow, and the major functional areas. FUNCTIONAL LAYOUTS —Functional layouts show the major functional areas of the computer. PHYSICAL LAYOUTS —Physical layouts show where each element/part of the computer is located. They do not show signal/signal flow. COMPUTER FRAMES/CABINETS —The Figure 2-36.—Example of a heat exchanger used by a large computer is housed in a frame or cabinet. The frame or cabinet may also contain the support areas (power supply and hardware for cooling). Frames and cabinets provide some protection against hazards such as shock, EMI or RFI, moisture, and personnel mistakes. SAFETY AND SECURITY DESIGN FEATURES —Gaskets provides moisture sealing protection and protection from RFI and EMI. Filters provide electronic (RFI and EMI) and environmental (dust and dirt protection). SUBASSEMBLIES —Sub assemblies are the electronic parts of the computer. They contain components such as transistors, resistors, and capacitors, and/or pcb’s. They may be sealed or computer mounted on the side of a module. unsealed. They may or may not have test points. 2-26

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PRINTED CIRCUIT BOARDS —Printed circuit boards (pcb’s) make up the majority of the computer’s functional areas. They contain all the circuitry that electronically manipulates the data that enters and leaves the computer. The number, size, and arrangement of pcb’s varies from computer to computer. Pcb’s maybe keyed to ensure they cannot be inserted incorrectly. Some pcb’s are color coded. Pcb’s have indicators and test points to help with maintenance. COMPUTER CONNECTIONS —The computer must have an organized way to exchange and route data and power signals internally and externally. CONNECTOR ARCHITECTURE —Con- nectors consist of a connector receptacle (jack) and a connector plug. They are designed to terminate pcb’s, conductors, and cables between electronic circuits within a system, between systems and subsystems, and their power sources. INTERNAL CONNECTORS —Connections are used inside the computer to interconnect the major individual units of the computer. EXTERNAL CONNECTORS —Extemal con- nectors receive electrical power from power sources, send and receive data to and from other computers or digital equipment, and interconnect units of the same computer system together. CABLE ARCHITECTURE —A cable consists of two or more insulated conductors in a common jacket. Cables are used to receive electrical power from power sources, to send data to and receive data from other computers and digital equipment, and to interconnect units of the same computer. COMPUTER COOLING SYSTEMS —Cooling systems are needed because the contents of any computer generate a lot of heat. Become familiar with the technical manuals, diagrams, and layouts for the computers you have responsibility for maintaining. Know how the computer system is configured and housed. Know the types of connections and cabling used. 2-27

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CHAPTER 3 COMPUTER OPERATOR CONTROLS AND CONTROLLING UNITS INTRODUCTION Although the computer can operate automatically under program instruction control, provisions to operate the computer manually are available. You may use keys and switches to affect overall computer operation, control parts of the operation, provide specific jump or stop conditions, or govern the speed of operation. You may use pushbutton indicators to modify all or part of the contents of registers. The computer’s technical and owner’s manuals, desktop guides, and system operating manuals are all excellent sources of information you can use to learn the operations of a computer and the functions of a particular system. Learn how to operate the computer in all modes to enhance your abilities as a technician. After completing this chapter, you should be able to: List the ways a technician can interface with a computer-the operator controls generally available Describe the types and functions of controls, indicators, keys, and switches usually available on operator and maintenance panels, display control units, keyboards, and teletypes to control computers and how they work Describe the controls and indicators used to monitor computer power and temperature Describe remote operator consoles and the ways to interface with the computer from a remote console Let’s start your study of controls with the types you will find with computers. We examine how they work. Then we discuss the different types of controlling and monitoring units with which you will be working. When we discuss these controlling and monitoring units, we discuss the different types of functions usually associated with each unit and the types of controls used to activate these functions. TOPIC 1—TYPES OF COMPUTER the basics, you can initiate operations and perform OPERATOR CONTROLS maintenance on any type of computer. Let’s take a look at the types of controls used—their functions and uses. To monitor operations or perform maintenance on a computer, you must understand how to manipulate the POTENTIOMETER CONTROL computer’s controls to initiate operations and to accomplish maintenance. Controlling units vary with As a rule, potentiometers are associated with the different types of computers; but if you understand a control. Potentiometers are usually used to vary 3-1

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standard and specialized tools. The specialized tools include solder and solderless repair tools. Become familiar with your computer’s publications and required documentation before you jump into the computer’s hardware. This will enhance your abilities as a technician. To perform this job effectively, you must understand how a computer is organized internally. You must be able to recognize the functional areas and what their capabilities are. You must understand how buses function internally to transfer information internally. The CPU is the computer’s brain. All the computational operations (logical and arithmetic) and operational decisions are made in the CPU. The CPU controls all computer operations. The organization of the central processor becomes increasingly more complex as you move from a relatively simple microprocessor to a mainframe computer. But basically CPU functions are the same whether you are talking about a mainframe, a minicomputer, or a microcomputer. The CPU comprises two interacting sections: the control section and the arithmetic logic unit (ALU). The control section directs the sequence of CPU operations, interprets the instructions, and provides the timing and control signals to carry out the instructions. The arithmetic logic unit implements arithmetic and/or logical operations required by these instructions. The CPU generally consists of timing circuits, registers, translators, selectors, comparators, adders, and subtracters. After completing this chapter, you should be able to: Recognize the internal parts and functions of a computer Describe how a control section of a CPU operates Describe how the functions of the arithmetic logic unit (ALU) are performed Describe the types of buses and how they operate TOPIC 1—CONTROL SECTION Like a traffic director, the control section decides when to start and stop (control and timing), what to do (program instructions), where to keep information (memory), and whom to communicate with (I/O). It controls the flow of all data entering and leaving the computer, from the beginning to the end of operations. It does this by communicating or interfacing with the ALU, memory, and I/O areas (fig. 5-2). It is also capable of shutting down the computer when the power supply detects abnormal conditions. In some computers it sends a signal to the control section to initiate computer shut-down. Specifically the control section manages the operations of the CPU, be it a single chip microprocessor or a full-size mainframe. The control section of the CPU provides the computer with the ability to function under program control. Depending on the design of the computer, the CPU can also have the capability to function under manual control through man/machine interfacing. The man/machine interface operating modes, the operations, and the functions, along with the control section, will allow you to control the operations and perform maintenance on the computer(s). NEETS Module 13, Introduction to Number Systems and Logic Circuits, and chapter 4 of this volume provide an excellent review of some of the circuits used in the control section. 5-2

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Figure 5-2.—Representative block diagram showing the relationship of the control section to the other functional areas of a computer. The control section consists of several basic logically defined areas. These logically defined areas work closely with each other. They are the basis for the operations of the control section in most computers. They include: Timing Instruction and control Addressing Interrupts Control memory Cache memory Read-only memory (ROM) TIMING Timing in a computer regulates the flow of signals that control the operation of the computer. Without timing, events in a computer would not take place. The computer’s operations rely on both synchronous and asynchronous operations. Synchronous operations means that certain events happen at regularly timed intervals. An example of this is the computer’s master clink. Asynchronous means that the completion of one event triggers the next event. An example of this is the execution of instructions located sequentially in memory. After an instruction is executed, the next instruction cannot be executed until the program counter has been incremented to fetch it. Timing gets the computer going. Timing circuits are used throughout the computer, as you will see when we discuss each of the functional areas. Not all computers rely on a sophisticated timing system. Some timing systems are very simplistic and rely only on the computer’s master clock and one or two other timing signals derived from the master clock to start and stop events. Still other more sophisticated computers rely on the master clock and timing circuits in each of the functional areas to start and stop operations. Some of the more common timing circuits you will encounter include the following: Master clock Main timing chain Main timing signals Timing sequences Sequence enables and control Real-time clock Monitor clock Programmable interval timers Arithmetic timing 5-3

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Figure 5-3 is an example block diagram of timing circuitry used in a computer’s CPU. Master Clock From our discussion in chapter 4, you learned that the master clock can either a single- or multiple phase master clock. A single-phase master clock can then be used to trigger a single-shot multivibrator that is used throughout the computer to enable and disable circuits in whatever sequence is necessary to properly execute the computer’s operations. Multiple-phase master clocks can use a pulse generator or delay line oscillator to generate two or more clock phases. A delay line oscillator will generate two basic clock phases and any additional phases are derived from taps on the delay line oscillator. Whether a pulse generator or delay line oscillator is used, they generate multiple phases sometimes referred to as odd θ1 (CP1) and even phases θ2 (CP0) or lettered phases (θΑ, θΒ, or θΒΑ). These phases from the master clock are then used to initiate the main timing chain flip-flops. The master clock in a computer can be suspended under certain conditions; the way it can happen varies with the type of computer. With a microcomputer, it is usually done by removing power to the computer. With a larger mainframe or minicomputer, you will need to remove the power works, too. However, certain types of HOLDS, MASTER CLEARS, and operating MODES selected at a console can also suspend master clock oscillations. Refer to your computer’s technical manual for details. Refer again to figure 5-3 for an example. Main Timing Chain The main timing chain consists of flip-flops arranged in a ring counter. It is used to count master clock phases. The flip-flops used in the main timing can be set and cleared by the two basic master clock phases and any additional master clock phases. The design of the computer determines how this is accomplished. The main timing (MT) chain is often Figure 5-3.—Example block diagram of timing circuitry used in a computer’s CPU. 5-4

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designed so that the odd flip-flops (MT11, MT21, and so on) are set and cleared by odd phases or lettered phases and the even flip-flops (MT12, MT22, and so on) are set and cleared by the even or lettered phases. The timing chain uses the set and/or clear sides of the flip-flops to enable and disable circuits throughout the computer and to generate main timing signals (phases) such as MT01 or MT02. Main timing signals can be used to generate other commands, such as starting arithmetic timing for computers with more sophisticated mathematical operations. Main Timing Signals Main timing signals are used in the CPU to enable and disable circuits or generate command enables that are used for control or arithmetic operations. The majority of data transfers affecting the registers and associated circuitry in the control section derive their enables from main timing signals. An example is a main timing signal used to generate a command enable such as sending data from one register to another. Timing Sequences Timing sequences are used to issue a series of commands to perform a particular instruction or operation. The minimum number of sequences per instruction or operation is determined by the requirements of the computer. An example is the command to enable an instruction sequence, which is used to acquire the instruction for translation. Some computers have separate control sections for each functional area. In that case, each function will operate independently of the others. That is, a computer that uses a controller for I/O operations has its own master clock/main timing chain/main timing signals, which are independent of the CPU’s master clock/main timing chain/main timing signals. Sequence Enables and Control Circuitry to control the sequence enables and to generate commands depends upon the type of instruction and method of addressing. Real-Time Clock (RTC) The real-time clock (RTC) is used to keep track of units of real time. The RTC can be loaded, read, enabled, and disabled by machine instruction. The register itself is incremented at a rate determined by the RTC oscillator circuit setting or the external RTC input frequency. The RTC is only incremented when the CPU is running. It allows the computer, through machine instructions, to keep track of the passage of time using readily processed units of time. To prevent register overflow from causing errors in the timekeeping process, most RTCs generate register-overflow interrupts when the register contents increment around to zero (change from all ONES to all ZEROS). The RTC can be enabled and disabled, and updated internally or externally. Monitor Clock The monitor clock register is used to keep track of time intervals by counting down from its loaded value to zero. The monitor clock can be loaded, enabled, or disabled by machine instruction. The monitor clock is decremented in the same manner as the RTC is incremented and only when the computer is running. When the enabled monitor clock reaches zero, a monitor clock interrupt is generated. A monitor clock interrupt usually indicates that a designated computer operation timed out before it was properly completed. This usually occurs when memory or I/O cannot honor a request for reasons of priority or hardware failure. There must be a time limit established to release the hold on CPU main timing or an indefinite period of inaction could occur. By using the monitor clock register to keep track, a time limit is imposed. Programmable Interval Timers For those microprocessors that do not have an RTC or monitor clock registers, there is an additional logic chip available called a programmable interval timer. This chip provides up to three counters or count registers that are software controlled. These registers can perform the RTC, the monitor clock, or any other time interval measurements. The timer communicates with the CPU over the control and data buses. The count registers are independent of each other, addressable (0, 1, or 2), and can be loaded with count values or have their current values read and sent to the CPU. These counters are decrementing or down counters only. They operate off of separate clock signal inputs so they can be configured to count at the same or different clock rates. They can also be programmed to interrupt the CPU when the count in a selected register reaches zero. 5-5

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Arithmetic Timing Arithmetic timing is initiated by a command from the CPU’s main timing chain. How far arithmetic timing advances is dependent upon the specific instruction. INSTRUCTION AND CONTROL The instruction execution and control portion of the control section includes the combinational and sequential circuits that make up the decision-making and memory-type functions. First we discuss some of the functions, operations, operand addressing, and operating levels. We include those items most common in all computers and any that are unique to a specific type of computer. Instruction and Control Functions In chapter 4 we discussed the circuits that are used by computers. In this topic we discuss some of the more common functions used by these decision-making and memory-type circuits to execute instruction and control operations. Some of the more common functions of the circuits in this area include the accumulators, index registers, instruction register, program counter, and status indicating registers. The registers (memory-type functions) work with decision-making functions (primarily data routing circuits) to channel the data inside the computer. Their functions are many in the CPU; therefore, we do not go into detail. Refer back to chapter 4 for their basic functions. These data routing circuits are capable of providing input to the registers and/or using their outputs to route data elsewhere in the computer. Among some of the data routing circuits included in the CPU’s control section are the following: Adders Command signals (enables) Comparators Demultiplexers Selectors Translators These are by no means all the functions contained in all computers, but they represent a general overview of the common functions needed to execute instructions Let’s look at the more common functions of the memory-type circuits that the CPU uses. ACCUMULATORS. —Located in the CPU are a number of general-purpose registers called accumulators that are used to temporarily store data or memory addresses. They are generally the same length (number of bits) as a memory word. There are typically 8-, 16-, or 32-bit accumulators, numbered from 0, depending on the size and type of computer or microprocessor. These registers are accessible to a computer programmer. In other words a programmer can control, by machine instruction(s), what data is placed in these registers and what manipulations take place on the data. In addition to the operation (op) code, instructions contain one or two multibit fields that specifically identify the accumulator register to be operated upon. In older computers each bit position’s flip-flop circuit had indicator lamps to indicate the contents of the register to the computer programmer/technician. In the newer computers, the majority of registers are nothing more than memory addresses in local storage areas. The register contents, however, are still accessible to the technician through the computer’s man/machine interface. INDEX REGISTERS. —Most CPUs contain a number of index registers (8-, 16-, or 32-bit). Index registers are addressable registers that are used for two purposes: address modification and counting. The value contained in a particular index register can be used to modify the operand address of a machine instruction without changing the instruction itself in memory. In this way a single instruction can be used to specify a large number of operands, indirectly. The count in an index register can also be modified by fixed values (incremented or decremented) to control program repetitions or iterations. INSTRUCTION REGISTER. —To translate and execute the instructions, the outputs of the instruction register are fed to logic circuits (selectors and/or translators) that are used to translate the binary codes into commands for the CPU to execute (fig. 5-4). PROGRAM COUNTER. —The program counter controls the selection of machine instructions. It holds the address of the next instruction to be executed. and control operations. Adders and registers are used to perform this function. 5-6

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Figure 5-4.—Example of instruction translation and execution circuitry. STATUS INDICATING REGISTERS. —The CPU must have some way to monitor the status of the computer’s internal operations. The name of these register or registers may differ between computers, but the general functions performed are the same. Some of the most common names are as follows: Condition code Status and control Program status Active status Flag These registers use the condition of individual bits in the register to indicate the status of opera- tions in the computer (fig. 5-5). Within the register, individual and sometimes groups of bits (2 or 3 bits) are hardwired to the computer logic. The 1 or 0 value in each bit position indicates the status of a particular activity or special function of the com- puter. The specific activities monitored by these registers varies between computers, but consist of the following general areas: arithmetic operation or comparison results (carry, overflow, zero, negative, and so forth) Figure 5-5.—Example of a status register; indication of a program fault. 5-7

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(fig. 5-6), a variety of interrupt conditions, task or executive state status, and hardware status (memory lockout, hardware faults, and so forth). These registers are often used with instructions where branching conditions are used to change the sequence of instruction execution. The status indicating registers’ contents can be sensed, loaded with new data bits, or stored into memory by machine instruction. Many machine instructions, particularly branching instructions, are designed to sense the condition of specified register bits to determine how the instruction itself is to be executed. Other instructions are designed to modify the contents of the register(s) to change state (executive or task) or to enable/disable classes of interrupts; this is accomplished by indexing. The contents of the status indicating register(s) is/are normally stored into memory as part of the interrupt processing operation. Instruction and Control Operations The control portion of the CPU for computers is responsible for fetching, translating, and executing all instructions (fig. 5-7). The CPU calls up or reads the instructions one at a time either from consecutive addresses or as dictated by the program from main memory or read-only memory (ROM). The general process of execution of a machine instruction can be divided into four major parts: fetch (read) the instruction, update the program counter or equivalent, translate the instruction, and execute the instruction specified by the function or op code. Figure 5-6.—Example of an arithmetic detecting circuit used to indicate a subtraction overflow condition. 5-8

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Figure 5-7.—Basic operation of a fetch and decode (translate) of an instruction in a CPU. FETCH (READ) THE INSTRUCTION. —The instruction is fetched by reading the instruction from the memory (main memory or ROM) address specified by the contents of the program counter or equivalent. The instruction is temporarily stored in an instruction register, while the program counter is being incremented to the next instruction’s address. UPDATE THE PROGRAM COUNTER. —The program counter controls the selection of the instruction. The program counter contains the memory address of the next machine instruction to be executed. Most of the time machine instructions are executed sequentially. The program counter is incremented to the address of the next instruction. Usually an index adder is used to perform this function. When an instruction is completed, the new count in the program counter points to the next instruction to be fetched from memory and executed in turn. The memory word size of the computer has an effect on the value that is used to increment the program counter. For those computers in which the majority of instructions are contained in one memory word, the program counter is incremented by one (1) for each instruction. For computers with smaller memory words (8-bits), instructions are often assembled from several sequential bytes and the program counter must be incremented by a value that will point to the first byte of the next instruction to ensure correct translation of that instruction’s operation code. There are times, however, when a change in the sequence of instruction execution, called branching or jumping, is required. Branching or jumping can be accomplished through the man/machine interface by using switches on the controlling consoles. Examples Figure 5-8.—Block diagram of an operation to determine an absolute address. are the stop and jump switches. In these cases instead of being incremented, the address in the program counter is changed to anew address to start sequential execution of a different section of machine instructions in the program. Branching or jumping can also be accomplished through program instructions. In some computers, the program counter contains the relative or offset address of the instruction being executed. An additional set of registers called base registers are used to provide the base address of a block of memory. The program counter value must be added to a selected base register value (fig. 5-8) to determine the absolute address of the next sequential instruction. TRANSLATE THE INSTRUCTION. —An instruction register holds the machine instruction while it is translated by other CPU logic (translators). The binary data that makes up the instruction op code determines the operation the CPU is to perform. The derived func- tion codes are then sent to other parts of the control section of the CPU to execute the instruction. The translation of the instruction determines which command sequences will be used to execute the instruction. EXECUTE THE INSTRUCTION. —Execution of the instruction will generate command enables that are used throughout the computer to transfer data between registers and other parts of the computer. The logic consists of gating and amplifying circuits, which produce or inhibit control signals appropriate to the combination of conditions at their inputs. The controlling conditions are supplied by the timing circuits (master clock, main timing chains, and timing sequences) and function code translator and associated circuitry (selectors, registers, adders, and comparators). An execution technique used in newer microprocessors contains a logic assembly called an instruction queue. It is used to speed up computer operations and increase efficiency. The instruction queue allows the microprocessor to fetch a number of sequential instructions or instruction bytes and hold them in a queue for execution by the execution unit of the microprocessor. The instructions are fetched by the bus when the memory section is available for access and in some cases pretranslated while the processor is 5-9

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executing other instructions. Instructions or instruction bytes are added to the rear of the queue until the queue is full. When the execution unit has completed an instruction, it simply takes the next instruction or several instruction bytes from the front of the queue. Instruction Operation Levels The CPU executes instructions at two levels or states: the executive state and the task state. Data bits in the status indicating registers(s) are used to select the desired active state. Executive state —Executive state, also called inter- rupt state, instructions are designed to process what are known as executive functions (primarily I/O and inter- rupt processing) for multiprogramming operations. These functions are included in the operating system programs. There may be as many as four separate executive states in newer computers, one for each class of interrupts. Task state —Task state instructions execute what are called application functions. These functions actually perform the work, such as solving the fire control problem in a CDS/NTDS platform or computing a sonobuoy pattern on a TSC platform. The majority of machine instructions can be executed in either the task or executive states. There are a limited number of instructions that can be executed only in the executive states. An example is privileged instructions that are part of interrupts, which you will learn more about later in this topic. Those computers that have task and executive states have at least one set of addressable registers for each state. These addressable register types (accumulators, index registers, base registers, and the like) are only accessible by machine instruction when the computer is in the applicable state. The register sets are enabled and disabled automatically as the computer changes states. In computers with four executive states, there are five sets of addressable registers, one for the task state and one for each executive state. INSTRUCTION OPERAND ADDRESSING Addressing is the process of locating the operand (specific information) for a given operation. It is similar to the process of obtaining your address so that information can be sent to you. Once the computer knows where to obtain the location of the operand, the instruction can be carried out. If for instance, the operand is in memory, the addressing technique determines how to obtain the memory address of the operand and how to use this address to locate the operand and fetch it. If the operand is in one of the CPU’s registers, addressing is the means by which the instruction specifies the selected register and the operand is fetched. Because the length of instructions and the number of bits per memory cell vary between types of instructions and computers, there is a variety of ways the operand maybe obtained. INTERRUPTS Up to this point we have covered timing and instruc- tion control and execution. The following information is designed to the together the overall operation of the computer through the study of interrupts and interrupt processing. We first cover the definition of an interrupt and the types and classifications of interrupts you will encounter in computer systems. Then, we cover how computers handle interrupts and what happens within the computer hardware and software. An interrupt is defined as a break in the normal flow of operation of a computer caused by an interrupt signal. The break occurs in such a way that the operation can be resumed from the point of the break at a later time with exactly the same conditions prevailing. Interrupts are a method of diverting the attention of the computer from whatever process or program it is performing to the special condition or event that caused the interrupt signal. Interrupts allow the computer to respond to high priority demands and still be able to perform normal or lower priority processing. When the condition that caused the interrupt signal to occur has been addressed or processed, the computer’s attention can be returned to the process or program it was executing before the interrupt with the exact same conditions prevailing. Interrupts can occur either asynchronously or synchronously within the CPU program. The handling of a synchronous interrupt occurs with the actual event that caused the interrupt; whereas the handling of an asynchronous interrupt may occur much later in time than the actual event that caused the interrupt. We discuss the classification, types (micro, mini, and mainframe computers), priorities, codes, and handling processes of interrupts. Classifications of Interrupts There are two major classifications of interrupts: internal interrupts and external interrupts. Internal interrupts —Internal interrupts occur as a result of actions or conditions within the sections of the computer (CPU, IOCs, or memory). Internal interrupts tend to indicate the completion or termination of I/O operations, or the ending of defined time periods; or they signal some type of error. 5-10

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External interrupts —External interrupts are received from external peripheral devices. They are used to synchronize the execution of computer programs to the readiness of the peripheral device to transmit or receive data. They are also used to identify peripheral equipment problems/errors to the computer. Now let’s look at how interrupts work in each major type of computer. MICROCOMPUTER INTERRUPT TYPES. — The microcomputer receives both internal and external interrupts. Internal interrupts are received from the real-time clock, system clock, and other conditions that effect the operation of the microprocessor. External interrupts are received from disk drives, CD-ROM drives, sound boards, etc. These are classified as external interrupts, even though the devices are physically installed in the microcomputer case. Microcomputer interrupts fall into two basic categories: maskable and non-maskable. The CPU of the microcomputer has two interrupt signal lines, one for each category of interrupt. External hardware interrupts are maskable inter- rupts. The interrupt request signal indicates the pres- ence of one or more of these interrupts. The specific interrupt type is defined by accompanying interrupt code words. The interrupt code and a ROM or program- mable ROM (PROM) lookup table are used to direct the processor to the address of the interrupt processor pro- gram for the particular interrupt type. Maskable inter- rupts can be masked out or locked out for short periods of time by the software to allow the CPU to perform critical operations. The programmer is responsible for ensuring that interrupts are managed in a timely manner. Nonmaskable interrupts cannot be masked out. They are used for conditions that require immediate attention by the microcomputer. Examples include interrupts from the internal hard disks, modems, fax cards, and sometimes a power out-of-tolerance condition. If this feature is available, a power out-of- tolerance condition will force the microcomputer to execute its save data program. The interrupt request (IRQ) line provides the input signal path for all interrupts. If the interrupt enable bit in the status indicating register is set, the interrupt is processed at the end of the current instruction cycle. If the interrupt enable bit is clear, the interrupt signal is ignored by the microcomputer and the next sequential instruction is executed. Each hardware interrupt has a unique IRQ channel assigned. Some of these channels are preassigned and cannot be changed, while several are available for the user to install additional hardware into the microcomputer. Table 5-1 lists the hardware interrupt channels used by most microcomputers. Note that in Table 5-1.—Common IRQ Assignments for Microcomputers 5-11

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Table 5-1, IRQ5 is assigned to parallel port 2; this port is generally available in most microcomputers and is commonly used by most sound cards. When microprocessors expanded from 8-bit to 16-bit proces- sors, the amount of hardware supported also grew. This required the addition of more IRQ channels. Manufac- turers added an additional 8-channel processor and cas- caded them by connecting IRQ2 on processor to IRQ9. The latest development in microcomputer technol- ogy concerning interrupt processing is the Plug-n-Play feature. A true plug and play system requires three components to work together; the hardware, the BIOS, and the operating system. During the power-on cycle of computers that are Plug-n-Play capable, the firmware contained in the basic input/output system (BIOS) interrogates each component in the system to determine the type of board, IRQ channel requirements, DMA channel requirements, and ROM requirements. The board responds with the specifications it requires, then the BIOS assigns IRQs, DMA, ROM resources, etc., to all the boards, ensuring that there are no conflicts. The functions of the BIOS are covered in detail later in this chapter. This process is repeated every time the computer is turned on. Controllers that are not Plug-n-Play compatible can be installed by using the standard configuration program and locking the resource to those unique settings. MINI AND MAINFRAME INTERRUPT TYPES. —Within larger computers, interrupts are divided into a number of separate classes. Multiple classes of interrupts are needed because there are several levels of processing within these computers and many different types of operations and conditions that have to be monitored. Some operations and conditions are more important than others. There are generally three or four classes of interrupts, which we designate class I, II, III, and IV. Interrupts are prioritized by these classes and by the types of interrupts within a class. Class I interrupts are the highest priority or most important interrupt class as far as the computer is concerned. The other classes (II, III, and IV) are in turn lower in priority than Class I. Class I Interrupts. —Class I interrupts function during all computer operations; in other words, they will interrupt any computer program or instruction. These are the highest priority interrupts. Known as fault and hardware or hardware error interrupts, these interrupts indicate there is a serious hardware problem with the computer, or more accurately within the CPU or its communication buses. The following are some of the more common class I interrupts: Power fault or power tolerance Memory parity errors Memory resume errors Bus communication errors The most common class I interrupt is the power fault or power tolerance interrupt. This interrupt indicates that the power supply voltage has fallen below a certain tolerance level and that the computer should execute its power failure processing routines before there is a total loss of power. The actual routines will vary from computer to computer based on the device’s automatic restart and backup storage power capabilities. Class II Interrupts. —Class II interrupts are used to identify faults and errors within the CPU or IOC instruction execution and program timing processes. These software interrupts can indicate the following conditions: Execution of illegal instruction operation (op) codes (CPU or IOC instructions) Execution of privileged instructions in the task mode Floating-point math underflow or overflow conditions Real-time clock (RTC) overflow Monitor clock timeouts Class III Interrupts. —Class III interrupts are primarily I/O operation interrupts. They indicate such functions as the following: External interrupts Input or output chain interrupts Intercomputer timeouts Input data ready or output data ready interrupts Class IV Interrupts. —In some computers, there is a class IV interrupt that indicates executive state entrance. In others, the executive state entrance is a class II interrupt. A limited number of instructions can be executed only in the executive states. Among them are privileged instructions. MINI AND MAINFRAME INTERRUPT LOCKOUT OF CLASS I, II, III, AND IV TYPES. —Computers that operate with different levels of interrupts are equipped with the logic circuitry to 5-12

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lockout or disarm classes of interrupts and often specific interrupts within a class. Lower levels of interrupts (class II through IV) can be locked out (disarmed) or enabled (armed) by machine instruction. The terms prevent/allow are also used in place of enable/disable with some computers. The lower priority interrupts are locked out so that they do not interfere with higher level computer operations (executive state or class I interrupt processing) while they are in progress. There are usually several specific class I interrupts that cannot be locked out by instruction. These interrupts would normally include any of the following: Power fault CPU instruction fault IOC instruction fault interrupts INTERRUPTS AND INTERRUPT CODES. — Interrupt signals, as a rule, cause the computer to reference a freed address in memory and execute the subroutine (a series of instructions) identified by the contents of the address. The interrupt signal only identifies the class of interrupt. Multiple interrupt types within a class are usually defined by an accompanying interrupt code or interrupt code word. In older and smaller computers, the interrupt code parallels the interrupt signal. In other words both the interrupt signal (class I, II, or III) and identifying code are received and processed by the CPU at the same time. Since the interrupt processor tends to lockout interrupts of the same class, this process tends to hold up or even lose interrupts of the same or lower priority classes that occur while the first interrupt is being processed. Newer computers retain multiple interrupt codes of the same class in an interrupt stack or interrupt queue, usually contained in the I/O section. There usually is a stack or queue for each interrupt class (I, II, or III). Interrupt queues store their codes in first-in, first-out (FIFO) order. The interrupt signal would indicate to the CPU the presence of at least one interrupt of the particular class. The stack and queue arrangements allow the CPU to sample the interrupt codes at its convenience. As each code is processed, it is removed from the stack or queue until the stack or queue is empty. The interrupt signal would only drop if the stack or queue becomes empty. New interrupt codes would simply be added to the stack or queue as they occur. An empty stack or queue would generate an interrupt signal when the first new code is added to the stack or queue by the I/O circuits. INTERRUPT HANDLING PROCESS. —CPUs follow a specific sequence of events when processing an interrupt. Remember interrupt processing has priority over normal program execution. We discuss the general interrupt handling process in order of its sequence. Figure 5-9 illustrates the general sequence Figure 5-9.—General sequence of an interrupt response. 5-13

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of an interrupt response by the CPU. Refer to this figure as we describe the process. Terminate Current Program Execution. — Computers are not designed to instantly stop all current operations when an interrupt signal is received. They do not halt the current operation until the machine instruction (macro or micro) being processed has been completed. Interrupt terminations effectively occur between instructions. There is usually a check for interrupt signals at the end of the current instruction execution cycle. In our example, an interrupt is received during the execution of the third instruction. At this time, the program counter has been incremented to the next instruction’s address, and all register operations are complete from the execution of the instruction in the instruction register, the third instruction. The program counter reflects the address of the next instruction in the current program and the register contents are stable. It is at this point that the interrupt process will be initiated. Lock Out All Interrupts. —The first event that takes place in interrupt processing is the locking out of all new interrupts. This is done to protect the integrity of the process that ensures returning to the same conditions after processing the interrupt. There are a few machine instructions and other processes that must be performed to save the current register data so that it can be restored to the preinterrupt conditions. The interrupt lockout prevents any new interrupts from interrupting this process and potentially losing data or even worse losing track of where the computer was in the interrupted program. Store Program and Register Data. —Once all interrupts have been locked out, the computer can store the current process’s register data in the applicable memory locations. Each class of interrupt is assigned a block of memory locations to store at least the following register contents: program counter and status register(s). The program counter data will allow the interrupted process to be restarted as if the next instruction is being executed as in normal operation. The status register contents are saved to be able to reinstate the computer’s operational status at the time of the interrupt once the interrupt has been processed. In our example, the data from the three previously executed instructions is stored in memory. The address of the fourth instruction of the current program is also saved. In newer computers, the accumulator, index, and other addressable registers do not require saving since there is a separate register set for each task and executive state. When a new state is entered, the instructions being executed can only address or modify the registers assigned to that state. Any other task or executive state registers are disabled and their contents are protected until the appropriate state is reentered. Retrieve Interrupt Processor Data. —After the register data is saved, the new executive state’s registers are loaded with the interrupt processor program data. The program counter is loaded with the starting address of the processor program (instruction number 1 of the interrupt routine), the status register(s) is/are loaded with the operational status data required by the program. The interrupt processor data for each class of interrupts is stored in an assigned block of memory cells where it can be retrieved for each interrupt. Enter Executive State and Enable Desired Interrupts. —The loading of the status register(s) allows the computer to enter the required executive state and enable the interrupts that can in turn interrupt the interrupt processor. The data bits loaded into the status register(s) effectively change the executive state class (I, II, III, or IV), and enable the active status register set. The new status register bits also set or clear interrupt lockouts to enable or disable specific interrupt classes. The new data in the status register(s) would only enable higher priority interrupts than the interrupt being processed. Execute Interrupt Processor Program. —The address in the active state’s program counter will now allow for the execution of the interrupt processor program, instruction number 1 of the interrupt routine. The interrupt processor samples the interrupt code words and determines the appropriate action in response to the interrupt. Return to Original Process. —Upon completion of the interrupt processor routine, the active state will be switched to the next lower state, either task state or a lower priority executive state, and the program counter and status register(s) for that state will be reloaded with the saved data. The program counter can then call up the next sequential instruction (instruction number 4 of the current program) in the interrupted process and the program will continue as if no interrupt had occurred. The computer will normally return to the task state program only when all executive state procedures have been completed. 5-14

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CONTROL MEMORY Control memory is a random access memory (RAM) consisting of addressable storage registers. It is primarily used in mini and mainframe computers. It is used as a temporary storage for data. Access to control memory data requires less time than to main memory; this speeds up CPU operation by reducing the number of memory references for data storage and retrieval. Access is performed as part of a control section sequence while the master clock oscillator is running. The control memory addresses are divided into two groups: a task mode and an executive (interrupt) mode. Addressing words stored in control memory is via the address select logic for each of the register groups. There can be up to five register groups in control memory. These groups select a register for fetching data for programmed CPU operation or for maintenance console or equivalent display or storage of data via a maintenance console or equivalent. During programmed CPU operations, these registers are accessed directly by the CPU logic. Data routing circuits are used by control memory to interconnect the registers used in control memory. Some of the registers contained in a control memory that operate in the task and the executive modes include the following: Accumulators Indexes Monitor clock status indicating registers Interrupt data registers CACHE MEMORY Cache memory is a small, high-speed RAM buffer located between the CPU and main memory. Cache memory buffers or holds a copy of the instructions (instruction cache) or data (operand or data cache) currently being used by the CPU. The instructions and data are copies of those in main memory. Cache memory provides two benefits. One, the average access time for CPU’s memory requests is reduced, increasing the CPU’s speed by providing rapid access to currently used instructions and data. Two, the CPU’s use of the available memory bandwidth is reduced. This allows other devices on the system bus to use the memory without interfering with the CPU. Therefore, cache memory is used to speed up the flow of instructions and data into the CPU from main memory. This cache function is important because the main memory cycle time is typically slower than the CPU clocking rates. To accomplish this rapid data transfer, cache memories are usually built from the faster bipolar RAM devices rather than the slower metal-oxide-semiconductor (MOS) RAM devices. The RAMs used for cache memory may be either dynamic RAMs (DRAMs) or static RAMs (SRAMs). Cache memories are not part of the memory section and they are transparent to programmers (i.e., not accessible by machine instruction). Their size varies with the type of computer, usually they are no more than 64K. PROPERTIES OF CACHE MEMORY. —All caches share the following properties: A buffered memory or cache memory consists of a small high-speed memory with main memory information. This information may be addresses, data, or instructions. The speed of the small memory is usually on the order of one magnitude faster than main memory, and its capacity is typically one or two orders of magnitude less than main memory. A cache memory system requires an identifier or tag store to indicate which entries of main memory have been copied into it. Such an area is usually referred to as the directory or tag store. A cache memory requires a logical network and method of replacing old entries. A cache memory uses timing and control. CACHE PROCESS. —The cache process takes place when a CPU with a cache initiates a memory reference. The address of the needed item is generated and the cache is searched. The method of search depends on the type of cache mapping used by the computer system. We can generalize the cache process into three areas as follows: Searches —Reads from the cache directory with a hit indicating that the data from the requested address is present, while a miss indicates that the data is not present. Updates —Writes to the cache data as well as to the directories with new information. Invalidates —Writes only to the directories; this effectively removes an address that previously resided in cache. 5-15

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If the particular address is found in the cache, the block of data is sent to the CPU, and the CPU goes about its operation until it requires something else from memory. When the CPU finds what it needs in the cache, a hit has occurred. When the address requested by the CPU is not in the cache, a miss has occurred and the required address along with its block of data is brought into the cache according to how it is mapped. Cache processing in some computers is divided into two sections: main cache and eavesdrop cache. Main cache is initiated by the CPU within. Eavesdrop is done when a write to memory is performed by another requestor (other CPU or IOC). Eavesdrop searches have no impact on CPU performances. CACHE MAPPING TECHNIQUES. —Cache mapping is the method by which the contents of main memory are brought into the cache and referenced by the CPU. The mapping method used directly affects the performance of the entire computer system. Direct mapping —Main memory locations can only be copied into one location in the cache. This is accomplished by dividing main memory into pages that correspond in size with the cache (fig. 5-10). Fully associative mapping —Fully associative cache mapping is the most complex, but it is most flexible with regards to where data-can reside. A newly read block of main memory can be placed anywhere in a fully associative cache. If the cache is full, a Figure 5-10.—Example of direct mapping used in cache Figure 5-11.—Example of fully associated mapping used in cache memory. replacement algorithm is used to determine which block in the cache gets replaced by the new data (fig. 5-11). Set associative mapping —Set associative cache mapping combines the best of direct and associative cache mapping techniques. As with a direct mapped cache, blocks of main memory data will still map into as specific set, but they can now be in any N-cache block frames within each set (fig. 5-12). CACHE READ. —The two primary methods used to read data from cache and main memory are as follows: Figure 5-12.—Example of set association mapping used in memory. cache memory. 5-16

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Look-through read —In look-through read, the cache is checked first. If a miss occurs, the reference is sent to main memory to be serviced. This is known as a serial read policy. Look-aside read —A look-aside read presents both cache and main memory with the reference simultaneously. Since the cache will respond faster, if a hit occurs, the request can be terminated before main memory responds. This is known as a parallel read policy. CACHE REPLACEMENT POLICIES. —When new data is read into the cache, a replacement policy determines which block of old data should be replaced. The objective of replacement policies is to retain data that is likely to be used in the near future and discard data that won’t be used immediately. The replacement policies include the following: FIFO —The first block that was read into cache is the first one to be discarded. LRU —The block that hasn’t been used in the longest period of time is replaced by the new block. Random. —Blocks are replaced randomly. Optimum —This cache replacement algorithm is psychic and has perfect knowledge of the future. Optimum replacement is what the other three strive for, with LRU coming the closest. CACHE WRITE. —Since the cache contents area duplicate copy of information in main memory, writing (instructions to enter data) to the cache must eventually be made to the same data in main memory. This is done in two ways as follows: Write-through cache —Writing is made to the corresponding data in both cache and main memory. Write-back cache —Main memory is not updated until the cache page is returned to main memory. READ-ONLY MEMORY (ROM) Every computer comes with a set of software instructions supplied by the manufacturer. This enables the computer to perform its I/O operations. These permanent instructions (routines) reside in a read-only memory (ROM). ROM is often referred to as firmware: software permanently contained in hardware. The instructions are considered permanent or nonvolatile, since they are not erased each time the computer loses power or is turned off. The ROM contains the program that defines its uniqueness compared with all other types of computers. The ROM is programmed at the time of manufacture and cannot be altered. It is tailored to system requirements. It cannot be altered except by removing and replacing it—either a module or IC chip on a board. The contents of the ROM are electrically unalterable. Other variations of ROMs called PROMS can be reprogrammed as required. This and other variations are covered in further detail in chapter 6 on memory. In connection with the ROM, you will hear the term boot procedure used. The ROM initiates the boot procedure-a sequence of steps followed when you turn on the power to the computer or initiate the boot procedure. The steps required to successfully boot the computer depend on the type of computer. Other terms that have the same meaning as boot include boot up, booting, or bootstrap. They all refer to the process of loading the software. Consult your computer’s technical or owner’s manual for the exact procedures for your computer system. We use two types of ROMs to discuss some of the programs associated with the ROM: nondestructive readout (NDRO) memory and basic input/output system (BIOS). Nondestructive Readout (NDRO) Memory A nondestructive readout (NDRO) memory is usually associated with a militarized main/frame or minicomputer. The NDRO is a small module that occupies two or more slots. For mainframes, it is located in the CPU module. For minicomputers, it is located in the chassis that contains the CPU’s pcb’s. The functions of an NDRO are controlled from the computer’s controlling device: a maintenance console or equivalent. The sizes of the NDRO addresses vary with the type of computer and its requirements. Selection of a particular word in the NDRO is via the NDRO address select, line selector, and current switch logic. AN NDRO consists of hardwired circuits to create the bootstrap programs or a ROM or PROM. Some of the programs contained on an NDRO include the following: Two bootstrap programs—Used to load programs from peripheral equipments into main memory Autostart programs 5-17

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Computer start programs—Used to start a program from a controlling device, locally or remote Interrupt routines Diagnostic programs —Load failure analysis, memory test, interface test, and computer interconnection system Program development memory User-specified programs Inspect and change programs Basic Input/Output System (BIOS) A basic input/output system (BIOS) is usually associated with a microcomputer. The BIOS performs the same basic function that an NDRO does in larger computers except for a few major differences. The BIOS is located in the CPU/memory pcb. It is contained on one or more IC chips on the pcb, and the functions of the BIOS are initiated when the computer is powered on. Among the tasks performed are diagnostic testing, environmental inventory, and boot procedure. Figure 5-13 is a basic diagram of installing a BIOS along with the operating system into RAM of a microcomputer. DIAGNOSTIC TESTING. —Diagnostic testing or Power-on Self Test (POST) is initiated when you initially power up the micro. These tests generally do the following: Test CPU registers and flags Figure 5-13.—Basic diagram of installing a BIOS. Compute and check a checksum for the ROM Check the direct memory access (DMA) Test the interrupt controller Test the timer Perform a checksum test on the BASIC (programming language) ROMs Test the video Test the CRT interface lines Test the memory Test the keyboard ENVIRONMENTAL INVENTORY. —This portion of the BIOS includes, just as the name implies, taking inventory of the presence or absence of key items. It includes the following tasks: Initialize installed adapters if necessary and return to BIOS startup. Adapters include hard disk controllers, enhanced graphics adapter (EGA), and local-area network (LAN) adapters. Check disk controllers for floppy and hard drives. Determine the number of printers and serial ports attached. BOOT PROCEDURE. —Once the testing and inventory are complete, batch files are executed. These are the files that have been written to execute the sequence of instructions needed when the system is powered up and the system configuration files are loaded. The ROM chip program searches for the operating system files on either the floppy drive diskette and/or the hard disk depending on the system setup. As soon as the operating system is located, it is loaded into memory and control is turned over to the operating system. To let you know the microcomputer is ready to use, an opening message (a prompt) is displayed. TOPIC 2—ARITHMETIC AND LOGIC UNIT (ALU) The arithmetic and logic unit (ALU), also called the arithmetic section, is designed to perform the arithmetic and logical operations for the CPU. The data required to perform the arithmetic and logical calculations are inputs from the designated CPU registers and operands. The ALU relies on basic items to perform its operations. We have discussed some of these basic items in previous 5-18

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chapters and topics. They include the number systems, data routing circuits (adders/subtractors), timing, instructions, and operand/registers. In this topic, we discuss the instructions, timing, and operand/registers and how they apply to the ALU and the ALU operations. Figure 5-14 shows a representative block diagram of an ALU of a microcomputer. Chapter 4 of this volume and NEETS Module 13, Introduction to Number Systems and Logic Circuits, provide a review of number systems, adder/subtracter circuits, timing, instructions, and operands/registers. Also refer to NEETS 13 for detailed information of the types of number systems and information basic to all number systems; their identification, operations (addition and subtraction including radix-minus-1 complement and radix-minus-2 complement computations), and conversion. They are discussed in more detail, and it would benefit you to review them to gain a better understanding of how they apply in the ALU operations. INSTRUCTIONS The instructions tell the CPU which type of mathematical or logical calculation the ALU will perform. They will also tell the CPU the location of the data on which the ALU will perform the calculations and where to store the results. Results can be used immediately or stored for use later. Special codes within the instructions can also affect arithmetic or logical operations. They can be used for branching or setting flag registers. TIMING Figure 5-14.—Representative block diagram of an ALU. Timing in the ALU is provided by the CPU’s timing circuits. Larger computers have their own arithmetic timing circuits independent of the CPU’s timing circuits. In this case, arithmetic timing is initiated by a command from the CPU’s main timing chain and the length of the arithmetic timing chain is dependent upon the specific instruction. OPERANDS/REGISTERS The registers and operands provide the computer the sources of the data needed to perform the calculations. They also provide the destination for results. Computers can be designed to include the use of whole-word, half-word, and quarter-word operands and the use of single-length and double-length word/operands to carry out the arithmetic operations. Double-length memory words or operands will be used for mathematical operations in which the size of the result would be greater than the length of either of the two registers used to provide inputs to the ALU or the operands being input to the ALU are larger than a single word. The sign bit in double-length memory words or operands is the most significant bit (msb). Flag registers of one to three bits may be used by the ALU to indicate the status of the last arithmetic or logical operation. The last arithmetic or logical calculation used to set a flag register is often followed by a branching operation. Some of the items indicated by flag registers include the following: Equal to zero (= 0) Greater than (> Less than (<) Positive sign (+) Negative sign (–) Carry or borrow Overflow Other items used in the ALU include selectors and counters. The selectors are used to transfer the data between the various registers (accumulators) used in the ALU. Counters are used to keep track of shifts used in the various arithmetic and logical calculations. 5-19

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ALU OPERATIONS ALU operations in the CPU include calculations of integers and/or fractions. All the computations are performed using the binary number system. ALU operations also include signed arithmetic operations. First we discuss how the binary equivalents of decimal numbers are represented in fixed-point representation (integers), then we discuss floating-point representation (fractional). Fixed- and floating-point operations are important for the computer. They make the computer versatile when performing arithmetic and logical types of ALU operations. Fixed-Point Operations Fixed-point arithmetic operations are performed on integral or whole numbers where the binary point is assumed to be to the right of the least significant bit (bit 0). For example, if we have an 8-bit register, we may express integer decimal numbers between 0 and 2 8 minus 1 (or 255), by converting the decimal number to its binary equivalent. If we have a 16-bit register, we can store integer decimal numbers between 0 and 2 16 minus 1 (or 65535). Because the binary point is fixed and always to the right of the least significant digit, fractions are not represented. The magnitude or absolute value of the number is always represented by 2 N minus 1 where N is the number of bits within the register or memory cell where the number is being stored. In fixed-point operations, the computer can perform calculations on signed numbers (positive and negative). The most significant bit (msb) is used as a sign bit. A zero (0) in the msb indicates a positive or true form number, and a one (1) in the msb indicates a negative or one’s complement/radix-minus-1 form number. When dealing with binary numbers, we can take this one step further; we find the two’s complement or radix-minus-2 of the number. It is important to understand the concepts behind 1’s and 2’s complement. It is the basis by which the computer performs arithmetic and logical calculations. Now if you want to accommodate an equal amount of positive and negative numbers, a 16-bit register can contain numbers from –32768 to +32767 or –2 15 to 2 15 minus 1. The reason they are not both 2 15 is because one combination is taken up for the zero value. This is more easily seen if we examine a 4-bit register. The combinations are shown in table 5-2. 5-20 Table 5-2.—Binary and Decimal Values of a 4-Bit Register That is, there are 2 3 or 2 N combinations and one combination is for the number zero. Negative numbers are represented by their two’s complement and the most significant bit (regardless of the word or operand size) is the sign bit. Fixed-point operations can include double-length arithmetic operations, where operands contain 64 bits and bit 2 63 is the sign bit. Floating-Point Operations Floating-point operations are used to simplify the addition, subtraction, multiplication, and division of fractional numbers. They are used when dealing with fractional numbers, such as 5.724 or a very large number and signed fractional numbers. When performing arithmetic operations involving fractions or very large numbers, it is necessary to know the location of the binary (radix) point and to properly align this point before the arithmetic operation. For floating-point operations, the location of the binary point will depend on the format of the computer. All numbers are placed in this format before the arithmetic operation. The factional portion of the number is called the mantissa and the whole integer portion, indicating the scaled factor or exponent, is called the characteristic.

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By rewriting the number in an exponent form, it is often much easier for the computer to manipulate; but, as noted, we give up the digits that were rounded. As a result, some resolution (the number of digits in the fraction) is usually lost. For instance, the number 325786195 could be expressed as 3.26 × 10 8 or .32579 × 10 9 . Still, this concept is useful. The computer, however, is limited by the hardware in the number of bits its registers and memory cells can accommodate. FLOATING-POINT FORMAT. —The format for the characteristic and mantissa during floating-point operations will vary with the register size. However, the binary (radix) point is usually located between the sign bit and the msb of the mantissa. Typically, floating-point numbers use a 32-bit word size. Let’s illustrate a couple of examples—one with a fractional number and another with a very large number. Refer to figure 5-15, frames A and B, during our discussion. We use one’s complement in our examples with 32-bit size words. We’ll use the number 6.54321 8 as our example of a fractional number (fig. 5-15, frame A). Our fractional number will require two 32-bit words. In this case, notice the integral characteristic can have a maximum positive or negative value of 2 15 minus 1 and comprises the least significant 16 bits of the word. Bit 15 contains the one’s complement sign, which is extended through the most significant 16 bits of the word. The mantissa is the fractional part of the number and is processed as a 32-bit number including the sign. Figure 5-15.—Floating-point numbers: A. Fractional number; B. Very large number. 5-21

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The second example is a very large number 7665543322211111 8; refer to figure 5-15, frame B. After the number has been put in exponent form, it, too, will require two 32-bit words. FLOATING-POINT PRECISION. —Floating- point formats include the use of single- and double-precision (refer to figure 5-16, frames A and B). The names single- and double-precision imply their usefulness: precision. Notice the double-precision floating-point format, two 32-bit words where the characteristic is small compared to the mantissa in which precision accuracy is required. FLOATING-POINT ROUND. —Floating-point operations also include rounding instructions, which are used for rounding the mantissa’s results; rounding up when the mantissa is equal to or greater than one-half of one and rounding down when it less than one-half of one. Rounding can also be applied to double-length results of mantissas. If the sign bit is destroyed (overflowed into) during mantissa rounding or division, the computer will make corrections to the mantissa or quotient. FLOATING-POINT INTERRUPTS. —Float- ing-point interrupts can be generated when retain improper conditions are detected. The interrupts inform the program of these conditions and permit either notation or corrective procedures. Some conditions include: Underflow (negative excess) or overflow (posi- tive excess)—When a floating-point char- acter exceeds an absolute value of 2 N - 1 where N is the msb. Divisor —Equals zero in a divide instruction The control section will be notified and an interrupt will be generated. Figure 5-16.—Floating-point numbers: A. Single precision; B. Double-precision. 5-22

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Operation Types From the simplest microprocessor (8-bit) to a large mainframe with an embedded microprocessor, the types of ALU operations range from basic add and subtract operations to sophisticated trigonometric operations and separate coprocessor and math pacs, which operate independent of the ALU. The types of instructions most ALUs canperform can be divided into two categories: arithmetic operations and logical operations. The ALU uses the logical products of the logic gates to perform the arithmetic and logical instructions. Depending on the sophistication of the computer, the logic gates are arranged to perform the instructions included in the computer’s set of instructions. Computers can be designed to have an adder to perform its adding and subtracting or a subtracter to perform its adding and subtracting. Or they can have a combined adder/subtracter system. Because a computer can really only add or subtract, the add and subtract capabilities allow the computer to perform the more complicated arithmetic operations: multiply, division, and square root functions. Addition and subtraction functions are embedded in division, square root, and the more complicated arithmetic functions, such as trigonometric and hyperbolic, to name a couple. The computer can be designed where a single instruction will accomplish the results or a series of instructions can be written to produce the results. The only drawback to a series of instruction is they consume more time to accomplish the results. The multiply, divide, square root, and trigonometric instructions are examples. Computers can multiply by repetitive adding or they can use a series of left shift instructions both using a compare instruction, which may be how a computer with a dedicated multiply function accomplishes the function anyway. The same principle can be applied to the divide and square root functions. A divide can use repetitive subtractions or a series of right shifts with a comparison function. A square root would use a combination of additions/subtractions and comparisons for the multiplying and dividing necessary to accomplish a square root function. A trigonometric function using separate instructions would use logical instructions to accomplish the same results that a single trigonometric instruction would accomplish. ALU operations include signed operations. Depending on the sophistication of the computer, ALU functions can include the following functions: 5-23 Arithmetic —Add, subtract, shift, multiply, divide, negation, absolute value. (The more sophisticated ALUs can perform square root, trigonometric, hyperbolic, and binary angular movement or motion (BAM) functions.) Logical —AND, OR, NOT (complement), and EXCLUSIVE OR (compare). Also depending on the design, numeric data coprocessor and math pacs are used in some computers in addition to the normal arithmetic instructions available. They execute the arithmetic instructions the CPU’s ALU cannot, and they are still controlled by the CPU’s program control. These additional logic circuits can be used to amplify the capabilities of the ALU and arithmetic section in general. Remember, the ALU is part of a CPU module or a microprocessor chip on a printed circuit board. The numeric data coprocessor and math pac are separate modules or chips. NUMERIC DATA COPROCESSOR. —The numeric data coprocessor is a special-purpose programmable microprocessor designed to perform up to 68 additional arithmetic, trigonometric, exponential, and logarithmic instructions. The coprocessor performs numeric applications up to 100 times faster than the CPU alone and provides handling of the following data types: 16-, 32-, and 64-bit integers; 32-, 64-, and 80-bit floating-point real numbers; and up to 18-digit binary coded decimal (BCD) operands. The numeric data coprocessor operates in parallel with and independent of the CPU using the same data, address, and control buses as the CPU. In effect, the coprocessor executes those arithmetic instructions that the CPU’s ALU cannot. The CPU is held in a wait mode, while the coprocessor is performing an operation. The CPU still controls overall program execution, while the coprocessor recognizes and executes only its own numeric operations. MATH PAC. —Math pac is a module used as a hardware option for some militarized minicomputers. The math pac module provides the hardware capability to perform square root, trigonometric and hyperbolic functions; floating-point math; double-precision multiply and divide instructions; and algebraic left and right quadruple shifts. TOPIC 3—COMPUTER INTERNAL BUSES To transfer information internally, computers use buses. Buses are groups of conductors that connect the

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functional areas to one another. This is how the functional areas communicate with each other. A bus is a parallel data communication path over which information is transferred a byte or word at a time. The buses contain logic that the CPU controls. The items controlled are the transfer of data, instructions, and commands between the functional areas of the computer: CPU, memory, and I/O. The type of information is generally similar on all computers; only the names or terminology of the bus types differs. The name of the bus or its operation usually implies the type of signal it carries or method of operation. The direction of signal flow for the different buses is indicated on figures in the computer’s technical manuals. The direction may be unidirectional or bidirectional depending on the type of bus and type of computer. Consult the computer’s technical manual for details. After becoming familiar with the basic functions and operations of buses, you’ll see that regardless of the names, their basic concepts are consistent throughout the computer. They provide avenues for information to be exchanged inside the computer. BUS TYPES The preferred method for data/information transfer between system components is by a common data bus. Where point-to-point data transfer is required, the digital format is the preferred method. General Requirements for Electronic Equipment Specifications, MIL-STD-2036 series, provides a list of the industry accepted standard internal data buses. They include the standard and the interface as follows: IEEE 696 —IEEE Standard 696 Interface Devices, S-100 IEEE 896. l —IEEE Standard Backplane Bus Specification for Multiprocessor Architecture, Future Bus IEEE 961 —Standard for an 8-bit Microcomputer Bus System, STD Bus IEEE 1014 —Standard for a Versatile Backplane Bus, VMEbus IEEE 1196 —Standard for a Simple 32-Bit Backplane Bus, NuBus IEEE 1296 —Standard for a High-performance Synchronous 32-Bit Bus, Multibus II All computers use three types of basic buses. The name of the bus is generally determined by the type of signal it is carrying or the method of operation. We group the buses into three areas as you see them in their most common uses. They are as follows: Control (also called timing and control bus), address, and data (also called a memory bus) buses Instruction (I), Operand (O), Input/Output Memory (I/O MEM) or Input/Output Controller (IOC), and Computer Interconnection System (CIS) Time multiplexed bus Control Bus The control bus is used by the CPU to direct and monitor the actions of the other functional areas of the computer. It is used to transmit a variety of individual signals (read, write, interrupt, acknowledge, and so forth) necessary to control and coordinate the operations of the computer. The individual signals transmitted over the control bus and their functions are covered in the appropriate functional area description. Address Bus The address bus consists of all the signals necessary to define any of the possible memory address locations within the computer, or for modular memories any of the possible memory address locations within a module. An address is defined as a label, symbol, or other set of characters used to designate a location or register where information is stored. Before data or instructions can be written into or read from memory by the CPU or I/O sections, an address must be transmitted to memory over the address bus. Data Bus The bidirectional data bus, sometimes called the memory bus, handles the transfer of all data and instructions between functional areas of the computer. The bidirectional data bus can only transmit in one direction at a time. The data bus is used to transfer instructions from memory to the CPU for execution. It carries data (operands) to and from the CPU and memory as required by instruction translation. The data bus is also used to transfer data between memory and the I/O section during input/output operations. The information on the data bus is either written into 5-24

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memory at the address defined by the address bus or consists of data read from the memory address specified by the address bus. Figure 5-17 is an example of a computer’s bus system; control, address, and data buses. Instruction (I) Bus The instruction (I) bus allows communication between the CPU and memory. It carries to the CPU the program instruction words to be operated on by the CPU from memory or returns instructions to memory. The I bus is controlled by the CPU. It is capable of sending or receiving data while the operand (O) bus is receiving or sending data at the same time, but only in one direction at a time. Operand (O) Bus The operand (O) bus allows communication between the CPU and memory or the CPU and an I/O Controller (IOC). The CPU controls the operation in both cases. The O bus is capable of sending or receiving data, while the I bus is receiving or sending data at the same time, but only in one direction at a time. The direction of the data depends on whether the CPU is reading data from memory or data is being written back into memory. I/O MEM Bus or Input/Output Controller (IOC) BUS The I/O memory bus allows communication between an I/O controller (IOC) and memory. It is Figure 5-17.—Example of a computer’s bus system; control, address and data buses. controlled by the IOC. To respond to the CPU, the I/O MEM bus must use the O bus. Figure 5-18 is an illustration of communications between a CPU, memory, and an IOC without a computer interconnection system. Pay close attention to the direction of signal flow and which buses allow communication between functional areas. Computer Interconnection System The Computer Interconnection System (CIS) provides the complete functional replication of the computer intraconnection among CPUs, IOCs, and memories in separate computers. This allows the internal buses to be extended beyond their own enclosure. The CIS consists of two independent halves: the requestor extension interface (REI) and the direct memory interface (DMI). REQUESTOR EXTENSION INTERFACE (REI). —The requestor extension interface (REI) is a bus extender. It extends the bus up to 15 other computer cabinets providing an interconnected system of memory modules, CPUs, and IOCs. The REI takes the requests from the requestor ports and goes through a priority network to determine the order in which it is to respond to the requesters. Once the REI has responded to a request, it puts the address onto the output bus, Figure 5-18.—Bus system between a CPU, memory, and IOC without CIS. 5-25

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checks parity, and examines a code to determine the correct sequence. After the sequence is established, the REI broadcasts the requests and the address to all DMIs connected to it. The signals on the REI external interface are expanded to guarantee capture at the DMI operating synchronously to the REI, which can be located up to 500 cable-feet away. Once the REI makes a request, it can send write data if it is performing a write operation or wait for a response and pass it to the requestor. The REI responds to the requestor just as memory does, including faults and aborts (terminates a process before it is completed). DIRECT MEMORY INTERFACE (DMI) BUS. —The Direct memory interface is a responder or slave on the REI bus. The DMI bus is used in some computers that use an I, O, and IOC bus. The DMI bus is used to send requests from other enclosures (computers) to the module (CPU or IOC) requested. It acts as the requestor and makes requests to the CPU. When it requests an IOC, it uses IOC read and write requests. When it requests memory, it uses operand read or write, instruction read, or replace. Time Multiplexed Bus Another variation of the address and data bus is the time multiplexed bus. This single bus transmits both addresses and data using a four cycle clock (tl, t2, t3, and t4). The address is transmitted during the t1 clock cycle, the direction of data movement is selected during t2, and the data is transmitted during t3 and t4. BUS OPERATIONS The bus control function is performed by a bus interface unit or logic circuitry similar to it. Control of a bus line and the proper protocol of requesting a bus depends on the design of the computer. In computers with no IOC, the CPU has control of the bus lines. In computers with an IOC, the CPU will control the instruction and operand buses and the IOC will control the memory buses. Bus control is necessary to handle the large number of bus transactions that take place in a very short period of time in the computer. There are basically two factors that must be taken into consideration in bus communications: transfer priority and source/destination of the data being transferred. Bus transfers are done on a priority basis. The priorities of bus transfers are determined by the design of the computer’s firmware. What part makes the request is also determined by the design of the computer’s firmware; requests may be made by a CPU, an IOC, and/or a DMI. Examples of priorities that a computer must deal with include the following (these examples are not in any type of priority and do not cover the frill range of priorities you may encounter): Transfers from memory to the CPU, these transfers move instructions and operands to the CPU for execution and modification Transfers from the CPU to memory Transfers by the I/O in and out of memory The specific request will identify the source and the destination of the data. The computer’s controlling bus continually and repeatedly checks the bus signal lines for requests. When it receives a request, it provides the control signals needed to initiate the transfer. Since most transfers deal with memory, each transfer consists of an address exchange and a separate data exchange. The data will either parallel the address as in a write operation or move in the opposite direction after the data has been read from the memory word identified by the address. In some computers, the bus systems use holding registers in both the source and destination sections to prevent data loss and to help coordinate the data exchange. In the source logic, the data is placed in a holding register until it is accepted by the destination logic. The outputs of the holding register feed the bus circuitry. In the destination logic, the bus inputs to a holding register. After accepting the data, the destination logic can then move the data from the holding register to other parts of the logic for processing. A variety of command signal names are used to coordinate the exchange of data on the buses by both the source and the destination logic. The source logic generates a ready or signal equivalent when the data is in the holding register and on the bus. The destination logic sends an acceptor equivalent signal when it has sensed the ready signal and captured the data on the bus in its holding register or other logic circuits. MICROCOMPUTER ARCHITECTURE AND BUSES The microcomputer has uses four main types of buses. These are the Processor bus Address bus 5-26

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Memory bus I/O bus The I/O bus has historically been the slowest of all buses, and the main focus when computer design engineers try to improve bus speeds. Processor Bus The processor bus is communications path between the CPU and the main bus. It is also used for communications between the CPU and the processor support chipset. The processor support chipset includes chips such as an external memory cache and the bus controller chip found on some microcomputers. The size of the processor bus matches the size of the data words used by CPU. For example, the 80486DX chip uses 32-bit words; therefore the processor bus has 32 data lines, 32 address lines, and the control lines. The Pentium processors have 64-bit words and use 32-bit addresses. Processor buses can have a maximum data transfer rate of the motherboard clock. Memory Bus The memory bus transfers data between the RAM and the CPU. This bus can be the processor bus or will be implemented by a dedicated chipset that controls the memory bus. In most computers that have a motherboard clock that is faster then 16MHz, a special memory controller chipset will control the memory bus. Address Bus The address bus transfers the next memory or I/O address to be used in the next data transfer. The address bus in 486 and Pentium systems is 32 bits wide. I/O Buses To thoroughly understand the I/O buses used in modem microcomputer systems, an understanding of the development and evolution of bus systems is required. The microcomputer’s architecture is directly related to the type of buses in the computer. Originally, microcomputers used a bus system called the S-100 bus. Using this system, any board could be plugged into any open slot. The S-100 bus has 62 lines, each connect to each of the 62-pin connectors. This system dedicated eight lines for the eight data bits used in the Intel 8088 microprocessor. Twenty lines are used for memory addressing. The same 20 lines are also used to address I/O devices. A control line determines whether the data on these 20 lines will be a memory address or an I/O address. There are also several control lines and power distribution lines. The S-100 bus also provided four lines to designate channels for Direct Memory Accessing (DMA). A DMA channel allows a device, such as the hard drive, to transfer data directly into RAM, vice transferring data to the CPU and then having the CPU transfer it to the RAM. The DMA channel number identifies which device is requesting and transferring data on the data bus. Buses also need to be clocked to properly transfer data. The early microcomputer buses were designed to run at the speed of the microprocessor that was installed on the board. The 4.7 MHZ 8088 microprocessor clock was also used to clock the bus. The 7.16 MHZ microprocessor clocked the bus at the same rate. The ISA standard set the bus clock speed at 8 MHZ. To maintain compatibility with the older controller boards, this speed is still common in many computers today. This speed is fine when getting input from a mouse or a keyboard, even for most disk drives. The biggest problem with bus speeds has occurred because of the increase in video resolution, the development of video capture boards and some network interfaces. INDUSTRY STANDARD ARCHITECTURE (ISA). —As the microcomputer evolved, the eight data lines and 20 address lines became insufficient to handle the increased data capacity of the 16-bit processor. This led to the development of the Industry Standard Architecture (ISA). To be compatible with the boards used in eight-bit computers, an additional 36-wire connector was added to the circuit boards and the bus. This added eight more data lines, four more address lines, four more DMA channels, and five more IRQ channels. LOCAL BUSES. —A local bus is a bus that is a dedicated path between the processor and a specific board. There are several local buses built into various types of computers to increase the speed of data transfers. Local buses for expanded memory and video boards are the most common. Some high-end computers also provide a local bus for the hard drive. The VESA Local Bus is one of the more popular buses and was developed to increase the speed of data transfer between memory and the video processing board (video graphics adapter). VESA stands for Video Electronics Standards Association. The VESA Local Bus is a direct bus that connects the video processor 5-27

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with the processor bus. The VESA Local Bus operates at the speed of the video processor. Several other bus systems have been developed, many of which have not found widespread acceptance in the PC world. Each of these has introduced some technology that is common in the modem bus systems. MICROCHANNEL ARCHITECTURE (MCA). —The MicroChannel Architecture (MCA) bus was developed by IBM in 1987 and increased the bus speed to 10 MHZ. The MCA Bus also introduced the ability to configure the boards IRQ and DMA channels through a software configuration program. MCA was the first system to use bus mastering. Bus mastering is a system that allows an intelligent controller board to take control of the bus system for a specified period of time. This allows operations to be completed quickly. Bus mastering differs from DMA in that DMA allows for direct transfer from a peripheral controller to RAM, Bus mastering allows for direct transfers between controllers. An example of bus mastering is the ability of a hard drive to transfer graphics directly to the graphics driver, bypassing the CPU and RAM. The major disadvantage of MCA was that it is not compatible with the old ISA standard. Therefore, if you have an MCA machine, the old ISA controller boards will not work. EXTENDED INDUSTRY STANDARD ARCHITECTURE. —To compete with MCA, The Extended Industry Standard Architecture was (EISA) developed. The EISA Bus included the following features: 32-bit data path 64K of I/O address Capability to address up to 4 gigs-bytes of memory Software configuration of boards Bus mastering Unfortunately, the EISA Bus still operates with an 8 MHZ clock, and did not add any additional DMA or interrupt channels. PERIPHERAL COMPONENT INTERCON- NECT (PCI). —The Peripheral Component Interconnect (PCI) system was designed to increase I/O bus speeds while still maintaining compatibility with previous ISA and EISA boards. A PCI computer has two separate banks of expansion slots, one bank for PCI boards and one bank for the older ISA/EISA boards. The PCI bus uses a “bridge circuit” to isolate the processor bus from the main I/O bus. This bridge circuit is designed so that I/O functions can run independently from the CPU. The PCI bus is a 64-bit data bus, but can also support 32-bit computers. This makes the PCI bus useful in both Pentium and 486 systems. The PCI bus can operate a speed up 33 MHZ and also supports bus mastering. Finally, the PCI bus supports the Plug-n-Play standard for software configuration of peripheral boards. SUMMARY—CENTRAL PROCESSING UNITS AND BUSES This chapter has introduced you to central processing units (CPUs) and buses. The following information summarizes important points you should have learned: CENTRAL PROCESSING UNITS —All the computational operations (logical and arithmetic) and operational decisions are made in the CPU. The CPU controls all computer operations. The CPU has a control section and an arithmetic logic unit (ALU). CONTROL SECTION —The control section directs the sequence of CPU operations, interprets the instructions, and provides the timing and control signals to carry out the instructions. TIMING —Timing in a computer regulates the flow of signals that control the operation of the computer. Computer operations rely on both synchronous and asynchronous operations. Timing circuits are used throughout the computer. INSTRUCTION AND CONTROL —The instruction execution and control portion of the control section includes the combinational and sequential circuits that make up the decision-making and the memory-type functions. The general process of execution of a machine instruction is fetch the instruction, update the program counter or equivalent, translate the instruction, and execute the instruction. INTERRUPTS —Interrupts are a method of diverting the attention of the computer from whatever process or program it is performing to handle the special condition or event that caused the interrupt signal. Interrupts allow the computer to respond to high priority demands and still be able to perform normal or lower priority processing. An interrupt is defined as a break in the normal flow of operation of a computer caused by an interrupt signal. The break occurs in 5-28

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such away that the operation can be resumed from the point of the break at a later time with exactly the same conditions prevailing. CPUs follow a specific sequence of events when processing an interrupt. Interrupt processing has priority over normal program execution. CONTROL MEMORY —Control memory consists of addressable storage registers. It is used as a temporary storage. Access to control memory data requires less time than access to main memory. This speeds up CPU operation by reducing the number of memory references for data storage and retrieval. CACHE MEMORY —Cache memory is a small, high-speed RAM buffer located between the CPU and main memory and used to hold a copy of the instructions or data currently being used by the CPU. It is used to speed up the flow of instructions and data into the CPU from main memory. READ-ONLY MEMORY —Every computer is supplied with a set of software instructions to enable the computer to perform its I/O operations. These permanent instructions (routines) reside in a read-only memory (ROM). ROM is often referred to as firmware: software permanently contained in hardware. The instructions are considered permanent or nonvolatile, since they are not erased each time the computer loses power or is turned off. The ROM is tailored to system requirements and initiates the boot procedure —the steps followed when you turn on computer power. ARITHMETIC LOGIC UNIT —The arithmetic logic unit (ALU) implements arithmetic and/or logical operations required by the instructions. The instructions tell the CPU which type of mathematical or logical calculation the ALU is to carry out. The registers and operands provide the computer the sources of the data needed to perform the calculations. Tuning in the ALU is provided by the CPU’s timing circuits. ALU OPERATIONS —ALUs can perform arithmetic and logical operations. An ALU can be designed to perform arithmetic operations in fixed-point representation (integers) and floating-point representation (fractional). The types of arithmetic operations range from add and subtract operations to sophisticated trigonometric operations. Some computers have a separate numeric data coprocessor or math pacs to perform arithmetic functions independent of the ALU. INTERNAL BUSES —Buses transfer information internally in computers. A bus is a parallel data communication path over which information is transferred a byte or word at a time. The direction of signal flow may be unidirectional or bidirectional. BUS OPERATIONS —The bus control function is performed by a bus interface unit, or logic circuitry similar to it. Control of a bus line and the proper protocol of requesting a bus depend on the design of the computer. Bus transfers are done on a priority basis. Basically two factors must be taken into consideration in bus communications: transfer priority and source/destination of the data being transferred. By studying this chapter, you should have learned how the CPU works through its control section and its arithmetic logic unit. You also should have learned how buses are used to transfer instructions, data, and information throughout a computer. These concepts are important to understanding how to troubleshoot and diagnose malfunctions and repair or replace CPU parts. 5-29

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CHAPTER 6 COMPUTER MEMORIES INTRODUCTION The memory of a computer holds (stores) program instructions (what to do), data (information), operands (affected, manipulated, or operated upon data), and calculations (ALU results). The CPU controls the information stored in memory. Information is fetched, manipulated (under program control) and/or written (or written back) into memory for immediate or later use. The internal memory of a computer is also referred to as main memory, global memory, main storage, or primary storage. Do not confuse it with secondary or auxiliary memory (also called mass storage) provided by various peripheral devices. In newer computers you also will encounter a number of small and independent local memories that are used for a variety of purposes by embedded microprocessors. You have already learned about cache memory that lies between the CPU and main memory. After completing this chapter, you should be able to: Describe the organization of memory Describe the operation of main memory Recognize the types of memory and describe how they function TOPIC 1—MEMORY ORGANIZATION AND OPERATION The main memory of a computer is used for storing programs, data, calculations, and operands. Memory is used in all types of computer systems includ- ing mainframes, minicomputers, and microcomputers. The amount of main memory each type of computer has varies according to the configuration. A wide variety of memory types is being used. To simplify our discussion, we have divided memory into two general categories: read/write (random access) memory and read-only memory. Within the read/write group, we discuss magnetic (core and film) memories and semi- conductor (static and dynamic) memories. Read-only memory can be subdivided into factory programmed parts called read-only memory (ROM) and user pro- grammable devices called programmable read-only memory (PROM). This classification system is illus- trated in figure 6-1. Let’s take a look at some of the termi- nology used with regard to the computer’s memory. TERMINOLOGY The following terms need to be explained at this point: Memory —Memory generally refers to the actual hardware where the programs, data, calculations, or operands are stored. Memory address —A memory address is a particular location of a larger memory array. Usually one memory address contains one word of data. A word is one packet of information for the computer and is usually composed of many bits. Computers exist that use 1-bit words, 8-bit words, 16-bit words, 32-bit words, and 64-bit words. Handling computer data in 8-bit words is so common that the 8-bit word has its own name, the byte. Half of a byte is called a nibble (4 bits). Capacity (memory size) —Capacity is an important aspect of system performance; it is a useful and convenient way to describe the size of memory. At the individual part level, a computer’s memory maybe 6-1

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Data Terminal Equipment (DT13) —Any device that can transmit or send data; for example, a computer. EIA —Electronics Industry Association. External Function (EF) data —The purpose of the EF function is to transfer command information by using the appropriate control signals from the transmitting computer to the receiving device. The word size and bit format of the EF data will be specified by the appropriate system design data or the individual equipment specifications. External Interrupt (EI) data —The purpose of the EI function is to transfer status information by using the appropriate control signals from a transmitting device to the receiving computer. The word size and bit format of the EI data will be specified by the appropriate system design data or the individual equipment specifications. Gateway —A device that serves as a shared entry point from a local area network into a larger information resource such as a mainframe computer. Handshaking —Signals necessary for complet- ing I/O operations. Hub —Repeats the signal on the cable. IEEE —Institute for Electrical and Electronics Engineers. Input —Input refers to input to the computer. Input/Output (I/O) word —The I/O word is defined as a digital word of a specified number of bits, which has been agreed upon as the basic unit of communication between interconnected units. Input Data (ID) —The propose of the ID function is to receive information using the appropriate control signals from a transmitting device by the receiving computer. The word size and bit format of the ID data will be specified by the appropriate system design data or the individual equipment specifications. IOA —Input/output adapter. IOC —Input/output controller. Output —Output refers to output from the computer. Output Data (OD) —The purpose of the OD function is to transfer information using the appropriate control signals from a transmitting computer to the receiving device. The word size and bit format of the OD will be specified by the appropriate system design data or the individual equipment specifications. Protocol —In a computer, protocol is the procedure required to initiate and maintain operations. For example, I/O operations of a parallel format use a request and an acknowledge protocol to perform input and/or output operations for the transfer of information between the computer and external equipment. RS —Recommended Standard. Sink —The sink is defined as that end of a channel that receives information frames. Source —The end of a channel that transmits information frames. TOPIC 2—INPUT/OUTPUT (I/O) ORGANIZATION All computers are capable of I/O operations. Some computers rely on the CPU to handle all operations including the I/O operations. These computers simply use the circuits in the CPU to handle the I/O operations. However, the majority of computers use an I/O processor (fig. 7-1) that enhances the capabilities of the computer and relieves the burden of I/O processing from being on the CPU. This allows the computer to perform other operations while still performing I/O operations. In this topic we discuss I/O operations in general terms, using an I/O processor. This includes the physical aspects, data arrangement, format, instructions, operations (modes of operation, timing, Figure 7-1.—I/O processor in a computer system. 7-2

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and control), categories of I/O operations, and I/O interfacing. INPUT/OUTPUT PROCESSOR For those computers that have an I/O processor, the physical organization of I/O is similar to the other major functional areas: CPU and memory. I/O processors can vary from many pcb’s that makeup a module/unit to a single pcb. Larger mainframe computers use the modular arrangement: multiple components on multiple pcb’s that comprise one or more modules or units. Mini- and microcomputers use chassis or assemblies, cages or racks, and motherboard/backplane arrangements. Minis and micros use multiple components on one pcb or groups of pcb’s (usually not more than seven) to form the I/O processor. The I/O processor controls the transfer of information between the computer’s main memory and the external equipments. I/O processors are packaged two different ways: (1) IOC/IOA modules or multiple IOC/IOA pcb’s, and (2) I/O pcb’s. Regardless of the setup, computers with an I/O processor will use some sort of controller to regulate the signals in the I/O processor itself (includes IOC/IOA setup) and memory. IOC/IOA Module or Multiple IOC/IOA Pcb’s I/O processors that are packaged as IOC/IOA modules or multiple IOC/IOA pcb’s are divided into two sections. The two sections are a single module/unit or group of pcb’s for the I/O controller (IOC) and a single module/unit or group of pcb’s for the I/O adapter (IOA) (fig. 7-2). Mainframes and some minis use this arrangement. IOC. —The IOC relieves the CPU of the necessity to perform the time consuming functions of establishing, directing, and monitoring transfers with external equipments. Data and control signals are exchanged with external equipments via the IOA. IOCs communicate by means of a bidirectional bus. An IOC is provided with a repertoire of instructions (commands) that varies with the type of computer. The IOC contains the necessary control and timing circuits (digital) necessary to function asynchronously with the CPU and controls the transfer of data between accessible main memory and the external equipments. IOC programs are initiated by instructions from the CPU and executed by a repertoire of IOC commands stored in main memory. Included in the repertoire are those commands that establish the conditions for data Figure 7-2.—IOC/IOA modules in a single cabinet configuration. 7-3

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transfers to and from the external equipments. See figure 7-3 for an example. IOA. —The IOA changes the input and output control and data signal voltages to the voltage requirements of the computer or external equipments. The IOA receives data and control signals from the IOC logic of the computer, and returns data and interfacing signals to the IOC logic. It also transfers data and control signals to the external equipments and receives data and interfacing signals from the external equipments. The IOA logic circuits consist primarily of line drivers/receivers (linear circuits) and timing circuits (digital circuits). ” Communication between the IOC and IOA is by means of a bidirectional bus. The IOA communicates with the external equipments via I/O channels/ports. The connectors for the input and output channels or ports are physically located atop the IOA unit (fig. 7-4) or on the rear of a computer cabinet (fig. 7-5). The type of interfacing will dictate the type of connectors for the channels or ports. The IOA is capable of receiving and sending parallel and serial data. IOC/IOA INTERFACING. —The IOA is a completely passive unit and functions under the direct control of the IOC. The driver circuits pass interfacing and data signals to the external equipments. The receivers pass data to the IOC. They are directed by the IOC using input and output control circuits. The request circuits pass interface signals to the IOC Figure 7-3.—Example of a repertoire of IOC commands. 7-4

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Figure 7-4.—IOA, top view with I/O connectors. 7-5

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Figure 7-5.—I/O connectors, rear of computer cabinet. 7-6

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Figure 7-6.—IOA/IOC interface. (fig. 7-6). Some of the data and control signals the pcb to match the electrical interface of the exchanged between the IOC and IOA include: Buffer enables Acknowledge enables Set/clear output register Data bits Request lines Input/output available I/O Pcb(s) In the I/O pcb arrangement, minis and micros have multiple I/O pcb’s or a single I/O pcb. When multiple I/O pcb’s are used, each I/O pcb will be assigned a number of external equipments for I/O operations. In this arrangement other circuitry will be used that basically performs the same duties as a controller. In the single I/O pcb arrangement, the functions that an IOA would perform are contained on external device(s) to that of the computer. The connectors for the input and output channels/ports are usually located on the rear of the I/O pcb (fig. 7-7). Figure 7-7.—Connector parts on the rear of a microcomputer. 7-7

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Some arrangements include assigning multiple ports to each channel (fig. 7-8). Micros usually have only one pcb for their I/O operations: the pcb has both a parallel and a serial port (fig. 7-7). Some minis and micros have dedicated pcb’s separate from the I/O pcb(s) to handle the interface for the peripherals and displays. For micros, the interfacing for the keyboard is usually located on the I/O pcb. INPUT/OUTPUT DATA ARRANGEMENT The function of any I/O operation is to exchange information between equipments. Regardless of the techniques used to move the information, there are consistencies in the architectures of the I/O sections used by computers. These consistencies include the arrangement of the information exchanged and the format of the information exchanged. Arrangement The types of information exchanged between the computer and the external equipments frill into two basic categories: data words and control words. The length of the information exchanged varies with the type of computer from 8-bit words to 32-bit words. DATA WORDS. —Data words represent the alphabetic and numeric information exchanged. Data words are always thought of with the computer as the reference point. Input data words are data entered in the computer from equipments external to the computer o Output data words are data sent out to the external equipments from the computer. Some computers transfer data words that include data and externally specified addresses and index addresses. CONTROL WORDS. —Control words specify an action to be accomplished by an external equipment. This might include an error or special condition of an Figure 7-8.—Assigning multiple ports to a single channel. 7-8

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external equipment or the status of an external equipment, in response to a computer control word. Some examples of control words used by computers include the following: Function (command) control words —Function control words are sent by the computer to an external equipment to specify the type of operation it is to perform. The signals used for the control words are often referred to as handshaking. An example of a control word would be a function code word telling a printer to print the contents of a specific accumulator register at the location specified by the address in the instruction. Computers that have a control memory use a control memory word to transfer data for I/O buffer operations. External interrupt words —External interrupt words are sent to the computer to specify that an error or special condition exists in an external equipment or the status of an external equipment. Review chapter 5 of this volume for a detailed discussion of interrupts: their classification, types (micro, mini, and mainframe), priorities (micro, mini, and mainframe), codes, and handling process. Format There are two formats of information exchanged by a computer: parallel and serial. ‘The type of interface will dictate the format of the information exchanged. PARALLEL. —When the computer exchanges information using a parallel configuration, all bits of information represented by a byte or word are input or output simultaneously. In figure 7-9, frame A, we illustrate how the character M is output from the computer to a printer in parallel format. SERIAL. —When the computer exchanges information using a serial configuration, all bits of information are input or output one at a time. Figure 7-9, frame B, illustrates the character M being output from the computer to a printer in serial format. INPUT/OUTPUT INSTRUCTIONS The heart of the I/O section is the input/output processor: an IOC/IOA or I/O pcb arrangement. All computers have I/O instructions. Computers without an IOC/IOA arrangement have other means of Figure 7-9.—Parallel and serial configurations: A. Character M transmitted in parallel; B. Character M transmitted serially. 7-9

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optimizing the CPU’s time, so the CPU is not involved in all transactions, including the I/O instructions. We cover those methods later in this topic. However, for computers that have an IOC, the IOC is a processor in its own right. we focus our discussion of I/O instructions on I/O processors with an IOC. An IOC is capable of executing its own set of instructions specifically designed to govern I/O operations for those channels/ports handled by the particular IOC. Figure 7-10 shows the format of an example IOC instruction. This format is used for some mainframes and some minis. The designators shown are for a typical I/O instruction and may vary with IOC instructions. Each IOC executes instructions stored in main memory in the same manner as the CPU executes instructions. There are two basic types of IOC instructions: command instructions and chaining instructions. Command instructions are executed by the IOC under the control of the CPU’s main program. Chaining instructions are executed under the command of an active channel (I/O operation in progress) chain. Some IOC instructions perform. the same functions whether it is a command or a chaining instruction. Command Instructions Command instructions provide control over IOC single or dual channel operations. They are executed individually using the following process. The CPU executes an I/O command start instruction, which is a CPU instruction. The I/O command start instruction specifies or addresses an IOC(s) and then halts further CPU processing. The addressed IOC then references specific main memory addresses (the command cell) and executes the IOC command instruction previously stored in the addresses. At completion of the instruction execution, the IOC will clear assigned bits of the command cells to indicate to the CPU that the command has been processed and to release the CPU to continue further processing. This is one instance in interrupt driven I/O operations where the CPU will delay processing while waiting for an I/O operation to take place. The instruction contained in the command cell will cause the IOC to perform a variety of channel activity functions. The most common operations deal with initiating a new chain or terminating a chain in progress. Other commands are used to master clear individual channels, enable or disable a variety of interrupts, monitor channel status, load or store control memory, and initiate the IOC built-in test (BIT). Chaining Instructions Chains of IOC instructions are stored in memory by the main CPU program before the I/O operation takes place. The actual execution of chaining instructions is independent of the CPU. Only a command instruction execution from the command cell will delay CPU processing. There can be an input chain and/or an output chain being executed for each channel. Input or output chains deal primarily with the transfer of blocks of information. A chain consists of IOC control words, command words, output data words, and specified locations for Figure 7-10.—IOC instruction format. 7-10

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external status words and data words returned (input) from the channel. The starting address of the chain (and other data) is provided by the load control memory command. The chain’s starting address is stored in the channel’s chain address pointer portion of I/O control memory. The contents of the I/O control memory are used by the IOC to control all channel operations including execution of chaining instructions. TOPIC 3—INPUT/OUTPUT OPERATIONS Input/output operations are initiated by the CPU. Computers with an IOC will begin I/O control functions only after an initiate I/O or equivalent instruction is executed by the CPU. I/O operations under the control of the computer program control the external equipment. Computer instructions inform the external equipment which type of operations to perform with function codes. Computer instructions also specify memory areas for input and output information. Input/output operations do not accept data from external equipments or send information to them unless memory areas for the data have been specified by the computer programs. Whenever an external equipment is ready to send or receive data, a request signal is sent to the computer. How the I/O section notifies or interrupts the control section that an external equipment is ready to send or receive information/data depends on the type of computer. Some constants in all I/O operations include the following: When the transfer will begin, How many words or bytes will be transferred, Word or byte size, When each individual word or byte is actually transferred, and, When the transfer will terminate. I/O operations require circuitry that must take action in a specific sequence of events to communicate with the external equipment. In I/O operations, we examine operating modes, I/O circuits, and I/O functions. OPERATING MODES Similar to the CPU, some computers have the capability to select operating modes. These options are usually found with computers that have an IOC. They can be found on the computer’s controlling device, usually a maintenance panel or some equivalent. You can use this option for troubleshooting purposes. Consult the operator’s section of your computer’s technical manual. As far as the operating modes for I/O operations, these options are usually established at the factory. Again, they usually apply to computers that have an IOC. Some of the operating modes for I/O operations include the following: Single-channel —The single-channel operating mode allows external equipments to communicate with the computer via one input/output channel. Dual-channel —The dual-channel operating mode is used by computers with smaller word sires, say 16 bits, to communicate with external devices using a larger word size (30 or 32 bits). In a dual-channel mode, the data lines for two channels are combined under control of the lower order channel. A pair of sequentially numbered channels (0 and 1, 2 and 3, and so forth) is used for dual-channel operations. The even numbered channel provides the control signals and lower half or lower order data bits. The odd numbered channel provides the upper half or upper order data bits only. The exchange of information over the dual channel is controlled by the even numbered channel’s interface signals. Dual channels may use the computer peripheral or intercomputer channel signals. Externally specified address (ESA) —The externally specified address mode provides the external devices with a means of specifying an absolute memory location for storage (write) or retrieval (read) of information on a word-by-word basis. Externally specified index (ESI) —The externally specified index mode is identical to regular transfers (input, output, external interrupt, and external function) except that the IOC requires the external device to specify an index address in main memory. Intercomputer channel (IC) —The intercomputer channel mode permits communication between two CPUs. In this mode, each computer appears as an external device to the other. During operations, the computer that is outputting the data is defined as the sending computer. The computer that is receiving the data from the sending computer is defined as the receiving computer. I/O CIRCUITS In chapter 4, we discussed the circuits used by computers. We also discussed some of the same circuit types in the CPU and memory sections. I/O is no 7-11

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different; but in addition, I/O operations include not only digital ICs, but also linear ICs. The linear IC circuits are the first and last type of circuitry the information interfaces with when entering and leaving the computer. In this topic, we discuss some of the more common circuits you will encounter when dealing with I/O functions. In addition to the circuits we have discussed in the CPU and memory sections, you must be familiar with driver and receiver circuits (linear ICs). Review chapter 4 of this volume and NEETS, Module 13, Introduction to Number Systems and Logic Circuits. They provide excellent reviews of the circuits and their functions covered in the remainder of this topic. The circuits include: Adders Command signals (enables) Decoders Line drivers and receivers Registers (includes RTC and Monitor Clock for IOCs) Selectors Timing Translators One of the primary uses of registers in I/O operations is to provide the interfacing between the CPU, I/O and memory. They enable and route control and data information between the CPU, I/O and memory using the internal bus system. In a computer with no I/O processor, a register will be designated as either an input or output register (fig. 7-11). Decoder circuits are used for address translation, control circuits for governing the operation of the interface, data registers, and status registers for information exchange. The data registers are used to hold or buffer data during interchanges between the very fast CPU and the slower external equipments. The status registers hold information for the CPU that indicates the operating condition and current activities of the external equipments. We discuss external interfacing later in this topic. INPUT/OUTPUT FUNCTIONS The input and output functions performed by an I/O processor are defined and enabled through the interpretation and execution of input/output and/or input/output controller (I/O(C)) commands obtained from main memory. the I/O circuits provide the Figure 7-11.—Computer operations with no I/O processor using registers. timing, control, temporary storage, routing, command translation, and interfacing (internal and external) to perform I/O operations. Timing Circuits As we discussed in the memory section, timing circuits also will provide the enables to manage the I/O control circuits used for I/O operations. Some computers use the computer’s master clock and one or two other timing signals derived from the master clock to control the flow of data in I/O operations; an example of this is the timing used in microcomputers. Still other more complex computers, such as mainframes and minicomputers, rely on a master clock and main timing circuits in the respective functional area (CPU, memory, or I/O to produce and distribute timing signals to the I/O control circuits. In computers with an IOC, their I/O master clock and timing circuits operate completely independently of the CPU timing. Their master clock is started when the computer is initially powered on or auto restarted. It can only be stopped or temporarily halted under 7-12

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certain conditions, such as a computer master clear or a read/write memory reference. Control Circuits The I/O control circuits are under the direct or indirect control of the program. The I/O control circuits decode I/O commands from the CPU and generate the required signals to execute the instructions. The timing circuits coordinate control circuit operations. Computers with an IOC operate independently from the CPU after they receive an initiate I/O instruction and control all I/O operations. Depending on the computer type, some of the more common uses of the control circuits include the following: Logic to decode I/O commands Logic to generate signals to execute I/O instructions Logic to evaluate priorities of I/O requests Logic to execute buffered and unbuffered requests A term used quite often with I/O control operations is the term buffer. A buffer is nothing more than a sequential set of memory locations that contains data to be sent out or an area that is set aside for data to be received. A buffer is considered to be terminated when all the words or bytes in the assigned memory locations have been sent or received. Unbuffered operations are where data is exchanged within the computer between the CPU and various parts of the computer. Unbuffered operations do not establish limits when transferring information. Buffered operations, on the other hand, are for the expressed purpose of transferring information to and from the computer and an external device; they have established buffered limits. For example, addresses 00 8 through 17 8 in memory maybe set aside to receive data into the computer. A buffer can also be called a frame. Sequencing The I/O processor executes I/O commands using sequencing circuits in a manner similar to the CPU. Like the CPU, the I/O processor’s sequencing circuits control the order in which events will be executed based upon the translated function code and modifying designators. To complete a particular I/O command, CPU instruction, or maintenance console/equivalent action (if available) may require the I/O processor to run one or more of the available sequences. A processor may have up to six sequences depending on the design of the computer. I/O Interface Circuits The CPU interfaces with the I/O processor through the CPU’s I/O instructions. These instructions cause the initiation of I/O operations. For computers with an IOC, the instructions allow the CPU to access the RTC or the monitor clock. This communication is done via the bus system. The communications lines include some of the following: Request lines (initiate I/O instruction) I/O(C) select lines Data lines Data ready Interrupt requests I/O Memory Reference The I/O processor references main memory during specific sequences such as an instruction or a maintenance console/equivalent action (if available). The bus allows this to be performed asynchronously. The I/O processor acquires I/O commands, output data, and operands from main memory and presents the information for storage into a main memory location over a bus. Some of the lines of communication include the following: I/O memory selection I/O read reference I/O write reference I/O Control Memory I/O processors can also use an I/O control memory, which is used primarily by mainframe and minicomputers containing an IOC. I/O control memory words are set aside in main memory to control data transfers for I/O buffer functions. I/O control memory is capable of handling parallel or serial information. PARALLEL OPERATIONS. —In parallel operations, each I/O channel has its own block of memory addresses (usually 16). They include blocks for input, output, external function, and external interrupt operations. Some of the items included in parallel operations are as follows: 7-13

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Buffer control words (BCWs) —Buffer control words control the type and number of words or bytes that are to be transferred by the pending operation. Transfers include 8-bit bytes, 16-bit single words, and 32-bit words. Buffer address pointers (BAPs) —Buffer address pointers specify the next memory address, within the buffer, for a transfer to take place. Chain address pointers (CAPs) —There is one chain address pointer for each input and output chain of a channel. Each CAP specifies where in memory the IOC can find the next chaining instruction. SERIAL OPERATIONS. —Serial operations are affected by character size (5 to 8 bits), parity selection (odd, even, or none), baud rate (50 to 9600 baud), and synchronous (sync) or asynchronous (async) interfacing. Some of the items included in serial operations are as follows: Monitor words —Monitor words are used to store characters for comparison with received (input) data characters. Suppress word —A suppress word contains a code that is used to remove specific characters from the serial transmission stream. CONTROL MEMORY OPERATIONS. —lhe contents of control memory are accessed and modified through the use of IOC command or chaining instructions. The exception is actual data transfers in which the IOC logic updates control memory for each word or byte transferred. The basic operations that deal with control memory are the following: Initiate transfer (command or chain) —Initiate transfer loads the input or output BCW and BAP in control memory for the channel specified and initiates the input or output transfers. Load/write control memory (chain) — Load/write control memory is used to load or write data into single control memory word locations. Store control memory (command or chain) — Store control memory is used to write the contents of a specified control memory address into a memory address for CPU processing. Set/clear flag (chain) —A set/clear flag is used to set or clear (zero) specified bits or bit groups in control memory or main memory locations or the channel status word. It is also used to set or clear the test bit in the channel status word for conditional jumps. 7-14 Search for sync/set suppress/set monitor (chain) —The search for sync/set suppress/set monitor enables or disables sync, monitor, and suppress capabilities indifferent serial configurations. Set/clear discrete (command and chain) — Set/clear discrete is similar to set/clear flags except that the set/clear discrete deals with serial interfaces exclusively. It is used to turn on or turn off specific serial channel signals such as data terminal ready. Channel control (command or chain) —Channel control performs a variety of single and multichannel functions. It can be used to master clear a single or all IOC channels, input or output. It is also used to enable or disable all, low priority, or a single channel’s interrupts (external or class III interrupts). CATEGORIES OF I/O OPERATIONS There are two ways that the I/O section will handle the transfer of data between the computer and the external units: direct CPU/external device (direct CPU interface) communication and direct memory access (DMA). Each method has it advantages and disadvantages. We begin with direct CPU/external device communication. Direct CPU Interface With direct communication, also called accumulator based I/O the peripheral devices are tied directly into the CPU communication bus (control bus, data bus, and so forth). In a simple I/O scheme, the CPU handles all I/O transactions by executing one or more instructions for each word of information transferred. Three techniques are used: memory mapped I/O polled I/O and interrupt driven I/O. MEMORY MAPPED I/O. —In memory mapped I/O the CPU accesses the I/O device by placing appropriate addressing information on the bus. The addressing information uniquely identifies the device and possibly several addressable locations within the device. Thus an addressable location in an I/O device might be treated as a memory location in the computer. This enables the CPU to transfer data to and from the I/O device in the same way as main memory transfers. The following is an example:

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Each I/O channel is assigned four memory addresses in main memory or in logic circuitry (registers) that replaces or overlays four sequential main memory addresses. These four addresses or registers are used to store the following data: address n — External Interrupt Code Word address n + 1 — Input Data Word address n + 2 — Output Data Word address n + 3 — Channel Control/Status Word These addresses also allow the IOC/CPU to perform interrupt driven or polled I/O operations. Addresses n + 1 and n + 2 can be used as single word buffers for polled operations with the channel status word (n+ 3) acting as the status word for the CPU to periodically sample (poll). POLLED I/O. —In polled I/O the CPU must regularly check—or poll —each channel or port in turn to determine if it has information for input or is ready to accept data for output. A flag register can be used to check the port’s status. Polling is time consuming. The CPU must pause between executing processing instructions and poll of each port. A port’s status is examined in case action is required by the computer. We use a keyboard as an example of polled I/O. Figure 7-12 shows a read operation. The CPU reads or receives 8-bit encoded characters as they are typed on the keyboard. The CPU is programmed to read the input characters from an external device, in this case a keyboard. The keyboard inputs parallel 8-bit character codes for each depression of the keys. Characters are entered slowly as compared to the CPU’s ability to Figure 7-12.—Polled I/O; read operation. process them. The dedicated CPU has to wait until the next character is entered each time. The CPU is programmed with what is known as an I/O wait loop. As the CPU executes the loop instructions, it periodically (say 20 times a second) checks the status code from the keyboard to see if a character has been entered. A data register, INBUF, in the keyboard interface receives the character data from the keyboard. It holds the data until read by the CPU. A status register, INSTATCODE, indicates whether there is a new character in the INBUF register. By continuously testing the status register, the CPU detects when the code for a data entry is present. The CPU then executes the instructions to transfer the data from the data register to the specified location in the computer. Once this has completed, the CPU returns to the wait loop and polling process. The same procedure can be used for output or write operations. Figure 7-13 shows an output operation. In this case, the data is moved from a computer location to the data output buffer of the output device. One of the disadvantages with polled I/O is that it involves the CPU throughout the input/output process. This is wasteful of CPU time. The CPU spends time executing input/output instructions that it could be spending performing other operations. Direct CPU interface has its place, particularly in small computers that are not concerned with high-speed operations and processing very large amounts of data. Most of the larger computers, however, use interrupt driven I/O. INTERRUPT DRIVEN I/O. —The interrupt technique requires more complex hardware and software, but makes far more efficient use of the computer’s time and capacities. In an interrupt driven I/O the I/O section itself is capable of accessing memory via the computer communication buses. The I/O processor can, while conducting I/O operations, Figure 7-13.—Polled I/O; write operation. 7-15

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read data from memory (output) or write data into memory (input). The CPU still provides overall control of the I/O operations, but it is not directly involved in the actual data transfers between memory and the external equipments. When the I/O section is capable of memory access, the CPU provides I/O commands to an I/O controller (IOC) or processor and then goes about processing other necessary operations. The IOC in turn controls all I/O operations and interrupts the CPU operation when necessary to inform it of event completion or problems with an I/O interface channel or external device. With this method, the CPU concentrates on its essential business of processing information. We use the keyboard again as our example. The keyboard is ready to input characters. The keyboard interface signals the CPU when a valid character is available in its INBUF buffer. The CPU is performing some computational task, when the keyboard sends an interrupt request that generates an interrupt in the CPU. When the interrupt request arrives, the CPU leaves its current task, but not before making arrangements to save all the data from computations just previous to the interruption. The CPU leaves its current task and executes the appropriate service routine. In this case it receives the input from the keyboard interface and promptly sends it to the desired location in the computer. When the information has been routed to its desired location and the input operation has been completed, the CPU returns to its previous task. Review chapter 5 of this volume for a detailed discussion of the interrupt process. An interrupt request can occur at any time. To avoid confusion, most computers use a priority system for requests in the event that two or more interrupts arrive simultaneously. Interrupt driven I/Os use a priority system to honor requests and interrupts. The priority system is divided into channel and function priorities. The channel priority performs priority determination of requests and interrupts based on the channel number. Figure 7-14 reflects channel priority of a computer with 16 channels. Notice how they are grouped and prioritized. Function priority determines the order of honoring requests and interrupts when channel priority honors more than one request per channel. See figure 7-15. Figure 7-14.—Channel priority determination. Depending on the type of computer, interrupts are categorized and the program can be written to meet specific requirements when an interrupt occurs. Some interrupt requests cannot be ignored. For example, when a power failure interrupt occurs, the computer is given the needed time to save information before the computer system shuts down. Direct Memory Access (DMA) When the CPU is directly involved in each of the I/O data transfers, it slows down the process of moving information in and out of the computer. The use of Figure 7-15.—Function priority determination. 7-16

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direct memory access (DMA) gives the computer an advantage— speed. It allows information to be moved quickly in and out of memory without the intervention of the CPU. DMA is given control and takes over from the CPU as director of electronic traffic on the computer’s network of communication buses. It allows blocks of information to be transferred directly in and out of memory and from and to an external device without any CPU intervention. Information is transferred at a speed compatible with the speed of the external device. Therefore, the use of DMA would be advantageous when using a high-speed external device, such as a magnetic disk. The DMA acts the same as an I/O processor; it is just another method to control the flow of informationo A DMA controller is usually placed between the external device and the computer’s bus. The controller uses circuits consistent with the computer’s other major functional areas. The controller consists of several functional parts. Two counter registers are used. One generates the next main memory addresses from which information is read or in which it is stored. This counter register is incremented by successive information transfers. The second counter keeps track of the number of information words that are remaining to be transferred. A data register serves as a buffer between main memory and the external device. And of course, the control circuits, will control DMA operations. Other registers are provided for more complex external devices. In its most usual form, a DMA assumes command of the computer’s bus when the DMA controller receives an interrupt signal from an external device. It then gives the CPU a hold/suspend operations message. The CPU will respond with a hold-acknowledge signal. It turns over control of the bus and then, in effect, takes a short break. Meanwhile, the DMA controller moves information between main memory and the I/O external devices and independently carries out the I/O transfers. The DMA controller will inform the CPU when it is finished with an interrupt. During DMA operations, the CPU performs other tasks. If the CPU and the DMA controller try to access main memory simultaneously, the DMA has priority. TOPIC 4—INPUT/OUTPUT INTERFACING Input/output (I/O) interfacing is affected by many factors. Among them are the method of connection, serial or parallel interfacing, and the type of equipment the computer is interfacing with. Input/output operations allow the computer to communicate with an assortment of external devices. Most computers use an I/O processor of some sort, so we concentrate our discussion in that area. The external devices are connected to the I/O processor via I/O channels or ports. An I/O channel or port is nothing more than the wiring necessary to interconnect the computer’s I/O processor with one or more external devices. The type of interfacing used will dictate the wiring of each channel or port. Computers may have a small number of channels or ports with multiple equipments connected to each channel, or they may, particularly in larger computers, have a number of I/O channels with limited numbers or types of external equipments on each channel or port. METHODS OF CONNECTIONS There is a great deal of variety not only in the types of external devices but also in the methods of connecting them to a computer. One thing that computer external devices have in common is that they communicate with the computer indiscrete binary data. The function of the external equipment may be to convert that data to other forms, but when a data exchange is done over I/O channels, the data exchange is in some form of binary data. We now look at two methods of connecting the external equipments where more than one external device is involved: daisy chaining and independent request control. Daisy Chaining When more than one peripheral device is connected to a single port/channel, a technique called daisy chaining is used. When daisy chained, the peripheral devices receive or transmit information over a common path. A separate set of addressing or control lines is used to identify (address) specific devices and to control the transmission or reception of information. When the CPU dictates the use of the computer’s bus, there is no difficulty in deciding which external device will have access to the computer’s bus. But in more complex situations, such as DMA transfers, simultaneous requests for the computer’s bus may be made by two or more external devices. Then a 7-17

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preset method decides the order in which the devices can use the computer’s bus. Refer to figure 7-16 as you read. An I/O controller of some type will correspond with the external devices. When an external device requests control of the bus, it signals the controller by activating the common bus request line. The devices on the line have ORed connections. The controller acknowledges the use of the bus on a separate line. The I/O controller will scan the chain with an acknowledge signal until it reaches the external device that requested the bus. The external device stop further propagates the acknowledge signal and accesses the bus. When two or more devices request control of the bus, the external devices closest to the I/O controller will be granted access to the bus first. Thus the order of connection on the daisy establishes the priority of which external devices are given access to the computer’s bus. Independent Request Control Independent request control (fig. 7-17) offers a faster and more flexible way to the control bus requests. In this method, separate lines are used for the request and acknowledge lines. The I/O controller assigns priority to each external device, which can be fixed or programmable. A combination of the two methods produces greater flexibility when dealing with simultaneous requests, particularly when dealing with interrupt driven I/O. When signaled on a common interrpt request line, the CPU can poll all external devices in a predetermined order to find which external device needs to be serviced. This method is entirely software. Generally speaking, computers that use a request and acknowledge system, prioritize the functions and the channels. Some of the functions, in descending order, include the following: External Interrupt External Function Output Data Input Data The channels/ports are also prioritized. Equipments are assigned a channel/port and usually the channel with the highest number will be serviced first by the computer. Figures 7-14 and 7-15 apply. I/O INTERFACING STANDARDS There are two major types of computer/extemal equipment communication formats: serial and parallel. The communication formats are governed by the standard that is identified by the interface. The interfacing standards provide valuable information. As a general rule the standards can be divided into four categories: mechanical, electrical, functional, and procedural. The standards can provide other standards that must be adhered to but do not fall into anyone of these four categories. Mechanical —The mechanical portion takes into account such things as the type of connectors to be used, the number of pin connections in the connectors, and the maximum cable lengths allowed. Electrical —The electrical characteristics include the allowable line voltages and the representations for the various voltage levels. Functional —The functional interface specifies such things as which signals—timing, control, data, or ground leads—are to be carried by each pin in the connector. Figure 7-16.—Connecting external devices in a daisy chain. 7-18

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Figure 7-17.—Independent request control. Procedural —The.procedural characteristics define how signals are to be exchanged and the environment necessary to input and output data. No matter the format, I/O interfacing components are generally used by most computers regardless of the computer type. I/O INTERFACING COMPONENTS The computer’s I/O processor, regardless of the type of computer and regardless of the type of format (serial or parallel) must ensure that the voltage levels between the computer and the external equipments are compatible. The primary circuitry that accomplishes this is located on an I/O pcb or modules/pcb’s that make up an IOA. Some of the primary I/O interfacing hardware includes universal receiver transmitters, line drivers, and line receivers. Universal Receiver-Transmitters Within a digital computer, the data is transferred internally using a parallel format. All the bits of a byte or memory word are exchanged simultaneously between registers, buses, and other computer logic. For the data to be communicated over a serial channel, it must be converted from parallel to a serial bit stream. Universal receiver-transmitters come in three types: universal asynchronous receiver- transmitters (UARTs), universal synchronous receiver- transmitters (USRTs), and universal synchronous/ asynchronous receiver-transmitters (US ARTS). A UART, USRT, or USART may be built into the computer or added as part of an I/O pcb or serial interface board. Modern UARTs, USRTs, or USARTs may consist of a single IC chip. We take a look at a USART as an example of this type of logic assembly. The USART is designed to function as a peripheral device to the microprocessor. The microprocessor transmits byte-oriented data (data and command/control words) to the US ART and receives byte-oriented data (data and status words) from the USART. The actual conversion from serial to parallel or parallel to serial is performed by the USART and is transparent to the microprocessor. The standard 7-19

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USART chip (fig. 7-18) is composed of logic circuits, which are connected by an internal data bus. The logic circuits are read/write control logic, modem control, data bus buffer, transmit buffer, transmit control, receive buffer, and receive control. The CPU communicates with the USART over an 8-bit bidirectional tristate data bus. The USART is programmable, meaning the CPU can control its mode of operation using data bus control and command words. The read/write control logic then controls the operation of the USART as it performs specific asynchronous interfacing. READ/WRITE CONTROL. —The read/write control logic accepts control signals from the control bus and command or control words from the data bus. The USART is set to an idle state by the RESET signal or control word. When the USART is IDLE, a new set of control words is required to program it for the applicable interface. The read/write control logic receives a clock signal (CLK) that is used to generate internal device timing. Four control signals are used to govern the read/write operations of the data bus buffer. They are as follows: The CHIP SELECT (CS) signal, when true, enables the USART for reading/writing operations. The WRITE DATA (WD) signal, when true, indicates the microprocessor is placing data or control words on the data bus to the USART. The READ DATA (RD) signal, when true, indicates the microprocessor is ready to receive data or status words from the USART. The CONTROL/DATA (C/D) signal identifies the write operation transfer as data or control words, or the read operation transfer as data or status words. MODEM CONTROL. —The modem control logic generates or receives four control or status signals used to simplify modem interfaces. They are as follows: Figure 7-18.—Universal synchronous/asynchronous receiver transmitter (USART). 7-20

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Data Set Ready (DSR) —A data set ready is sent from the computer to the external device to notify the external device that the computer is ready to transmit data when HIGH. Data Terminal Ready (DTR) —A data terminal ready is sent from the external device to the computer to indicate that the external device is ready to receive data when HIGH. Request to Send (RTS) —A request to send is sent from the external device to the computer to indicate that the external device is ready (HIGH) or busy (Low). Clear to Send (CTS) —A clear to send is sent from the computer to the external device as a reply to the RTS signal. TRANSMIT BUFFER/TRANSMIT CON- TROL. —The transmit control logic converts the data bytes stored in the transmit buffer into an asynchronous bit stream. The transmit control logic inserts the applicable start/stop and parity bits into the stream to provide the programmed protocol. A start bit is used to alert the output device, a printer for instance, to get ready for the actual character (bit). The signal is sent just prior to the beginning of the actual character coming down the line. A stop bit is sent to indicate the end of transmission. The parity bit is used as a means to detect errors; odd or even parity maybe used. RECEIVE BUFFER/RECEIVE CONTROL.— The receive control logic accepts the input bit stream and strips the protocol signals from the data bits. The data bits are converted into parallel bytes and stored in the receive buffer until transmitted to the microprocessor. Line Drivers/Receivers We discussed line drivers/receivers in chapter 4. Their basic function is to drive and receive (detect) the digital signal sent or received over a cable to other external equipments (including computers). The line drivers/receivers are designed to send and receive signals over short and long distances using serial or parallel format. Large voltages or currents are generated from small voltage or current using TTL or MOS circuitry. The two types most commonly used include single-ended and differential. The voltage levels and current amounts sent and received are dictated by the interface. The voltage and current characteristics required are also dictated by the interface. We discuss the voltage levels and some of the characteristics when we cover I/O channel/port configurations that include the various interfaces. I/O INTERFACE FORMATS There is a variety of serial and parallel I/O channel formats that you may encounter as a technician. Do not take for granted the type of interface a computer uses. A single different pin in a connector or a different voltage level used by a computer can make a vast difference when you are performing maintenance. Your computer’s technical manual will provide the standards to be used with the cabinet and cable con- nectors. They will match the standards that govern the requirements for parallel and serial interfacing. Table 7-1, from MIL-STD-2036, General Requirements For Electronic Equipment Specifications, provides you with some of the accepted standard external interfaces. We do not cover the General-Purpose Interface Bus (GPIB), Fiber Distributed Data Interface (FDDI), and TACTICAL. Other interfaces used but not listed in the table include RS-449, Centronics Parallel, ST-506/412, Enhanced Small Device Interface (ESDI), Integrated Drive Electronic (IDE), and Enhanced Integrated Drive Electronics (EIDE). We discuss signal designations in more detail later in this topic under serial and parallel I/O operations. First, let’s look at the various interfaces and some of their applications and any unique characteristics. As stated, each interface is governed by a standard. Table 7-1.—Standard External Interfaces from MIL-STD-2036 7-21

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NTDS Input/Output (MIL-STD-1397) The NTDS input/output interface is probably one of the most versatile of formats because it is designed to handle either parallel or serial formatted information, depending on the type of computer and its I/O requirements. This interface specifies three I/O control and data signal categories. We cover the first two under parallel and serial operations later in this topic. The categories include: Category I —Computer to external device Category II —Computer to computer, intercomputer (IC) Category III —External device to external device Within this standard, there are nine types of formats (A through H and J). They include both serial and parallel formats as described in the following paragraphs. TYPE A (NTDS) SLOW. —Type A transfers parallel data of up to 41,667 words per second on one cable. This type interface uses 0 vdc (logical 1) and -15 vdc (logical 0) to transmit bit groupings of 16,30, or 32 bits, depending on the type of computer. The relatively large voltage change between logic states, with its inherent time delays, limits the speed of data transmission. Type A can transmit digital signals up to 1000 feet. It is most frequently used in large mainframe and some minicomputers to interface with equipment found in the data processing, display, and communication subsystems. Type A uses a request and acknowledge protocol process. It transfers control and data words using two cables: one input and one output for the same channel. You may, however, encounter a few devices that use input only or output only portions of an NTDS slow channel. Type A signal designations for input and output include the following: EIE —External interrupt enable IDR —Input data request EIR —Extemal interrupt request IDA —Input data acknowledge EFR —Extemal function request EFA —External function acknowledge ODR —Output data request ODA —Output data acknowledge TYPE B (NTDS) FAST. —Type B transfers parallel data of up to 250,000 words per second on one cable. This type interface uses 0 vdc (logical 1) and -3 vdc (logical 0) to transmit bit groupings of 16, 30, or 32 bits depending on the type of computer. Type B can transmit digital signals up to 300 feet depending on the type of cable used. It is most frequently used in large mainframe or some minicomputers to interface with equipment found in the data processing, display, and communication subsystems. Type B uses a request and acknowledge protocol process. It transfers control and data words using two cables: one input and one output for the same channel. You may, however, encounter a few devices that use input only or output only portions of an NTDS fast channel. Type B uses the same input and output signal designations as type A. TYPE C (ANEW). —Type C transfers parallel data of up to 250,000 words per second on one cable. This type of interface uses 0 vdc (logical 1) and +3.5 vdc (logical 0) to transmit bit groupings of 16, 30, or 32 bits, depending on the type of computer. Type C can transmit digital signals up to 300 feet depending on the type of cable used. It is most frequently used in large mainframe or some minicomputers to interface with equipment found in the data processing, display, and communication subsystems. Type C uses a request and acknowledge protocol process. It transfers control and data words using two cables: one input and one output for the same channel. You may, however, encounter a few devices that use input only or output only portions of an NTDS ANEW channel. Type C uses the same input and output signal designations as type A. TYPE D (NTDS SERIAL). —Type D asynchronously transfers serial data using a 10 megabits per second (Mb/s) clock rate over a single coaxial cable. Two cables are required for bidirectional communications, a source line (computer to peripheral) and a sink line (peripheral to computer). The source line is used to transmit data and external functions, while the sink line is used to transmit input data and external interrupt codes. Type D transfers are accomplished using two types of bipolar pulse trains: (1) control frames and (2) control and data words. The actual input or output data is transmitted in 32-bit information frames. Control frames are three bits in length, a sync bit followed by two control bits. The signals required for input transfer will occur on the input channel (input request, input enable, and not ready) and the signals required for output transfer will occur on the output channel (output request, output enable, and not ready). A binary 1 will be a pulse of phase zero degrees and will be a high polarity followed by a low polarity. 7-22

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A binary 0 will be a pulse of phase 180 degrees and will be a low polarity followed by a high polarity. Type D can transmit digital signals up to 1,000 feet. TYPE E (NATO SERIAL). —Type E asynchronously transfers serial data of up to 10 million bits per second on single triaxial cable. Channel control is similar to NTDS parallel channels. This type interface uses a bipolar plus or minus 0.6 volt nominal (0.8 volt maximum). Type E can transmit digital signals up to 1,000 feet depending on the type of cable used. It is most frequently used in large mainframes to interface with external equipment found in the data processing subsystems (includes intercomputer communication). Interfacing with an external device uses a normal serial I/O interfacing: enable and request. The channel interface uses a SIS/SOS protocol, transferring control and data words using the following word transfers: external function, output data, external interrupt, and input data. The data (command or data) words are transmitted in serial bursts of up to thirty two 32-bit words (1,024 bits). The burst transmissions are coordinated using Sink Status (SIS) frames or Source Status (SOS) frames. The SIS frame is sent from the receiving device when it is ready to receive a burst. The SOS frame is sent by the transmitting device to inordinate and synchronize the burst transmission. TYPE F (AIRCRAFT INTERNAL TIME DIVISION MULTIPLEX (TDM) BUS). —Type F transfers serial data up to one million bits per second over a distance of 300 feet. A logical 1 will be transmitted as a bipolar coded signal 1/0 (a positive pulse followed by a negative pulse). A logic zero will be a bipolar coded signal 0/1 (a negative pulse followed by a positive pulse). This type interface transmits bit groupings of 20 bits: data, sync wave form, and parity bit. It is most frequently used in large mainframes to interface with equipment found in the data processing subsystems. Type F uses a command/response protocol. Transfers include command, data, and status words over a single channel. This interface can handle up to 32 external devices on one channel; one device must be a bus controller. TYPE G (RS-449). —Type G equates with the functional and procedural portions of RS-232. However, the electrical and mechanical specifications are covered by RS-422. Type G is intended to transfer serial data above 20 kilo bits per second and up to 2 million bits per second over a single cable. Type G can transmit data up to 200 feet. Signals are divided between 37-pin and 9-pin connectors, and the ground and common signals are handled separately for each cable. Type G can send asynchronous serial data up to 9600 bits per second. This type of interface is used to transmit bit groupings of 8, 16, or 32 bits depending on the type of computer. Type G can be used in mainframe and microcomputers. Type G uses primarily a command and response protocol. TYPE H (HIGH-SPEED PARALLEL). —Type H transfers parallel data of up to 500,000 words per second on one cable. This type interface uses 0 vdc (logical 1) and +3.5 vdc (logical 0) to transmit bit groupings of 16, 30, or 32 bits depending on the type of computer. Type H can transmit digital signals up to 300 feet. It is most frequently used in large mainframes to interface with equipment found in the data processing, display, and communication subsystems. Type H uses a request and acknowledge protocol process. It transfers control and data words using two cables—one input and one output for the same channel. It can also interface with external equipment having a type C interface. You may, however, encounter a few devices that use input only or output only portions of an NTDS slow channel. Type H uses the same input and output signal designations as type A. TYPE J (FIBER OPTIC NATO SERIAL).— Type J is used for the fiberoptic implementation of type E. A type J fiber optic channel converts a type E serial bit stream into light pulses that are carried by a fiber optic cable to a receiving device that converts the light pulses back into a digital bit stream. For further details on fiber optics, refer to NEETS 24, Introduction to Fiber Optics. Small Computer System Interface (ANSI X3.131) The small computer system interface (SCSI) uses a digital parallel format. SCSI is pronounced “skuzzy.” The SCSI is an 8-bit parallel, high-level interface. High-level means that instead of a host computer asking for data by specifying a track, cylinder, and sector number, all it asks for is a logical sector number. The SCSI then translates the logical sector number into the actual disk location. The SCSI also has other improvements over previous disk drive interfaces. For example, it can transfer data at rates up to 20 megabits per second, handle hard disk drives of almost any sire, disconnect itself from the host computer’s bus while it processes requests, and daisy-chain up to eight units off of one controller. 7-23

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The SCSI interface uses one 50-pin ribbon cable to connect the hard disk drive(s) to the controller card mounted on the host computer. Some computer manufacturers include the SCSI electronics in their motherboards and do away with a separate controller card. RS-232 (EIA RS-232 and MIL-STD 188) An RS-232 interface uses a serial format. It can be used for asynchronous and synchronous serial transfers. It can be used with mainframes, minicomputers, and microcomputers for communication with external equipments, particularly with microcomputer systems. RS-232 channels/ports are capable of transmitting from 50 to 19,200 baud of 7- or 8-bit asynchronous characters and 7- or 8-bit synchronous characters to 9600 baud. RS-232 limits cable transfers to 50 feet with a maximum transmission speed of 20,000 bits per second. In microcomputers and their external equipments, the configuration of the channel/port is normally hardware controlled through the use of DIP switches. The number of bits per character (7 or 8), baud rate (110, 300, 600, 1200, 4800, 9600, or 19200), parity setting (odd, even, or no parity), and protocol selection (ready/busy or X-ON/X-OFF) are examples of controlled configuration parameters. Some computer systems allow for software control of these parameters but most peripherals that accept the RS-232 have a DIP switch configurat.ion to make them compatible with a variety of computer interfaces. RS-232 serial channel/port uses a 25-pin cable connector (DB-25) and transmits signal levels of +5 to +25 volts (HIGH or SPACE) and -5 volts to -25 volts (LOW or MARK). An RS-232 receives and recognizes transition difference of 6 volts (+3 volts and -3 volts) (fig. 7-19). A positive difference and more than +3 Figure 7-19.—RS-232. volts indicates a HIGH and a negative difference and more than -3 volts indicates a LOW. Signal designations are discussed in serial I/O operations. An interface that uses RS-232 interface signals is VACALES (Variable Character Length Synchronous). It is synchronous to 32,000 baud transferring 1 to 16 bits. RS-422 (EIA RS-422) The RS-422 interface uses a serial format. RS-422 uses RS-232 functional specifications. RS-422 uses two separate wires to allow transmission at a higher rate. This technique, called balanced circuitry, doubles the number of wires in the cable, but permits very high data rates and minimizes the problem of varying ground potential. The high data rates include up to 10 megabits per second in distances of meters and 100 kilobits per second at 1.2 kilometers. RS-422 grounding requirements are much less critical than RS-232. With the elimination of the grounding problem, the receiver transition period is narrower: .4 volt (+.2 volt and -.2 volt). Token Ring (IEEE 802.5) Token ring is used for work group solutions and work station intensive networks. It transfers serial I/O data. It has the ability to operate at a 4- or 16-megabits per second rate of data communication. It allows PCs and mainframes to operate as peers in the same network. In a token-passing ring network, a stream of data called a token circulates through the network stations when they are idle. A station with a message to transmit waits until it receives a free token. It then changes the free token to a busy token, and transmits a block of data called a frame immediately following the busy token. The frame contains all or part of the message the station has to send. The system does not operate by having one station accept a token, read it, and then pass it on. Instead, the stream of bits that make up a token or message might pass through as many as three stations. Once a station becomes a busy station, there is no free token on the line. That means other stations must wait until the receiving station copies the data and the frame continues around the ring until it completes a round-trip back to the transmitting station. This guarantees that only one station at a time transmits data. A typical token ring (fig. 7-20) provides for unlimited expandability by use of multistation access units (MAUs) and hubs (concentrators). 7-24

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Figure 7-20.—A typical token ring network. The recommended cable for a typical token ring setup is two pairs of twisted wire covered by a foil shield. Maximum cable length between the token-ring hub and the attachment point for the network node cannot exceed 150 feet. Provisions are also available for linking hubs through fiber optic cable. Connectors include “D” shell for the twisted pair wire and fiberoptic connectors (MIL-C-28876). Cabling for the token-ring prevents one bad cable from bringing down the entire system. IEEE 802.3 (Ethernet DIX) IEEE 802.3 is a specification that describes a method for computers and data systems to connect and share cabling (i.e., PC’s and mainframes). It transfers serial I/O data in a specific packet format (fig. 7-21). The IEEE 802.3 standard is commonly referred to as Ethernet. Although Ethernet and 802.3 share the same cable access mode (carrier sense multiple access), they differ in both physical implementation and actual packet make-up. Ethernet preceded IEEE 802.3 by almost 10 years. Ethernet was developed by Robert Melcalf at Xerox’s Palo Alto Research Center. Ethernet is the forerunner of IEEE 802.3. Because of the differences in packet formation and physical construction of the equipment associated with each of these standards, the networking community currently follows the original Ethernet standard implementation by the DIX suffix (DIX stands for DEC, Intel, and Xerox, the original collaborators on the Ethernet standard). Figure 7-21.—802.3 and Ethernet packet formats. 7-25

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Figure 7-22.—Manchester code used in Ethernet Both Ethernet (DIX) and IEEE 802.3 can be used on the same data communications network, but they cannot talk to each other. Data in an 802.3 network is encoded using a Manchester code as shown in figure 7-22. The differences between an 802.3 packet and an Ethernet packet can be seen in figure 7-21. When viewing figure 7-21, pay close attention to the items directly below the vertical arrow in order to determine an Ethernet (type field <46) or an 802.3 (length field ≥46). Continuous transitions of the Manchester code allow the channel to be monitored easily for activity. This is part of the Collision Detection/Collision Avoidance characteristics of Ethernet (DIX) and IEEE 802.3. This ability to detect activity allows stations to release the channel after using it for a short period of time, thereby increasing data transmission through-put. Ethernet (DIX) and IEEE 802.3 may use a shielded coaxial cable (RG-58 A/U) to transfer serial data using baseband transmission at 10 megabits per second. Baseband information implies data transmitted without the use of a carrier and with only one channel defined in the system. When a station is transmitting, it uses the entire 10 megabits per second. The data is transferred PC to PC using a daisy chain configuration (fig. 7-23). Thin Ethernet is used in smaller systems using an overall coaxial cable length of 600 to 1000 feet. Thin Ethernet 802.3 uses T-connectors (UG-274) to connect the PCs. Thick-net (RG-11, BIG YELLOW CABLE) is used in larger systems with overall shielded coaxial cable lengths of 500 meters. Thick-net networks employ a file server and a transceiver (fig. 7-24) connected together using 15-pin “D” shell connectors. Terminating resistors are used at the end of each T-connector to ensure proper operation. Ethernet (DIX) and IEEE 802.3 networks are also commonly implemented using shielded and unshielded twisted pair cable. Coaxial cable implementations are known as 10Base5 (RG-58) and 10Base2 (RG-11 Thick-net). Shielded and unshielded twisted pair cable networks are known as 10BaseT. Figure 7-23.—Daisy chain in an Ethernet. 7-26

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Figure 7-24.—Ethernet/IEEE 802.3 transceiver. Centronics Parallel The Centronix compatible parallel channel is the alternate interface to the RS-232 on many microcomputer systems. This channel type is designed to transmit parallel 8-bit bytes over eight data lines simultaneously. The Centronics compatible channel is a single direction channel (output only) as far as data is concerned. Centronics Compatible Parallel uses a Command/acknowledge protocol. There are several control signals sent to the receiving device and status signals returned from the receiving device. We cover signal designation under parallel operations of single cables. ST-506/412 The ST-506/412 interface was developed by Seagate Technology, Inc. It is often used in the hard disk drives installed in older IBM-compatible desktop computers that have a maximum capacity of 125 megabytes. It is also the interface used to control most floppy drives today. This is one of the interfaces where most of the electronics is actually on a controller card mounted in the host computer. With this interface, the controller card does most of the work (moving the magnetic head, spinning the disk, and so on). The controller card also cleans any data coming from the disk drive by stripping off the formatting and control signals that were used to store the data onto the hard drive. A hard disk drive is connected to the controller card in the host computer via two ribbon cables (a 34-pin control cable and a 20-pin data cable). Floppy drives use only the 34-pin control cable to transfer both data and control signals. When this interface was originally developed in 1981, its 5-megabits per second transfer rate was considered too fast. It was actually slowed down by a 6:1 interleave factor so it could operate with the computers being built at the time. With today’s transfer rates pushing the envelop at 24 megabits per second, you can see that it is now one of the slowest interfaces. Enhanced Small Device Interface (ESDI) The enhanced small device interface (ESDI) is an optimized version of the ST-506/412 interface. The main difference is that with ESDI, most of the disk drive’s interface electronics is located in the disk drive itself, rather than on a controller card in the host computer. The result is a much faster transfer rate and more hard disk capacity. ESDIs have a transfer rate of up to 24 megabits per second. And, they can handle disk drives with a maximum capacity of 1.2 GB (gigabyte). The ESDI uses the same interface cables as the ST-506/412 interface, but that is where the similarity ends. With ESDI drives, only the clean data is sent to the controller card in the host computer. All formatting and control signals are stripped off at the hard disk drive. Integrated Drive Electronics (IDE) The integrated drive electronics (IDE) interface was developed as a result of trying to find a less expensive way to build computer systems. It includes all of the controller card electronics in the hard drive itself; thus, the hard drive does all the work. The hard disk drive connects to the host computer’s bus with a 40-pin ribbon cable. The ribbon cable connects directly to either a 40-pin connector on the host computer’s motherboard or a 40-pin connector on 7-27

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a small interface card that plugs into the host computer’s motherboard. This interface offers transfer rates of up to 1 MB and can handle hard drives with a maximum capacity of 300 MB. Enhanced Integrated Drive Electronics (EIDE) The Enhanced Integrated Drive Electronics (EIDE) was developed from the IDE standard. New features available with EIDE include Plug-n-Play compatibility, increased maximum drive capacity, faster data transfers, and the ability to use a CD-ROM or tape drive with an the interface. The IDE interface can address a hard drive with a maximum of 504MB. EIDE increases the maximum size of a hard drive by using an enhanced BIOS. The enhanced BIOS uses a different geometry when communicating with a program than it does when communicating with the hard drive. For example, the BIOS will tell a program that a hard drive with 2,000 cylinders and 16 heads is a drive with 1,000 cylinders with 32 heads. The BIOS controls the address translation to keep track of where the data is physically located on the hard drive. The EIDE interface uses a Programmed Input/output (PIO) mode to transfer data from the drive. There are five PIO modes that can be set to control data transfers. PIO Mode 0 is the slowest with a cycle time of 600 nanoseconds. Pio Mode 4 has a cycle time of 120 nanoseconds, which is 16.6 megabytes per second. Most high-end hard drives will support Mode 3 or Mode 4 operations. Using the enhanced BIOS, the hard disk responds to the Identify Drive command with information concerning the PIO and DMA modes the drive can support. The BIOS will automatically set the PIO mode to match the capability of the drive. If a drive is set to a higher mode than it is capable of supporting, data corruption will occur. I/O SERIAL DATA OPERATIONS Serial data operations exchange information via a single path, line, or wire. The channel/port itself is made up of several wires, but only one is used to transfer the binary data. Bidirectional channels may use two wires for data, one for each direction or a single tristate bidirectional line. The remaining wires are used for device addressing and to provide the protocol (channel control) for information exchange. The data is in the form of an asynchronous or synchronous bit stream. The bit stream is made up of a sequential series of data and/or control pulses in one of these two mutually 7-28 exclusive formats. Serial data operations can use a minimum of 4 conductors and up to 37 conductors to perform serial data operations. Serial operations generally exchange information between data communications equipment (DCE) and data terminal equipment (DTE). The DCE configured device is considered the controller for the interface. The DTE is either the computer or a channel controller. There are variations in the channel pin connections that depend on the device mode of operation (DCE or DTE). Asynchronous Data Exchanges Asynchronous data is also known as character framed data; only one character at a time is sent. Each character is composed of either 7 or 8 bits (depending upon the coding scheme used), and is identified by a start and stop bit. At the minimum, each character is preceded by a start bit and followed by one stop bit. Asynchronous data transmission protocol allows for a maximum of the following in sequence: one start bit, eight data bits, a parity bit, and one stop bit for each character to be exchanged. The purpose of a start bit is to notify the modem that a character is being sent (or received). The bits that make up the character immediately follow the start bit. After all these bits have been transmitted, a stop bit is inserted to indicate the end of the character. Start and stop bits can immediately follow one another or there can be a period of idle time following the stop bit, depending upon the hardware device in use. During an idle condition, in which no characters are sent, a continuous MARK signal (equivalent to a logic 1) is transmitted for one bit time. Asynchronous transmission is normally used when transmission rates are between 600 to 2000 bps. The particular format used varies between computers and may be hardware or software controlled depending on the type of interface logic and devices used. Synchronous Data Exchanges When more speed is required for sending information, synchronous data exchanges fulfill the requirement. Synchronous data is also known as message framed data. The bit stream is divided into blocks of sequential bits grouped into individual messages, without the need for start and stop bits. Again, each character is composed of either 7 or 8 bits. There are two methods for controlling the exchange of messages. External control and timing signals may be

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transmitted over the I/O channel control lines and used to synchronism the message transfer, or the message itself may be preceded and succeeded by a string of special synchronization (sync) characters. The sync characters allow the receiving device to frame and receive the message data. Messages preceded by sync pulses are followed by one or more special synchronization (sync) characters to indicate the end of a particular bit stream. Often several different types of messages are sent over the same channel. The message contents identify the type of message and the destination (addressed peripheral). DCE/DTE Serial I/O Cable Signals With serial operations, one cable will suffice to perform serial I/O operations with an external device. Each of the signal leads is assigned a specific function. These functions can be assigned one of four specific groupings: data (both primary and secondary), control (again, both primary and secondary), timing, and ground. Each of these groupings is indicated by a letter in figure 7-25 and is further described in the legend. We use an RS-232 as our example in this discussion. Although the connector itself is not specified in the standard, a 25-pin connector (such as the one shown in figure 7-25) has become the generally accepted Figure 7-25.—A typical RS-232 female connector. 7-29

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standard for implementing an RS-232 connection. Now, let’s take spin-by-pin tour of the RS-232 interface and look at the signals to see how they function. RS-232 Pin Description The 25 pins of the RS-232 have the following functions: Pin 1, Protective Ground —is connected to the equipment’s chassis and is intended to connect one end of a shielded cable, if such a cable is used. The shield of a shielded cable must NEVER be connected at both ends. Shielded cable is used to reduce interference in high-noise environments. Pin 7, Signal Ground —is the common reference for all signals, including data, timing, and control signals. In order for DCE and DTE to work properly across the serial interface, pin 7 must be connected at both ends. Without it, the interface would not work because none of the signal circuits would be completed. Pin 2, Transmitted Data Pin 3, Received Data —Pins 2 and 3 are the pins of most importance; for if it weren’t for the data that passes through them, the remaining pins would not be needed. Data is normally transmitted in the following manner. The DTE transmits data on pin 2 and receives data from the DCE on pin 3 as described in figure 7-25 and shown in figure 7-26. Figure 7-26 illustrates the absolute minimum wiring required under the RS-232 interface for normal DTE-DCE communication. Pin 4, Request to Send Pin 5, Clear to Send —Pins 4, 5, 6, and 20 are the handshaking signals. These pins establish the communications link. Normally terminals cannot transmit data until a clear to send transmission is received from the DCE. Pin 6, Data Set Ready Pin 20, Data Terminal Ready —Data set ready is used to indicate that the modem is powered on and is not in a test mode (modem ready). In dial-data or dial up applications, data terminal ready is used to create the equivalent of an off-the-hook condition. When the modem is in an auto-answer mode, the DTR is activated in response to the ring indicator and tells the modem to answer the incoming call. Pin 8, Data Carrier Detect —The modem activates the data carrier detect whenever it receives a signal on the telephone line of sufficient strength for reliable communications. Many types of DTE Figure 7-26.—A typical DTE to DCE connection showing the minimum wiring required under the RS-232 interface standard. require this signal before they will accept or trans- mit data. In applications where no modem is present, this pin is normally tied to pin 20, which in most cases is activated whenever the DTE is powered up. Pin 22, Ring Indicator —-The ring indicator signal is the means by which the DCE informs the DTE that the phone is ringing. All modems designed for direct connect to the phone network are equipped with auto answer. That is, the modem is able to recognize standard ringing voltage, indicate the ringing to the DTE, and answer (take the line off-the-hook) when told to do so by the DTE. The DTE tells the modem to answer the phone by activating pin 20, data terminal ready. The 10 pins and signals we have just described to you are the ones most often used of those defined in the RS-232 standard. Pin 15, Transmit Clock Pin 17, Receiver Clock Pin 21, Signal Quality Detector Pin 24, External C1ock —Synchronous modems use the signals on these pins. Pins 15, 17, and 24 control bit timing. Pin 21 indicates that the quality of the received carrier signal is satisfactory. Because the transmitting modem must send something (either a 0 or a 1) at each bit time, the modem controls the timing of the bits from the DTE. In turn, the receiving modem must output a bit and associated timing whenever received. Pin 15 (Transmitter Signal Element Timing—DCE 7-30

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source), and pin 17 (Receiver Signal Element Timing—DTE source) are used for these purposes. Pin 23, Data Rate Select —This entry according to figure 7-25 looks like there should be two pins as- signed, but actually it is either data rate select (DTE source) or data rate select (DCE source). Some modems, called dual-rate modems, allow switching between two transmission speeds. Sometimes the speed is selected automatically by the modem during the initializing sequence, or it may be selected by the transmitting DTE. The signal on pin 23 determines whether the modem uses the low or high speed. Usually the modem at the calling end sets the speed for the connection and informs its DTE. The calling modem signals the speed to the answering modem, which informs the called DTE by activating data rate select (DCE source). Pin 12, Secondary Data Carrier Detect Pin 13, Secondary Clear to Send Pin 14, Secondary Transmitted Data Pin 16, Secondary Received Data Pin 19, Secondary Request to Send —Some modems are equipped with both primary and secondary channels. The five secondary signals listed allow control of the secondary channel in the same way as described for the primary channel (pins 2, 3, 4, 5, and 8). In these modems, the primary transmission channel usually has the higher data rate, and the secondary channel transmits in the reverse direction with a much lower data rate, for example, 75 bps. Other signals that could be used (depending on the interface used) but not discussed include: send common, receive common, terminal in service, new signal, select frequency, local loopback, remote loopback, test mode, select standby, and standby indicator. I/O PARALLEL DATA OPERATIONS Parallel data operations provide a multiwire communication path between the computer and one or more peripheral equipments. Parallel data operations use a request/acknowledge protocol. Generally speak- ing, a parallel channel is designed to transfer all the bits of a given byte or memory word, depending on the size of the computer and interface requirements, simultane- ously. There is a separate data path or line for each bit that makes up the byte or word. The parallel channel handles data bytes or words in the same manner as the inter- nal workings of the computer. There is no requirement to convert the byte or word to a sequential bit stream as there is in serial channel operations. There is, however, the need to drive or receive (detect) the digital signals over the I/O cables. The IOA or line driver/receiver on a pcb provides the means to accomplish this. With parallel operations, there are two ways the computer can communicate with each external device. The computer can use a single cable to handle the parallel input and/or output operations or two cables: an input cable for the computer to receive information from an external device and an output cable for the computer to send information out to the same external device. The two cables will constitute one channel. Some computers can have up to 64 I/O channels. The I/O channels are usually identified by the octal numbering system. Thus, if you had a computer with 16 channels, the octal number assignments would be 0 8 through 178. Also, the channels are often arranged in groups with 4 channels per group. The parallel channel itself (fig. 7-27) consists of 8 or more data lines (8, 16, Figure 7-27.—Example of parallel channel architecture (two cables). 7-31

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30, 32, 64, and so forth), and a number of control lines for passing signals that govern the transfer of information and coordinate operations of the computer and the peripheral device. In most computers, the data lines themselves are used to transmit control information (external functions) to the peripheral device, and to pass device status (status words and interrupt codes) to the computer. We discuss parallel computer to external devices data operations using one and two cables; then we discuss intercomputer parallel data operations. Computer to External Equipment (Single Cable) With the computer to external equipment (single cable) set up, all the signals required to carry out parallel data operations are contained on a single cable. The number of lines in this setup can vary from 7 to 25; it will depend on the computer and the external device(s). We use an 8-bit computer as example of the lines used by a single parallel cable format (fig. 7-28). Other signals that amid be used, but are not discussed, include: page end, auto feed, error, initialize external device (specific device name), and select input. GROUND. —The ground signal ensures there is a complete circuit so there is current, thus enabling the signals to flow through the conductor and not collect at one end of the circuit (conductor). There are two grounds: one is a signal ground and the other a chassis ground connected to the device’s chassis or ground. These signals do not move in either direction. DATA STROBE. —The data strobe is sent from the computer to the external device. This signals the Figure 7-28.—Single parallel cable. external device that information is ready to be read from the data lines. The computer first puts the signals for all the data bits on the data lines, waits briefly to be sure the signal is stable, and then activates the data strobe line. When the external device sees that the data strobe signal has been sent, it accepts the character from the eight data lines. BUSY SIGNAL. —The busy signal is sent from the external device to the computer to tell it not to send any more data. The external device may be busy for various reasons. For example, it may still be in the process of obtaining information or the buffer maybe full. SELECT SIGNAL. —The select signal usually corresponds to some sort of switch that must be in the enabled position by the external device. An example is an ONLINE switch on a printer. If it is disabled, the computer will be able to sense that something is wrong. ACKNOWLEDGE SIGNAL. —The acknowl- edge signal is sent from the device to the computer to say that it has successfully received information (a character is this case). Thus instead of sending information at a constant rate, the computer waits for a positive indication that each character has been received before sending the next one. DATA LINES. —Input/output data and interrupt bits are sent or received from the computer on these lines. Single Cable Sequence of Events The general sequence of events for a single cable parallel operations is as follows: 1. The computer puts the character on the data lines and sends the data strobe signal to tell the external device the data is there. 2. As soon as the external device sees the data strobe, it turns on the busy signal, telling the computer to wait while it reads the character from the data lines into its buffer. 3. Once the external device has processed the character, it sends the acknowledge signal and simultaneously removes the busy signal. 4. This tells the computer that it is all right to send another character and the process is repeated. 7-32

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Computer to External Equipment (Two Cables) Two cables will makeup one channel. As stated with two cables, one cable will specifically handle input functions and the other cable will handle output functions. Refer again to figure 7-27. Notice the direction of information flow. Data request signals are always sent from the external equipment to the computer. The acknowledge signals are always sent from the computer to the external equipment. INPUT CABLE. —The input cable contains control lines and data lines. The number of lines will vary with the type of computer. They range from 8 to 64 lines. The operating mode (single, dual, and so on) has an effect on the number of lines affected. External devices send input data words and interrupt codes to the computer via input data (ID) lines. The information carried over these lines is as follows: External Interrupt Enable (EIE) —The computer sends the external interrupt enable signal to the external device to indicate it is ready to accept an external interrupt code word on that channel. Input Data Request (IDR) —The input data request control signal accompanies each input data word sent to the computer from the external device. The external device informs the computer that it has placed an input data word on the lines. External Interrupt Request (EIR) —The external interrupt request control signal accompanies each interrupt code sent to the computer from the external device. It informs the computer that an interrupt code is on the data lines. Input Data Acknowledge (IDA) —The input data acknowledge control signal informs the external equipment that the computer has sampled the input word or interrupt code on the input data lines on that channel. OUTPUT CABLE. —The output cable contains control lines and data lines. Again the number of lines will vary with the type of computer. They range from 8 to 64 lines. The operating mode (single, dual, and so on) has an effect on the number of lines affected. Output data words and external function words are sent to the external device via data lines. The information carried over these lines is as follows: External Function Request (EFR) —The external device sends the external function request signal to the computer indicating that it is ready to accept an EF code word on that channel. External Function Acknowledge (EFA) —The computer sends the external function acknowledge signal to the external device indicating that it has placed an EF code word on the OD lines of that channel. This signal accompanies each function code word sent to the external device. Output Data Request (ODR) —The external device sends the output data request control signal to the computer indicating that it is ready to accept an output data word. Output Data Acknowledge (ODA) —The computer sends the output data acknowledge signal to the external device indicating it has placed a word of data on the OD lines of that channel. This signal accompanies each output data word sent to the external device. It informs the external device that an output data word is on the data lines. Two Cable Sequence of Events The sequence of events using an input, output, external function (buffered), and external interrupt operations is described from the computer’s point of view. We begin from the point that an input data (ID), output data (OD), an external function (EF), or an external interrupt (EI) has been established for a channel. The computer and the external equipment on that channel transfer data as described in the following paragraphs. Refer back to figure 7-27. INPUT DATA (ID) SEQUENCE OF EVENTS. —We begin from the point that an ID has been established for a channel. The computer and the external equipment on that channel will do the following to transfer data: 1. 2. 3. 4. The external equipment places a word of data on the ID lines.. The external equipment sets the IDR line to indicate that a word of data is on the ID lines. The computer detects the setting of the IDR line in accordance with internal priorities. The computer samples the data word that is on the ID lines. 7-33

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5. The computer sets the IDA line, indicating that it has sampled the data word on the ID lines. 6. The external equipment detects the setting of the IDA line. The external equipment may clear the IDR line anytime after detecting the setting of the IDA line, but will clear the IDR before the computer will recognize the next IDR. 7. The computer clears the IDA line before reading the next word on the ID lines. OUTPUT DATA (OD) SEQUENCE OF EVENTS. —We begin from the point that an OD has been established for a channel. The computer and the external equipment on that channel will do the following to transfer data: 1. 2. 3. 4. 5. 6. 7. When the external equipment is ready to accept data, it sets the ODR line (this may already have happened before the OD buffer was established). The computer detects the setting of the ODR line in accordance with internal priorities. The computer places a word of data on the OD lines. The computer sets the ODA line to indicate that a word of data is on the OD lines. The external equipment detects the setting of the ODA lines. (The external equipment may clear the ODR line anytime after detecting the setting of the ODA, but clears the ODR line before the computer will recognize the next ODR). The external equipment samples the data word that is on the OD lines. The computer clears the ODA line before placing the next word on the OD lines. EXTERNAL FUNCTION (EF) SEQUENCE OF EVENTS (NORMAL). —We begin from the point that an EF has been established for a channel. The computer and the external equipment on that channel will do the following to transfer: 1. When the external equipment is ready to accept an EF code word, it sets the EFR line (this may have already happened before the EF buffer was established). 2. The computer detects the setting of the EFR line in accordance with internal priorities. 3. The computer places an EF code word on the OD lines. 4. 5. 6. 7. The computer sets the EFA line to indicate that the EF codeword is on the OD lines. The external equipment detects the setting of the EFA line. The external equipment may clear the EFR line anytime after detecting the setting of the EFA line, but clears the EFR line before the computer will recognize the next EFR. The external equipment samples the EF code word that is on the OD lines. The computer clears the EFA line before placing the next word on the OD lines. Forced external functions are the same as normal external functions except the computer does not require an external function ready signal from the external equipment, so the computer will not be delayed by steps 1 and 2. EXTERNAL INTERRUPT (EI) SEQUENCE OF EVENTS. —The computer and the external equipment do the following to transfer an EI code word: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. The computer, under program control, sets the EIE line when ready to accept an EI. The external equipment detects the state of the EIE line. When the status requires that the computer be interrupted, the external equipment places an EI code word on the ID lines. The external equipment sets the EIR line to indicate that the EI code word is on the ID lines. The computer detects the setting of the EIR line in accordance with internal priorities. The computer samples the EI codeword that is on the ID lines. The computer clears the EIE line. The computer sets the IDA line. The external equipment detects step (8) or both steps (7) and (8). The external equipment may clear the EIR line anytime after detecting the setting of the IDA line, but clears EIR line before the computer will recognize the next EIR. The computer clears the IDA line before sampling the next word on the ID lines. NOTE: Not all computers have the EIE lines; consult your computer’s technical manual. 7-34

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The computer and external device repeat these sequences for each successive word of data until they have transferred the block of data words specified by the input buffer control words. Intercomputer I/O Operations Parallel channels are often used to communicate between two stand-alone computers. In this mode, the computers will appear as external devices to each other. One computer will be designated the transmitting (outputting) computer; the other computer will be designated the receiving (input) computer. A similarity exists between intercomputer channels and normal channels. The two cables are identical; in this mode all the signals remain the same except ODA and ODR, which become ready and resume respectively. Figure 7-29 illustrates the interface between two computers. The two types of information transferred over the intercomputer channels data lines are command words and data words. Command words are used to exchange external function data, which includes external functions, forced external functions and external function buffer words, between the transmitting computer and the receiving computer. Data words are sent as part of output data buffers from the transmitting computer and accepted as part of the receiving computers input data buffer. Command words use additional interface signals to identify their function and to coordinate their transfer. When the transmitting computer generates an external function acknowledge signal with the ready signal, the data word transmitted is identified as a forced external function or an external function command word. The external interrupt enable signal is set to identify the command word as an external function command word. If the external interrupt enable is not set, the command word is a forced external function. The sequence of events for intercomputer command word and data transfers is as described in the following paragraphs. INTERCOMPUTER COMMAND WORD TRANSFER (BUFFERED). —Whenever the transmitting computer has an EFR line and the receiving computer has an EIE line, transfer of buffered command words is possible. As you read, refer to figure 7-29; we designate computer A as the sending computer and computer B as the receiving computer. Whenever an EF buffer has been established in the transmitting computer for a channel, the transmitting computer and the receiving computer do the following to transfer a command word: 1. 2. 3. Computer B, under program control, sets the EIE line when it is ready to accept an EF command word from computer A. In accordance with internal priority, computer A recognizes the EIE as an EFR and places the EF code on the data lines. The EF command word will be held on the data lines until computer B sets the resume line or until computer A’s program intervenes to resolve the no resume condition. Computer A sets the EFA line to indicate that the EF command word is on the OD lines. Figure 7-29.—Intercomputer interface. 7-35

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4. 5. 6. 7. 8. In accordance with internal priorities, computer B detects the setting of the EFA line of computer A (which will be recognized as the EIR line) and samples the ID lines. Computer B clears the EIE line. Computer B sets the IDA line. Computer A detects the setting of the IDA line of computer B (which will be recognized as the resume line). Computer A clears the EFA line before placing the next word on the OD lines, and computer B clears the IDA line before reading the next word on the ID lines. NOTE: Whenever the transmitting computer does not have an EFR line, or the receiving computer does not have an EIE line, a command will be transferred with force. For forced transfers, step 3 and step 7 are not used. Computer A and computer B repeat this sequent for each successive command word until they have transferred the block of command words specified by computer B’s EF buffer control words. INTERCOMPUTER DATA TRANSFER. — Whenever an OD buffer has been established in computer A and an ID buffer has been established in computer B for the same channel, computer A and computer B transfer data. Again refer to figure 7-29 with computer A as the winding computer and computer B as the receiving computer. The sequence is performed as follows: 1. 2. 3. 4. 5. Computer A places a word of data on the OD lines. The OD word is held on the data lines until computer B sets the resume line, or until computer A’s program intervenes to resolve the no resume condition. Computer A sets the ready line to indicate that a word of data is on the OD lines. In accordance with internal priorities, computer B detects the setting of the ready line of computer A (which will be recognized as the IDR line). Computer B samples the ID lines. Computer B sets the IDA line. 7-36 6. 7. Computer A detects the setting of the IDA line of computer B (which will be recognized as the resume line). Computer A clears the ready line before placing the next word of data on the OD lines, and computer B clears the IDA line before sampling the next word of data on the ID lines. Computer A and computer B repeat this sequence until they have transferred the block of words specified by the buffer control words. Buffer lengths specified by each computer are the same. SUMMARY—INPUT/OUTPUT (I/O) AND INTERFACING This chapter has introduced you to how computers communicate with and control other computers and external devices. The following information summarizes important points you should have learned: I/O ORGANIZATION —All computers are capable of I/O operations. Some rely on the CPU to handle I/O operations. Others have an I/O processor (IOC). An I/O processor enables the computer to perform other operations while still performing I/O operations. I/O PROCESSOR —An I/O processor (IOC) controls the transfer of information between the computer’s main memory and the external equipments. IOCs are packaged in (1) IOC/IOA modules or multiple IOC/IOA pcb’s, and (2) I/O pcb’s. The IOC relieves the CPU of the necessity to perform the time consuming functions of establishing, directing, and monitoring transfers with external equipments. Data and control signals are exchanged with external equipments via the IOA. The IOA changes the input and output control and data signal voltages to the voltage requirements of the computer or external equipments. Communication between the IOC and the IOA is by means of a bidirectional bus. I/O DATA ARRANGEMENTS —The types of information exchanged between the computer and the external equipments fall into two basic categories: data words and control words. Data words represent the alphabetic and numeric information exchanged. Control words specify an action to be accomplished by an external equipment. I/O DATA FORMATS —Computers exchange data in either parallel or serial format. When the computer uses a parallel configuration, all bits of information represented by a byte or word are input or

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output simultaneously. When the computer uses a serial configuration, all bits of information are input or output one at a time. I/O INSTRUCTIONS —All computers have I/O instructions. Command instructions are executed by the IOC under the control of the CPU’s main program. They provide control over IOC single-and dual-channel operations. A chain consists of IOC control words, command words, output data words, and specified locations for external status words and data words returned (input) from the channel. I/O OPERATIONS —Input/output operations are initiated by the CPU. Computers with an IOC begin I/O control functions only after an initiate I/O or equivalent instruction is executed by the CPU. Computer instructions inform the external equipment which type of operations to perform with function codes. They also specify memory areas for input and output information. OPERATING MODES —I/O operations include both digital and linear ICs. The linear IC circuits are the first and last type of circuitry the information interfaces with when entering and leaving the computer. Registers in I/O operations provide the interfacing between the CPU, I/O, and memory. They enable and route control and data information between the CPU, I/O, and memory using the internal bus system. The data registers are used to hold or buffer data during interchanges between the very fast CPU and the slower external equipments. The status registers hold information for the CPU that indicates the operating condition and current activities of the external equipments. I/O FUNCTIONS —The input and output functions performed by an I/O processor are defined and enabled through the interpretation and execution of input/output and/or input/output controller (I/O(C)) commands obtained from main memory. DIRECT CPU INTERFACE —With direct communication, also called accumulator-based I/O, the peripheral devices are tied directly into the CPU communication bus (control bus, data bus, and so forth). In a simple I/O scheme, the CPU handles all I/O transactions by executing one or more instructions for each word of information transferred. DIRECT MEMORY ACCESS (DMA) —DMA allows blocks of information to be transferred directly in and out of memory and from and to an external device without any CPU intervention. Information is transferred at a speed compatible with that of the external device. A DMA controller is usually placed between the external device and the computer’s bus. I/O INTERFACING —Computers may have a small number of channels or ports with multiple equipments connected to each channel; or they may, particularly in larger computers, have a number of I/O channels with limited numbers or types of external equipments on each channel or port. I/O INTERFACING STANDARDS —There are two major types of computer/external equipment communication formats: serial and parallel. The communication formats are governed by the standard that is identified by the interface. As a general rule, the standards can be divided into four categories: mechanical, electrical, functional, and procedural. I/O INTERFACING COMPONENTS —The computer’s I/O processor must ensure that the voltage levels between the computer and the external equipments are compatible. The primary circuitry that accomplishes this is located on an I/O pcb or modules/pcb’s that make up an IOA. Some of the primary I/O interfacing hardware include universal receiver-transmitters, line drivers, and line receivers. UNIVERSAL RECEIVER-TRANSMITTER — Within a digital computer, the data is transferred internally using a parallel format. All the bits of a byte or memory word are exchanged simultaneously between registers, buses, and other computer logic. For the data to be communicated over a serial channel, it must be converted from parallel to a serial bit stream. The USART is designed to function as a peripheral device to the microprocessor. The actual conversion from serial to parallel or parallel to serial is performed by the USART and is transparent to the microprocessor. The standard USART chip is comprised of logic circuits, which are connected by an internal data bus. LINE DRIVERS/RECEIVERS —The line drivers/receivers are designed to send and receive signals over short or long distances using serial or parallel format. Large voltages or currents are generated from small voltage or current using TTL or MOS circuitry. The two types most commonly used are single-ended and differential. I/O INTERFACE FORMATS —There is a variety of serial and parallel I/O channel formats. Your computer’s technical manual will provide the standards to be used with the cabinet and cable connectors. They will match the standards that govern the requirements for parallel and serial interfacing. 7-37

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I/O SERIAL DATA OPERATIONS —Serial data operations exchange information via a single path, line, or wire. The channel/port itself is made up of several wires, but only one is used to transfer the binary data. INTERCOMPUTER I/O OPERATIONS — Parallel charnels are often used to communicate between two stand-alone computers. In this mode, the computers will appear as external devices to each other. One computer will be designated the transmitting (outputting) computer; the other computer will be designated the receiving (input) computer. Learn all you can about how input/output operations enable the computer to communicate with and control the variety of equipments used in today’s computer systems. Learn about the internal I/O process and the interfacing process. This will help you to troubleshoot and diagnose input/output problems and to repair and/or replace I/O parts. 7-38

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CHAPTER 8 COMPUTER INSTRUCTIONS AND MAN/MACHINE INTERFACES INTRODUCTION You have probably heard people talk about the various computer programming languages used to write computer programs. Maybe you have even written some. Programming languages include procedural-type languages. Examples are COBOL (COmmon Business Oriented Language) to solve business-type problems, and FORTRAN (FORmula Translation) to solve mathematical-type problems. Other languages are interactive languages that enable a person to communicate with a computer in a conversational mode to develop programs. BASIC (Beginner’s All-purpose Symbolic Instruction Code) is an example of an interactive language. Another language called Ada is the language developed for the Department of Defense for use in embedded applications; for example, where a computer serves as a control system. (Ada is named for Ada Augusta Byron, Countess of Lovelace, for her achievements relating to computers. She was a full collaborator and suggested the use of the binary system rather than the decimal system to Charles Babbage, who is recognized as the father of computers.) These are all considered high-level programming languages in that their instructions are in human readable form, such as ADD A to B; LET X = Y; IF A > Y, THEN PRINT Y; and so on. These types of instructions must be translated into machine code for execution by a computer. This is accomplished through special language translation programs. For high-level languages, a compiler program maybe used. There are two other levels of computer languages: assembly language and machine language. Assembly languages use mnemonics, symbols, to represent operations. For example, “A” might mean add and “STR” might mean store. Like high-level languages, these must be translated before a computer can execute the instructions. To translate assembly language programs, an assembler program is used. By now, you have probably noticed that for an instruction to be executed, it must be in machine code that consists of a series of 0’s and 1’s—the only things a computer can understand. You have probably also realized that to write instructions in 0’s and 1’s would be tedious, difficult, and time consuming. Therefore, the assembly languages and the high-level languages provide easier means for people to use to interface with computers to specify the steps a computer is to perform. As a technician who is looking primarily at the internal functions of a computer, you need to understand machine code and how it works. Some of the operator/maintenance panels display information in binary, as you have already learned. It will be up to you to interpret codes as meaningful information. Other displays present information in commonly used words, terms, and numbers. In these cases a computer, through program instructions, translatet/interprets the binary codes into meaningful information. This information is then presented to you. 8-1

CHAPTER 8

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As we have just said, the machine instructions (code) provide the computer with the means to carry out various operations; both internal and external. Internal and external operations include processing the data and interfacing with other computers, peripherals, and display and communications systems as part of a computer system and performing maintenance. The man/machine interfaces enable you to communicate with the computer’s hardware and software through controlling devices and software/programs. After completing this chapter, you should be able to: Describe and recognize instruction types and their uses Describe the types of instructions, their designator and classes, used by computers Describe how to interface with a computer’s hardware and software We begin by discussing computer instructions; program types; and instruction levels, types, interpretation, formats, sizes, and operand addressing. TOPIC 1—COMPUTER INSTRUCTIONS Computer instructions tell the equipment to perform a designated operation. These machine instructions are contained in an instruction set (the computer’s repertoire of instructions). They will be processed by the CPU. Some computers have an I/O controller (IOC) unit with its own set of instructions. Each instruction in the set/repertoire contains at least an operation (op) code to tell the CPU what operation to perform. It may also contain an operand to identify the address part of the instruction and/or other information (designators) needed by the CPU to perform the operation. Before we discuss individual instruction types and formats, let’s look at some of the types of computer programs/software commonly used. TYPES OF COMPUTER PROGRAMS/SOFTWARE A computer program is a sequence of instructions, written in a specified way to perform a plan (an algorithm) and/or routine. Programs are written to manage a computer and its resources, solve a problem or type of problem, and/or diagnose malfunctions in a computer. Programs include hardwired (read-only) programs stored in a read-only memory (ROM) or programmable ROM (PROM). They also include programs that were written by programmers and can be altered (authorized software changes) as required. Hardwired programs are installed at the factory and cannot be altered except by replacing the ROM or reprogramming the PROM. Other programs are generally stored on magnetic media (tape or disk) or on optical compact disk (CD) ROM. These programs are loaded into computer memory when needed. You will encounter several general types of programs. These include operating systems, application/operational programs, and utility programs (utilities). Programs may be written to run on a stand-alone computer or interactively on two or more computers connected together. Operating Systems An operating system is a collection of many programs used by a computer to manage its own resources and operations. The types of operating systems include the following: Single tasking Multitasking Real-time Local-area network Wide-area network 8-2

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Virtual (VOS) Disk (DOS) Operating systems provide the link between the hardware and its user as well as enabling the execution of operational and/or application programs designed for specific use. Application/Operational Programs Programs for the computers you maintain will be used in tactical, tactical support, and nontactical platforms. These programs are designed to solve specific types of problems. They are commonly called application programs, operational programs, or processing programs. The programs used in tactical or tactical support platforms, such as CDS/NTDS or ASWOCs, are generally called operational programs. The programs used with the SNAP systems (I and II) are, as a rule, called application programs. Programs available commercially that are designed to solve specific classes of problems are often called packaged software or off-the-shelf software. These include word processing, database management, graphics, spreadsheet, and desktop publishing programs to name a few. Utility Programs Utility programs include general routines or diagnostics run by the computer to test other equipments or itself. A programmed operational and functional appraisal (POFA) to test magnetic tape units and a diagnostic test for a computer are examples. Utilities can be run as stand-alone programs, such as microcomputer diagnostics, a maintenance test program (MTP), a POFA, and a standard test program (SIP) using a standard test driver (STD). They can also be run as part of an operating system (if memory permits) or as online diagnostic tests such as on a SNAP system or NTDS. Utility programs also include programs and routines to perform general routine tasks, such as disk/tape copy and print. These, too, can be stand-alone programs or they maybe included with the operating system or other programs. LEVELS OF INSTRUCTIONS The CPU executes machine instructions, which manipulate the data within the functional units of the computer. In early computers, only one level of machine instructions was used. In modern computers, this only remains true in microprocessors and most microcomputers. For most computers, there are now two levels of machine instructions: microinstruction and macroinstructions. In larger microprocessor- based devices (minicomputers and mainframes), each microinstruction is in effect a predetermined and installed set of microinstruction. The particular device’s instruction set is made up of the highest levels (micro or macro) of machine instructions. The instruction set is the complete set of individual operations that can be executed or performed by the particular microprocessor or computer. In microprocessors, microcomputers, and microprocessor controlled peripherals, the machine instructions are referred to as microinstruction, and the microprocessor executes them to perform the desired operations. In mini and mainframe computers, the machine instructions are actually macroinstructions. Once again, a microinstruction is a predetermined or preset sequence of microinstruction. Since most of the larger devices are microprocessor driven, it is necessary to break down the larger macroinstruction into a series of smaller events that a microprocessor can handle. The microinstruction that make up the macroinstructions do not normally concern the computer programmer who uses only the microinstruction set. The microinstruction are usually stored in some form of local memory, accessible only to the microprocessor translating and executing the macroinstructions. Instruction sets differ to some degree between computers, particularly between those of different manufacturers, types, and generations of computers. The actual number of instructions in an instruction set has a direct affect on the overall operation of the device. Computers with small instruction sets are easier to understand, and this simplifies both programming and maintenance. A large instruction set tends to support more specialized activities or functions that make the overall operation of the device more efficient or more tailored to the user’s requirements. An example of a large instruction set is one used on large mainframes aboard a ship. TYPES OF INSTRUCTIONS The flow of data in a computer is the result of instruction execution. Data can be exchanged between registers. It can be moved from one register to another. It can be moved from a register to a memory location or vice versa. Arithmetic instructions can be performed using the contents of registers and memory locations. Logical instructions can be used to isolate bits in 8-3

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registers and memory locations. How machine instructions within an instruction set are classified differ by computer type and manufacturer. Instructions classified by Function Instructions can be classified in general terms by the type of operation they perform—data movement, transfer of control or program sequencing, arithmetic, and logical. MOVEMENT INSTRUCTIONS. —Movement instructions literally move the data in some way. They include internal, external, and data assignment instructions. Internal Instructions. —Internal instructions move the data within the confines of the computer. They include the following examples: Load —Load the A register with the contents specified by the operand Move (transfer) —Move the contents of one register to another register Store —Store the contents of a register into a specified memory address External Instructions. — Instructions dedicated to I/O are external instructions. They include inputting data from a peripheral device, such as a magnetic tape unit or outputting data to. a peripheral, such as a printer. Data Assignment (Special-Purpose) Instructions.— Data assignment instructions include those that set or clear status indicating bits that are normally held in an active status or flag register. Some examples of active status registers include state indicators, upper/lower control indicator of half-word instructions, interrupt lockouts, memory lockout inhibit, bootstrap mode, fixed point overflow, and compare designators. Some examples of flag bits are equal to zero, sign (+ or –), carry, and parity (odd or even). TRANSFER OF CONTROL OR PROGRAM SEQUENCING CONTROL INSTRUCTIONS.— Transfer of control or program sequencing control instructions enable the programmer to change the sequence in which instructions are executed by branching to another area of a program. They also include instructions for a subroutine to perform a functiono Branching Instructions. —Branching instructions make it possible to change the sequence in which the 8-4 computer performs instructions. An unconditional branching instruction always causes a jump to a new area of memory. An example is a jump (JMP) instruction. Branching instructions often use a modifier in the instruction to establish a condition to be met. These types of branching instructions are called conditional branching instructions. A conditional branching instruction causes a jump to a new area of memory only when a specific condition is met, such as IF A = 0 JUMP TO. . . . A conditional branching instruction may also rely on the setting of a switch on the computer’s controlling device to be included with the instruction, such as IF JUMP 1 SWITCH IS SET JMP TO . . . . Subroutine. —A subroutine may include a function that is routinely repeated, such as incrementing or decrementing an index register or a short multiply routine when no multiply instruction exists. Some functions performed in a subroutine may include stack pointer management and data buffering algorithms such as last-in, first-out (LIFO) and first-in, first-out (FIFO) methods. ARITHMETIC INSTRUCTIONS. —Arithmetic instructions include add, subtract, multiply, divide, shift, increment, decrement, clear, and negation instructions. Depending on the design of the computer, absolute numbers are involved in arithmetic calculations. Also depending on the design, math pac and numeric data coprocessor are used in some computers in addition to the normal arithmetic instructions available. They execute the arithmetic instructions the CPU’s ALU cannot and are still controlled by the CPU’s program control. LOGICAL INSTRUCTIONS. —Logical in- structions include and, or, not, exclusive or/nor, com- pares, and shift instructions. They are often used in computers with multiply or divide instructions, in calculations to isolate bits. They also include compare type instructions. Compare type instructions are greater than (>), less than (<), equal to (=), not equal to (<>), check for positive, and check for negative. Instructions Classified by Their Action on Operands Instructions may also be classified by their action on an operand. They may read, store, or replace an operand. For example, ADD LOGICAL PRODUCT is classified as a read instruction; STORE LOGICAL PRODUCT is classified as a store instruction; and REPLACE SELECTIVE CLEAR is classified as a

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replace instruction. Figure 8-1 illustrates instructions with their classification (read (R), store (S), or replace (RP)). Read —Read instructions acquire an operand from main memory. Store —Store instructions process an operand already acquired and store it in main memory. Replace —Replace instructions acquire and process an operand and then store it in memory. INSTRUCTION LANGUAGE INTERPRETATION The instruction format provides the means to customize each instruction. A list of instructions with their formats, symbols, and meanings provides you a means to interpret what an instruction will ultimately accomplish. This is a very useful troubleshooting tool to help isolate a specific malfunction. The in- structions differ between types of computers. Take a Figure 8-1.—Examples of computer instructions. 8-5

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few minutes to study figures 8-2, A and 8-2, B. Figure the op (function) in hex or octal, operation or name, 8-2, A shows two examples of instructions used in mnenonic, and description or Boolean/ arithmetic tactical data systems. Figure 8-2, B shows examples of operation. You will also notice the parts peculiar to a instructions used on a typical general-purpose specific computer and its instructions. Among those microcomputer. By looking at the information are addressing modes, status indicating registers, provided about an instruction, you will be able to tell coding format, and soon. Figure 8-2, A.—Examples of instruction interpretations for two mainframe computers. 8-6

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Figure 8-2, B.—An example of instructions for a typical microcomputer. INSTRUCTION FORMATS normally defines the location that contains the operand Instruction formats vary between microprocessors and minicomputers and mainframe computers. As the machine instructions are generally longer in larger computers with their larger memory words, the instruction format or how the instruction is translated differs. Each instruction is composed of fields. The lengths of instructions and the lengths and positions of the fields differ depending on the instruction and the computero An operation (function) code is part of all instructions. How the remainder of the instruction is translated and the names assigned to the parts vary. Let’s take a look at two examples of computer instruction formats, one for a microcomputer and one for a mainframe. We begin with the op (function) code, which is common to both; only the length differs. A typical machine instruction begins with the specification of an operation to be performed, the operation (op) code. Refer back to figure 8-1. The op code tells the computer/processor what basic operation to perform. The op code, apart of every instruction, is usually located at the beginning of each instruction format. Following the op code is information, if needed, to define the location of the data or the operand on which the operation is to be performed. This location in memory, called the operand address, at the start of the operation (the source), or that will contain the modified operand upon completion of the operation (the destination). The remainder of the instruction and how it is structured differs from one computer or computer type to another. The designators in each field and the positions of the fields within the instruction determine how the instruction will affect the operand, registers, memory, and general flow of data in and out of the computer. We discuss the fields and the designators as we discuss the two instruction formats. Microcomputer Instruction Formats A basic 16-bit microinstruction is divided into a number of separate fields. Refer to figure 8-3 as a reference. You’ll notice the lengths of the fields vary. The op code is located in the most significant bits (2 15 through 2 13 ). B (bit 2 12 ) tells the computer to use all 16 bits as a word or divide the 16 bits into 8-bit bytes. Figure 8-3.—Example of microinstruction format. 8-7

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D (bits 2 9 through 2 6 is a code identifying the destina- tion portion of the instruction. S (bits 2 3 through 2 0 ) identifies the source portion. T D (bits 2 11 and 2 10 ) and TS (bits 25 and 24 are bits in the instruction word that identify the type of addressing mode being used to locate the destination and source addresses. As shown in figure 8-4, two or three memory words are required for some instructions depending on the addressing mode indicated by T D and TS. Addressing modes are discussed in the next section. Microcomputers may have more than one instruction format for the one word instructions. The format depends on the type of instruction being used. Mainframe Computer Instruction Formats The instruction formats for large mainframe computers vary greatly between types, generations, and manufacturers of computers. For our example, we selected the instruction format for CPU instructions of a mainframe computer with 32-bit computer instructions. These instructions can have up to seven basic formats designated I, II, III, IV-A, IV-B, IV-C and V. The majority of these instructions are full memory word (32-bit) instructions. Only formats IV-A, IV-B, Figure 8-4.—Microcomputer instruction formats with two and three memory words. and IV-C are upper or lower half-word (16-bit) instructions. The instructions are divided into a number of single or multibit fields that each perform a specific function during instruction execution. Two fields called the function code (f) and the accumulator or index (a) designator fields are consistent throughout all the formats. The f field is the 6-bit function code (op code) and the a field is the 3-bit accumulator register designator field. The function code (f) defines the complete operation to be performed or it may be used in conjunction with other fields called subfunction designators to define an operation. The accumulator register designator (a) field is used to identify the particular accumulator (0-7), index (0-7), or stack pointer register (0-7) needed for the operation. The formats and instruction fields are described in the following paragraphs. Formats I, II, and III —These three formats (fig. 8-5) make up the majority of instructions in the example computer’s repertoire of instructions. Format I instructions perform the basic load, store, replace, and simple mathematical operations for the computer. Format II instructions are concerned with single precision mathematics, interrupt, and I/O commands. Format III instructions are used for program sequence control (jumps, return jumps, and switch controlled or manual jumps). The three formats have many fields in common. The nine most significant bits (2 31 through 2 23 ) are made up of the f and a fields. Only bits 2 22 through 2 20 differ between the three formats. In format I, the 3-bit field is called the k field or operand interpretation designator. This field is used primarily during mathematical operations. In format II instructions, the three bits become a subfunction code (f2). And in format III instructions, the three bits become a two-bit subfunction code (f3) and a single-bit k code that is always ZERO for format III instructions. NOTE: Subfunction codes, f 2 through f6 are used as part of the op code unless otherwise specified. A subfunction code of two bits has a maximum value of 3 (11 2). A subfunction code of three bits has a maximum value of 7 (1112). For example, the format II op code 07 could have a subfunction 7 and format III op code 53 could have a subfunction code of 3. The remainder of the instruction, bits 2 19 through 2 0 , is the same for all three formats. There is a 3-bit index register designator code (b), a single-bit indirect 8-8

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Figure 8-5.—Illustrations of instruction word formats I, II, and III. addressing designator (i), a 3-bit base designator or are combined to define one of the following: special selection code (s), and a 13-bit address dis- operand, a constant that can be modified by an index, a placement or operand designator (y). The b code (2 19 jump address, an indirect address, or a string of through 2 17 ) is used to identify the index register (0-7) identifier bits. being used for indexing or operand address Formats IV-A and IV-B —The formats are for modification. The i code (2 16 ) is a ZERO when in 16-bit or half-word instructions. These instructions direct addressing mode and a ONE when in indirect reside in the upper or lower half-word of a memory addressing mode. The s and y codes (2 15 through 2 0 ) location. They are normally stored two to a memory 8-9

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Figure 8-6.—Illustration of instruction word format IV-A. word. First the computer executes the upper half-word instruction then the lower. If only one of these format instructions is to be stored in a memory word, then it is stored in the upper half-word location. An active status register (ASR) bit (2 15 ) is used to keep track of upper/lower half instruction execution. Format IV-A instructions are used for a variety of computer operations that do not require an operand or operand address to be part of the instruction. These operations include but are not limited to mathematics and comparison operations, IOC commands, task and executive state operations, and real-time or monitor clock operations. The format IV-A instruction (fig. 8-6) is made up of an f field, a field, f4 field, an index designator (b) field, and i field, which is unused unless specified. The only field we have not covered is the f4 field, a 3-bit subfunction code. This field can be used to identify code memory registers (CMR) for CMR operations. Format IV-B instructions are used to shift data stored in an accumulator. The accumulator designator specifies an accumulator in control memory. The shift count designator specifies a shift count or a source of a shift count. Instruction format IV-B (fig. 8-7) is made up of an f field, an a field, and a shift designator (m) field. Format IV-C —Format IV-C instructions (fig. 8-8) are used for individual bit operations. These operations include setting, clearing, or testing an individual bit of a specified accumulator register. The 5-bit n field provides the bit position pointer to specify the register bit to be operated on. Format V —Format V instructions are full-word format instructions (fig. 8-9) used for single and double-precision floating-point math operations and other large magnitude number functions. In this format the f, f5, and f6 fields are used to define the specific operation to take place. The a and b fields are used for accumulator and index register definition. The m field provides decimal point positioning values for floating point operations. INSTRUCTION OPERAND ADDRESSING The types of operand addressing usually available are direct, extended, immediate, implicit, indexed, indirect, and relative. Direct Operand Addressing In direct operand addressing, the address of the operand’s memory location is contained in the instruction. Figure 8-10 shows an example of direct addressing format. Figure 8-7.—Illustration of instruction word format IV-B. 8-10 Figure 8-8.—Il1ustration of instruction word format IV-C.

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Figure 8-9.—Illustration of instruction word format V. Extended Operand Addressing Extended addressing is used when an address of a memory location is too large to fit in one word. For example, on a computer with an 8-bit word (1 byte), only memory locations with addresses within the range of 0 through 255 can be addressed in 1 byte. To enable the computer to address memory locations with larger addresses, two bytes can be interpreted as one address. See figure 8-11. Immediate Operand Addressing When the immediate format is used, the operand itself is contained in the instruction. In this instruction format, the destination is a general-purpose register defined by the destination register code (fields or designators) located in the instruction. Figure 8-12 is an example of immediate addressing. Implicit (Implied) Operand Addressing Figure 8-10.—Example of direct addressing format. Figure 8-11.—Example of extended addressing format. In implicit (implied) operand addressing, the operand location is implied by the op (function) code of the instruction (fig. 8-13). For example, the op code CLA could mean “clear the accumulator.” No address needs to be specified because the op code contains all the information needed. Figure 8-12.—Example of immediate addressing format. Indexed Operand Addressing In the indexed mode, the operand address must be generated when the instruction is being prepared for execution. This is done by adding the address given in the instruction to a value contained in a specified register. The register to be used is specified along with the operand address in the instruction. See figure 8-14. In this example, the parentheses are used to tell that the index mode is needed. The CPU will add the operand whose address is ADDR1 + the value in register 1, R 1, Figure 8-13—-Example of implicit (implied) addressing format. Figure 8-14.—Example of indexed addressing. 8-11

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to the contents of register 2, R 2. By changing the value in R1, different operands may be addressed. This is particularly useful for addressing memory locations in arrays. Indexing is a very useful troubleshooting tool. A short routine can be written to forma program loop to isolate on a specific malfunction. On some computers, a CPU register is dedicated to this indexing function. In those cases, it is called an index register and is usually 3-bits or more depending on the computer type. Some computers permit a general-purpose register to be used as an index register. Indirect Operand Addressing Indirect addressing enables the operand address to vary during program execution by specifying a location in memory or a register in the instruction that tells where the address will be stored. See figure 8-15. In this example, the braces are used to tell that register 2 has been specified to hold the operand address. This means the contents of the main memory location whose address is contained in R 2 are added to the contents of R1. Like the indexed mode of addressing, the indirect mode of addressing offers flexibility and is useful in addressing an array of data. Because the actual address pointing to an array can be stored separately from the program in memory, a large number of array pointers can be used. Relative Operand Addressing In many computers, particularly those with multiprogramming capabilities, a separate set of registers called base registers is used to define the start of particular blocks or segments of memory. Each block of memory could contain a separate application program. The contents of a base register is called the base address. Any execution of instructions or referencing of operands within the block of memory defined by the base requires that an offset or relative address be used. The offset is added to the base during instruction execution to allow reference of the correct instruction or operand address. INSTRUCTION SIZE Each address of memory (main or ROM) contains a freed number of binary positions or bits. The number Figure 8-15.—Example of indirect addressing. of bits stored at a single address varies among types and generations of computers. For example, some store 8 bits (1 byte) at each location; others store 16,32, or more bits at each location. The size of each memory location or memory word has a direct effect on the execution of machine instructions. Basic instructions deal with full word exchanges as the register size is usually the same as the memory word size. In most computers, particularly those with large memory words, the capability exists to transfer less than a full memory word of information between memory and the applicable register. This allows memory words and registers to be further divided into economically sized bit groups for the most efficient use of memory for information storage and handling. For example, it is preferable to store two 8-bit characters in one 16-bit memory location than to waste an extra 16-bit location for the second character. Let’s examine some of the various instruction sizes. Full- or Single-Word Instructions A full- or single-word instruction simply uses all the data contained in the instruction word to execute the instruction regardless of the size: 8-bit, 16-bit, and so on. Refer back to figures 8-3 and 8-5 for examples of full- or single-word instructions, 16-bit and 32-bit. Half-Word Instructions Half-word (upper or lower half) instructions consist of one-half of the normal instruction word size. The half-word instructions are executed by acquiring the complete normal instruction word, consisting of the half-word instruction to be executed and the next sequential instruction. After the first half-word instruction is executed, it is followed by the execution of the next sequential half-word instruction. If only one half-word instruction is used, it is usually located in the upper half of the instruction word with all zeros in the lower half of the instruction word. Refer back to figures 8-6 and 8-7 for examples of a half-word instruction. Character-Addressable Instructions In computers with word lengths greater than 8 bits, character-addressable instructions allow specified bit fields (called characters) of a word to be processed by the instruction. This is done in lieu of processing a whole-, half-, or quarter-word operand. Character addressing is permitted only when the instruction is executed in the indirect address mode. The particular operand bit field to be acquired is specified by the 8-12

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indirect word addressed by the instruction. In computers with an 8-bit word, no special instruction is needed because each character has its own address. Double-Length Instructions Double-length instructions consist of two adjacent words stored in memory. Multiple-Word Instructions Multiple-word instructions can be used to process two or more sequential words from memory. This concept is commonly used in microcomputers where the instruction word is 16 bits and the memory word size is 8 bits (a byte). In this case two or more sequential bytes from memory are transferred into two or more 16-bit registers for processing; or multiple word store instructions are used to process 16-bit registers into sequential bytes in memory (two bytes for each register). Refer back to figure 8-4 for an example of a multiple-word instruction format. TOPIC 2—MAN/MACHINE INTERFACES To use or maintain a computer, you must be able to control the computer’s operation through some form of a man/machine interface. The man/machine interface is accomplished by the CPU and will vary with the type of computer. However, there are no major differences in the functions performed by the interfaces. You studied the controlling devices in chapter 3. The controlling devices allow you to interface with the computer. The methods are discussed in this topic. The controlling devices used by operator and maintenance personnel vary with different types and generations of computers. In some cases the particular devices used are the same for both general system operation and the more specific maintenance functions. In many cases the man/machine interfaces have evolved from large panels containing many pushbutton/ indicators, and pushbutton/toggle switches, and switches (fig. 8-16) on a maintenance panel to more Figure 8-16.—Pushbutton/indicators, pushbutton/toggle switches, and switches on a maintenance panel. 8-13

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sophisticated microprocessor controlled assemblies using the functions of the controlling devices. The data containing display panels and data entry keyboards (fig. display capability is used to provide hardware status and 8-17) on a display control unit (DCU). other system description data to you. The data display In all cases, the man/machine interface provides capability can also allow you to react in some cases you with some form of data entry and data display using menus to choose various operations. The capability. The data entry function is used to enter man/machine interface is the primary path you use commands or set parameters for computer operations, when requesting information on computer faults and for status, and test activities. The data entry can be made the computer to display the requested data. Figure 8-17.—Display panels and data entry keyboards on a display control unit (DCU). 8-14

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MAN/MACHINE OPERATING MODES Controlling the tempo of instructions through man/machine interfaces can be executed in several modes of operation. The two most commonly encountered operating modes are run and stop. Other modes are step, sequence, and phase. Run Mode When the computer is in run mode, it continually executes instructions one after another as directed by its logic circuits and software. The speed of execution is determined by the timing circuits or clock of the CPU. Stop Mode When the computer is stopped, it is not executing an instruction and will not execute an instruction until directed by an operator action (START or RUN pushbutton with the instruction address in the program counter). A running computer can be stopped by manual action (STOP pushbutton) or by execution of a STOP instruction under program control. Many microcomputers and embedded microprocessors do not have or do not use their STOP mode except from the device maintenance panel. During normal operation, they are designed to run continually from firmware programs once the equipment they are in is powered up. The only way to stop a microcomputer is to power it down. Step Mode Most computers or microprocessor controlled peripherals with maintenance panels offer the technician other modes of operations, specifically some form of instruction step. In the instruction step mode, individual instructions are executed one at a time as directed by the technician (pushbutton or toggle switch action) or in some machines at a slower than normal rate as determined by a manually adjustable low-speed oscillator. The contents of the computer registers and memory locations can be tested by the technician at the end of each instruction to verify proper operation or to aid in troubleshooting the computer. In newer computers, instruction step may be divided into two levels: macro step or micro step. MACRO STEP. —A macro step allows the execution of a single microinstruction. Those computers using macroinstructions composed of a series of micro instructions may give you the option to instruction step at either level, macro by macro or micro by micro within an individual microinstruction. MICRO STEP. —A micro step allows the execution of a single microinstruction. Sequence Mode Sequence mode allows the execution of one sequence of an instruction at a time. Each operation of an instruction has an established set of sequences to complete the instruction. This enables you to execute one sequence of an instruction at a time. This is useful for detailed troubleshooting of an instruction. Phase Mode Phase mode allows the execution of one phase of an instruction at a time. If a computer has six main timing phases, you can execute one phase at a time. You can see what the instruction has accomplished at the end of each phase. This is also an aid for detailed troubleshooting. MAN/MACHINE OPERATIONS Interface capabilities available vary from computer Micros rely on keyboards and mouse devices to interface; consult your computer’s manuals for detailed operations. Because more hardware is used on mini and mainframe computers, their interface capabilities provide a greater range to set parameters and control the operations of the computer more closely. This is particularly useful in the preventive and corrective maintenance aspects of your job. Without going into detail, the following functions are commonly available to the technician through the man/machine interface operating modes. Some are self-explanatory; we describe their basic operations. Master Clear —Clears all I/O and CPU registers and will stop the computer if it is in the run mode Start/Run —Starts the function determined by the operating mode(s) Stop (computer control) —Causes computer operations to stop Stop (program control) —causes corresponding stops to occur under program control Jump —Causes corresponding jump to occur under program control Bootstrap —Addresses NDRO (ROM) depending on position of AUTO RECovery or MANUAL switches 8-15

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Real-time clock —Allows real-time clock to be updated internally or externally Consult your technical manuals for exact operations used in the different computer operating modes. MAN/MACHINE INTERFACE FUNCTIONS The man/machine interface is used to perform a variety of general functions. These functions include, but are not limited, to the following: Configure the computer/processor system Apply power Enter data and display data Execute internal diagnostics Execute bootstrap Initiate operational programs Execute auto restart operations Execute diagnostics Patch or revise software Not every man/machine interface function applies to every type of computer; therefore, we look at the three general types of computers (microcomputers, minicomputers, and mainframes) and give an overview of the man/machine interfaces used for each particular type as it applies to you. We do not address microprocessors as such. We consider them as replaceable or repairable components of the larger device. We also do not discuss peripheral devices used for system control and configuration operations. The following discussion covers only those man/machine interface devices considered as components or assemblies of the particular type of computer. With all types of computers, consult the appropriate documentation for your system to ensure proper operation. This last statement cannot be over emphasized. Microcomputers The man/machine interfaces used with the microcomputers you maintain will be system oriented. Let’s take a look at the options available to you for microcomputers. CONFIGURE THE PROCESSOR. — Microcomputer systems are designed to be flexible in their configuration. You can easily modify most desktop systems to incorporate additional disk units (hard or floppy), expanded memory, other components, as well as specific operator requirements. The ROM-based firmware that the system uses for booting the operating system as well as other system software must be configured for the current system interconnection scheme. Three methods are commonly used to inform the processor of the system configuration. They are DIP switches, jumpers, and battery protected storage of confi guration data. DIP Switches. —Dual-inline package (DIP) switches are made to be installed into integrated circuit sockets or board connections. Each switch in the package (fig. 8-18) normally indicates one of two conditions by its ON/OFF status. The board mounted DIP switches are designed so you can manually position them during component installation, removal, or initial system configuration to inform the processor of the availability of the particular components as well as the requirements of the system operators. They affect such operations as video display (color and resolution) and port(s) selections. Individual switches or combinations of two or three switches are used to specify a variety of configuration options. Jumpers. —In some units, jumpers are used to make additional configuration changes. Jumpers (fig. 8-19) can be likened to dual-inline package (DIP) Figure 8-18.—DIP switches. 8-16

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Figure 8-19.—Jumper connections. switches except that you must physically remove and reinsert them. A jumper connector is designed for easy removal and reinsertion. They are permanent unless a configuration change is required. The jumper connector consists of a receptacle and plug arrangement. The receptacle is normally mounted permanently on the pcb’s and/or backplane/ motherboard inside the micro’s chassis. A plug (with or without a cable) makes the appropriate connection. It disables, enables, selects, and expands. Jumpers define the configuration of each pcb, which will eventually affect operations. Some of the functions affected include mode of operation (fast or normal), clock speed, wait states, and I/O connections. Like DIP switches, jumpers are designed so you can manually position them during component installation, removal, or initial system configuration to inform the processor of the availability of the particular components, as well as the requirements of the system operators. Individual jumpers or combinations of two or three jumpers are used to specify a variety of configuration options. Battery Protected Storage. —Many newer microcomputers have a hardware setup/configuration program stored as firmware. It has the capability to display system configuration data on the display screen and to update system configuration data via the keyboard. The configuration data is stored in a random access memory (RAM) protected by a rechargeable battery so the data is retained for long time periods when the micro itself is powered down. The battery is located on the backplane/motherboard. Configuration Options. —Both DIP switches and battery protected storage provide the same basic configuration data to the micro. System setup/ configuration options include the following: Date/time data (battery protected storage only) Base and expansion memory size Floppy disk drive identifiers (A, B, C or O, 1,2) Storage capabilities (number of Kbytes of storage per drive) Hard drive data Boot drive identifier Type of video display Video refresh time period APPLY POWER. —Power is applied to the microcomputer with a simple ON/OFF switch usually mounted on the back of the desktop computer chassis (fig. 8-20). A separate monitor requires its own power switch. Portable micros usually have fixed time period rechargeable batteries (6, 8, or 12 hours) with a normal ac power option. Presence of system power is indicated by single indicator lamps on the front of the chassis and the monitor mounting. Sometimes in the same area as the ON/OFF switch, a selectable switch (fig. 8-20) called a voltage or line select switch allows the microcomputer to operate on voltages in the range of 100 to 130 volts or 200 to 230 volts. USE CONTROLS, DATA ENTRY, AND DATA DISPLAY. —Micros, either portable or desktop Figure 8-20.—Desktop computer back panel. 8-17

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Figure 8-21.—A typical microcomputer with data entry and display devices. (fig. 8-21), combine both maintenance and operational functions in the same data entry and display devices. Virtually all operator/technician commands are passed from the keyboard to the microprocessor. With the exception of a few simple indicator lamps, virtually all data is displayed on the monitor or display screen. Together the keyboard and monitor allow you to run software programs, perform tests, and view results. The keyboard and monitor on a microcomputer limit you to only data entry and display functions; there are no controls for power, cooling, or battle short conditions. With microcomputers, you can also use a mouse with the keyboard to interface with the computer. EXECUTE INTERNAL DIAGNOSTICS. —As part of the power on sequence, microcomputers usually run a series of internal diagnostic programs. These are stored as firmware and take several seconds when the computer is turned ON. If everything is correct, the disk operating system (DOS) will load and the appropriate DOS displays will display. If there is a computer failure of any test, the computer tries to display an error message (fig. 8-22) on the display/monitor screen. Error messages identify the likely cause of the problem and possible solutions. Follow the recommended. solutions closely and document the error message. If no error message is displayed or if the recommended solution does not fix the problem, more troubleshooting will be required. Most manuals will have a section that provides a detailed troubleshooting guide. The troubleshooting guide includes diagnostics that can be run from user selected tests available from the boot ROM program or disk based diagnostics. Many micros are equipped with a more comprehensive set of internal diagnostics called ROM-based diagnostics, stored as firmware. These can be selected and executed using a special firmware controlled display. Some of these diagnostics are executed as part of the power on sequence, while others can only be executed from the display screen menu. These diagnostics do not require any program loading. They are resident within the computer and accessible through a menu driven display (fig. 8-23). This enables you to select the desired diagnostic procedure and observe test status and error in- dications. Figure 8-22.—Example of an error message information. Figure 8-23.—Example of a menu driven display. 8-18

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The ROM-based diagnostics menu provides you access to the following types of tests, again depending on the type of computer and the system configuration: disk read, keyboard, base memory, expansion memory, printer, and power on. Additional board mounted diagnostic light-emitting diode (LED) indicators (fig. 8-24) are normally provided on the computer backplane and I/O logic circuit modules. This simplifies the diagnostic software and aids in fault isolation and identification. The LEDs on the backplane/motherboard for power remain on as long as the microcomputer is on. The LEDs on the I/O pcb extinguish as each test is successfully completed, except the READY LED. It will extinguish after an operating system is read from disk. The features of ROM-based diagnostics of micros differ based on manufacturer and system configuration. They are normally designed to provide at least 90% Figure 8-24.—Examples of LED indicators. resolution on detected faults to a single large scale integration (LSI) circuit or supporting integrated circuits. RAM and ROM errors are usually identifiable to the specific IC chip. The ROM-based diagnostics are designed to verify and fault isolate enough of the computer’s logic to allow for loading and executing more comprehensive diagnostic programs stored on disk (floppy or hard disks). EXECUTE BOOTSTRAP. —Micros are normally designed to boot or initially load the disk operating system (DOS) program from either the installed floppy or hard disk assemblies, based on the system configuration. The operating system program provides for operator control of the loading and executing of application programs used within the microcomputer system. There are two ways to boot a micro. Firmware stored in PROM or ROM will automatically reference the configured disk for the operating system program as part of the power on sequence. Turn the micro ON and it automatically looks for the operating system program on the configured disk. If it finds it, the operating system automatically loads. If it does not find it, you will need to ensure the disks are setup correctly and depress a combination of keys to cause the system to boot. INITIATE OPERATIONAL PROGRAMS. — For microcomputers, once the microcomputer has been booted, how the computer is configured will dictate how to initiate the operational program, the software, to be used. EXECUTE AUTO RESTART OPERA- TIONS. —There is also a particular combination of keyboard keys (such as Ctrl, Alt, and Del) that will cause the operating system program to reboot and restart. This can be used in the event of a software failure. You can also reboot by turning the computer OFF and then ON. EXECUTE DIAGNOSTICS. —YOU can load and execute disk based diagnostics using DOS command structures or a diagnostic monitor program. To execute these, you usually load the programs by a different power-up and boot sequence. The diagnostic monitor program displays a test selection menu similar to the internal diagnostic menu. Because these diagnostics are more comprehensive than the ROM-based diagnostics, you will be given more information on the menu than you are with the ROM driven display. The test selection menu provides for diagnostic selection, test status, and error indications. The selection, test 8-19

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status, and error indications are displayed on the microcomputer’s monitor (fig. 8-25). PATCH OR REVISE SOFTWARE. —While microcomputers have the same basic capabilities as larger computers, they are not designed to allow for the manual insertion and revision of machine code. At this time, revisions to operating system, application, or diagnostic software are provided by the system or software manufacturer or designer. Minicomputers The man/machine interfaces of the minicomputers you will maintain are more machine oriented and less system oriented. CONFIGURE THE COMPUTER SYS- TEM. —Minicomputers are primarily factory configured. There are a number of options you can incorporate by simply changing a module in the installed computer. As far as the computer itself, ensure that the controls and switches are set up properly for the intended operations. DIP switches and jumpers are also used in some minicomputers to meet the required interconnection scheme for the current system. In addition, make sure any peripherals or other equipments are configured correctly to ensure correct operation. APPLY POWER. —Applying power to militarized minicomputers is somewhat more complicated than with commercially available micros. There can be a number of switches to power up the computer (fig. 8-26). Usually there is a remote panel that supplies power. Then at the unit itself there maybe a number of switches. Some use a circuit breaker that must be on before any of the other power switches will operate. Once the circuit breaker has been turned on, Figure 8-25.—Examples of diagnostic selection, test status, and error indication displays. 8-20

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Figure 8-26.—Power up switches located on a maintenance control panel. an ac power switch is activated to apply ac power to the have two panels, others one panel. When two are used, computer. The circuit breaker will kick-OFF in the event the computer power supplies draw excessive current. The ac switch allows ac voltage to be fed to the blower fans and dc power supply. Indicators, usually one for PRIMARY and one for LOGIC, show the presence of stable dc power when illuminated. Some minicomputers will have a 4-digit time meter to record the accumulated hours that logic power has been applied. Some minicomputers are equipped with a battle short switch to allow the computer to run even when the temperature exceeds the normal allowable operating temperature established by the manufacturer. An audible alarm and/or indicators can also be used to indicate excessive temperature. USE CONTROLS, DATA ENTRY, AND DATA DISPLAY. —The controls, data entry, and displays used on minicomputers vary. Some minicomputers one panel is used for control and the other for maintenance. When one panel is used, the control and maintenance functions are located on the same panel. Refer again to figure 8-26. The panels on some minicomputers can be likened to the keyboard of a microcomputer; they deal primarily with the operating system and software programs. But with some minicomputers, you have more options. They include controls and indicators that deal with power and temperature. These two conditions were included in the apply power man/machine interface. In addition to a number of control switches and indicator lamps, some minicomputers use a keyboard for data entry and numeric displays to show the contents of registers or display status. This is also illustrated in figure 8-26. EXECUTE INTERNAL DIAGNOSTICS. — Internal diagnostics are built-in tests (BITs). Firmware and testing features are designed into the logic modules 8-21

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Figure 8-27.—Example portion of a fault isolation table. or an NDRO that can be executed at any time by the technician or operator. The BIT is designed to test the computer hardware (CPU, IOCs, and any optional circuits) and return pass/fail results to the operator/technician. Pass/fail results are displayed on the control, data entry, and data display man/machine interface. The BIT itself can consist of several levels of tests and subtests controlled from the computer’s front panel. Some internal diagnostics are designed to test all or selected sections of the computer. Errors can be displayed on the front panel using the data display man/machine interface. The computer’s technical manuals or a ready reference index located on the front panel will enable you to decipher the error code. A fault isolation table (FIT) lists the error code and the location of the recommended module(s) that will correct the problem. Figure 8-27 shows an example. On the pcb’s in some minicomputers, LEDs are also used to aid in fault isolation and identification. EXECUTE BOOTSTRAP. —Minicomputers are normally designed to boot or initially load the operating system program using a hardwired module (NDRO) located in the CPU. The NDRO is tailored at the factory and will select a particular peripheral device (disk, tape, and so forth) based on the position of the bootstrap switch located on the computer’s controlling panel. Figure 8-26 shows a maintenance control panel with a bootstrap switch with two positions (1 or 2). The bootstrap program allows a more comprehensive program to be loaded from the selected peripheral into main memory and be executed. NDROs are also designed to perform a BIT, fault analysis program, or load a failure analysis program. To execute bootstrap, depress the run or load switch. INITIATE OPERATIONAL PROGRAMS. — After the computer is booted, the operational program 8-22 is loaded, initialized, and started. The operational program is tailored to meet the command’s operational requirements or application. EXECUTE AUTO RESTART OPERA- TIONS. —Auto restart operations are used when power is restored after a power loss. EXECUTE DIAGNOSTICS. —Execution of external diagnostics can be loaded into the computer and controlled using an external control device. They can also be loaded into the computer from a peripheral (disk or magnetic tape unit) but initiated and controlled by the computer. These diagnostics are very thorough and also offer the option of testing all or specific sections of a computer. They are more comprehensive than the BITs. Figure 8-28 shows the test results of an external diagnostic test as they amid be displayed on a controlling monitor. Figure 8-28.—Examples of test results from an external

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PATCH OR REVISE SOFTWARE. — Minicomputers have the option to allow you to manually insert and make revisions to machine code or insert revisions using external peripheral devices. Patches or revisions to the software are written by authorized personnel only. The patches or revisions are entered using inspect and change routines or equivalents using the controls, data entry, and data display man/machine interface. Mainframes The mainframe computers used for tactical and tactical support data systems use a number of units and panels to control computer operations. Their controlling devices offer more options to perform the man/machine interface but their functions are the same. CONFIGURE THE COMPUTER SYS- TEM. —Mainframes are generally designed to work in large systems. In addition to a number of peripherals, they also work with major subsystems (display and communications). The software is designed to manage the computer and its resources based on the amount of hardware. Most large mainframe computer systems use two or more computers. This gives the system the capability to run in the event one of the computers goes down with hardware problems. Therefore, it is very important that you understand and know how to configure the system for full and reduced configurations. You accomplish this by knowing the capabilities and limitations of the software based on the quantity of hardware for your system and by ensuring all controls and switches on the computer(s), switchboard panels, and display and communication subsystems are correctly set. APPLY POWER. —Applying power to mainframes also requires more than just turning on the ON/OFF switch. First, you must ensure there is power to the remote panel. Then at the unit itself, usually a circuit breaker must be applied, then blower and logic power. Indicators are usually provided for blower and logic to show there is stable power. Power to a mainframe is critical and you must ensure there is a stable power source. In addition to the circuit breaker protection, interrupts are generated if there are abnormal power fluctuations in which case the computer will shut itself down. Mainframes also use a 4-digit time meter to record the accumulated hours that logic power has been applied, except when there is a time meter for each module unit. Some mainframes have a separate power controlling device devoted entirely for power. It is usually on the front of the unit. Figure 8-29 is an example of a panel of such a device. It also monitors the temperature of the computer set. Mainframes are also equipped with a battle short switch (also indicated on figure 8-29) and an audible alarm to allow the computer to run even when the temperature exceeds the normal allowable operating temperature established by the manufacturer and to indicate excessive temperature in the modules. USE CONTROLS, DATA ENTRY, AND DATA DISPLAY. —Mainframes will use operator, maintenance panels, and/or display control consoles/units located near the unit. For our example, Figure 8-29.—Example of the panel of a power controlling device. 8-23

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we show a display control unit (DCU) in figure 8-30. Remote units are also available to provide initial startup just like the operator and display control units. Control, data entry, and data display man/machine interfaces of mainframes are your primary means of operating and maintaining a mainframe computer. You can control all operations from this man/machine interface. Newer mainframes, in addition to controls, switches, and pushbutton indicators, use displays and keyboards to display status and to address the contents of registers. EXECUTE INTERNAL DIAGNOSTICS. —On mainframes, internal diagnostics are also available using built-in tests (BITs) or tests available on an NDRO. They are designed to test the computer hardware (CPU, IOCs, and any optional circuits) and return pass/fail results to the operator. Pass/fail results are displayed on the control, data entry, and data display man/machine interface shown on figure 8-30. Similar to minicomputers, the BIT itself can consist of several levels of tests and subtests controlled from the computer’s front panel. Some internal diagnostics are designed to test all or selected sections of the computer. Errors can be displayed on the front panel using the data display man/machine interface. The computer’s technical manuals will enable you to decipher the error Figure 8-30.—Example of a display control unit. 8-24

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Figure 8-31.—Example of diagnostic error codes. code. Figure 8-31 is an example. You can use this error code for fault analysis. EXECUTE BOOTSTRAP. —Execute bootstrap works in a manner similar to the function on minicomputers. An NDRO is used to perform this function. The NDRO is tailored at the factory and will select a particular peripheral device (disk, tape, and so forth) based on the position of the bootstrap switches (0, 1, or 2) located on the computer’s controlling panel (maintenance, control, display control, or remote unit). To execute bootstrap, select bootstrap switch 0, 1, or 2 and depress the start switch (fig. 8-30). NDROs on mainframes may also be designed to perform a variety of tests or other functions that may be selected by use of the DIP switches. INITIATE OPERATIONAL PROGRAMS. — After the computer is booted, the operational program is loaded, initialized, and started. The operational pro- gram is tailored to meet the command’s operational require- ments or application. It is important that you know the software capabilities and limitations based on your hardware. Be sure your system is configured correctly. EXECUTE AUTO RESTART OPERA- TIONS. —Auto restart operations are used when power is restored after a power loss. EXECUTE DIAGNOSTICS. —External diag- nostics can be loaded into the computer, executed, and controlled using an external control device. They can also be loaded into the computer from a peripheral (disk or magnetic tape unit) but initiated and controlled by the computer. These diagnostics are very thorough. They offer the option of testing all or specific sections of a computer. They are more comprehensive than the BITs. Figure 8-32 shows an example of a defective card Figure 8-32.—Example of a defective card index (DCI). 8-25

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index (DCI) with error stop and recommended corrective measures: Replace pcbs in locations 4C28-4C30. PATCH OR REVISE SOFTWARE. — Mainframes also have the option to allow you to manually insert and make revisions of machine code or insert revisions using external peripheral devices. Patches or revisions to the software are written by authorized personnel only. The patches or revisions are entered using inspect and change routines or equivalents using the controls, data entry, and data display man/machine interface. SUMMARY—COMPUTER INSTRUCTIONS AND MAN/MACHINE INTERFACES In this chapter we introduced you to computer instructions and to ways you can interface with a computer. The following information summarizes important points you should have learned: COMPUTER INSTRUCTIONS —Computer instructions are commands to the computer to tell the equipment to perform a designated operation. The instructions are processed by the central processing unit. PROGRAMS. —Programs are sequences of instructions written for various purposes to solve problems or types of problems on a computer, to manage the computer’s own resources and operations, and/or to maintain computers. LEVELS OF INSTRUCTIONS. —Instructions may be either microinstruction or macroinstructions (a predetermined set of microinstruction). INSTRUCTION TYPES. —Instructions may be classified by what they do, their operation. They may also be classified by their action on an operand-read, store, or replace. INSTRUCTION SIZES. —Instruction sizes vary depending on the instruction and the computer. INSTRUCTION FORMATS. —Every instruc- tion has an operation (op) code to tell the computer what to do. It may also have an operand to give the address of the data to be operated on or to give other fields or designators. INTERFACING WITH COMPUTERS. —The man/machine interfaces enable operators/technicians to control the computer’s operation. These include control panels and operator panels/consoles. MAN/MACHINE OPERATING MODES. — Computers can be operated in a variety of modes. This is very helpful when you are troubleshooting. Run mode continually executes instructions one after another. Stop mode causes the computer to stop; it will not restart until directed by some operator action. Step mode enables you to have the computer execute one instruction at a time so you can test the contents of computer registers and memory locations to verify correct operation or identify a problem. MAN/MACHINE INTERFACE OPERA- TIONS. —Many operations can be accomplished by providing information to the computer through an interface. MAN/MACHINE INTERFACE FUNC- TIONS. —Many general functions can be performed through an interface. It is up to you to learn all you can about how the computer systems you work with process instructions and what capabilities are available to you through man/machine interfaces. This will enable you to interpret computer instructions and interface with the computer to diagnose and isolate problems. 8-26

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CHAPTER 9 MAGNETIC TAPE STORAGE INTRODUCTION Computers use three types of storage devices to store and access data. These are main memory storage, secondary memory storage, and tertiary storage. Main memory is the memory in the computer itself. It can be semiconductor RAM, magnetic core memory, or thin film memory. Secondary memory storage is memory used to store data that is not immediately required by the computer. The most common secondary memory is some type of magnetic disk. Tertiary memory storage is used to store large amounts of data that are not required by the computer on a regular basis. Magnetic tape can be used as secondary storage, but it is generally used as a tertiary storage media. After completing this chapter you will be able to: Describe the physical properties of magnetic tape Describe the proper procedures for handling, storing, and packaging magnetic tape Describe magnetic tape failures due to normal wear and tear, accidental damage, environmental damage, and winding errors Describe the function and operation of the magnetic tape read, write, and erase heads Describe the different methods of encoding data on magnetic tape State the purpose of the major functional areas of a magnetic tape unit Describe the operations performed by a magnetic tape unit Describe the operation of a magnetic tape transport Magnetic tape units may be categorized by the form of media they are designed to use: open-reel, cartridge, and cassette. The standard tape units use open reels. Cartridge or cassette units use cartridge tapes and cassette tapes, respectively. The units most commonly used in the Navy are industry standard open-reel tape units and cartridge tape units. TOPIC 1—MAGNETIC TAPE Magnetic tape can be used to store large amounts Magnetic tape is one form of magnetic storage of data in a variety of convenient package sizes (reels, media. It consists of a thin film of magnetic oxide cartridges, or cassettes) material bonded to a polyester-based strip. Magnetic Magnetic tapes are easily interchangeable tape offers several useful features: between similar units of different systems 9-1

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Describe the physical characteristics of a fixed disk system Describe the data encoding methods used to write data on magnetic disks Describe disk interleaving effects on hard drive operations Explain the methods for recovering data from a fixed disk drive Explain the methods for preventing, detecting, and removing computer viruses from fixed disk systems Describe the precautions to be followed in handling and storing floppy disks, disk packs, and fixed disks — — — The popularity of disk systems has grown because of their speeds and large capacities to store data. Disks are generally thought of as random access memory devices, although this is not entirely true. To find data on a disk, first the read/write heads must seek a track, then wait while the disk spins to the desired sector. When the sector is reached, the heads can read or write data. In our study of disk storage devices, we explore what tracks and sectors areas well as the three major types of disk devices: floppy disk drives, disk file units, and fixed disk drives. We also examine how data is stored on a disk. When discussing floppy and fixed disk systems in personal computers, we are referring to IBM and compatible computers using Intel 80286 or greater microprocessor system. References to DOS refer to the Microsoft Disk Operating System (MS-DOS). TOPIC 1—FUNDAMENTALS OF MAGNETIC DISKS AND DISKS DRIVES Magnetic disks are generally termed as secondary storage for computer systems. They are used to temporarily hold data that is not immediately required for computer operations and to store programs that are not currently being executed. Through the years, magnetic disk data capacities have increased at tremendous rates. The first fixed disk drives had a capacity of just 5 megabytes. Today, fixed disk capacities are approaching several gigabytes. The same holds true for floppy disk drives. The original 8-inch floppy was a single-sided disk with a total capacity of 180 kilobytes. Today we have 3.5-inch floppy disks with a capacity of over 1.4 megabytes. Also, there are disk file units with removable disk packs that have capacities of several gigabytes. Disk file units are used with mainframe computer systems with large databases to speed up access times and to provide flexibility to system configuration. TYPES OF DISKS As mentioned previously, there are currently two types of disks: the hard disk and the floppy disk or diskette. Hard Disks Hard disks are divided into two groups, the disk packs used with disk file systems and the fixed disks. DISK PACKS. —Diskpacks contain large (usually 14”) platters. They are packaged in vertical stacks of up to 16 disks. Each disk surface is coated with a magnetic medium and can be used for data storage, although the top and bottom surfaces of the pack are usually used as protective surfaces. Disk packs are easily removed from the drive system. They have very large capacities and can store from 500 megabytes to 10-2

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Figure 10-1.—A magnetic disk pack. several gigabytes. An example of a disk pack is shown in figure 10-1. Disk cartridges are another form of disk pack with the heads and head actuator assemblies contained within a sealed cartridge. Since the disk pack is never removed from the cartridge, disk cartridges suffer less contamination problems from dust and dirt than standard disk packs. FIXED DISKS. —Fixed disks are small sealed units that contain one or more disk platters. Fixed disks are known by several terms, such as Winchester drive, hard drive, or fixed disk. For clarity, we refer to them as fixed disks throughout this chapter. Fixed disks are used in minicomputers and personal computers. They can also be adapted for use in mainframe computers instead of having separate disk file units. Floppy Disks Floppy disks come in several sizes and densities. They are called floppy disks because the magnetic coating is placed on a thin flexible polyester film base. THE 8-INCH FLOPPY DISK. —The 8-inch floppy disk was the first disk widely used for commercial purposes. It is available as both single- or double-sided and single- or double density. The 8-inch disk is quickly becoming obsolete. THE 5.25-INCH FLOPPY DISK. —The 5.25- inch floppy disks are used with both personal computers and minicomputers. The standard double-sided, double-density disk has a capacity of 360 kilobytes (K). Quad-density disks hold 720K, while the newest high-density disks can hold 1.2 megabytes (M). THE 3.5-INCH FLOPPY DISK. —The current disk of choice is the 3.5-inch floppy disk. These disks are also used with personal computers and minicomputers. These smaller disks have data capacities of 720K for double-density disks and 1.44M for high-density disks. ORGANIZING DATA ON DISKS Before data can be stored on a magnetic disk, the disk must first be divided into numbered areas so the data can be easily retrieved. Dividing the disk so the data can be easily written and retrieved is known as formatting the disk. The format program divides each data surface into tracks and sectors. Tracks —Concentric rings, called tracks, are written on the disk during the formatting process. Floppy disks have 40 or 80 tracks per side. Fixed disks and disk packs can have from 300 to over 1,000 tracks per side. Figure 10-2 shows an example of how tracks are written on a disk surface. Each track is assigned a number. The outermost track on a disk is assigned number 00. The innermost track is assigned the highest consecutive number. Sectors —Each track is divided into sectors. Sectors are numbered divisions of the tracks designed to make data storage more manageable. Without sectors, each track would hold more than 4,500 bytes of information and small files would use an entire track. Figure 10-2.—Tracks on a segment of a magnetic disk. 10-3

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Figure 10-3 shows how a disk surface is divided into sectors and tracks. A 360K floppy disk is divided into 9 sectors per track and 40 tracks per side. Each sector is capable of holding 512 bytes. Simple math tells us the 512 bytes per sector times 9 sectors per track times 40 tracks per side times 2 sides equals 368, 640 bytes. Cylinder Addressing Disk drives generally use the cylinder addressing method to store and retrieve data. In a disk drive, the read/write heads are positioned concurrently by parallel access arms to the same track number. In other words, if one head seeks track 20, then all heads move to track 20 of their respective recording surface. This means that all identically numbered tracks on the disk pack recording surfaces form a vertical cylinder. The cylinder number corresponds to the track number. All track 00s form cylinder 00. All track 200s form cylinder 200 and so on. Figure 10-4 shows an example of a disk drive seeking cylinder 20 of a disk pack. If a disk pack has 10 recording surfaces with 800 tracks per surface, then it would have 800 cylinders. Data is stored or retrieved by using the cylinder address. The cylinder address consists of the cylinder number, sector number, and head or recording surface number. Formatting As we have seen, formatting a disk writes the tracks and sectors on the disk. In addition, the format program used with personal computers also examines the disk for bad areas and creates the root directory, the file allocation table (FAT), and the disk boot sector. The boot sector contains information to tell the computer what type of disk is being used, what format the data is in, and other information that the DOS needs to read the disk. Fixed disks used in personal computers need an additional high-level format that defines the type of drive and the operating system being used. Once a disk is formatted, it is ready to have data written on it. How the data is stored in the sectors is primarily driven by the disk operating system (DOS). The following section shows how DOS organizes data on floppy and fixed disks by using directories. Directories DOS stores data in directories. A directory is a file system that enables DOS to manage files. There are two types of directories: the root directory and the subdirectories. Figure 10-3.—Sectors and tracks on a magnetic disk. 10-4

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Figure 10-4.—Disk pack access arm seeking cylinder 20. Root Directory —Formatting a disk creates the root directory. This directory is limited in size according to the type of disk you have and what version of DOS you are using. With a DOS version of 3.x or greater, all floppy disks and 10M fixed disks have 128 entries in the root directory. Fixed disks with 20M+ capacity have a root directory with space for 512 entries. Subdirectories —Subdirectories are directories that are treated as data files. There is no limit on how many entries they can have. To help you keep data organized, you can also make subdirectories for subdirectories. Table 10-1 illustrates a typical directory tree for a fixed disk. In table 10-1, the directories \DOS, /DATABASE, and \WORDPROC are subdirectories of the root directory C:\. The directory WILES is a subdirectory of \WORDPROC. Table 10-1.—A Typical Directory Tree 10-5 DOS stores files in these directories. When you create a file, you must give the file a name to store it. The name can be up to eight characters in length, followed by a period and a three character extension. The file extension is used to help identify the type of file. Program file extensions are .EXE (execute) or .COM (command). A .BAT extension designates a batch file. Looking at a directory entry, you will find that each entry is 32 bytes long. Table 10-2 illustrates the breakdown of a DOS directory entry. File attributes designate whether the file has been marked by the creator as a read-only file, a hidden file, a system file, or a subdirectory, or if the file has been archived. Table 10-2.—DOS Directory Entry

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The date and time fields are updated every time the file is changed. The starting cluster field indicates where the beginning of the file is stored on the disk. DOS uses clusters to define disk areas. Depending on the type and capacity of a disk, a cluster can be from 1 to 128 sectors. A 5.25-inch, 360K floppy disk has 2 sectors per cluster. A 32M freed disk has 4 sectors per cluster. DOS uses the starting cluster field to reference the file allocation table (FAT) to get information as to where the entire file is stored. File Allocation Table The file allocation table (FAT) is created during the formatting process. There is a FAT entry for each cluster on the disk. A FAT entry will be — a zero (0), to indicate the cluster is available for storage, — an end of file code, — a bad cluster code (written during formatting), or — a number that points to the next cluster in the file. Suppose we have a file named EVAL.ABC on a 5.25-inch, 360K floppy disk. The file is 4,608 bytes long and could be stored in 4.5 clusters. DOS cannot use partial clusters so this file would occupy 5 full clusters. The directory entry for the starting cluster indicates cluster 25 as the first cluster of this file. Table 10-3 illustrates what the FAT entries for this file might look like. As illustrated in table 10-3, the disk had clusters 25, 26, and 27 available to store EVAL.ABC, then had more data so the rest of the file was stored in clusters 70 and 71. Note also the FAT is a one-way pointer. That is, by examining the contents of the entry for cluster 70, we see that the file continues in cluster 71, but we don’t know the previous cluster was cluster 27. TOPIC 2—FLOPPY DISKS AND DISK DRIVES Floppy disks are available in a variety of densities for each size of disk. The disks are labeled as to the maximum density each is designed to handle. Table 10-4 shows the sizes and densities of some floppy disks. The differences between the disk types listed in tables 2-4 and using them in various drives is covered in detail later in this chapter. Table 10-3.—Contents of a File Allocation Table Table 10-4.—Floppy Disk Density Formats 10-6

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Floppy disk drives are the simplest of all magnetic disk devices, but contribute to a large number of problems in personal computer operations. Most of the floppy disk and drive problems you will encounter as a technician are caused by improper system operation. By thoroughly examining the operation of a floppy drive, you can eliminate many of these errors. In the following sections, we explore the construction of 5.25-inch and 3.5-inch disks and the operation of a typical disk drive unit. THE 5.25-INCH FLOPPY DISK CONSTRUCTION When you examine a 5.25-inch floppy disk, you notice several holes and notches as well as the disk itself. Figure 10-5 shows a 5.25-inch floppy disk. The 5.25-Inch Disk The disk is visible through the media across hole on either side of the disk. The disk is made of thin flexible polyester film that is coated with a magnetic material. This material is iron-oxide on low-density disks (360K) and cobalt on high-density disks. Disk Jacket The disk is enclosed in a plastic jacket to protect the disk surface from contamination caused by dust, dirt, and smoke. The inside of the disk jacket is lined with soft felt to clean the disk as it spins. On the bottom of the disk jacket are two notches called stress relief notches. They help prevent the disk from warping and relieve stress on the disk. Some drives also use these Figure 10-5.—The 5.25-inch floppy disk. notches to keep the disk in the proper position in the drive. Media Access Hole Below the large hole in the middle of the disk is a large oval hole called the media access hole. There is a media access hole on each side of the disk. When you insert the disk in a drive, the heads are positioned over these holes to read or write on the disk. Index Hole Just to the right and above the media access hole is a small round hole known as the index hole. If you were to look at the disk, you would notice a small hole near the big hole in the middle. This index hole indicates the start of sector 1 on each track. SOFT-SECTORED DISKS. —Soft-sectored disks have only one index hole. The sectors are physically written on the disk during the formatting operation. The index hole indicates the starting point for sector 1 on each track. HARD-SECTORED DISKS. —Some disks have eight or nine index holes. These are known as hard-sectored disks and each hole represents the start of a sector. Never try to use a hard-sectored disk in a drive designed for soft-sectored disks as it will drive the machine crazy trying to find sectors 2 through 9. Write Enable Notch On the right edge of the disk jacket, about 1 inch from the top is a small notch in the jacket. This is the write enable notch. In order to write on a disk, this notch must be present. If you want to protect a disk from accidental loss of data, cover this notch with a strip of tape. Strips of tape for write protection are usually provided in the box with the disks. Central Hub Access Hole In the center of the disk is a big hole known as the central hub access hole. When you insert the disk in a drive and close the door, a cone-shaped clamp centers the disk and clamps it to the spindle motor. Due to the pressure, many clamps exert on disks, most disks have a reinforcement ring around the edge of the disk to prevent damaging it. 10-7

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THE 3.5-INCH FLOPPY DISK CONSTRUCTION Figure 10-6 shows a 3.5-inch disk. The 3.5-inch and 5.25-inch disks are constructed of the same basic materials. The disk is a thin flexible polyester film base that is coated with a magnetic compound. This compound is iron-oxide for standard and double- density disks and a cobalt ferric compound for high- density disks. Disk Case The 3.5-inch floppy disk’s rigid plastic case stabilizes the disk as it spins. This allows for greater densities of data to be written on the disk. Media Access Hole and Shutter Examining the case of a 3.5-inch disk, you’ll notice several differences from the 5.25-inch disk. The first difference is the metal shutter covering the media access hole. This shutter is spring loaded and moves out of the way to expose the disk when the disk is loaded into a drive. When the disk is not loaded in a drive, this shutter covers the hole and eliminates the need for a disk jacket to store the disk. Write Protect/Write Enable Slide Write protection for the disk is accomplished by means of a slide switch in the lower left comer of the disk. Figure 10-6 illustrates the location of the write protect/write enable slide switch. When the slide switch is positioned so you can see a hole through the case, the disk cannot be written on. Media Indicator Hole On the lower right corner of some 3.5-inch disks is another hole that designates the disk as a high-density disk. When a high-density disk is loaded into a high-density drive, a sensor checks for the presence of this hole. If it is present, the disk can be formatted in the 1.44M mode. If this hole is not present, the disk can only be formatted as a 720K disk. FLOPPY DISK DRIVE OPERATION Several basic components are common to all floppy disk drives. To properly test, install, or service a disk drive, you must be able to identify these components and understand their functions in the drive. Figure 10-7 shows a typical 5.25-inch disk drive with the major components labeled as follows: Spindle assembly/drive motor Drive electronics circuit board Connectors Head actuator assembly Read/write head arm assembly Spindle Assembly/Drive Motor Figure 10-6.—The 3.5-inch floppy disk. The spindle holds the disk in place while it spins. The drive motor spins the spindle at the proper speed. Most floppy disk drive motors spin at 300 rpm except the 1.2M drive, which spins at 360 rpm. Almost all half-height drives use a direct drive motor to turn the spindle, and the speed cannot be adjusted. Some older Ml-height drives use a belt-driven motor. These belt-driven drives usually have a strobo-disk mounted on the underside of the drive set to both 50 Hz and 60 Hz. To adjust the speed, you remove the drive and issue a command to get the motor running. Look at the strobo-disk under a fluorescent light and adjust the drive speed until the outer strobo-disk spokes appear to be standing still. The inner disk is setup for 50 Hz operation, the frequency of European main power. 10-8

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Figure 10-7.—A typical floppy disk drive. Drive Electronics Circuit Board Mounted to the disk drive is the drive electronics circuit board. This board contains the circuitry that (1) controls the electromechanical parts of the disk drive, (2) controls the operation of the read/write heads, and (3) interfaces the floppy disk drive to the disk controller in the computer. Connectors On the back of the drive electronics circuit board are at least two connectors. The 4-pin, in-line connector supplies power to the drive. The 34-pin edge connector provides control signals to the drive and exchanges data between the drive and the disk controller in the computer. Head Actuator The head actuator assembly is a mechanical motor assembly that actually moves the heads over the disk. It does this by using a stepper motor. This motor moves in very small fixed increments or steps. Each increment of the stepper motor defines one track; therefore, if we want to read data on track 20, and the heads are at track 10, the stepper motor must be incremented 10 times to reach track 20. Read/Write Head Assembly Floppy disk drives have two read/write head assemblies, one for each side of the floppy disk. The heads are mounted on arms that connect to the head actuator assembly. Since the heads are mounted to a single head actuator, they move in unison with each other. 10-9

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Table 10-5.—The 5.25-Inch Disk Densities and Coercivities Figure 10-8.—Construction of a floppy disk drive read/write head. HEAD CONSTRUCTION. —Heads are made of a soft ferrous material with electromagnetic coils for reading and writing. The read head picks up changes in magnetic flux as the disk moves past the head surface. An electric current fed through the write head creates a magnetic field around it. If the force of the magnetic field is strong enough, the area on the disk is also magnetized. By controlling the direction of current flow through the head, we can also control the direction of the magnetic field. The write (record) head is centered between two erase heads. Figure 10-8 illustrates the construction of a floppy disk drive read/write head. ERASE HEAD OPERATION. —As data is written on the disk, the erase heads clip each edge of the track, ensuring that data from one track does not “spill over” to the next track. This form of recording is known as tunnel erasure. DENSITY AND COERCIVITY Density is the measure of how much data can be stored on a disk. The higher the density of the disk, the more data can be reliably stored on the disk. Disk density is measured in two ways: longitudinal density and linear density. Longitudinal Density —Longitudinal density is defined by how many tracks per inch can be reliably written on a disk. Longitudinal density is generally expressed in tracks per inch (tpi). Linear Density —Linear density is how many bits per inch (bpi) can be stored on a disk track. Coercivity is the magnetic field strength required to properly record data. It is measured in oersteds. Coercivity is affectedly the magnetic material used and the thickness of the material. The 5.25-Inch Disk Densities and Coercivities The 5.25-inch disks are rated by their density capabilities and whether data can be stored on one or both sides. A 360K disk is rated as DSDD, or double-sided, double-density disk. The rating “double- density” on these disks goes back to the very early days of floppy disk development. Single-density disks are no longer manufactured and the DSDD disk is often called a low-density disk. Table 10-5 show the common 5.25-inch disks in use today with their densities and coercivities. 10-10

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The 3.5-Inch Disk Densities and Coercivities The 3.5-inch disks are constructed and rated in much the same way as 5.25-inch disks. Table 10-6 shows the densities and required coercivities for 3.5-inch disks. USING LOW-DENSITY DISKS IN HIGH-DENSITY DRIVES A high-density drive will read a low-density disk with no problems. A problem occurs when you try to use a high-density drive to write on a low-density disk that was previously used in a low-density drive. Referring back to table 10-5, you see that the track width on a 360K disk is approximately .33 mm. The tracks written by a 1.2M drive are approximately .16 mm. When you try to overwrite data that was originally produced by a 360K drive, you are writing a little skinny track through the middle of a wider track. If you take this disk back to a 360K drive, the bigger heads will not only try to read the skinny track but will also read some of the data that was supposed to have been overwritten by the high-density drive. The only way to avoid these read errors is to format anew (unformatted) 5.25-inch disk in the high-density drive. Refer to your DOS user’s manual for the proper command to format a 5.25-inch disk for 360K with a 1.2M drive. Use this disk to write any data that you want to transfer to the 360K drive. Another problem can occur if you format a 360K, 5.25-inch disk as a 1.2M disk. DOS will allow this operation. Again referring back to table 10-5, you see that a 1.2M disk requires twice as much write current as a 360K disk. Writing this strong magnetic field on the iron oxide of a 360K disk will cause the bits written on the disk to change position. That is, adjacent opposite magnetic poles will migrate toward each other, and similar magnetic poles will migrate away from each other and your data will be lost. The 3.5-inch drives do not have this problem, since the 1.44M disks have a high-density medium indicator hole in the disk case. If you try to format a 720K, 3.5-inch disk as a 1.44M disk, DOS generates an error message. A high-density disk can never be used in a low-density drive. The low-density drive cannot generate the required write current to write data on a high-density disk. FLOPPY DISK DRIVE INSTALLATION AND CONFIGURATION The physical installation of a floppy drive in a personal computer is fairly simple. Remove the computer case, place the drive in the bracket supplied in the installation kit, and install the drive in the computer. Configuring the drive for the computer is a bit more complicated. Most disk controller cards used in personal computers can control two floppy drives and two fixed disk drives. The floppy drives are usually daisy chained on the same cable to a single connector on the disk controller card. The drive electronics card has several jumpers including the following: Drive select jumper Terminating resistor Disk changeling/ready jumper Media sensor jumper Drive Select Jumper The drive select jumpers are located on the drive electronics card. They are usually labeled DS0, 1, 2, and 3. These designations are not standard and some manufacturers use different labels or numbers. The drive select jumpers could be labeled DS1, 2,3, and 4. Before you can properly configure the drive address, it is important to check the floppy drive cable. The cable has three connectors, one at each end and one in the middle. Carefully examine the cable to determine if pins 10 through 16 are twisted near the end of one Table 10-6.—The 3.5 Inch Disk Densities and Coercivities 10-11

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connector. Configuration procedures are different when a twisted cable is used rather than a straight cable. INSTALLING A FLOPPY DRIVE WITH A STRAIGHT CABLE. —To install a floppy drive with a straight cable to be used as drive A, set the drive select jumper to DS0. Connect the end of the cable to this drive. To install a second drive (drive B), place the jumper in the second position (DS1) and connect the drive to the middle connector of the cable. INSTALLING A FLOPPY DRIVE WITH A TWISTED CABLE. —The twisted cable was developed by manufacturers to retie assembling computers at the factory easier. With a twisted cable, both floppy drive select jumpers are set to DS1, and the twist in the cable provides the actual drive select. Table 10-7 shows how the twist works to select drives A and B. To select a drive, both the motor enable signal and the drive select signal must be present. To select drive B, the controller would enable pins 12 and 16 and the drive would be turned on. To select drive A, the controller enables pins 10 and 14. Because of the twist, pin 10 is routed to pin 16 on drive A and pin 14 is routed to pin 12. Since drive A thinks it is drive 1, it turns on and works. Terminating Resistor Also on the drive electronics board is a terminating resistor. The terminating resistor looks like a standard 14-pin DIP IC. It maybe labeled TR or T-RES. The terminating resistor provides the proper load to the disk controller card, but only the floppy drive at the end of the cable is terminated. The floppy drive connected to the middle of the cable should have the terminating resistor removed. To remove this resistor, simply pull it out of the socket. Some manufacturers solder the terminating resistor in place and use a jumper to take it out of the circuit. Disk Changeline/Ready Jumper The disk changeling/ready jumper is used to indicate the disk has been changed and therefore the directory must be reread. Media Sensor Jumper The media sensor jumper is only found in 3.5-inch, 1.44M floppy drives. It enables the media sensor to inform a high-density drive when a 720K disk has been loaded into the drive. By sensing the type of disk loaded, the drive can control the write current for high- and low-density disks and prevent improper formatting of a disk. Enabling and disabling the media sensor varies with manufacturer, so you will need to refer to the installation instructions to properly configure the drive. FLOPPY DISK CARE AND HANDLING Floppy disks are very durable and reliable with a minimum of care. Inserting a 5.25-inch disk in its storage envelope and storing the disk in a disk file box is the best practice for storing disks. The 3.5-inch disk’s plastic case and shutter eliminate the need for the storage envelope. These are best stored in a disk file box designed for 3.5-inch disks. Other precautions for handling disks are illustrated in figure 10-9. Referring to figure 10-9, precaution 4 states that you should keep disks away from machines with magnetic parts. We all know that the large power transformers aboard ships can generate electromagnetic fields that can damage disks. But these electromagnetic fields can be in places we don’t ever think about. A Table 10-7.—Interface Connections between the Floppy Controller and Drives (Twisted Cable) 10-12

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Figure 10-9.—Floppy disk handling precautions. telephone with a bell ringer uses an electromagnet to ring the bell. If you keep a disk next to a phone, every time the phone rings a 90-volt electromagnetic field is generated around the phone. In time, the data on your disk will start to mysteriously disappear. Another hidden electromagnetic field is in the monitor connected to your personal computer. Almost all monitors manufactured today have an automatic degaussing circuit. This circuit is design to demagnetize the screen of the cathode-ray tube (CRT) by generating a large electromagnetic field every time the monitor is turned on. Again, your data starts disappearing. Despite your best efforts to protect your disks, disaster can strike. For example, a cup of sugar and cream laden coffee spills on your 5.25-inch disk. You have no back-up copy of this disk and to reconstruct the data will take several weeks. What to do? The following procedure is considered an emergency recovery procedure and should be used only in emergency situations. First, take the damaged disk and very carefully cut the top edge of the disk cover. Remove the disk and wash it in a mild detergent with very light pressure to avoid damaging the oxide coating. Rinse the disk thoroughly. Dry the disk by laying it flat on a lint free cloth and allow it to dry completely for at least 24 hours. When the disk is dry, take a new disk and cut the protective rover and remove the disk. Throw away the new disk. We have to sacrifice the disk to get a clean cover. Place the damaged disk in the new cover and carefully tape the top closed. Insert the disk into the drive and copy the information onto another disk. Discard the damaged disk when you have finished copying it. TOPIC 3—DISK MEMORY SETS Magnetic disk memory sets are mass storage systems used to store large amounts of computer data on interchangeable disk packs. A magnetic disk set can be configured to operate with shipboard or shore-based computers using parallel 16- or 32-bit CDS computer channels and is found in a variety of mainframe systems. A magnetic disk memory set is composed of variable configurations of magnetic disk recorder/ reproducers (disk unit controllers) and disk memory units (memory units) housed in air-cooled or water-cooled electronic equipment cabinets. Our study of disk memory sets uses the AN/UYH-3 as the main example, but the functions described are similar to other disk memory sets used in the Navy. 10-13

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The magnetic disk recorder/reproducer (RD) or disk unit controller contains the circuitry to control the reading and writing of data on a disk pack. It also controls the interface with the computer. The disk unit can control from one to four memory units (disk packs). The memory units (MUs) contain only the logic circuitry to record data on and read data from their own disk packs. They do not contain controllers. They operate only as slave units to the disk unit controller. MAGNETIC DISK PACKS The recording medium for a magnetic disk memory set is a removable disk pack made up of one to over ten 14-inch disks, depending on the type. Disk Pack Construction The disks are coated with magnetic iron oxide. The top and bottom platters of some disk packs are used as protection for the inner disks recording surfaces. The disk pack comes with a storage canister consisting of a top and bottom cover as shown in figure 10-10. The top cover is used to install the disk pack in the desired disk or memory unit and to remove the disk pack from a unit for storage. The bottom cover is removed just before installation of the disk pack and replaced after the disk pack has been removed from a unit to protect the disk pack from physical damage and contamination. Disk Pack Data Surfaces Looking at a disk pack with five platters, the top and bottom platters are used to protect the six inside surfaces (fig. 2-10). Five of the six inner disk surfaces are used for data storage. Each recording surface contains 823 tracks. Of the 823 tracks, 822 are addressable and can be used for data storage with the remaining track being used for maintenance applications. The tracks occupy a 2-inch band around the circumference of the disk’s recording surface. The individual tracks are .0026-inches apart. Each track can store 6,038 BPI with a storage capacity per disk pack (5 recording surfaces) of 640 million bits (megabits). Disk Servo Surface The sixth surface, called the servo surface, contains prerecorded dibits used to control the movement of the read/write heads to the desired position (cylinder) on the recording surfaces, and to maintain alignment of the read/write heads over the centerline of the track. Dibit is an abbreviation of a dipole bit. It is an analog bit with a positive or negative signal used to indicate odd or even tracks on the disk. As the read-only servo head moves Figure 10-10.—A disk pack and storage canister. 10-14

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across a track, the signal from the dipole bits are summed. When the result of this summing equals zero, or null, the heads are centered on track. During a seek operation, the heads move across the dibit tracks, a counter is incremented for each track crossed. The heads continue to move until the counter reaches the desired track. DISK FILE UNIT CONTROLS AND INDICATORS The disk memory set can be controlled from several control panels. These are as follows: Operator’s panel Status/maintenance panel Disk status panel Power supply panel Operator’s Panel Atypical operator’s panel is shown in figure 10-11. It contains the switches and indicators used to turn the disk file or memory unit (MAIN POWER) and spindle drive motor (SPDL MOTOR) on, and to indicate the readiness of the disk drive (DISK STATUS) and controller (CONTROLLER STATUS) during and after the power on sequence. The operator’s panel. also indicates the disk drive address (LOGIC UNIT). The READY indicator is lit when the disk rotation is up to speed, the heads are loaded, and no-fault conditions exist. It also indicates Figure 10-11.—A disk memory set operator’s panel. when the disk is protected from a write operation by switch action or fault condition (WRITE PROTECT). In addition the FAULT indicator indicates the detection of a variety of faults as defined by the STATUS/ MAINTENANCE PANEL fault indicators. Status/Maintenance Panel The status/maintenance panel, shown in figure 10-12, is found on the disk unit. The panel is controlled by a microprocessor and contains the ELAPSED TIME meter, the WRITE PROTECT (this unit’s drive only) switch, the LOGIC UNIT SELECT CODE (disk drive address 0, 1, 2, or 3) switches, and some fault and status indicators for the disk drive (3,100 RPM, TEMP FAULT, COVER LOCK) The 3,100 rpm indicator is illuminated when the spindle has reached normal rotation speed. TEMP FAULT indicates an abnormal temperature condition. COVER LOCK indicates the spindle is rotating more than 175 rpm and the shroud cover is locked, a normal condition. The remainder of the panel is used for operator command entry and status message display readout. The FUNCTION/MESSAGE digital display comprises four digits of the five-element display. The FUNCTION/MESSAGE readout is used to enter a large variety of hexadecimal coded operator commands or responses (FUNCTIONS), and for displaying controller coded displays (MESSAGEs) for the operator or Figure 10-12.—A status/maintenance panel (disk unit only). 10-15

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technician. The single-digit FAULT indicator displays one of eight fault codes as defined in table 10-8. Table 10-8.—Status/Maintenance Panel Fault Codes Figure 10-13.—A disk status panel (memory unit only). 10-16 Disk Status Panel The disk status panel, shown in figure 10-13, is found on the memory unit (MU). It performs the same functions as a status/maintenance panel with the exception of the FUNCTION/MESSAGE and FAULT readout. As the memory units do not have a controller, the readout is replaced by a number of FAULT indicators and a CLEAR push button. The faults indicated are the same as the eight fault readout conditions listed in table 10-8. The CLEAR pushbutton does not clear the fault condition, it clears the indicators only if the fault condition causing the indication has been corrected. Some disk memory sets have a FORMAT WRITE PROTECT switch. It is designed to protect the disk packs from being inadvertently formatted when the pack contains data that would be lost. When the switch is in the ON position, disk pack testing commands from the CDS computer and formatting commands from the CDS computer or the STATUS/MAINTENANCE panel are rejected. If the disk memory set in your sys- tem has this switch, it should be left in the ON position except when a disk pack is being tested or formatted. Power Supply Panel The power supply panel shown in figure 10-14 contains switches for MAIN POWER and for advancing the FAULT DISPLAY (FAULT ADVANCE) in the event of multiple power supply faults. A two-digit FAULT DISPLAY displays a two-digit code indicating POWER ON status or fault condition. DISK MEMORY SET CONTROLLER The controller has five functional areas as shown in figure 10-15. They are as follows: Microprocessor Buffer memory Controller to disk drive interface Data bus control unit (DBCU) CDS channel interface Controller Intercommunications The functional areas of the controller are interfaced by a bus arrangement. Two buses are used: (1) the processor input and output bus and (2) the data bus. All data and commands to/from the microprocessor move

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Figure 10-14.—A power supply panel. Figure 10-15.—A controller block diagram. 10-17

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on the processor input or output bus. The processor input and output bus allows the microprocessor to communicate directly with the disk drives and the data bus control unit. Two holding registers, the processor input bus holding register and the processor output bus holding register, allow the microprocessor to receive data from and send data over the data bus. The 16-bit bidirectional data bus is used primarily to transfer read/write data, external function commands, interrupt codes, and status codes between the CDS channel interface, buffer memory, the disk control logic, and the microprocessor bus holding registers. The data bus control unit, under control of the microprocessor, directs the flow of data over the data bus. Microprocessor The microprocessor controls the overall operation of the controller circuitry and therefore the overall operation of the magnetic disk set. All communications between the microprocessor and other elements of the controller pass over the processor input or output buses. The actions of the microprocessor are governed by 8,192 microinstruction stored as firmware in read-only memory (ROM) or micromemory. Address logic in the microprocessor determines which instructions will be read out of micromemory and executed. Under normal operation, a microinstruction is read out of micromemory and executed every 250 nanoseconds. The address of the next microinstruction to be executed may be conditional, depending on the presence or absence of a condition, signal, or interrupt, or the next instruction to be executed may be unconditionally specified by the current microinstruction. A large variety of hardware conditions is sensed by the microprocessor logic in determining the microinstruction to be executed. Much of the information used by the microprocessor is contained in a look-up table. The look-up table is a 2,048 address ROM containing the following information: micromemory jump addresses, data masks, constants, and code conversion tables for the status/maintenance panel function/message codes. Additional random access memory (RAM) is provided by 256 16-bit words of RAM called the FILE. The file is used for temporary storage of diagnostic test parameters and other variable quantities during operation of the magnetic disk set. 10-18 Buffer Memory Buffer memory is used to prevent the loss of data when reading from or writing onto disk. The CDS channel interface and the disk drives may operate at different speeds. A direct transfer from the channel interface to the drive could result in the loss of data. The 4,096 16-bit addresses of buffer memory, expandable to 8,192 addresses, are used as a temporary storage area for blocks of data when performing read or write operations. During a write operation, data is transferred from the CDS channel interface over the data bus to the random access buffer memory and stored in blocks. The blocks of data are then transferred a word at a time over the 16-bit data bus to the disk control logic and written on disk. The opposite applies in a read operation. Data is read from disk and transferred into buffer memory and then transferred to the channel interface for input to the computer. Read and write operations do not occur at the same time. Controller to Disk Drive Interface The controller to disk drive interface provides for control of up to four disk drives, one internal to the disk unit and up to three drives installed in memory units. As shown in figure 10-16, there are two separate Figure 10-16.—A cable and B cable interfaces and signals.

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interfaces with each disk drive, one from the microprocessor called the A CABLE and one from the disk control logic called the B CABLE. The two interfaces combine to provide all timing, control, and data lines needed for disk drive operation. THE A CABLE. —The A cable connects the disk drives to the processor input and output buses. The disk drives are daisy chained on the A cable and only the selected drive will respond to the microprocessor commands. The A cable is used for microprocessor control of the drives. The microprocessor passes commands to the drives using three command lines called TAG lines and eight BUS OUT lines. The three-bit TAG CODE on the tag lines identifies the type of command while the bus out lines carry the command code or address data to the drives. Status data from the selected disk drive is passed over eight bus in lines to the microprocessor. Additional sector mark and index signals are sent from the selected drive to the microprocessor. THE B CABLE. —The B cable connects the individual disk drives with the disk control logic. Each disk drive has its own unique B cable. The B cable is used for read/write operations. The selected disk drive (A cable under microprocessor control) sends a MODULE ADDRESSED signal to the disk control logic indicating it has been selected. The selected drive provides a SEEK END signal indicating it has positioned the heads over the addressed cylinder and an INTERRUPT signal indicating the start of the addressed sector. Both the seek and sector addressing operations are controlled by the microprocessor over the A cable. Timing for the read/write operations is provided by the SERVO CLOCK and READ or WRITE CLOCK signals. The servo clock originates from reading the servo track dibits on the servo surface of the disk pack. The servo clock provides the basic timing for the read/write operations. The read clock is generated by the disk drive during the read operation and is used to control the transfer of the serial read data from the drive to the disk control logic. The write clock is generated by the disk control logic during a write operation and is used to control the transfer of serial data over the bidirectional line to the disk drive. DISK CONTROL LOGIC. —The disk control logic is used during read/write operations. Its two major functions are (1) to convert the parallel 16-bit data words from the data bus into a serial nonreturn-to-zero (NRZ) pulse train (B cable) when writing to disk and (2) to convert the NRZ pulse train inning from the selected disk into parallel 16-bit words for output on the data bus during read operations. The disk control logic is enabled by the microprocessor and provides requests to the DBCU for data transfer with buffer memory when reading or writing. Overall timing for read and write operations is provided by the SERVO CLOCK signal. The SEEK END and INTERRUPT signals (B cable) notify the disk control logic when to begin read/write operations. Data Bus Control Unit (DBCU) The data bus control unit (DBCU) controls the transfer of data from source to destination on the data bus. The microprocessor defines the source, destination, and number of words to be transferred (buffer length) to the DBCU. The DBCU transfers the data a word at a time from the specified source to the specified destination until the transfer is complete. The DBCU contains a control file and a count file that contain the necessary information to control the data exchanges. The control and count files are loaded by the microprocessor definition commands. Once the files are loaded, the actual data transfers occur on a request basis. The requests for data bus transfers are handled on a priority basis. The highest priority transfers are between the disk control logic and buffer memory (read/write operations). Next come the processor input and output holding register requests and the lowest in priority are the input/output channel requests. CDS Channel Interface The CDS channel interface controls all data exchanges between the magnetic disk set and the CDS computer. The interface can be configured for up to four 16-bit or 32-bit parallel input/output channels. Basic I/O operations including external functions, interrupts, and input/output data transfers are controlled by the interface logic. DISK DRIVE UNIT The addressable disk drives (0, 1, 2, 3) contain the electromechanical portions of the magnetic disk set and the read/write circuitry. The disk drive performs the actual recording and reading back of data as commanded by the controller logic contained in the disk 10-19

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unit. The controller selects the desired head and direct seeks the read/write head assemblies to the selected cylinder position. During a write operation, data is output from the controller buffer memory to the disk write circuitry and recorded on the disk using the modified frequency modulation (MFM) encoding method. Modified frequency modulation encoding is covered in detail later in this chapter. During a read operation the drive recovers data from the disk and transfers it to the controller. The disk drive uses a motor driven belt and pulley arrangement to rotate the mounted disk pack at a speed of 3,600 rpm ± 3.5%. The speed of disk pack rotation is monitored by a spur gear and photodcell arrangement. The read/write heads, five addressable read/write heads, and one read-only head (servo head) are mounted on arm assemblies controlled by an actuator assembly. The disk pack must be rotating above 3,100 rpm before the actuator assembly will load the heads or move them over the recording surfaces. The heads are designed to float above the disk pack recording surfaces on the air cushion provided by the high-speed rotation. Any contact between the read/write heads and the disk recording surfaces will result in a head crash and damage to both heads and recording surfaces. The heads are automatically unloaded or retracted if the drive motor power is turned off or the rotation speed of the disk pack drops below 3,100 rpm. The movement of the read/write heads to the desired cylinder position is controlled by a closed-loop servo system. Prerecorded data written on the servo surface is used to (1) determine the present position of the read/write heads, (2) control the movement of the read/write heads when seeking a new cylinder, and (3) maintain alignment of the heads to the tracks on the recording surfaces when data is being read or written. The disk drive is divided into the following electronic and electromechanical assemblies and functional areas: Drive motor assembly Spindle assembly Speed sensor Actuator assembly Velocity transducer Head/arm assemblies Servo circuit 10-20 Track servo circuit Read/write circuits Drive Motor Assembly The drive motor, which drives the spindle assembly, is a 1/2-horsepower induction motor. Power is transferred to the spindle via a flat, smooth surfaced belt that connects the pulleys of the spindle and drive motor. The speed of the drive motor is sensed by an optical switch and controlled by the motor supply module in the power supply. Spindle Assembly The spindle assembly is the physical interface between the disk drive and the disk pack. The surface of the disk pack mounting plate on the spindle mates directly with the center of the disk pack. Mating surfaces of the disk pack and spindle are engaged by rotating the cover handle of the disk pack when you install the pack in the drive. When the pack and the spindle are fully engaged, the canister cover is released from the disk pack. You can then remove the cover. The spindle is driven by the drive belt, which connects the spindle to the drive motor pulley. A static ground spring is mounted at the lower end of the spindle assembly to protect against the buildup of a static charge. A spur gear is mounted on the lower end of the spindle drive shaft. The teeth of the gear pass through the optical switch and are used as part of the speed sensor. Speed Sensor The speed sensor monitors and controls the rotating speed of the spindle and its attached disk pack. The speed sensor is made up of the spur gear and the speed sensor photocell in the optical switch. The teeth of the spur gear pass through and interrupt the light path between the emitter lamp and photocell. The pulsed output generated by the speed sensor is sent to the power supply module. The power supply varies the drive motor current to control the speed of the drive motor and to maintain spindle speed within the required limits. Actuator Assembly The actuator assembly is the mechanism that supports and moves the head/arm assemblies. The actuator is made up of a carriage and voice coil

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assembly, a rail bracket assembly, and a magnet assembly. The carriage is attached to the voice coil. The carriage supports the head/arm assemblies and provides the vehicle for head/arm positioning. The voice coil moves the carriage in (extended) or out (retracted) as determined by servo logic commands. The rail bracket assembly provides a stable support and guide for carriage movement. The carriage bearings move along the upper and lower carriage rails as the carriage is extended or retracted by the voice coil. The magnet assembly is a very strong permanent magnet that forms the core of the voice coil and is used to mount components of the velocity transducer. Velocity Transducer The velocity transducer helps to control the acceleration and deceleration of the carriage assembly during seek operations. The transducer coil has a voltage induced in it by the motion of the transducer core attached to the carriage. The voltage polarity and amplitude are sensed by an operational amplifier and used to indicate the direction and speed of carriage assembly movement to the servo circuit logic. Head/Arm Assemblies There are six head/arm assemblies in each disk drive. One of the head/arms holds the read-only servo head. The other five assemblies hold read/write heads. The servo head/arm assembly and two of the read/write head/arm assemblies are upper surface head/arm assemblies. The three remaining read/write head/arm assemblies are lower surface head/arm assemblies. The read/write heads are mounted on cam controlled head load springs. As the head/arm assemblies are loaded (extended) the head load springs apply force (loading force) to the read/write heads to move them toward the rapidly spinning disk surface (3,100 rpm minimum). The air cushion above the surface of the disk causes the head to float above the recording surface. As the head assemblies are unloaded (retracted), the head spring loading force is restrictedly the cams and the heads are moved away from the recording surface. Servo Circuit The servo circuit is a closed-loop servo system. It is used to move the read/write heads to the desired (addressed) cylinder when commanded by the controller. The servo circuit is designed to maintain a NULL or 0 voltage when the heads are in the correct cylinder position. A position error signal is used to indicate when the heads are not in the proper cylinder location. The position error is fed to the voice coil and results in carriage movement toward the addressed cylinder. A feedback signal is developed using the velocity transducer to oppose the position error and to dampen carriage movement for smoother operation. Track Servo Circuit The track servo circuit is used for maintaining head position over the track centerline. The track servo circuit positions the read/write heads based on information obtained from the servo tracks written on the servo surface of the disk pack. The read-only servo head reads the data written on the servo tracks and is positioned accordingly. The read/write heads mounted above (heads 0 and 1) and below (heads 2, 3, and 4) the servo head are physically aligned to the servo head. By positioning the servo head, all read/write heads are positioned over the center of the correct track on their respective recording surface of the cylinder. Read/Write Circuits The read/write circuits perform the following functions: When writing, they (1) convert serial NRZ signals from the disk control logic to MFM data signals, and (2) generate and control drive current to the write heads for developing the flux fields used to store information on the disk surface. When reading, they (1) detect flux changes from the disk, (2) convert the analog MFM signals to digital MFM data, (3) convert MFM data to NRZ serial pulse train and send it to the disk control logic, and (4) generate the read clock signal. DISK MEMORY SET OPERATIONS The disk memory set receives data from the host computer for storage on the disk and retrieves data from the disk and transfers it to the computer. Because of the relatively fast access time of the disk memory set, the host computer uses the disk as temporary storage of data as well as permanent storage of programs and data. Before a disk can be used, it must first be formatted. 10-21

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Disk Formatting Operations Disk memory sets can format disks in a variety of modes to match the host computer’s operating system. The formatting of a disk pack is very similar to that of a floppy disk in that the tracks and sectors are written on each data surface. The locations of the tracks are controlled by the servo tracks that are prerecorded on disk surface. The number of sectors per track is selectable by either the SECTOR SELECT switch or a set sector size command from the computer. In the file management mode, the disk will have nine sectors per track, with 512 32-bit words per sector. Formatting a disk can be done offline using the status/maintenance panel entries or online using the format disk command. A disk pack can be partitioned so that part of the disk pack is formatted in one mode and another part of the disk pack is formatted in a different mode. If a disk pack is partitioned operating system must be able to operate with the two modes. Write Operation A write operation is initiated by the computer via an external function. This external function defines how many words are to be written and whereon the disk they will be written. The disk memory set then receives the data and stores it in buffer memory. Once the proper cylinder and track have been reached, the first word is transferred from buffer memory to the write data holding register. The write data holding register transfers the data to a shift register that converts it to a nonreturn to zero (NRZ) serial pulse train. This serial data is then sent to the disk drive’s NRZ-to-MFM converter via the B cable read/write data line. The NRZ-to-MFM converter converts the pulse train into MFM data and sends it to the write drivers. The write drivers develop the proper write current for the heads to record data on the disk. When the entire word is written, a signal is sent to the controller, indicating that the disk is ready to write the next word and the cycle is repeated. Read Operation A read operation is also initiated by an external function defining cylinder, track, head, and number of words to be read from the disk. The heads are positioned to the right cylinder address, and the data is read from the disk. The serial MFM data is converted to a digital NRZ pulse train and sent to the controller’s shift register. The shift register gates in each bit and transfers the data to the read data holding register. The read data holding register transfers the word to the buffer memory where it is stored until it is transferred to the computer. MAGNETIC DISK PACK CARE AND HANDLING Because of the rotation speed of the disk pack in a disk memory set, the heads are designed to float or fly on a cushion of air. The distance the heads fly above the disk is called the flying height of the heads. As densities of disks have increased, the flying height of the heads has decreased to a point where any contaminant is larger than the flying height of the head. Figure 10-17 shows an example of the flying height of the head compared with common contaminants such as smoke, dust, fingerprints, and hair. WARNING Never attempt to remove a disk pack from a drive until all rotation of the disk pack has stopped. Figure 10-17.—The flying height of a disk read/write head compared to common contaminants. 10-22

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The following guidelines will help you keep your disk pack in peak condition: Always keep the disk pack in its container when it is not being used. Reassemble the disk pack canister, even when it is empty. Never touch the disk pack’s recording surfaces. Do not expose the disk pack to stray magnetic fields. Always store a disk pack flat. Never store a disk pack on its edge. Store the disk pack in the same environment in which the disk memory set operates. TOPIC 4—FIXED HARD DISK SYSTEMS Fixed hard disk systems are commonly found in minicomputers and microcomputers. They are called fixed disks because the disk is enclosed in a sealed case and is inaccessible to the user. The technology of these disk drives is one of the fastest changing in the computer world. In the 14 years that fixed disks drives have been in common use, capacities have increased from 10 megabytes on a 5.25-inch full height drive, to over 10 gigabytes on a 3.5-inch half height drive. Additionally, data transfer rates have increased ten-fold, while the average seek times have decreased from more than 85 milliseconds (ins) to less than 10 ms. The cost of these systems has also decreased significantly. A 10 MB drive originally cost about $1,500.00 or an average of $150.00 per megabyte of disk space. Today the cost is less than $0.25 per megabyte. FIXED HARD DISK DRIVE CONSTRUCTION Most fixed disk systems have the same basic components and similar operational characteristics. A typical hard drive’s components include: Disk platters Head actuator assembly Read/write head assembly Cables and connectors The heads, head actuator, and platters are usually contained in a sealed unit commonly referred to as a head disk assembly (HDA). The HDA requires a dust free environment when opened to avoid contaminating the disk. Figure 10-18 illustrates atypical fixed disk. Figure 10-18.—A typical fixed disk drive assembly. 10-23

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Disk Platters Head Crash Effects The size of the disks platters varies, depending on intended use, capacity, and speed. Sizes of the disk platters commonly used are 5.25-inch, 3.5-inch and 2-inch. Fixed disk systems may contain from 1 to 11 platters, depending on size and capacity. The number of platters in a drive is limited by the size of the drive. Half-height 5.25- and 3.5-inch drives contain a maximum of eight platters. Full-height drives are currently limited to 11 platters. Since the platters are sealed in the HDA, all of the surfaces are used for data storage. Platters are made of aluminum alloy metal coated with a magnetic material (medium). The two most common media for fixed disk platters are iron oxide and thin film. IRON OXIDE COATED PLATTERS. —Iron oxide platters are found in many older low-density drives. The oxide is applied to the platter, then cured and polished. The iron oxide is generally applied to a thickness of 30 millionths of an inch. After the platter is polished, a protective lubricant is applied to help prevent damage caused by head crashes. THIN FILM COATED PLATTERS. —Thin film coated platters can hold much greater data densities because the magnetic coating is much thinner and more perfectly formed than the iron oxide coating. Two processes, plating and sputtering, are used to manufacture thin film disks. Platting —Platting is a process in which the medium is applied to the disk using an electroplating mechanism. The final layer is a cobalt alloy of approximately 3 millionths of an inch. Sputtering —Sputtering is a process in which the cobalt alloy is applied in a near vacuum. The magnetic material, as thin as 2 millionths of an inch, is deposited on the disk in much the same way metallic films are applied to silicon chips in the creation of semiconductors. A hard carbon coating is then applied to protect the disk. The result, on both plated and sputtered disks, is an extremely thin and hard medium on the disk. The hard surface increases the probability that the disk will survive a high-speed head crash with little or no damage. 10-24 A head crash occurs whenever the heads come in contact with the disk’s surface. Severe damage can occur if the heads crash with the disk spinning at full speed. The heads can scratch the oxide material or the heads themselves can be damaged. Whenever the disk is powered down, there is a minor head crash as the disk slows down. Many fixed disks have a designated landing zone for the heads, but you have to position the heads in this landing zone. To do this you should run a program designed to park the heads in this landing zone before removing power. The thinner medium requires a smaller space on the disk to store data. Also the heads can fly closer to the disk, further reducing the space and magnetic field strength required to accurately store data and increase densities. Read/Write Heads The read/write heads used infixed disk systems are very similar to the read/write heads on the disk memory set. There is one head for each disk surface. These heads are joined to the head actuator and move in unison across the disk. There are currently two types of heads in use: the composite ferrite head and the thin film head. COMPOSITE FERRITE HEAD. —The composite ferrite head is the traditional type of head used in magnetic recording. It consists of an iron oxide core wrapped with electromagnetic coils. To write data on the disk, an electric current is passed through the coils and a magnetic field is induced on the ferrous material of the disk surface. Changing the direction of current flow through the head’s coil will result in a reversal of the magnetic field on the disk. THIN FILM HEAD. —The thin film head is actually a specialized integrated circuit chip. The head has a precise U-shaped groove in its bottom to allow the right amount of air pressure for the head to fly at the proper height. This lightweight head flies closer to the disk than the composite ferrite heads. A thin film head’s flying height can be as little as 5 millionths of an inch above the disk. The closeness of the head to the platter increases the signal-to-noise ratio, which increases the accuracy of the disk system.

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Head Actuator Systems The mechanical system that moves the heads across the disk is known as the head actuator. These mechanisms have to be extremely precise to position the heads over the proper cylinder. The two types of head actuators are called stepper motor actuators and voice coil actuators. STEPPER MOTOR SYSTEMS. —The stepper motors used in freed disk systems are very similar to the ones used in floppy disk systems. The stepper motor is generally located outside of the HDA, with just the shaft of the motor penetrating the HDA. Attached to the shaft is a steel band. The other end of this band is attached to the head/arm assemblies. As the motor moves through its detents, the band will wind or unwind around the shaft and move the heads. A stepper motor in a fixed drive system has two major disadvantages. It is temperature sensitive and the band can stretch over time. Ambient air temperature can cause minute changes in the size of the disk and stepper band. Since the tracks on a fixed disk can be l/1000th of an inch, these size changes can be significant enough to cause a loss of data. Anew drive should be allowed to reach operating temperature before it is formatted. This will ensure that the data will be centered on the tracks unless there is a drastic change in temperature. The band that connects the head/arm assembly with the stepper motor shaft is made of steel and can stretch over time. Again this will cause the heads to be misaligned with the tracks. A good safeguard against losing data to this problem is for you to backup the data and do a low-level format once a year. VOICE COIL HEAD ACTUATOR. —A voice coil head actuator works in the same way that an audio speaker does. An electromagnetic coil is connected to the head/arm assembly. As current is applied to the coil, it moves along a track and moves the heads. Movement of the heads in a voice coil actuator is very smooth, but the heads need a signal to tell them when to stop at the right track. One side of one of the disk platters can be dedicated to head positioning by having servo tracks permanently written on it. The heads are then positioned in a manner similar to the disk memory set. Another method of head positioning used in voice coil actuators is to embed the servo signals in the sector gaps of the data tracks. This eliminates the need for a dedicated surface. Voice coil actuators have several advantages over the stepper motor actuators. Since the heads are positioned in relationship to the control signal on the disk, they are not temperature sensitive. The heads of a voice coil actuator are self-parking. When power is removed from the drive, the electromagnetic field that positions the heads collapses causing the heads to retract to the park position. Spindle Motor The spindle motor actually spins the disks. A direct drive system is used in all fixed disk drives. Originally, 3,600 rpm was the standard speed used by almost all fixed disk systems. Today, the speeds range from 3,600 rpm to 7,200. The spindle motor is controlled by a tachometer and feedback loop that monitor and adjust the speed of the motor. Logic Boards All fixed disk drives have at least one logic board. Logic boards provide power to the motors and actuator, and monitor the speed of the disk. They also perform data conversions to a form usable by the controller. DATA ENCODING METHODS Data is stored on the disk by changing the direction of the magnetic field or flux reversals. The flux reversals generate pulses when being read from the disk. Flux reversals are sensed as a positive to negative or negative to positive pulse. In storing data in nonreturn to zero format, a flux reversal would indicate a logic ONE and no flux reversal would indicate a logic ZERO. When reading data from a disk drive, the drive and the disk controller must be synchronized for proper operation. The disk controller uses the flux reversal pulses as timing and synchronization signals in addition to data. Therefore, if a long string of zeros are being read from the disk, the possibility exists that the controller could “get lost” because of a lack of pulses. To prevent a loss of synchronization, several methods of encoding data have been developed. These are as follows: Frequency modulation (FM) Modified frequency modulation (MFM) Run length limited (RLL) 10-25

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Frequency Modulation (FM) Frequency modulation (FM) is the simplest method of encoding data to include enough timing pulses so that the controller and disk drive remain synchronized. Using FM, each data bit is split into two clock periods. A logic ONE is encoded as two pulses or flux reversals. A logic ZERO is encoded as a pulse followed by no pulse. Therefore the byte 11000101 would be encoded on the disk as PPPPPNPNPNPPPNPP (P = pulse, N = no pulse). FM is an effective method for encoding data, but it wastes a lot of space on the disk. To maximim data storage on the disk, a method is needed that reduces the number of pulses yet does not allow too many no pulse time periods. Modified Frequency Modulation (MFM) Modified frequency modulation (MFM) refines data encoding to reduce the number of pulses written on the disk. Using MFM, a logic ONE is always encoded as no pulse followed by a pulse. A logic ZERO, when preceded by a logic ONE, is encoded as two no pulses. A logic ZERO, when preceded by another logic ZERO, is encoded as a pulse followed by no pulse. Using MFM, the byte 11000101 would be encoded NPNPNNPNPNNPNNNP for a total of six pulses or flux reversals on the disk. Compare this with the 12 pulses required to store the same data using FM. MFM is currently used with all floppy drives, most large disk memory sets, and many fixed disk systems. Run Length Limited (RLL) The run length limited encoding schemes take data encoding to a new level. Usually the RLL specification will be followed by two numbers such as 1, 7 or 2, 7. These numbers represent the minimum and maximum run of O bits between two 1s. The most common RLL scheme is RLL 2,7. RLL 2,7 is a complex encoding scheme that groups bits together and uses a table to encode the data in these groups. for example, 1100 is encoded as NNNNPNNN, 1101 is NNPNNPNN, and 111 is NNNPNN. RLL increases the density and transfer rate of data by 50 percent. A 20M MFM drive can store 30M if formatted as an RLL drive. Whether a drive is MFM or RLL depends on the controller and not the drive. FIXED DISK CONTROLLERS The disk controller determines what encoding scheme will be used and interfaces the disk with the computer. You can change the disk controller to make a 20M drive into a 30M drive by changing from an MFM controller to an RLL controller. RLL encoding requires that the drive work harder; therefore, be sure your drive can handle the demands of a new controller. Of particular concern is the type of head actuator and the magnetic medium of the drive. Stepper motor head actuators are slower and the problems they can encounter with temperature can cause the drive to be very unreliable if formatted as an RLL drive. Iron oxide medium has a lower signal-to- noise ratio than the thin film medium. The noise picked up by the heads can be interpreted as data and result in read errors. FIXED DISK INTERLEAVE FACTOR The interleave factor is a method of numbering the sectors on a fixed disk to provide the optimal transfer of data between the controller and the computer. When a freed disk is formatted, sector numbers are written on each track. Interleaving refers to the relationship between the physical sectors on a track and the logical sectors on a track. Each sector on a fixed disk in a personal computer has 512 bytes per sector. Most files are larger than 512 bytes; therefore, it is assumed that if you want to retrieve the data at cylinder 225, sector 1, you will next need the data in sector 2. Since the fixed disk spins at 60 revolutions per second, the heads read data at 512 bytes per sector, 17 sectors per track or a data rate of over 500 kilobytes per second. With no interleave factor, the head reads the data from sector 1 and sends it to the controller. While the controller assembles the data to send it to the computer, sector 2 is under the head but the controller is not ready to accept the data. So the disk must make another revolution to retrieve the data from sector 2. To avoid this problem, the disk is interleaved. This means the logical sector numbers do not necessarily follow the physical sectors. Figure 10-19 illustrates the sector numbering of a disk with a 3:1 interleave. Physically the sectors are numbered 1, 7, 13, 2, 8, 14, 3, 9, 15, 4, 10, 16. . .12, and back to 1. With a 3:1 interleave, the head reads logical sector 1 and sends the data to the controller. While the controller processes the data, the next physical sector and part of the following sector pass by 10-26

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Figure 10-19.—A 3:1 disk interleave. the head. When the controller is ready for the data from sector 2, the disk is approaching logical sector 2. In this way, interleaving speeds up data retrieval and transfer. Today many fixed disk controllers are fast enough to handle a 1:1 interleave. FIXED DISK INTERFACES The last area of a fixed disk system is the type of interface used to transfer data between the computer and the disk. Several drive interfaces are in use today: ST-506/412 IDE EIDE ESDI SCSI ST-506/412 Interface The ST-506/412 Interface was one of the first fixed drive interfaces designed and became a standard for many fixed disk systems. It was originally designed for a 5M drive. As manufacturers improved the perform- ance of their drives, a need developed to tell the com- puter about the characteristics of the drive as far as how many disks and heads are in the drive. This was accom- plished by installing a drive table in the computer’s BIOS ROM, and then having the technician tell the computer what freed disk system was being used by running the set-up program. The original ST-506/412 specification dictated that modified frequency modulation be used as the encoding scheme, but lately the interface has been upgraded to include RLL 2, 7. The ST-506/412 interface also requires the data encoder/decoder be on the disk controller. This means that raw data is transferred from the disk to the controller over the data cables. To reduce the possibility of data loss during this transfer, fixed disk data cables are kept as short as possible. Enhanced Small Device Interface (ESDI) The Enhanced Small Device Interface (ESDI) is a high performance, high-speed interface and controller. ESDI controllers increase reliability by putting the data encoder/decoder circuitry on the drive logic board. This eliminates the data errors caused by noise and signal loss in the cables. ESDI is capable of transferring data at a rate of 24 megabits per second. Most ESDI drives today are limited to 10 or 15 megabits per second due to limitations of the host computer’s I/O bus. ESDI drives are capable of being formatted to 60 sectors per track or higher, although 32 sectors per track is most common. All ESDI controllers can support a 1:1 interleave. One of the most important features of ESDI systems is that the controller can read the drive parameters directly off the disk. With this capability, the controller can tell the BIOS the type of drive installed. This eliminates the need for the user to run the setup program. Also, this feature allows for defect mapping, further improving the drive’s reliability. Integrated Drive Electronics (IDE) The Integrated Drive Electronics (IDE) interface was originally developed as an interface for hard cards. A hard card is a small drive mounted on a controller board which plugs directly into the personal computer’s expansion slot. IDE has been expanded to include 5.25-inch and 3.5-inch fixed disk systems. IDE drives connect to the motherboard of the host computer with a 40-pin connector. IDE drives have much of the controller and interface circuitry on the drive logic card. Recently, computer manufacturers introduced motherboards with IDE controllers and interfaces. One major drawback of IDE drives is that you can damage the drive if you try to perform a low-level format on the drive. 10-27

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Enhanced Integrated Drive Electronics (EIDE) The EIDE interface was developed to overcome many of the limitations of the IDE interface. As we saw in chapter 7, EIDE provides the capability for addressing fixed disks with over 540 MB of storage capacity. EIDE also provides faster data transfers and the ability to use a CD-ROM drive in an EIDE system. Small Computer Systems Interface (SCSI) The Small Computer Systems Interface (SCSI) is really a systems level interface, not just a disk interface. SCSI (pronounnced scuzzy) uses a host adapter that plugs into the computer. The SCSI has eight I/O ports. One is dedicated as the interface between the host computer and the adapter. The other seven ports are available for other device controllers, such as disk drives, CD-ROM readers, and digital scanners. The SCSI is a smart interface. When the host computer requests data from a device connected to the SCSI, the SCSI will disconnect itself to free up the computer while it processes the request. The SCSI is capable of transferring data at up 100 megabits per second. FORMATTING FIXED DISKS Fixed disk systems operate in much the same manner as the floppy disks and the disk memory set. Before anew fixed disk drive can be used in a personal computer, it must be formatted. The formatting of a fixed disk is performed by two or three separate operations. These are as follows: Low-level format Creating a DOS partition High-level format Low-Level Format The low-level format program writes the tracks and sectors on the disk. Low-level format programs vary according to the type of drive and controller. Many controller manufacturers now include the low-level format program in a ROM on the controller. You can access this program by using the DOS DEBUG routine. Refer to the controller’s documentation to find the starting address for the format program. When you install and format a new freed disk drive, it is extremely important to enter the defective tracks from the list supplied by the manufacturer. These bad tracks are usually listed on a label on the drive, with another hard copy supplied with the documentation. When the low-level format program is executed, it will mark any bad tracks with a checksum error that will prevent these tracks from being used for data storage. In addition, the low-level format program will check all areas of the disk to see if any additional bad tracks are detected. If you are formatting a new disk, only the tracks on the manufacturer’s list should be bad. If you are reformatting an older disk and find that additional tracks are listed as bad, the disk is showing signs of severe damage and should be replaced. CAUTION DO NOT run a low-level format program on an IDE drive. Serious damage could result by trying to low-level format this type of drive. There are two additional terms you need to be familiar with to low-level format or troubleshoot fixed disks. These are write precompensation and reduced write current. Write precompensation and reduced write current are also used in some disk memory sets. Write Precompensation —Write precompensa- tion is used to prevent problems that can occur when data is written on the higher numbered cylinders. A disk is divided into sectors and tracks. Each sector can store 512 bytes of data. The sectors on the outside of the disk surface are physically larger than the ones on the inside of the disk. As data is recorded on the disk, like poles of magnetic fields are repelled away from each other and opposite poles are attracted to each other. As the heads move toward the center of the disk, the write precompensation circuitry changes the spacing of the magnetic fields. after the natural attraction or repelling of the magnetic domains is complete, the magnetic fields are in the proper place. Reduced Write Current —Reduced write current also compensates for problems that can arise when writing on the inner tracks of a disk. As the system writes on the inner tracks of the disk, less current is required because the data is more densely packed. Using the same current on the inner tracks that is required on the outer tracks would cause the data to run over each other. Manufacturers’ data sheets included with new drives will indicate what cylinder write precompensation and reduced write current are 10-28

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invoked. You will need this information when you low level format some fixed disk drives. If the write precompensation value. is the same as the highest numbered cylinder on the disk, it means that the disk does not require write precompensation. Creating a DOS Partition Upon completion of the low-level format, a fixed disk to be used in a personal computer needs to be partitioned. To partition a disk, run the DOS FDISK program. Partitioning a fixed disk divides the disk into one or more logical drives. The drive must be partitioned even if the entire drive will be one large partition. DOS 3.3 allows a maximum partition of 32M. DOS versions 4.0 and greater allow DOS partitions of up to 4 gigabytes. If you have a drive larger than 32M, and are using DOS 3.3, you can divide the disk into two logical drives to fully use the disk. Refer to the primary partition as drive C and the extended partition as drive D. Running FDISK on the disk prepares the DOS boot sector so the high-level ‘format program will operate correctly. Partitioning will also allow you to have two different operating systems on the same disk. The primary partition will have DOS, where the extended partition can be set-up to run with OS/2, UNIX, or some other operating system. High-Level Format The last step in preparing a fixed disk for use in a personal computer is to run the DOS high-level format program. This program creates the FAT and an empty root directory so DOS can manage files. If the drive is to be used to boot the computer, this format will also write the two hidden system files and the COMMAND.COM file. Use the command FORMAT C: /S to create a bootable disk. If the disk is to be used for data storage only, do not be use the/S switch. RECOVERING DATA FROM FIXED DISK DRIVES Loss of data on a fixed disk drive can result from several causes. These range from accidental erasure to infection by a computer virus to actual hardware failure. When disaster does strike, the main objective is to recover as much data as possible from the disk. Recovering Data From an Erased File There are many ways that a file can be accidentally erased. The important thing in recovering an erased file is detecting the error quickly. DOS does not actually erase the data areas of a file when you delete it, DOS merely changes the code in the FAT to indicate that the cluster is available for use. Therefore, to completely recover an erased file, you must try the recovery before DOS reuses the clusters that the file was in. You can manually recover an erased file by using the DEBUG program in DOS. This method is long and tedious. Several commercial programs are available that will try to restore an erased file. These programs will look at the deleted directory entry to find where the starting cluster of the file was, then check the size of the file to determine how many clusters the file should have occupied. The recovery program will then check the FAT and see if the clusters are available. For example, if a file occupied clusters 75 to 79, a check of the directory entry would show that the beginning of the file was cluster 75. The program would then try to recover all the data in clusters 75 to 79. The problem arises if the file was fragmented. That is, the file was in clusters 75, 83, 100, and 101. In many cases when the file is fragmented, it cannot be recovered. To avoid file fragmentation, there are also several file unfragmenter programs for use in personal computers. These programs will check the disk for fragmented files, and rewrite the fragmented files so they are contiguous. Computer Viruses A computer virus is any program designed to be willfully destructive. A virus can be spread by several methods. The methods include loading the virus from a bulletin board system and loading a virus onto your fixed disk from a floppy disk. When the word of a virus infection is spread, the first reaction of many users is to panic. Knowing how a virus is spread can help you find the source of the virus. In IBM personal computer systems and compatible systems, a virus can only be spread in .COM and .EXE files. Some viruses maybe harmless pranks, such as displaying a message on the screen every time the virus is activated. Others are much more harmful and may format your freed disk or they may erase the FAT or master boot record (MBR). The three common types of viruses are the worm, the Trojan horse, and the logic bomb. 10-29

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Worm Virus —A worm virus is a program that copies itself endlessly, tying up computer time and eventually overloading the disk. Worms can also spread copies of themselves over networks and disrupt the network by overloading all the computers on the network. Trojan Horse Virus —A Trojan horse virus is a program that embeds itself into other programs. When an infected program is run, the virus further infects other programs or causes damage to your system. Trojan horses can contain worms or logic bombs. Once active, the Trojan horse worm component will seek out other programs to infect. Trojan horses are commonly used as an initial source of infection o Logic Bomb Virus —A logic bomb is a virus that is embedded in a program or operating system that waits for an event to occur. The logic bomb is activated by a date, a time, or by some other parameter. When the conditions of the logic bomb are met, the bomb is activated. Logic bombs can reside undetected in a personal computer for long periods of time, waiting for the proper conditions to set it off. Logic bombs are traditionally the most destructive of all viruses. PREVENTING VIRUS INFECTIONS. —Virus infections can be prevented with a little caution and common sense. Viruses reside in the disk’s boot records or in .COM or .EXE files. Your system cannot be infected by data files. Further precautions you can use to prevent viral attacks include: Never use pirated software. Most virus attacks occur as a result of people using pirated software. Note: Pirated software is very common in the Far East, where it is sold complete with pirated manuals and documentation. Make regular backups. Backups may be needed to restore data files in the event of a virus infection. Be sure to maintain several copies of your backups. A good plan is to have one backup that is a week old and one that is a month old. If a virus does infect your personal computer, these backups can help you discover when the infection happened and you can restore some data without reintroducing the virus. Report all virus infections to the command’s ADP Security Officer. The Navy is tracking all virus infections in an attempt to discover the source of each infection o Use only authorized software on personal computers. Do not bring software from home or copy it from other systems. Periodically check for virus infections. One simple way to check for virus activity is to keep an eye on the COMMAND.COM file in DOS. Copy the original COMMAND.COM file under a new name that does not contain a .COM or .EXE extension. Periodically compare the size of this new file with the COMMAND.COM file. If the COMMAND.COM file has gotten larger, something caused it to grow. Suspect a virus. REMOVING VIRUS INFECTIONS. —If a virus does infect your system, there are several ways to remove it. The longest and most tedious is to low-level format your freed disk and restore all your files from your backups. Another method is to use one of the several commercial virus detection and removal programs on the market today. These programs, when used properly, can detect and remove viruses before they have done permanent damage to your system. Recovering Data After a Hardware Failure You come to work in the morning and find that your personal computer is dead. You haven’t made backups of your data in the last year. Don’t panic, even after a severe head crash some data can usually be recovered from a fixed disk drive. Your main priority should be to get as much data off the disk as possible, but first you need to get it running. To do this, the first step is to determine exactly what is wrong with the drive. Check the computer’s setup and ensure that the information about the drive is still there. The setup is stored in the computer. A battery provides power to keep this information in the computer. If the battery dies, when the computer tries to boot from the hard drive, it won’t find the hard drive if the setup is gone. Check the temperature of the computer and the drive. Some drives will not work if they are too hot or too cold. Check the drive’s cables and connectors. Are the connectors on tightly? Connectors can work themselves loose, or they may not have been tightly installed. If you have an extra set of cables, try replacing them. A pinched cable can breakdown from stress in time. Does the disk spin? If not, make the following checks. (1) Check the power supply to see if all the proper voltages are present. (2) Check for stiction; it is another cause of the failure of the disk to spin properly. Stiction can result from the lubricant on the disk getting too hot. The heat softens the lubricant. When the drive 10-30

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is turned off, the lubricant hardens as it cools causing the heads to stick to the disk. The heads will prevent the disk from spinning. To solve this problem, remove the drive and try to free the disk by manually turning the spindle motor shaft. You may have to remove the drive’s logic board to gain access to the spindle motor. Once free, the drive will probably operate normally. (3) If your drive has a stepper motor head actuator, check to see if it is operating properly. A stepper motor can develop dead spots or become stuck. Try to move the stepper motor manually if it is not operating properly. This will move it off the dead spot and the drive may operate long enough for you to recover the data you need. Finally, check the controller. If you have an identical controller, try installing it in the computer and see if this will solve your drive problems. If you don’t have a spare controller, try reseating the chips on the controller board. FIXED DISK CARE AND HANDLING Fixed disks require very little care and handling precautions. Since the head/drive assembly is a sealed assembly, you can’t very easily fix it, so you might as well take care of it. The following tips are designed to help you keep a fixed disk in good condition: Limit the number of times you turn the machine on and off. The power surge from turning on a disk drive can exceed 400 watts. If the heads were not parked, this start-up power surge going through the heads could damage data on the disk. Protect your system from bad power. A good surge protector, power conditioner, or uninterruptible power supply can protect your entire system from being destroyed by a power surge or blackout. If you are using a surge protector, be sure it is one that has been accepted by the Navy for use with personal computers. Mount fixed disk drives using the manufacturer’s instructions and hardware. Low-level format a fixed disk drive in the position and at the temperature that it will be used. Most fixed disk drives will work fine if the computer is stored on its side, but the fixed disk must be formatted in this position to avoid track alignment problems. Park the heads. This is extremely important to do every time you shut the power off if your disk has a stepper motor head actuator. Voice coil head actuators are self-parking when power is turned off. Parking the heads moves them to a safe landing zone so they do not damage the disk. CAUTION Certain IDE drives may be damaged by trying to park the heads. Refer to the manufacturer’s instruction on head parking. Keep the area around a fixed disk system clean. Avoid eating, drinking, and smoking around fixed disks. SUMMARY—MAGNETIC DISK STORAGE This chapter has introduced you to the major types of magnetic disk storage devices. The following information summarizes important points you should have learned: TYPES OF DISKS —Disks are classified as floppy disks or hard disks. Hard disks are furthered classified as disk memory sets that have removable disk packs or fixed disk systems. Infixed disk systems, the disk pack is in a sealed head/drive assembly and is not accessible to the user. ORGANIZING DATA ON DISKS —Data is stored on disks by dividing the disk into tracks, cylinders, and sectors. A track is a concentric ring on the disk. A cylinder consists of all vertical tracks. A sector is apart of a track. Before a disk can be used, it must be formatted. Formatting is the process of writing the tracks and sectors on each recording surface of a disk or disk pack. On disk systems used in personal computers, program and data files are stored in directories and subdirectories. FLOPPY DISKS AND DISK DRIVES —Floppy disk drives are the simplest of all magnetic disk storage devices. Two sizes are commonly used today: 5.25 inch and 3.5 inch. Floppy disks come indifferent densities. THE 5.25-INCH FLOPPY DISK CON- STRUCTION —The 5.25-inch floppy disk consists of a flexible magnetic disk contained in a disk jacket. The jacket has several standardized cutouts. The media access hole provides for the heads to access the disk. The index hole indicates the start of the track. The write enable notch can prevent the disk from being written on if it is covered with a strip of tape. The stress relief notches help to properly position the disk in the drive and prevent the disk from warping while in the drive. 10-31

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THE 3.5-INCH FLOPPY DISK CON- STRUCTION —The 3.5-inch floppy disk is in a hard plastic case. The media access hole is covered by a metal spring loaded shutter. Write protection is provided by a slide switch on the bottom of the case. High density, 3.5-inch floppy disks have a media indicator hole in the disk. A disk without this hole cannot be formatted as a high density disk. FLOPPY DISK DRIVE OPERATION —Several components are common to all floppy disk drives. The spindle assembly/drive motor turns the disk at the proper speed. The drive circuit board controls the reading and writing of data on the disk. Connectors and cables connect the disk drive to the disk controller. The read/write heads actually read data from a disk and write data on a disk. DENSITY AND COERCIVITY —Density is the term that describes how much data can be stored on a disk. Coercivity is how much magnetic force, measured in oersteds, is required to properly write data on a disk. The density and coercivity of a disk is directly related to the magnetic media of the disk. USING LOW-DENSITY DISKS IN HIGH- DENSITY DRIVES —Avoid using low-density disks in high-density drives, especially in 5.25-inch drives. This is because of the difference in the size of the tracks that high-density drives use. Never format a low-density 5.25-inch disk as a high-density disk. The 3.5-inch disk drives do not have these problems because the media indicator hole in the disk case prevents using a low-density disk in a high-density format. FLOPPY DISK DRIVE INSTALLATION AND CONFIGURATION —When installing a floppy disk, you have to determine how the disk is to be configured. You have to set the drive select jumper. Drive selection is also dependent on the type of drive-to-controller cable used. You must also determine the correct setting for the terminating resistor, the diskette change line/ready jumper, and the media sensor jumper. FLOPPY DISK CARE AND HANDLING — Taking care of floppy disks will improve the reliability of the data stored on the disk. It is important to be aware of all potential sources of stray magnetic fields when storing your disks. DISK MEMORY SET —The disk memory set is also commonly referred to as a disk file unit or mass memory storage unit. These devices have large removable disk packs and are mainly for use with mainframe computers. 10-32 MAGNETIC DISK PACKS —Magnetic disk packs are hard platters coated with a magnetic oxide. They range is size from just 1 disk to over 14 disks. Many disk packs have a servo surface that contains permanently recorded data used for positioning the heads. DISK FILE UNIT CONTROLS AND IN- DICATORS (DISK UNIT) —The disk memory set’s controls and indicators allow the operator and technician to set operating modes and monitor the operation of the disk memory set. DISK MEMORY SET CONTROLLER —The disk memory set’s controller manages the operation of the disk memory set. It has six main functional areas: the controller intercommunications bus, microprocessor, buffer memory, controller to disk drive interface, the data bus control unit, and the CDS channel interface. DISK DRIVE UNIT —The disk drive unit controls the rotation of the disk pack, the positioning of the read/write heads, and the reading and writing of data on the disk. DISK MEMORY SET OPERATIONS —Disk memory set operations include disk formatting, write operations, and read operations. CARE AND HANDLING OF MAGNETIC DISK PACKS —Properly taking care of the disk packs can prevent major head crashes and data loss. FIXED HARD DISK SYSTEMS —Fixed hard disk systems are also commonly referred to as hard disks. They are common in minicomputers and personal computers. FIXED HARD DISK DRIVE CONSTRUC- TION —Fixed hard drives consist of one or more disk platters in a sealed head/drive assembly (HDA). The HDA also contains the read/write heads and the head actuator assembly. The head actuator assembly can be a stepper motor or voice coil. It controls the movement of the heads. The spindle motor is mounted outside of the HDA. The spindle motor shaft penetrates the HDA and turns the disk. The logic board of a fixed disk drive controls the position of the heads and read/write operations. DATA ENCODING METHODS —Methods for encoding data on disks were developed to increase data reliability and keep the controller synchronized with the drive. The two most common encoding methods in use are modified frequency modulation (MFM) and run length limited (RLL).

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FIXED DISK CONTROLLERS —Fixed disk controllers control the disk drive. The controller can determine what encoding method is used, what the interleave factor of the disk is, and what interface is used to communicate with the host computer. It is very important that the disk drive and controller are compatible with each other. Some disk controllers are located on the drive logic boards, while other disk controllers are on a separate circuit board with the interface. FIXED DISK INTERLEAVE FACTOR — Interleaving is a method for logically numbering sectors to allow time for the controller to process data. The fastest drive/controller combinations can support a 1:1 interleave. FIXED DISK INTERFACES —Fixed disk interfaces determine how the disk controller communicates with the host computer. In some cases the disk controller is on the same circuit board as the intcrface. The most common interfaces in use are the ST-506/412, the Integrated Drive Electronics (IDE) Interface, the Enhanced Small Device Interface (ESDI), and the Small Computer Systems Interface (SCSI). FORMATTING FIXED DISKS —Before a fixed disk can be used in a personal computer, it must be formatted. Total formatting consists of a low-level format, making a disk partition, and a high-level format. RECOVERING DATA FROM FIXED DISK DRIVES —Most of the time data can be recovered from a fixed disk. Accidentally erased files can be recovered. If your computer is infected by a virus, it is sometimes possible to recover files and get rid of the virus. Broken drives can be revived long enough to get important files off them. The best protection from data loss is regular and complete backups of your data files. 10-33

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CHAPTER 11 CD-ROM STORAGE INTRODUCTION As the uses of computers expand, the need for disseminating large amounts of information to multiple users also increases. This information can be software or raw data. The use of a CD-ROM is ideally suited for these purposes. In the Navy, CD-ROMs are currently being used in several areas including the Naval Intelligence Processing System (NIPS) and the Naval Command and Control Systems. After completing this chapter, you should be able to: Describe the physical characteristics of a CD-ROM Describe the storage structure of the data on a CD-ROM Describe the operation of a CD-ROM drive Describe the different applications that use CD-ROMs The evolution of CD-ROM technology has expanded to the point that multimedia CD-ROMs are now in use. A multimedia CD-ROM is a disc that stores digital data, digitized audio data, and digitized video data. The same CD-ROM drive can be used for all three functions; in many cases, using the computer to drive the audio and video portions of the CD-ROM. NOTE: Disc or disk? The original audio compact disc distributors referred to the CD as a disc, while the manufacturers of floppy disks used the disk spelling. When the compact disc was developed as a digital storage medium, the manufacturers kept the disc spelling. In this manual, we stay with the current use of disc when referring to the CD-ROM compact disc. The CD-ROM for use as a data storage medium was a result of the popularity of the audio compact disc. The major problem that had to be overcome was that digital data storage had to be much more precise than digital audio. A reliable data encoding and error correction scheme was developed to solve this problem. This chapter will introduce you to the CD-ROM and the CD-ROM drive. TOPIC 1—THE COMPACT etching a series of pits, or little holes, between flat spots. DISC The flat spots on the disc are called lands. The information is stored on a continuous spiral track that The compact disc is capable of storing any type of starts at the inside of the disc and travels toward the digital data. The information is stored on the disc by outer edge. 11-1

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PHYSICAL CHARACTERISTICS OF A COMPACT DISC The base of a CD is a clear, hard plastic, known as polycarbonite. The CD is molded from a master that forms the pits and lands. The top of the plastic disc is coated with a reflective material, such as aluminum, that reflects the light of the reading laser. The entire disc is coated with a protective lacquer and a label is printed on the top of the disc. Figure 11-1 shows a typical compact disc. The diameter of the disc is 120 mm. The center hole is 15 mm in diameter. The area closest to the center hole is the clamping area, and no data is written in this area. The clamping area is generally 26 mm to 33 mm wide, measured from the center of the disc. The data area is approximately 38 mm wide and is divided into three sections. Figure 11-2 illustrates a cross section of a CD-ROM’s data area. The table of contents for the entire disc occupies the first 4 mm of the data area. The next section is the program area, and occupies 33 mm if the disc is filled to capacity. The third area of the disc is the lead-out area and it is used to tell the drive it has reached the end of the disc. No data is written on the outer edge of the disc; this allows for handling. ADVANTAGES AND DISADVANTAGES OF CD-ROM CD-ROM has several advantages over magnetic media in the dissemination of digital information. The greatest advantage is the amount of data. A single CD-ROM can store over 500 megabytes. The data on a CD-ROM can also be a mixture of digital information. The CD-ROM can store audio, video, graphics, text, and programs. CD-ROMs that combine different types of data (audio, graphics, and so on) are known as CD-I, or compact disc-interactive. The CD-ROM is extremely durable and difficult to damage. Since the CD-ROM is an optical storage medium, the read head never comes in contact with the disc. Therefore, it does not suffer from damage caused by head crashes as magnetic disk media do. The CD-ROM does have disadvantages. Because of the way the CD-ROM drive reads data, the access time is much slower than for a high performance fixed disk system. The CD-ROM is designed to hold a large amount of data for a large number of users. The initial high cost of producing the master disk precludes sending unique information to just one or two users. DATA STORAGE STRUCTURE Information is written on a CD-ROM as a series of pits and lands and read from the disk by detecting reflections of a laser from the lands. When the laser Figure 11-1.—A typical compact disc. 11-2

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Figure 11-2.—A cross section of CD-ROM with data areas defined. beam is over a land, the light is reflected back to a photodetector. When the laser beam is over a pit, the light is defused and not detected by the photodetector. The data on a CD-ROM is written in a continuous spiral, much like the groove of a phonograph record, and was adapted from the CD audio standard. The data track is 0.5 micrometers wide. The space between the turns of the track is 1.6 micrometers. This equates to a track density of 16,000 tracks per inch (tpi) and a maximum of 640 megabytes per disc. The actual capacity of a CD-ROM is dependent on the mode used to produce the disc. Two modes of recording data on a CD-ROM are currently in use. Mode 1 writes 2,048 data bytes per sector, followed by error correction codes. Mode 2 writes 2,336 data bytes per sector and eliminates the error correction codes. In chapter 2 of this manual, you saw that a disk is divided into tracks and sectors. The disk rotation speed is constant and data is accessed by defining the track and sector. On a CD-ROM disc, the data is also stored in sectors of 512 bytes. The size of the sectors on a CD-ROM disc remains the same, regardless of the physical location of the sector. The spiral increases in size as it winds toward the outer edge of the disc, thus the number of sectors per rotation increases. Constant Linear Velocity Constant linear velocity is the technique that the CD-ROM drive uses to access data from a disc. To properly read the data from the disc, the speed of the disc must decrease as the laser moves to the outer edge of the disc. Rotation speed of the disc while reading the inner tracks is approximately 500 rpm. As the read head moves to the outer edge of the disc, rotation speed decreases to 200 rpm. Sector addresses on CD-ROM are adaptations of the CD audio standard and are recorded on the disc in terms of minutes, seconds, and sector (minute: second: sector). To find a sector, the read head is slewed to the approximate position of the data, the rotation speed of the disc is adjusted, and the drive reads the position data in the header of the next sector to determine the location of the read head. The read head is then fine positioned to the desired location by repeating this procedure until the proper sector is found. This process can lead to access times of about 1 second. Once the proper sector is found, data transfer is 150 to 300 kilobytes per second, depending on the type of CD-ROM drive. These relatively slow access times and data transfer rates are among the biggest problems with CD-ROMs. Manufacturers are striving to improve these rates and have introduced double-speed, triple-speed, and higher multiple-speed drives. Eight-to-Fourteen Modulation The eight-to-fourteen modulation technique for encoding data on a CD-ROM disc was developed to increase the accuracy of the data read from the disc. Each byte has a corresponding 14-bit code. When the disc is manufactured, the data is recorded in the eight-to-fourteen code. When the data is read from the 11-3

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disc, the conversion from coded information back to a byte is accomplished from a look-up table. This table is in a ROM on the disc drive. Three additional bits are added to each 14-bit code to provide separation and low-frequency suppression. TOPIC 2—CD-ROM DRIVES Although still relatively new, CD-ROM drives are becoming popular as a tertiary storage media device. CD-ROM drives vary by manufacturers in the method the data is read from the disk and the laser system used, but the basic operation is similar. In this section, we cover the common components and operation of CD-ROM drives. The basic components of the CD-ROM drive are the following: Optical head Turntable Computer interface section Microprocessor based control system Figure 11-3 shows a basic block diagram of a CD-ROM drive. OPTICAL HEAD The optical head maintains the circuitry to read the data from the disc. This unit usually consists of four main subassemblies; (1) the laser, used to generate a light beam; (2) a lens system, to focus the laser beam on the disc and to direct the reflected light to the photodetector; (3) a series of servomotors that controls the position of the laser and lenses to ensure proper tracking and focus; and (4) a photodetector, that evaluates the reflected light and converts the light to electrical impulses. Laser The laser in a CD-ROM drive is generally a small injection laser diode that emits light in the infrared band. An injection laser is energized by injecting it with an electric current across a semiconductor junction. Injection laser diodes are the smallest laser light source. They are highly efficient and mass produced. Figure 11-3.—A CD-ROM drive block diagram. 11-4

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The laser beam is directed to the disc using several different methods, depending on the system preferred by the manufacturer. One type of system deflects the laser beam off a semitransparent mirror, through the lenses, and onto the disc. When the laser beam strikes a land, the reflected light passes through the semitransparent mirror into the photodetector. Lenses The lenses in a CD-ROM drive are used to focus the laser beam onto the compact disc. When the laser is turned on, the beam tends to diverge as it travels away from the source. The beam first passes through a collimating lens that reduces the divergence. The beam then passes through the objective lens, where it is focused onto the surface of the disc. The final component used to focus the beam on a compact disc is the disc itself. The diameter of the laser beam as it exits the objective lens is approximately 1 mm. The refractive properties of the clear plastic material of the disc further focus and reduce the diameter of the laser beam so that it is 1.0 µm when it reaches the information surface of the disc. This fine focus of the laser is one of the factors of the high durability and reliability of the compact disc. Tracking and Focusing Once the optical head is positioned over the area to be read, a system is needed to properly hold the optical head on the track and maintain proper focus. Errors in tracking and focus can occur because the compact disc is not perfectly flat. Several methods are used to determine tracking and focus. In the optical head system described earlier in this chapter, the reflected laser beam passes through the semitransparent mirror. The reflected laser beam is next split into two beams by a prism. These two beams are directed to the photodetector. The photodetector consists of four photodiodes. Figure 11-4 shows how the reflected light strikes the photodiodes if the tracking Figure 11-4.—Photodiodes detecting tracking and focus of the laser beam. 11-5

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is off to the left, off to the right, or on track. The output of the photodiode is fed to a differential amplifier. If the laser is on track, the output voltage of the photodiodes is equal. If the laser beam is off to the left or right, a control voltage will be generated by the differential amplifier that is fed to the track following servo. The amplitude and polarity of this control voltage determines the direction and distance of correction needed. The same four photodiodes are also used to determine the focus of the laser beam as it strikes the disc. Figure 11-4 shows how the photodiodes will react to detect if the disc is too close to the laser or too far away from the laser, or if the laser is in focus. Again, the output of the photodiodes is fed to an amplifier and correction of focus is made by moving the objective lens. The output of these four photodiodes is also summed and contains the encoded data on the disc. It is then sent to the control section for decoding. CD CONTROLLER The CD controller processes the signals received from the optical head, attempts to correct any errors in the data, and controls the speed of the turntable. The information from the photodiodes that is received by the controller is still encoded in eight-to-fourteen modulation (EFM) data. The decoding of EFM data is done by the microprocessor. The code addresses a ROM that contains the proper byte for the encoded data. The output of the ROM is stored in a RAM where it is checked for errors. TURNTABLE The turntable rotates the disc and is driven by a servomotor. Since the data is written in a continuous spiral, the speed of the turntable must be adjustable so that the information passes over the optical head at a constant speed. The audio CD requires a speed of 1.3 meters per second. This speed was adapted for use in computer applications, but proved to be extremely slow when compared to the processing and data transfer speeds of modem computers. The 2X CD-ROM drive doubled the speed the data track passed over the optical head. The 4X, 6X, and 8X CD-ROM drives spin the disc even faster. The speed multiplication factor is based on the original speed of 1.3 meters per second. Initial speed adjustments are made when the optical head is positioned in the approximate area of the data. The header of each sector contains a synchronization pulse that is fed into a sawtooth wave generator. The sawtooth wave is fed to the turntable servomotor. The frequency of the wave is used to make fine adjustments to the turntable speed. INTERFACE SECTION The interface section provides for the transfer of data between the computer and the CD-ROM drive. Many CD-ROM drives are manufactured with the small computer systems interface (SCSI), although some proprietary interface units are available. TOPIC 3—CD-ROM APPLICATIONS Applications that use CD-ROM are rapidly expanding throughout the Navy as systems are updated and the need for reliable storage of large amounts of information increases. DATABASES AND PUBLICATIONS CD-ROMs are used in command and control systems, intelligence systems, and the supply system. These applications use large databases. Databases, such as a part number cross-reference list, can significantly reduce the amount of paper storage space required. The CD-ROMs allow information to be quickly retrieved, cross-referenced, and displayed to the user. Many publications and instructions are also being stored on CD-ROM in an effort to reduce printing and mailing costs. As publications are updated, anew disc is made and sent to all users, who then replace the old disc. MULTIMEDIA (CD-I) APPLICATIONS Multimedia or compact disc-interactive (CD-I) applications combine machine executable code (programs), text, audio, video and graphics all on the same CD-ROM. The microprocessor in the CD-ROM drive reads the code at the beginning of each sector to determine if the information that follows is audio, video, graphics, etc. The data is then output on the appropriate channel of the CD-I drive. 11-6

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SUMMARY—CD-ROM STORAGE This chapter has introduced you to the CD-ROM and CD-ROM drive. The following information summarizes important points you should have learned. COMPACT DISC —A compact disc is an optical storage medium that can store over 500 megabytes of information. PHYSICAL CHARACTERISTICS —The disc is 120 mm in diameter with a 15 mm hole in its renter. The disc is made of a polycarbonite plastic and coated with a reflective material. Data is stored by etching small holes in the reflective material called pits. The nonetched areas that reflect light are called lands. ADVANTAGES OF CD-ROM —The advantages of using CD-ROM include: Capability to store large amounts of information Ability to store data, graphics, audio, and video on the same disc Durability—since the optical head of the CD-ROM drive never contacts the disc, there is no danger of a head crash, wear and tear, or accidental data corruption that magnetic media suffer. DISADVANTAGES OF CD-ROM —The disadvantages of CD-ROMs include: High initial cost to produce a single disc Slow access and data transfer times compared with high performance fixed disk systems” DATA STORAGE STRUCTURE —Data is stored on a CD-ROM disc in a continuous spiral that starts at the inside of the disc. The spiral is divided into sectors that each hold 512 bytes. Sectors are addressed by minute: second: sector. The number of sectors per revolution of the disc varies as the spiral moves toward the outer edge. The disc drive varies the speed of the disc so that the data passes over the optical head at a constant 1.3 meters per second. This is known as constant linear velocity. Data is encoded on the disc using a method known as eight-to-fourteen modulation. Eight-to-fourteen modulation uses 14 bits to represent 1 byte and aids in error detection and correction. CD-ROM DRIVES —-The CD-ROM drive reads the information stored on a compact disc. The methods used to read data from the disk and the laser systems used in CD-ROM drives vary by manufacturer, but have several similarities. The basic components of the CD-ROM drive are the optical head, a turntable, a computer interface, and a microprocessor-based control system. OPTICAL HEAD —The optical head is the heart of the CD-ROM drive. It contains a small laser diode to read the data on the disc. The optical head also contains circuitry and optics to control the tracking and focus of the laser beam. CD CONTROLLER —The CD controller receives the raw data signals from the optical head and converts the eight-to-fourteen encoded data to eight-bit bytes. The controller also prepares the data for transfer to the computer via the interface and controls the speed of the turntable. INTERFACE SECTION —The interface section controls the data exchange between the computer and the CD-ROM drive. CD-ROM drive interfaces can be SCSI or proprietary systems. CD-ROM APPLICATIONS —CD-ROMs are used to distribute large amounts of information, such as databases and publications. CD-ROMs can also combine types of information, such as audio, video, data, and graphics. These systems are compact disc interactive or CD-I. 11-7

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CHAPTER 12 PRINTERS INTRODUCTION Printers have been around since the early days of the computer. The first printers were actually typewriters and teletypewriters that were adapted to print binary data. These printers were often slow and noisy. Today, there are printers that print entire pages of text and/or graphics at astonishing speeds. After completing this chapter, you should be able to: Define the terms character set, font, point, and orientation as they pertain to printers Describe impact and nonimpact printers Describe the operation of line printers Describe the operation of dot matrix printers Describe the operation of daisy wheel printers Describe the operation of laser printers Describe the operation of electrothermal printers Printers are classified as impact or nonimpact printers, depending on the method used to print the characters on the paper. Impact printers use hammers or pins to strike an inked ribbon and print the character on paper. Nonimpact printers print characters using electricity, a chemical process, or a combination of both. Impact and nonimpact printers can be sub-divided into three types: Character printers Line printers Page printers Character printers output data to the printed form one character at a time, line printers print one line of information at a time, and page printers print one whole page of data at a time. Character, line, and page printers can be either impact or nonimpact printers. 12-1

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TOPIC 1—FUNDAMENTALS OF PRINTING The purpose of any printer is to transform information from computers into characters or pictures on paper so that humans can read the information. In other words, printers provide a hard-copy output that we can understand. This topic will introduce you to the fundamentals of printing: character sets, line characteristics, and orientation. CHARACTER SETS A character set is a predefine table of characters that a printer will print. Early printer and computer manufacturers often defined their own codes to represent each character to be printed. Since the computers and printers from different manufacturers didn’t talk the same language, users trying to build customized systems often ran into major communications problems. These problems led to the development of the American National Standard Code for Information Interchange (ASCII, pronounced as-key). The ASCII Character Set ASCII codes are 8-bits long, and standardize the codes for alphanumeric characters, some special characters, and some control codes. Codes 0 through 31 and 127 are control codes. Codes 32 through 126 are printable character codes. Table 12-1 lists the printable ASCII codes with their decimal codes. Table 12-1.—Printable ASCII Codes 12-2

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Referring to table 12-1, if you want to print the word Navy, you would send the decimal codes 78, 97, 118, and 121 to the printer. An 8-bit code can represent decimal values from 0 through 255 making it possible to represent 256 different codes with one character set. ASCII only defines the first 128 codes. The other 128 codes are used by software developers and printer manufacturers for additional characters. The additional characters are called the alternate character set. Alternate Character Sets With the development of printers capable of printing graphics and nonstandard characters, the second half of the ASCII character set (128 through 255) became available to define additional special characters and features. Because software programmers found that having only one character set severely limited the capabilities of graphic capable printers, additional character sets were developed. Today, it is not unusual to find programs with eight or more complete character sets. These additional character sets may contain math symbols, foreign alphabets such as Greek, Russian, or Japanese, and other special symbols. To print the characters in an additional character set, you must have a graphics-capable printer and the program must specify the character set as well as the character code. Therefore, the characters printed are a combination of hardware and software capability. To make all this work together, software programmers must write a routine called a printer driver that performs several functions. A printer driver is written for each printer the software will support. The driver tells the software what the capabilities of the printer being used are and tells the printer how to print each character in the character set or sets. CONTROL CODES To make a printer print, the computer must have a method to control the printer. Printer control is accomplished with control codes. The original ASCII code contains 32 control codes. However, additional codes are needed to control the special features in modern printers. Most printers use a combination of the ASCII control codes and escape codes to enable and disable printer functions. Table 12-2.—Selected ASCII Control Codes ASCII Control Codes Table 12-2 shows examples of the ASCII control codes. Some of them you will recognize, such as carriage return and line feed. When printing, if the printer reaches the end of a line, the software must send a carriage return and a line-feed code. Without the line-feed code, the printer would overstrike the data just printed. The start-of-text tells the printer that all the codes following are data codes to be printed. Some printers have a selectable option that will automatically generate a line feed for every carriage return. Escape Control Codes The technology of printers has grown so that the original ASCII control codes can no longer support all the capabilities of most modern printers. Escape control codes are used to enhance printer operations beyond the limitations of the ASCII codes. Escape refers to the ASCII code 027, or the code generated by the ESCAPE key of the keyboard. Escape control codes can be used to change the style of print, the size of the print, whether the print is bold, and various other features of the printer. Escape codes are not standard and are defined by the printer manufacturer. 12-3

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Figure 12-1.—Samples of different fonts. An escape control code is the ASCII escape code (27) followed by one or more additional characters. For example, a dot matrix printer may use ESCAPE C to start underlining text and ESCAPE D to stop underlining. Another example of an escape control code could be ESCAPE (s1S) to select italics as the style of print. The decimal representation of this string is 027, 040, 115, 049, 083. Controlling the medium- and high-speed printers used with mainframe computers is accomplished with external function messages from the computer. These printers use ASCII codes to determine the characters to be printed. LINE CHARACTERISTICS Line characteristics refer to the method of character spacing, the size of the characters, the number of characters printed per line, and the number of lines per inch. Character Spacing Depending on the type of printer being used, character spacing can be freed or proportional. Fixed spacing means each character, upper and lower case, requires the same amount of space on the line. With proportional spacing, narrower letters use less space than wider letters. For example, a lowercase i requires less space than an upper case W. With proportional spacing, the number of characters per inch is an approximation. With fixed spacing, the number is always the same. Character Size Character size can be affected by many factors, depending on the type of printer being used. Drum printer character size is freed and difficult to change. Most dot matrix and laser printers can print a wide variety of character sizes and fonts. Font refers to the style of the typeface, such as Courier, Times New Roman, or Ariel, combined with the size of print and the stroke weight (for example, bold). Figure 12-1 illustrates several common fonts. Character size is also selectable on many printers. Character size is expressed in terms of pitch (characters per inch) or point size. Point refers to a printer's measure of print height. One point is equal to 1/72 inch. All the fonts illustrated in figure 12-1 are 12-point fonts. Note how the typeface affects the character spacing. Figure 12-2 illustrates the same typeface printed in several different point sizes. ORIENTATION Orientation refers to how the characters are printed on the page. There are two modes of orientation: portrait and landscape. When portrait mode is selected, the data is printed across the width of the page. Figure 12-2.—Samples of different point sizes of the same typeface. 12-4

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All printers need to communicate with the host computer. Communications is handled in the interface section. Printers connected to mainframe computers generally have a communications protocol that is designed for the computer, such as NTDS fast or NTDS slow interface. Smaller printers used with personal computers will have either serial or parallel interfaces. The most widely accepted serial interface is “Recommended Standard-232” or simply RS-232. The most widely used parallel interface is the Centronics standard parallel interface. RS-232 Serial Interface RS-232 was developed by the Electronics Industry Association (EIA) to be a universal serial interface standard for any serial device such as a modem, printer, or keyboard. For a printer to properly receive serial data, the parallel bytes that the computer works with must be converted into a serial data string. Once the data string is received by the printer, it must be reconverted to parallel data for the printer to use. These conversions are accomplished by a special circuit called a universal asynchronous receiver/transmitter (UART). The UART can perform both parallel to serial and serial to parallel conversions. UARTs do not need extra control lines to control the flow of data, so the UART never knows when anew character is arriving. To send a data word, the UART must attach from two to four extra bits. First, the UART inserts a binary ZERO to represent a The text that you are reading now is printed in portrait mode. In landscape mode, the page is rotated 90 degrees and the data is printed across the length of the page. Using standard paper, portrait mode is aligned 8.5 inches wide × 11 inches long; in landscape mode the paper is aligned 11 inches wide × 8.5 inches long. Orientation is selectable on some dot matrix printers, ink jet printers, and all laser printers. TOPIC 2—BASIC PRINTER CHARACTERISTICS All printers have the same function, that is to print data on paper. The method they use to put the information on paper varies with the type of printer. This section covers areas of the printer that are common to most printers: interface, control, paper feed, and power supply. INTERFACE SECTION start bit. The next seven or eight bits represent the actual data code. Although some printers still work with seven data bits, eight bits is the standard found on most printers today. After the data code is sent, the parity of the data is checked and a parity bit maybe added. Whether a printer uses even or odd parity is determined by the manufacturer and is set up when the printer is connected to a computer. To end the data word, the UART adds one or two stop bits. Configuring the UART for a printer is accomplished by setting a number of dip switches of the circuit board. The RS-232 interface cable is connected to the computer and printer by a DB-25 sub-miniature connector. The DB-25 connector is a 25-pin D-type connector. Although the connector has 25-pins, serial communications with software handshaking needs as few as three of the pins connected. Handshaking signals are signals that control the printer. Software handshaking uses the ASCII codes such as XON/XOFF and ETX/ACK. Hardware handshaking uses an additional line to indicate data terminal ready (DTR) to the computer’s data set ready (DSR) pin. When hardware handshaking is used, the printer cannot send data to the computer. Centronics Parallel Interface The Centronics parallel interface uses a 36-pin Centronics connector at the printer end of the cable and a DB-25 subminiature connector at the computer. The parallel interface is an eight-bit, two-way interface between the computer and the printer. When the computer sends data to the computer, it places the data on the data lines and sets a strobe signal. The strobe signal indicates to the printer that the data is ready for transfer. When the printer samples the data, it will set the acknowledge line to tell the computer it has sampled the data. CONTROL SECTION The control section of a printer directs all printer operations. This section receives and decodes computer data from the interface section. If the data contains characters to be printed, the control section determines what character it is and when to activate the print mechanism. The print mechanism can be a print hammer, a series of print wires, a laser beam, or some other mechanism. The control section receives signals from various parts of the printer as to the presence of paper, carriage position, and print head temperature. 12-5

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CONTROL PANEL The control panel allows the operator to set the printer’s operating parameters such as font, characters per inch, and print quality. The operator may also be able to run a self-test to check various fonts and print quality. The control panel can also be used to advance the paper to the top of the form or advance the paper one line. There is usually a switch to control whether the printer is online or offline. When operators perform any actions with the control panel, they should be sure the printer is offline to prevent any stray interrupts being sent to the host computer. PAPER-FEED ASSEMBLIES The two most common methods of feeding paper through a printer are the tractor feed and friction feed. Some printers may have both friction feed for single-sheet paper and tractor feed for continuous paper. Tractor Feed Tractor feed is probably the most common of all paper-feed methods. It is easily recognized by the type of paper used and the tractors that actually move the paper. Figure 12-3 shows the basic components of a tractor paper-feed assembly. Tractor feed uses continuous paper with perforated holes on each side. The paper is threaded through the printer’s platen to the tractor’s sprockets. The perforated holes on each side of the paper are lined up with the sprockets and the paper is held in place when the sprocket covers are closed. The paper is advanced by a paper-feed motor. This is generally a stepper-type motor, where each step advances the paper one line. The paper-feed motor turns the platen, which is connected to the tractors by a drive belt or a set of gears. Friction Feed Printers using a friction-feed paper advance are capable of handling both continuous flat folded and single sheets of paper. With friction feed, the paper is held firmly against the platen by a pressure roller. To advance the paper, the paper motor turns the platen, which causes the paper to advance. Another type of friction feed, the sheet feeder, is common in laser printers and uses a series of rollers to transport the paper through the printer. Figure 12-4 illustrates the basic operation of this type of paper feed. The pick up roller picks the top sheet of paper in the tray. A separation pad ensures that only one sheet of Figure 12-3.—A tractor-feed assembly. 12-6

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Figure 12-4.—A laser printer paper feed. paper is picked up. The registration rollers align the paper so that it is straight. The registration rollers feed the paper to the transfer roller. The transfer roller presses the paper against the drum to transfer the toner from the drum to the paper. The paper then passes through the fusing rollers. The fusing rollers are heated rollers that melt the toner to the paper. The paper is then fed to the paper output tray. POWER SUPPLY All printers have a power supply to provide the proper operating voltages for the printer. The output voltages and current of the power supply depend on the type of printer. TOPIC 3—IMPACT PRINTERS Impact printers form characters on the paper by striking a device against an inked ribbon and into the paper, causing a character to be imprinted on a sheet of paper. Common impact printers include the following: Drum printers Band printers Dot matrix printers Daisy wheel printers Impact printers can be line printers or character printers. LINE PRINTERS Line printers receive data to be printed from the computer and store the data until a complete line is ready to be printed. The line printer will print several characters at a time. The types of impact line printers commonly used in the Navy are the drum, chain, and band printers. Drum Printers In a drum printer, the character set is inscribed as raised fonts on a hollow metal drum. These raised characters are formed into lines or bands on the drum. Figure 12-5 shows atypical print drum. All the A’s are on one line, all the B’s are on the next line, and so forth, until all the characters in the set form a line each. The character set is repeated for each column that the printer Figure 12-5.—A print drum showing character lines. 12-7

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is capable of printing. If the printer is an 80-column printer, the drum has 80 characters on each line. The character drum is rotated at a high speed. As the desired character faces the paper, a print hammer for that column is activated or fired, forcing the paper and inked ribbon against the drum. The character on the drum is imprinted on the paper as shown in figure 12-6. Normally, the hammer bank contains one hammer for each character column of a line. If the printer has a capacity to print 132 columns, then the hammer bank will consist of 132 hammers. As a line is printed, each hammer is fired as the character to be printed in its column faces the paper. A drum printer prints one line of data for each rotation of the drum. Drum printers can print from 300 to 1,200 lines per minute, depending of the rotational speed of the drum and how fast the printer can setup to print the next line. Chain and Band Printers Chain printers use a print chain as a source of raised characters. The links of the chain are engraved character-printing slugs. The chain is made up of several sections; each section contains one complete character set. The print chain is rotated at a high rate of speed past the print positions (columns). As the desired character faces the paper, the print hammer for that column is fired, printing the character on the paper. Band printers work on the same principle as chain printers except that a scalloped, steel print band is used instead of a print chain. Figure 12-7 illustrates part of the band printer’s print mechanism. To change the font (typeface) on a chain or band printer, you change the print chain or band. Character sets of the chain and band printers vary, but are typically 48 to 64 characters. Since hammers are of a freed size, Figure 12-6.—Drum, ribbon, and paper relationship during printer operations. 12-8

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Figure 12-7.—Band, paper, ribbon, and hammer relationship in a typical band printer. changing the size of the fonts is not possible because each column printed must have its own print hammer. Band and chain printer characters are generally printed at 10 characters per inch (cpi), although a few printers have been manufactured to print 12 cpi. Chain and band printers are medium- and high-speed printers. They print over 300 lines per minute. CHARACTER PRINTERS Character printers print one character at a time. Most character printers are impact-type printers. The notable exception to this is the ink jet printer, which sprays ink on the paper to print characters. The common impact character printers are the dot matrix and the daisy wheel printers. Dot Matrix Printers A dot matrix printer forms characters by printing a series of small dots. The heart of the dot matrix printer is the print head. The print head contains a series of print wires, small pins that strike the page to create characters and graphics. The quality of print from a dot matrix printer is directly related to the number of print wires in the print head. The most common print heads use 9 or 24 print wires. Figure 12-8 illustrates the nine-pin print head. Figure 12-8.—A single column, nine-pin print head. The print wires in the print head are independently driven by individual solenoids. A pulse applied to the selected solenoid forces the print wire into the ribbon and the paper. The print wire is returned to its normal position by a spring that holds it in the print head. The firing of the print wires can occur over 300 times per second. The print wire solenoid driver pulse generates heat. The print head is usually mounted on a heat sink because of the speed at which the print head operates. The heat sink uses ambient air to disperse heat that, if left unchecked, would damage the print wires. The quality of print generated by dot matrix printers has improved greatly over time. Older printers contained only seven print wires and the dots were clearly visible. Because of this, dot matrix printers were often used for only draft work and the final document was reprinted on a daisy wheel-type printer or manually typed. Today, many dot matrix printers have a print mode refereed to as near letter quality (NLQ). Letter quality refers to the quality of print typically generated by a typewriter. Near letter quality print has become acceptable for all but the most formal of communications. A dot matrix printer using the nine-pin print head shown in figure 12-8, will initially print a character in the draft mode. The paper is then advanced one-half dot space and the character is printed again. This will fill in the space between the dots and the characters will appear smoother. A 24-pin print head prints near letter quality faster because it has two vertical columns of print wires. The print wires in column two are slightly offset from 12-9

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Figure 12-9.—A typical print wire arrangement in a 24-pin dot matrix print head. column one as shown in figure 12-9. Near letter quality can be printed with just one pass of the print head. The print wires are smaller in diameter than the ones on a nine-pin print head, resulting in even smoother characters. The dot matrix print head is mounted to a low friction slide that is mounted to one or two carriage rails. The carriage rails are usually finely polished steel to further reduce friction. The print head is moved across the length of the platen by a wire, belt, or chain that is connected to the print head mount and to the carriage motor. As the motor turns, it pulls the mount either right or left. On the rails are right and left limit switches that prevent the carriage motor from pulling the print head too far in either direction. The limit switches maybe mechanical switches or optical sensors. Figure 12-10 shows a basic carriage assembly. Daisy Wheel Printers The daisy wheel printer uses a single print hammer and produces letter quality print. A daisy wheel is a small plastic disk with a number of petal-like projections. A character die is located on the end of each projection as shown in figure 12-11. The daisy wheel is rotated by the print head mechanism until the desired character is in the proper position to be struck by the print hammer. The hammer drives the die into the inked ribbon, which prints the character on the paper as shown in figure 12-12. The print head is then moved one space, the wheel is rotated to the next character to be printed and the hammer is fired again. This process is repeated until the entire line has been printed. Many daisy wheel printers are capable of bidirectional printing. The daisy wheel print head is mounted to a carriage assembly that is very similar to the assembly used with dot matrix printers. Daisy wheel printers are slow and limited in the characters printed to those on the wheel. Despite these limitations, they are still used for their ability to print letter quality documents and make carbon copies. TOPIC 4—NONIMPACT PRINTERS Nonimpact printers form characters using methods other than striking an inked ribbon and the paper. Types of nonimpact printers include the following: Laser Electrothermal Inkjet Electrosensitive Electrostatic Figure 12-10.—A basic printer carriage. 12-10

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Figure 12-11.—A daisy wheel. LASER PRINTERS Laser printers are a type of electrostatic printer that produce a very high resolution print on plain paper. Laser printers are classified as page printers; that is, they print a whole page at a time. Laser printers can print from four to eight pages per minute with a resolution of 300 to 600 dots per inch (dpi). The development of a laser engine by Canon U. S.A., Inc., is largely responsible for the laser printer’s Figure 12-12.—A daisy wheel print mechanism. popularity and affordability. The Canon engine combines the print drum, toner, and other parts into a single, easily replaced disposable cartridge. Laser Print Cycle The laser printer’s disposable cartridge is the heart of the printer’s system. The cartridge contains the print drum, primary corona wire, a supply of toner, cleaning blade, erase lamp, and rollers. The laser printer’s image formation process is illustrated in figure 12-13. Figure 12-13.—A laser printer’s image formation process. 12-11

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The print drum is an aluminum cylinder coated with a photosensitive material. This material is highly conductive when exposed to light and has low conductance in darkness. The laser source is from a small laser diode that generates a single wavelength light in bursts of a millionth of a second or less. The laser is focused on the drum and illuminates areas of the drum to form characters. To start a print cycle, the drum is first cleaned, both physically and electronically. The cleaning blade wipes any residual toner from the drum. The erase lamps are turned on and neutralize any charge that maybe on the drum. A negative charge of approximately -600V is applied to the entire drum surface by the primary corona wire. The laser beam is applied to the drum, causing the exposed areas of the drum to become positively charged. Figure 12-14 shows the basic laser imaging and scanning mechanisms. The laser beam is directed through a shutter to a rotating hexagonal mirror. As the mirror rotates, the area of the drum that the reflected beam strikes changes. This is the horizontal scan of the laser. To properly charge the drum, the laser shutter controls when the laser beam will actually strike the drum. When one horizontal scan is completed, the drum is advanced one dot space and the process is repeated. The characters are actually formed through a series of dots, much like a dot matrix printer. As the drum is rotated, it passes by the toner reservoir. The toner consists of a very fine powder of metal, dyes, and plastic particles that are easily attracted by static electricity. As the exposed drum passes by the toner, the positively charged areas of the drum attract the toner while the other areas remain clean. While all this is happening, the paper-feed section of the printer picks one piece of paper from the tray. The paper is lined up with the registration rollers and is ready to be printed on. The paper is passed over the transfer corona at the same time the charged area of the drum is over the paper path. The transfer corona charges the paper at a higher charge than the drum, pulling the toner from the drum to the paper. The paper never actually contacts the drum. The image is now on the paper but it is not permanent. The paper is fed through the fusing rollers. The fusing rollers apply heat and pressure to the paper, causing the toner to melt and permanently bind to the Figure 12-14.—A laser imaging system. 12-12

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paper. Because the toner is melted to the paper, the print appears very smooth and loses the appearance of dots that are common with dot matrix printers. The coating of the print drum is very soft. It can be easily scratched or chipped. Once the print drum has a scratch or chip in it, that area will show up as a blotch or line on all subsequent copies. Also, any of the rollers can get bent, scratched, or develop some type of irregularity and cause blotches. How do you determine what part failed? All of the rollers and the drum shown in figure 12-13 are different sizes. By measuring the spacing between the blotches on the paper, you can get a fairly good idea which area has the problem. Table 12-3 lists the approximate circumferences of the rollers inmost laser printers. Laser Printer Page Languages Currently there are two basic types of desktop laser printers, the Hewlett-Packard (HP) and the Adobe PostScript. Each has its own page description language. Just about all laser printers use or emulate one of these two languages. HEWLETT-PACKARD SYSTEM. —When Hewlett-Packard developed its LaserJet series of printers, the fonts were largely developed from the existing dot matrix printer bit maps. A bitmap is a table that tells the printer when and where to place the dots. With the Hewlett-Packard system, a font definition is required for each font to be printed. Fonts can be resident in the printer’s ROM, contained in a font cartridge which holds additional ROMs, or they can be soft fonts. Soft fonts are loaded into your computer’s memory and transferred to the printer’s RAM as they are needed. Table 12-3.—Laser Printer Roller Circumferences These printers offer very high resolution, a large variety of fonts, and the capability to print graphics. Depending on the model and manufacturer, the Hewlett-Packard and compatible laser printers, can print from four to eight pages of text per minute. Printing graphics can slow down the printer considerably. POSTSCRIPT PRINTERS. —The PostScript family of printers, developed by Adobe Systems, uses an entirely different method for defining characters and graphics. Where the HP system needed a definition for each size font, the PostScript printer needs only one definition for each character in a character set. The definition of the font is a series of mathematical calculations instead of a fixed number of dots. From this definition, the PostScript printer uses mathematical scaling of the character to print it any size from 5 to 5,000 points. By being described mathematically, the image can be manipulated in a number of ways. It can be rotated, shrunk, expanded, twisted, shadowed, or placed in a 3-dimensional prospective. With the exception of how characters are defined, the basics of the PostScript printer are the same as the HP printer. They both use the same print mechanisms and interfaces. ELECTROTHERMAL PRINTERS Electrothermal printers use the heat of wires or pins to create images on a special heat sensitive paper. The paper changes color when exposed to heat, allowing the characters to appear. INK JET PRINTERS Ink jet printers form images and characters by spraying fine drops of ink on the paper. The most common type of inkjet printer is the drop-on -den and print head. Drop-on-demand printing means that ink is ejected out of the nozzles as needed. 12-13

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Figure 12-15 shows atypical inkjet print head. The ink in the reservoir is fed to the nozzles. Characters are formed by spraying the ink in a series of dots, similar to the dot matrix printer. At the output of each nozzle is a small piezoelectric crystal that vibrates when an electric signal is applied to it. The piezoelectric crystals act as small pumps to squeeze the ink out. When a dot is needed, the control circuits send a driver signal to the crystal, which causes it to vibrate, squeezing the nozzle tube and forcing a drop of ink onto the paper. Some ink jet printers use the bubble jet printing process. In this process, the piezoelectric crystals are replaced with small heaters. When a drop of ink is needed, a pulse applied to the heaters causes an air bubble to form in the ink nozzle. This rapidly expanding air bubble forces a drop of ink out of the nozzle and onto the paper. When the drive pulse is removed, the heaters cool almost instantly, creating a vacuum in the nozzle, which draws more ink from the reservoir. Ink jet printers produce letter quality print. They are quiet, fast, and flexible. Some color printer manufacturers prefer the inkjet method for printing. To print color, three print heads are activated simultaneously. The amount of each primary color sprayed on the paper combines with the others to form all the colors of the spectrum. SUMMARY—PRINTERS This chapter has introduced you to the basic concepts of several different printers and printing techniques. The following information highlights important points you should have learned. FUNDAMENTALS OF PRINTING —All printers exist to transform electronic digital data to a hard copy that we humans can comprehend. To ensure that printers and the host computer are speaking the same language, several printing standards have been developed. CHARACTER SETS —A character set defines all the characters a printer can print. The original character set is known as the American Standard Code for Information Interchange, or ASCII codes. With the development of graphic capable printers, most word processing programs offer a wide range of character sets. LINE CHARACTERISTICS —Line character- istics refers to how the characters are printed on a page. They include the typeface, spacing (fixed or proportional), and size. ORIENTATION —Orientation is how the text is printed on a page: portrait or landscape. In portrait mode, text is printed across the width of the page; in landscape mode, text is printed across the length of the page. BASIC PRINTER CHARACTERISTICS —All printers have several functions in common: interface section, control section, control panel, paper-feed assemblies, and power supply. INTERFACE SECTION —The interface section controls the exchange of data between the host computer and the printer. There are several types of interfaces. Mainframe computers used with shipboard systems use standard NTDS interface protocols. Minicomputers and personal computers use either a Figure 12-15.—An ink jet print head. 12-14

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serial or parallel interface. Among these, the RS-232 in the most common serial interface and the Centronics parallel interface is the most common parallel interface. CONTROL SECTION —The control section of a printer receives data from the interface section, decodes the data to determine whether it is a control word or data to be printed. The control section will then take the appropriate action. CONTROL PANEL —The control panel lets the operator set some of the operating parameters of the printer and paper. PAPER-FEED ASSEMBLIES —The paper-feed assemblies move the paper through the printer. Tractor feed and friiction f&dare two main types of paper feed. POWER SUPPLY —The printer’s power supply converts the ac line voltage to the required voltages for the printer to operate. IMPACT PRINTERS —Impact printers form the characters by striking a device, such as a print hammer or print wire, against an inked ribbon and the paper. LINE PRINTERS —Line printers are capable of printing at high speeds. They use rotating print drums, print chains, and print bands with raised character dyes to print characters. Character sets with these printers are limited to the characters on the drum, chain, or band. CHARACTER PRINTERS —Character printers print one letter or character at a time. Two of the more common character printers are the dot matrix printer and the daisy wheel printer. The dot matrix forms characters using a series of print wires. The daisywheel printer uses a small plastic wheel with the character dyes on the spokes of the wheel. NONIMPACT PRINTERS —Nonimpact printers use methods other than striking the paper through an inked ribbon. LASER PRINTERS —Laser printers are a type of electrostatic printer that produce a very high resolution output. The laser printer uses a laser diode to form the image to be printed on a charged photosensitive drum. ELECTROTHERMAL PRINTERS —Elec- trothermal printers form characters on a special heat sensitive paper. Small heaters are activated to form the characters, and the heat causes the paper to change color. INK JET PRINTERS —Ink jet printers use a fine spray of ink to paint characters on paper. 12-15

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CHAPTER 13 DATA CONVERSION DEVICES AND SWITCHBOARDS INTRODUCTION Data conversion is the process of modifying a signal into a form usable by the destination equipment. This conversion can be analog-to-digital (A/D), digital-to-analog (D/A), or digital-to-digital (D/D). An analog-to-digital converter is a device that converts a continuously variable input signal into a representative number sequence. A digital-to-analog converter (DAC) produces an analog signal proportional to the digital value. In digital-to-digital conversion, data is. manipulated into a form usable by the destination equipment. This could consist of changing the logic levels of the signal or shilling data. Switchboards are used to interconnect various combat direction systems’ equipments with each other and with other shipboard systems. After completing this chapter, you should be able to: Define digital-to-analog and analog-to-digital conversion Define sampling, quantization, encoding, Gray code, and binary-coded decimal (BCD) as these terms apply to data conversion Describe the operation of synchro systems Describe the operation of a multiplexing data converter Describe the operation of manual and remotely controlled digital and analog switchboards TOPIC 1—FUNDAMENTALS OF DATA digital-to-analog conversion, and digital-to-digital CONVERSION conversion. Within each of these categories, there are Shipboard data conversion equipment handles a several different types of conversions, each unique in its own way.variety of types of data when communicating with other shipboard subsystems and equipment. In a number of ANALOG-TO-DIGITAL (A/D) ANDinstances, digital equipment must communicate with DIGITAL-TO-ANALOG (D/A)one or more analog or digital devices. A variety of CONVERSIONSequipment is installed throughout the fleet. Data conversion equipments encompass a large number of An analog signal is a signal that varies continuouslymultifunction (MULTIPLEXED) and single function devices. with time. Its amplitude or other variables such as frequency or phase represent a value within a given set In general terms data conversion falls into three of limits. For instance, different values may be main categories: analog-to-digital conversion, expressed or transmitted by changing the amplitude of 13-1

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the signal. Digital quantities on the other hand are represented by binary numbers (ONEs and ZEROs). The binary ONEs and ZEROs indicate the value at a particular instant in time. Each bit position represents a portion of the overall quantity. The summation of the value of the set bits (ONEs) is normally the quantity to be represented. By setting or clearing particular bit positions in the binary word, different values within a set of limits maybe expressed. ANALOG AND DIGITAL QUANTITY COMPARISONS Let’s compare an analog quantity and a digital quantity representing the same range of values, say from 1 to 31 miles. The analog signal will be a linear single-phase ac sine wave. The ac signal is variable between 2 volts and 34 volts peak to peak. An amplitude of 2 volts peak to peak will indicate O miles, the minimum limit value, and an amplitude of 34 volts will indicate a value of 31 miles, the maximum limit. In this example, the increasing signal amplitude indicates an increase in range in miles. The digital value will be expressed by five binary bits. Each bit position when set (a binary ONE) indicates a portion of the quantity. Bit 2 0 indicates a value of 1 mile, bit 2 1 a value of 2 miles, bit 2 2 a value of 4 miles, bit 2 3 a value of 8 miles, and bit 2 4 a value of 16 miles. Zero miles is indicated when all bits are clear (binary ZEROs). The maximum of 31 miles is indicated when all bits are set (binary ONEs), 31 miles being the sum of the value of all the set bits (1+2+4+8+16=31). Figure 13-1 shows the analog and digital representations of the same quantity through the range Figure 13-1.—Analog and digital quantity comparisons. 13-2

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of the values. At 0 miles, the analog signal is 2 volts peak to peak and the digital value is all ZEROS. For an indication of 5 miles, the analog signal increases to 7 volts peak to peak and the digital value now has bits 2 0 and 2 2 set. At 20 miles, the ac signal has increased to 22 volts peak to peak and bits 2 2 and 2 4 are set in the digital value. Finally when the maximum value is reached, the ac signal is 34 volts peak to peak and the digital value has all its bits set. You should be aware that the values we have covered are extremely limited compared to the capabilities of most analog and digital devices. Much greater accuracy and ranges are commonly encountered; however, the basic fundamentals you have just learned will apply. THE ANALOG-TO-DIGITAL CONVERTER An analog-to-digital converter is a device or component of a larger device that receives an analog signal and converts it into a digital quantity with a given accuracy and resolution. The analog signal input is compared to a given reference signal, and the difference between signals is used to compute the digital quantity indicated by the analog signal. The reference signal is normally equivalent to the maximum value of transmitted data: The basic analog-to-digital conversion process can be divided into a series of operations. Each operation performs a specific task in the conversion process. The analog-to-digital conversion operations are sampling, quantization, and encoding. Sampling Sampling is the first operation that takes place in an analog-to-digital conversion. Basically, the inputted analog signal is sampled or tested repeatedly over a period of time. This is done to determine the characteristic that contains the analog quantity, such as the signal’s amplitude. A constantly varying input must be sampled at a much higher frequency than its own to ensure the accuracy of the conversion. Figure 13-2 shows a pulsed sampling of an ac signal. For each sample taken, a voltage level is determined. By comparing the voltages detected by the sample pulses, the largest voltage would tend to indicate the peak and hence the amplitude of the input signal. A sampling is performed on an analog signal only when a conversion is required. Quantization Quantization takes the sampled analog value and converts it to the nearest binary value or quantity. The accuracy of a binary quantity is limited to the value of the least significant bit (2 0 ). In the example in figure 13-1, bit 2 0 was the 1 mile bit, meaning the smallest value that could be indicated was 1 mile and the greatest accuracy was plus or minus 1 mile. Smaller values of 1/2 or 1/4 miles or less could not be indicated. Quantization, in effect, rounds out the conversion to the value of the least significant bit (LSB). Encoding The encoding operation reduces the result of the conversion to a binary code acceptable to the digital equipments that use the data. There is a variety of coding systems in use. You have already been introduced to one of the most common ones, natural binary code. This binary code expresses quantities as a weighted sum. Each bit position represents a specified value when set. The sum of the values of the set bits defines the value of the quantity. The bit with Figure 13-2.—Sampling pulses. 13-3

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the greatest weight is the most significant bit (MSB). The bit with the least weight or representing the smallest value is the least significant bit (LSB). Natural binary code is used in a system of digital data transmission and conversion called binary angular measurement (BAM). Other coding systems such as Gray code and binary-coded decimal (BCD) are also used by analog-to-digital converters. BINARY ANGULAR MEASUREMENT. — Binary angular measurement words (BAMs) are standardized binary words used to transfer angular measurements between shipboard tactical data system equipments. BAM data words are used to transfer quantities between digital equipments, from digital equipments to D/A converters, or from A/D converters to digital equipments. BAM data words are specifically designed to indicate up to 360 degrees of angular values in binary form, often in steps or increments of as small as 0.009766 degree (the LSB value). Figure 13-3 shows one example of a BAM word. This 12-bit word (2°-2 11 ) can indicate 360 degrees of angle in steps of 0.088 degree. The LSB is equal to 0.088 degree when set (ONE), while the MSB is equal to 180 degrees when set. When all 12 bits are set, a maximum angle of 359.902 degrees is indicated. ZERO or 360 degrees is indicated when all bits in the BAM data word are clear (ZEROS). BAM words are also used to transmit non-angular values such as range or height. When non-angular values are being used, the LSB value indicates the smallest step or increment of the quantity being transmitted. The MSB value represents half the maximum value that may be transmitted. The sum of all bits when set indicates the maximum quantity that can be transmitted. This corresponds to the 0- to 360-degree capability of common shipboard synchro systems. GRAY CODE. —Gray code or reflected binary code is used in devices where a transition from one consecutive value to another takes place, such as angular measurement and encoding. The code is designed to change from one value to the next with only one bit change. Table 13-1 shows the relationships between Gray code, BCD, and natural binary code. BINARY-CODED DECIMAL (BCD). —BCD represents decimal values with a 4-bit code, called the 8-4-2-1 code. Each of the 4-bit groupings represents one decimal digit. BCD encoders allow for immediate decimal display of the converter output. They are found in such devices as digital voltmeters and other types of decimal display devices. Table 13-1 shows the relationships between BCD, Gray code, and natural binary code. SYNCHROS Up to this point, we have discussed basically single-phase analog data signals. One of the most common shipboard analog signals requiring conversion is the 3-phase or 5-wire synchro signal. Synchros are used throughout naval ships for the rapid transmission of analog information between equipments and stations. They are found in just about every weapon, communication, underwater detection, and navigation system in use in the Navy. Numerous kinds of information involving angular displacement or ranges of values are transmitted. For the combat direction system (CDS) equipments to use this information, the synchro signals must be converted to their digital equivalent. The following information provides a limited overview of synchros as they apply to digital systems and synchro-to-digital (S/D) conversion. Figure 13-3.—A 12-bit binary angular measurement (BAM) word. 13-4

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Table 13-1.—Comparison of Binary-Coded Decimal (BCD), Gray Code, and Natural Binary Code Synchro Systems The term synchro is an abbreviation of the word synchronous. It is the name given to a variety of rotary, electromechanical, position sensing devices. Synchro signals are used to transmit the angular position (0 to 360 degrees) of a rotor shaft in a synchro transmitter. When the signals are applied to one or more synchro receivers, the rotor shaft in each receiver is positioned to match the transmitter’s shaft position (figure 13-4). In this example, the receiver shaft in turn drives an indicator dial to display the transmitted information. The combination of synchro transmitter and receivers is called a synchro system. There are two major classifications of synchro systems: torque systems and control systems. Figure 13-4.—Torque synchro system transmitter and receivers. Torque systems provide torque or turning force to drive light loads such as indicator dials, pointers, or other mechanical outputs. Control synchro systems provide an electrical output used to control the power that performs mechanical work. The control synchro normally feeds a control transformer, not a control receiver. The control transformer output is fed to devices such as a servo system to control larger systems and devices. The synchro signals converted by CDS equipment may be either control synchro signals or torque synchro signals; however, control synchro signals are preferred because they are generally more accurate than torque synchro signals. OPERATING VOLTAGES AND FRE- QUENCIES. —Most shipboard synchro systems operate on a supply voltage of 115 volts ac at a frequency of 60 or 400 Hz. Synchros operating at 115 volts 400 Hz are generally more accurate than the 60-Hz synchros. Most newer weapon systems use 400-Hz synchros exclusively. SINGLE-SPEED, MULTISPEED, AND DUAL-SPEED SYNCHRO SYSTEMS. —The accuracy of the data to be transmitted is a factor in any synchro system. If the data covers a wide range of values, then the basic synchro system is unable to detect small changes in the data. When this happens, the accuracy of the system decreases. Multispeed synchro systems were developed to correct this deficiency. Multispeed synchro systems use more than one speed of data transmission. The speed of data transmission is the number of times the synchro transmitter rotor must turn 360 degrees to transmit a fuIl range of values. In a 1-speed system, one rotation of the transmitter rotor covers the full range of values. The 13-5

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rotor is geared to its mechanical input and one rotation of the input results in one revolution of the transmitter’s rotor. The speed of a synchro transmitter is tied to the gear ratio between the mechanical input to the transmitter and the transmitter’s rotor; that is, 1:1,36:1, and soon. In a 36-speed synchro system, the rotor of the synchro transmitter is geared to rotate 36 times for one revolution of the input shaft (36:1). Units transmitting data atone speed (1-speed, 36-speed, and so forth) are called single-speed synchros. The entire range of data to be transmitted is contained in the output of the single-synchro transmitter. It is quite common for shipboard synchro systems to transmit data using two different speed synchros with the same reference or supply voltage. For example, ship’s course (ownship’s heading) information is usually transmitted to other locations using a 1-speed synchro and a 36-speed synchro. A synchro system that transmits data using two different speed synchros is called a dual-speed synchro system or a double-speed synchro system. COARSE AND FINE DATA TRANSMIS- SION. —Dual-speed synchro transmissions are combined to improve the accuracy of the data transmitted. The use of two transmitting synchros allows for a coarse value and a fine value to be sent at the same time. The synchro with the lowest ratio (1:1) sends the coarse value. The synchro with the highest ratio (36:1) sends the fine value. The coarse and fine values transmitted can be likened to the hour and minute hands of a clock. The course value represents the time in hours. The fine value represents the time in minutes. The two values must be combined to give the time in hours and minutes. Let’s look at a coarse synchro and a fine synchro transmitting an angular position such as ship’s course (ownship’s heading), which can be from 0 degrees to 359 degrees true. The coarse synchro (1:1) indicates 360 degrees of ship’s course with one rotation. However, the accuracy of the data is limited to plus or minus 1 degree of heading. This degree of accuracy is not enough for most navigation systems to keep an accurate track of ship’s movement. The fine synchro (36:1) rotates 36 times for each rotation of the coarse synchro. This means the fine synchro rotates once each 10 degrees (360/36). Within its 10-degree segment, the fine synchro is 36 times as accurate as the coarse synchro. The use of dual-speed synchros requires two S/D conversions to take place; one to determine the position of the rotor in the coarse synchro transmitter and one to determine the position of the rotor in the fine synchro transmitter. SYNCHRO SIGNALS. —A single-speed synchro transmitter outputs three waveforms that indicate the angular position of the rotor in the transmitting synchro, for example a control transmitter (CX). Waveforms are induced in the stator coils by the magnetic field of the rotor coil. The two rotor connections of the CX (R1 and R2) are fed from a 115-volt ac supply voltage (also called the reference voltage). This voltage is also fed to the synchro-to-digital (S/D) converter circuitry. The reference voltage is important in the conversion process. It provides a reference for the S/D converter to use when sampling the stator voltages. The amplitude of the voltage output between the stators (S1 to S2, S1 to S3, and S2 to S3) at any instant is dependent on the position of the rotor in the CX. The 115-volt supply voltage induces an ac voltage into the stator windings. The phase relationship of the signals induced on each stator winding is dependent on the angular position of the rotor within the CX. The rotor can normally be rotated 360 degrees within the synchro. The range of values being transmitted is tied to this 360 degree rotation. The minimum value is normally transmitted with the rotor at the 0-degree position and the maximum value is sent when the rotor is positioned to approximately 359 degrees. All three stator signals are ac voltages that have the same characteristics (frequency and amplitude). They have a 120-degree phase difference (phase displacement) from each other due to the 120-degree separation of the wye windings of the stator coils in the synchro transmitter. At any instant, a phase relationship exists between the rotor supply (excitation) voltage and the three stator voltages. This phase relationship is the key to the S/D conversion process. Basically, the phase relationship of the individual stator voltages, across terminals S1, S2, and S3, varies with the rotor supply voltage (R1-R2) as the rotor is rotated within the synchro transmitter. Each position of the rotor has a unique stator voltage phase relationship to the supply (reference) voltage. At any instant, the amplitude and polarity of the stator signals when compared to the supply voltage indicate the angular position of the rotor. For dual-speed synchro systems, two sets of stator voltages are transmitted, one set for the coarse synchro and one set for the fine synchro. A single supply voltage (reference) is used for both synchro 13-6

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transmissions. In other words, both speeds are converted using the same reference signal. Synchro-to-Digital (S/D) Conversion Two methods are currently in use to convert synchro data to digital words (BAMs): the sector method and the octant method. Both methods of conversion require a reference voltage input for conversion to take place. SECTOR CONVERSION. —The sector conversion method uses the reference voltage to determine the time to sample the stator voltages for conversion to take place. The ideal time to sample the stator voltages is when the reference voltage is at or near the positive or the negative peak of its cycle. Sixty-Degree Sector Determination. —Once the negative or the positive peak of the reference is detected, the sector in which the rotor is positioned may be determined. There are six 60-degree sectors within the 360-degree rotation of the rotor. The relationship of the stator voltages to the reference defines the sector. Table 13-2 shows the sector limits and the phase relationship of the stator voltages to the reference in each sector. Stator Voltage Selection. —When the sector angle is determined, two of the three stator voltages are used to identify the ratio angle within the sector. The ratio angle is determined by a ratio between the two voltage samples. The two stator voltages selected depend on the sector. The appropriate voltages are gated to the conversion circuitry and converted to binary data. The sector angle and the ratio angle of the two stator voltages are summed to determine the binary angle of the rotor position in BAMs. Table 13-2.—Phase Relationship of Stator Voltages to Reference OCTANT CONVERSION. —The octant conversion method divides the 360 degrees of angular measurement into eight 45-degree octants. The conversion process first defines the octant and then the binary representation of the trigonometric angle within the octant. Octant Determination. —The 5-wire synchro signal (R1, R2, S1, S2, and S3) is first converted into two dc voltages representing the sine and cosine of the synchro angle. The polarity of the sine and cosine voltages and their respective amplitude to each other are used to select the octant that defines the three most significant bits of the BAM word (figure 13-3). Successive Approximations. —The remaining bits of the BAM word are determined through a process of successive approximations. The sine and cosine voltages are combined into a ratio voltage that is used to determine the condition of each of the remaining bit positions in the BAM word, starting at the MSB of the remaining bits. A trial and error method is used. A trial binary angle is generated and tested against the ratio angle until the trial angle equals the ratio angle, completing the conversion process. Single-Speed/Dual-Speed Synchro Conversions Synchro-to-digital conversions do not occur on a continuous basis. The synchro data is sampled as required by the controlling computer, usually on a periodic basis. A single BAM word is generated by the S/D conversion for both single- and dual-speed synchros. When dual-speed synchro data is being converted, two S/D conversions are required to generate one BAM word. The coarse synchro signal is converted immediately before the fine synchro signal. The summation of the two conversions is represented by a single binary word, indicating one angular value. Conversions for single-speed synchros are considered coarse conversions only. NOTE. —For more detailed information on synchros and synchro systems, refer to NAVEDTRA 172-15-00-80, NEETS, Module 15, Principles of Synchros, Servos, and Gyros. DIGITAL-TO-ANALOG CONVERSION Digital-to-analog (D/A) conversion is required when digital devices must communicate with an analog system or equipment. Three types of D/A conversion are commonly encountered on shipboard systems: digital-to-linear, digital-to-scalar, and digital-to- synchro (D/S). Linear signals are ac or dc voltages that 13-7

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normally represent a quantity based on their amplitude with respect to a reference voltage. Scalar Signals consist of two waveforms that represent the sine and cosine of an angle. The device that performs these types of conversions is a digital-to-analog converter (DAC). The DAC may be either a component of a larger device or a stand-alone equipment such as the Digital-to-Analog Converter CV-2517B/UYK Digital-to-synchro conversion is required when communicating with systems that use synchro data transmission. Digital-to-synchro converters are usually found as components of multipurpose conversion equipment. However, a DAC may be modified with a scott-tee transformer to generate synchro signal outputs from scalar voltage waveforms. DIGITAL-TO-LINEAR/SCALAR CONVERSION A digital-to-analog converter (DAC) is a device that receives digital information in the form of a binary word and transforms that information into variations of an analog signal. The DAC outputs an analog signal derived from a reference signal. Normally both the converter and the analog device receiving the data operate off of the same reference. The reference signal is normally greater than or equal to the maximum limit of the output of the converter. The continuous output signal is varied in steps based on the binary inputs to the converter. BAMs are normally used as the binary input for CDS DACs. As a bit position changes in the binary data, the output signal is stepped up or down, based on the value of the bit position orbit positions changed in the input. The output signal only changes when the input data changes. Each converter outputs a single proportional voltage signal. this signal is suitable for linear operations. Two converters are required for scalar or synchro conversions. two separate proportional voltages must be developed to represent the scalar sine/cosine angle which may in turn be fed to a Scott-tee transformer to generate a 3-wire synchro signal. THE DIGITAL-TO-ANALOG CONVERTER CV-2517B/UYK The Digital-to-Analog Converter (DAC) CV-2517B/UYK is a multipurpose converter capable of accepting parallel digital data and converting it to 400-HZ linear, resolver, or synchro outputs. The DAC (figure 13-5) provides the means for digital combat direction systems to communicate with analog gun, electronic countermeasures (ECM), or sonar subsystems. Figure 13-5.—DACs and mounting base. 13-8

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The DAC is mounted on an Electronic Equipment Mounting Base MT-3574B/USQ-20(V), referred to as a BASE. The BASE can accommodate two DACs, as shown in figure 13-5. It provides all electrical interfaces, elects DAC operating modes (TRIGONOMETRIC or LINEAR), and provides simulated digital data for test purposes. There is an accessory to the DAC called the Analog-to-Analog Converter (AAC) CV-2518/UYK The AAC provides signal conversion from linear ac to linear dc or linear dc to linear ac. Each DAC is divided into two identical channels, designated channels A and B. Each channel can output two linear voltages, a sine/cosine resolver (scalar), or a single-speed synchro, depending on the operational mode selected. For simplicity, only one base with one channel of a DAC connected in the converter 1 position is covered here. The base and converter operate as one unit and are discussed as one. digital output channel (DOC). Both the KCMX and DOC functions are covered in this chapter. The output passes through the mounting base, which is transparent for normal computer operations. The output buffer consists of an external function (EF) word, a control address word, and up to eight data words. The EF word master clears the DAC and initiates the receive data from unit computer (RDUC) operations. The control address word defines the control address of the DAC to receive the data words. The individual DAC’s control address is set using the eight-position CONTROL ADDRESS switch on the DAC front panel (figure 13-6). If the data is properly addressed to the DAC, the DAC initiates RDUC operations to process the data words coming from the computer. Each data word contains a data address code (0-7) to define the DAC channel (A or B) that is to process the data. Both DAC channels receive the data; however, only the channel with the CHANNEL DATA ADDRESS switch in the position to match the dataThe DAC normally receives computer output from a 30-bit parallel keyset central multiplexer (KCMX) address will process the data. Figure 13-6.—DAC front panel. 13-9

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DAC Functional Description The DAC can be divided into three major sections: the digital section, the analog section, and the power supply section, as shown in figure 13-7. DIGITAL SECTION. —The digital section processes the EF word and the control address word upon receipt of the EF signal from the computer. If the control address matches the channel A or B address, the digital section generates the output data request (ODR) signal to the computer to start the data word processing. The computer provides a data word along with the output acknowledge (OA) signal. The converter then drops the ODR indicating it has accepted the data. The data bits are fed to the digital section holding registers for the applicable channel and subchannels. The output of the holding registers is fed to the analog section for conversion to proportional voltages. ANALOG SECTION. —The primary function of the analog section is to convert the data words received from the digital section into proportional analog voltages. The form of the analog output is dependent on the mode of operation (TRIG or LINEAR) and, during the TRIG mode, the type of output selected (synchro or resolver). The switches for selecting the converter mode (TRIG/LINEAR) are located on the base (figure 13-8). The switches for selecting synchro or resolver operation in the TRIG mode are located on the DAC front panel (figure 13-6). Each DAC channel (A or B) is in turn divided into two subchannels (A1 and A2 or B1 and B2). The data words accepted by the DAC channel are made up of two 13-bit data words consisting of a polarity bit and a 12-bit code. In the TRIG mode, the 12-bit code represents the sine or cosine outputs. In the LINEAR mode, the 12 bits are converted directly to linear voltages. Channel A1 outputs the sine waveform in the TRIG mode or one of the linear waveforms in LINEAR mode. Channel A2 outputs the cosine waveform in the TRIG mode and the second linear waveform in the LINEAR mode. The polarity bits are used to determine the quadrant in which the angle lies in the TRIG mode and the polarity of the linear output in the LINEAR mode. The actual digital-to-analog conversion is performed using two resistive ladder networks (one each for channels A1 and A2). The logic state of the data and polarity bits controls the operation of analog switches, which route currents from a ladder network into a summing network. A reference voltage for the ladder network is supplied from selected reference transformers. The selection of the reference transformers is dependent on the mode of operation and the state of the applicable polarity bit in the data word. When the proper reference voltages are selected, the currents through the ladder network are summed and applied to the output selection circuit as proportional voltages. The channel A1 and channel A2 proportional voltages represent the sine and cosine voltages for resolver output. For synchro output, the sine and cosine voltages are fed to a Scott-tee transformer by the output selection circuitry. The Scott-tee output consists of the 3-wire, single-speed synchro output. Figure 13-7.—DAC block diagram. 13-10

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POWER SUPPLY SECTION. —The power supply section provides five regulated dc voltages (-4.8, -15, +15, -26.65, and +26.65 vdc) that support the operation of the digital and analog sections of the DAC. The power supply section receives primary ac power from the mounting base. Base Controls and Indicators The mounting base (figure 13-8) provides controls and indicators for the operation of the mounting base and the two associated converters (CONVERTER 1 and CONVERTER 2). MODE CONTROL LOCAL/REMOTE. —This rotary switch selects either REMOTE control of converter operating modes or LOCAL control via the BASE switches. DIGITAL INPUT NORMAL/TEST. —This rotary switch selects either NORMAL digital inputs from the computer or TEST digital inputs simulated by switches on the BASE. OA/EF. —The OA (output acknowledge) and EF (external function) pushbuttons are used to simulate their respective control signals to the converters in TEST mode. CONVERTER 1 POWER ON/OFF. —This switch applies ac power to converter 1 and the right half of the BASE indicator lights. (Because both converter switches and indicators are identical, we will only cover converter 1.) CONVERTER 1 CHANNEL A. —This group of switches and indicators is used to select and monitor the channel mode (TRIG/LINEAR toggle switch) and the subchannel linear voltage type (CHANNEL A1 AC/DC and CHANNEL A2 AC/DC toggle switches) when the BASE is in LOCAL or REMOTE. (Because both channel A and channel B switches and indicators are identical, we only cover channel A.) THIRTY TOGGLE SWITCHES. —A row of 30 toggle switches is used to simulate EF and data word binary data bits when in the TEST mode. DAC Controls and Indicators The DAC provides controls for addressing channels A and B, selecting the TRIG mode (synchro or resolver), and test points for verifying individual channel functions. CHANNEL A MODE SYN/RSVR. —When the TRIG mode is selected at the BASE, this switch selects synchro or resolver output. CHANNEL A DATA ADDRESS. —This 7-position switch is used to select the address for channel A. (Because both charnel A and channel B controls are identical, we only cover channel A.) Digital-to-Synchro (D/S) Conversion A digital-to-synchro (D/S) converter converts BAM data words to single-speed synchro output signals. The D/S converter requires a reference voltage input (115 volt, 60/400 Hz). The D/S conversion is effectively a reverse of the S/D conversion process. The BAM word is used to generate two analog voltages representing the sine and cosine of the synchro rotor angle to be transmitted (figure 13-9). These two voltages are developed by modulating the stepped down reference voltage in phase and amplitude. The phase relationship and amplitude of the sine and cosine signals are based on the data contained in the BAM word. The sine and cosine signals are then stepped up and fed to a Figure 13-9.—Digital-to-synchro (D/S) conversion. 13-12

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Scott-tee transformer to develop the 3-phase stator voltage outputs (S1, S2, and S3) of the single-speed synchro transmission. D/S converters are designed with holding circuits that retain the contents of the BAM words between computer updates of BAM data. The synchro output of the D/S converter is continuous in nature, indicating a new rotor angle only when a BAM word received from the controlling computer contains anew angular value. DIGITAL-TO-DIGITAL (D/D) CONVERSION This section covers those forms of digital data handled by various shipboard data conversion devices. These devices are used to convert digital data from shipboard weapon, radar, and other subsystems to the voltage levels and formats acceptable to the CDS computers. The types of data converted include control and status signals, ready digital (RD) data, demand digital (DD) data, demand digital interrupt (DDI) data, and digital input channel/digital output channel (DIC/DOC) data. Control and Status Signals Control and status signals are discrete ac or dc signals that indicate or control a single function (on/off, true/false, and so forth) or condition in a subsystem. Signals transmitted by CDS equipment to another subsystem are referred to as control signals because they generally initiate an action in the receiving system. Discrete signals received by CDS equipment are referred to as status signals because they generally indicate the status of a condition or function in another subsystem. CONTROL SIGNALS. —Control signals are generated from individual bit positions in a control word. Each bit position of the control word represents one control signal. The individual bits from the control word are fed to relay circuits. A binary ONE will cause a relay closure to take place and an ac or dc signal to be generated from the appropriate supply voltage. A binary ZERO will cause the relay to de-energize, open its contacts, and prevent the voltage transmission. STATUS SIGNALS. —Statis signals are ac or dc voltages received from external subsystems. Each status signal is assigned to an individual bit position in a status word. The status bit becomes a binary ONE when a status voltage is sensed. Lack of a status voltage signal causes the status bit to remain a binary ZERO. Status words are sampled periodically by the controlling computer to determine the current condition of the individual status signal bits. Ready Digital (RD) Data Ready digital (RD) data is 12-bit parallel digital data generated by the CDS radar azimuth converters (RACs). The data indicates the antenna or sweep position of each individual ship’s radar. This data is transmitted to the CDS computer as requested by the computer for program processing and tracking of radar contacts. Demand Digital (DD) Data Demand digital (DD) data is parallel digital data input from manual entry devices. Two input channels are normally used. Each channel may be used by up to eight daisy-chained devices. Each device is identified by an address in the input word. DD data is sampled periodically by the computer to test for operator entries. Demand Digital Interrupt (DDI) Data Demand digital interrupt (DDI) data is parallel digital data similar to DD data. The major difference is in the method of data entry. DDI devices cause an interrupt to be generated to the controlling computer when an entry is made from the applicable device. Digital Input Channel/Digital Output Channel (DIC/DOC) Data Digital input channel/digital output channel (DIC/DOC) channels are multiplexed parallel digital computer channels used to increase the input/output capabilities of the controlling computer. Up to four DICs and four DOCs are provided. The channels may be used for input only, output only, or input/output (I/O) with external peripheral devices or computers depending on the mode or format selected. TOPIC 2—SHIPBOARD DIGITAL/ANALOG SYSTEM INTERFACES In this topic, you will learn about specific equipments and groupings of equipments involved in the data conversion and interfacing process aboard ship. These equipments permit nominally independent 13-13

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shipboard systems or subsystems to communicate or interface with the combat direction system (CDS). MULTIPLEXING DATA CONVERTERS Each shipboard tactical data system has at least one multiplexing data converter. Multiplexing data converters are, in effect, computer-controlled multipurpose devices that operate between one or more digital computers and a number of control, status, digital, and analog devices located in remote subsystems. The individual devices may vary from each other in design due to technological advances and equipment improvements. As a group they perform multiple functions by allowing analog or digital conversion and communications with a variety of equipments or subsystems using multiple data forms (analog, discreet digital, or parallel digital) at the same time or within a very narrow time period (time division multiplexing). Several different versions/generations of multiplexing data converters are currently in use. These include the Keyset Central Multiplexer (KCMXs) CV-2036/USQ-20 and CV-3263/USQ-20 and the Signal Data Converters (SDC) OU-95/UY, CV-2953A, and the Mark 72 Mod 11/12. Individual capabilities vary from device to device. Table 13-3 lists the various converters and compares the range of their capabilities. The particular converter used with the tactical data system depends primarily on ship class. KCMXs are found on the CG or DDG classes and the CV/CVN aircraft carriers. ICKCMXs are found on the DDG TDS Table 13-3.—Comparison of Multiplexing Data Converters 13-14

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systems, while the CV-2953A is found on the DD-963 class of ships. Mark 72 SDCs are found on the CGN-38 class of cruisers. The KCMX handles the widest range of functions of any of the converters. For that reason we selected it as our representative training device. KEYSET CENTRAL MULTIPLEXER (KCMX) The keyset central multiplexer (KCMX) (figure 13-10) provides the means of exchanging data, control, and status information between either one of two Figure 13-10.—KCMX (front view). 13-15

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computers and a variety of input/output devices including multiple control, status, and synchro signal interfaces. The KCMX allows the controlling computer to receive data and status information from external subsystems (missile, gun, electronic warfare [EW], antisubmarine warfare [ASW], and so forth) and to transmit data and control information to external subsystems. A simplified block diagram of the KCMX is shown in figure 13-11. Duplexer and Input/Output (I/O) Logic The duplexer (figure 13-11) allows the KCMX to be controlled by two computers on a one at a time basis. The duplexer is controlled by external function commands from the computers. Three external function commands are used to control the duplexer logic: request control, release local, and release remote. REQUEST CONTROL. —The request control (RC) command permits the requesting computer to gain control of the KCMX if the other computer is not in control. RELEASE LOCAL. —The release local com- mand relinquishes control of the KCMX. RELEASE REMOTE. —The release remote command is a high-priority code that allows one computer to take control of the KCMX from the other computer. I/O LOGIC. —The KCMX communicates with the digital computers over standard CDS slow I/O channels. Digital Control Logic The digital control logic (figure 13-11) puts the KCMX in one of its seven operating modes as specified by the controlling computer. The KCMX operating modes are neutral, duplex, transmit data from unit computer (TDUC), receive data from unit computer (RDUC), TDUC and RDUC, interrupt, and keyset error. NEUTRAL MODE. —Neutral mode is the at-rest mode when neither of the controlling computers is requesting control of, or is in control of, the KCMX. Figure 13-11.—KCMX block diagram 13-16

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DUPLEX MODE. —The duplex mode is the primary control mode for the KCMX. Either of two computers may have control of the KCMX at one time. Each computer must request control by means of an external function. Once the desired mode selections and data exchanges have taken place, the controlling computer must place the KCMX in a neutral state through the use of a release local external function. RECEIVE DATA FROM UNIT COMPUTER (RDUC) MODE. —To output data to the KCMX, the controlling computer must place the KCMX in the RDUC mode by external function. In the RDUC mode, the KCMX is capable of receiving data consisting of DOC output words or control words. DOC data and control signals are the only KCMX functions used to transmit information to external subsystems or equipment. TRANSMIT DATA TO UNIT COMPUTER (TDUC) MODE. —The TDUC mode is used to input addressed data to the controlling computer. The computer places the KCMX in TDUC mode. The external function command specifies the address or addresses of the data to be transmitted to the computer. TDUC AND RDUC MODE. —The KCMX can be placed in the TDUC and the RDUC modes at the same time. Both modes will operate simultaneously under the control of one computer. INTERRUPT MODE. —The KCMX operates in the interrupt mode when indicating an abnormal condition (Type I interrupt) or upon receipt of high-priority data from DDI addresses or DIC external functions or interrupts (Type II interrupt). KEYSET ERROR MODE. —The computer places the KCMX in the keyset error mode to send an error signal to the addressed keyset. Demand Digital (DD) Inputs The 16 demand digital (DD) inputs (figure 13-11) use 30-bit words. Eight DD devices are daisy chained on each of two cables. Each DD device (keyset) is controlled by three control signals: enter, read, and error. A total of 24 control signals is required for the eight DD devices on an input cable. The eight DD devices on the first cable are called group 1 and are assigned KCMX addresses 1 through 10 (all KCMX addresses are octal). Group 2 consists of the other eight devices on the second cable and are referenced by KCMX addresses 11 through 20. Group 1 DD devices may function in either a data (DD) mode or an interrupt (DDI) mode. Group 2 devices function only in the data mode. ERROR SIGNAL. —The error signal is activated by the KCMX under computer control and is a program-controlled function. It is normally generated in response to a format error in the operator entered data. The signal lights the error indicator on the DD device. ENTER SIGNAL. —The enter signal is generated by the DD device when it has a data entry input ready for transmission to the controlling computer. The KCMX, when requested by the controlling computer, samples (reads) the data on the data lines from the DD device. READ SIGNAL. —The read signal is used to activate the DD device data lines. The KCMX activates the read signal for the addressed DD device and waits 200 msec before sampling the data. When the DD de- vice receives the read signal, the data lines back to the KCMX are activated. The KCMX waits the 200 µsec, samples the data, and inputs the data to the controlling computer. DEMAND DIGITAL INTERRUPT (DDI) INPUT. —A demand digital interrupt (DDI) is nothing more than a demand digital device assigned to group 1 when that group is in the interrupt mode. Group 1 is placed in the interrupt mode by a computer external function command. The enter signal is processed differently in the interrupt mode. The KCMX automatically tests and honors the DDI enter signals through an interrupt priority sequence. The KCMX reads the entered data and inputs it to the controlling computer as an interrupt code rather than as a data input word. There is no delay in waiting for the computer to request a data input (DD mode). READY DIGITAL (RD) INPUTS. —There are up to eight inputs for ready digital data (figure 13-11); KCMX addresses 63 through 71 are used for 12-bit data while address 72 is used for 30-bit words. This data is obtained from synchromechanical devices such as the radar azimuth converters (RACs). The data normally represents a digitized analog antenna position. The eight ready digital (RD) inputs occupy separate cables and use only one control signal (enter signal) each. These eight separate signals inform the KCMX that the data on the line is valid and can be sampled. The data is sampled by the KCMX when the corresponding address is designated by the controlling computer to be interrogated and have the data entered (TDUC). If the KCMX attempts to sample the data lines and the enter signal is temporarily false, the 13-17

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KCMX will delay the sampling for 300 µsec. If the enter signal is still false at the completion of this time period, the KCMX will return a data word of all ONES to the computer for that address. If at any time during this delay the enter signal becomes true, the KCMX will sample the data and gate the data into the computer input register and transfer it to the computer with an input data request (IDR). The 12 data bits from addresses 63-71 will occupy the lower 12 bits of the computer input word. Address 72 data bits occupy the entire 30-bit word. Digital Input Channels and Digital Output Channels The KCMX is capable of receiving and transmitting data over four 30-bit CDS I/O channels (DIC1 through DIC4 and DOC1 through DOC4). The input channels are assigned KCMX addresses 73 (DIC1) through 76 (DIC4). The DIC/DOCs (figure 13-11) maybe used for input only devices, output only devices, or a DIC/DOC pair (DIC1/DOC1, DIC2/DOC2, and so forth), which can communicate with an I/O device. The KCMX DIC/DOCs allow the computer controlling the KCMX to communicate with four or more digital devices. The KCMX may function as a computer or as a peripheral device when communicating with the external digital devices. Devices linked by the DIC/DOCs will conform to standard CDS format 30-bit parallel transfers using either computer or peripheral control logic signals. The DIC/DOCs themselves can be manually set to one of two data transfer formats designated peripheral (PERIPH) or computer (COMPUTE). (Both types of transfers involve 30-bit parallel data. Computers generate function codes, while peripherals generate interrupts; peripherals generate requests such as output data requests (ODRs), while computers generate acknowledgments such as output data acknowledges (ODAs), and so on.) In the peripheral format, the KCMX appears as a piece of peripheral equipment to an external computer. In the computer format, the KCMX appears to be a computer to the external peripheral device. The DIC/DOC interfaces have limitations. External functions can only be transmitted from the controlling computer over the DOCs. Interrupts can only be received by the controlling computer from an external device over the DICs. Devices connected using output only or input only configurations may require a DIC/DOC pair to be connected to allow both computer control by external function and device interrupt capabilities. In other words, a single DIC or DOC hookup loses the external function control capability (DIC only) or the external interrupt capability (DOC only). DIGITAL OUTPUT CHANNELS (DOCs).— The cabling for each of the four DOCs is the same as that of a computer or peripheral output channel. A manual switch for each DOC selects either peripheral or computer interfacing for the device connected on that channel. DOC Computer Operation. —The KCMX acts as an interface between the external device (peripheral) and the controlling computer. The KCMX accepts data one word at a time in a buffer from the controlling computer. Up to the first seven words of the buffered data may be external function commands for the external equipment. External function commands sent by the controlling computer to the KCMX setup the buffer size (number of data words) and the number of external function command words in the buffered data. The KCMX generates the external function signals for the external function commands setting up the external equipment and then transmits the remainder of the buffered words as normal computer output data. A maximum of 255 computer words (external functions and data) may be sent by the controlling computer in a single buffer. DOC Peripheral Operation. —In the DOC peripheral operation format, the KCMX acts as an interface between the external device (computer) and the controlling computer. The data buffer from the controlling computer is inputted to the external computer as interrupts or data words. The controlling computer’s external function commands define the number of interrupt words (maximum seven) that precede the data words in its output buffer. DIGITAL INPUT CHANNELS. —The four digital input channels (DICs) are interrogated by the controlling computer on a regular basis. Each DIC is assigned an address (DIC1 address 73 through DIC4 address 76). If the data word being received by the KCMX is not an external interrupt or external function, the KCMX will wait until the DIC address is interrogated before sending the data word to the controlling computer and indicating acceptance of the word to the external device. 13-18

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DIC Computer Operation. —In the DIC computer operation format, the KCMX acts as a computer to an external peripheral device. When the computer receives an input data request (IDR) from the device, the KCMX will store both the request and the input data word. Upon interrogation from the controlling computer, the KCMX will transfer the DIC data to the computer and send an input data acknowledge (IDA) to the external device. DIC Peripheral Operation. —In the DIC peripheral operation format, the KCMX acts as a peripheral to an external computer. The KCMX generates an ODR to the external computer. The computer responds with data and an output data acknowledge (ODA). The KCMX holds the data until interrogation and transfer with the controlling computer. The KCMX then generates another ODR to the external computer. DIC Interrupts. —The KCMX may generate interrupts to the controlling computer for DIC addresses upon receipt of external function commands from the external computer in peripheral format or external interrupts from the external peripheral device when in the computer format. Status Signals Sixty status signals may be received by the KCMX (figure 13-11) via status inputs connected to KCMX addresses 61 and 62. Each KCMX status address provides a 30-bit status word when interrogated by the controlling computer. The condition of each status bit in the two status words is dependent on the condition of its associated status relay coil. The status relays complete the circuit between the KCMX and the external devices generating the status signals. Supply voltages used to generate status signals include but are not limited to 26 vdc, 50 vdc, and 115 vac 60/400 Hz. All 60 status lines and associated supply voltages are connected to the KCMX via 5 status plugboards. Each status signal relay is wired to a status signal return line on a plugboard. A plugboard is an electrical connector wired with short jumper wires to provide flexibility in the connection configuration. The plugboards are wired when the system is installed, depending on the system configuration. Control Signals The control signals (figure 13-11) are generated by the KCMX in response to control word outputs from the controlling computer. Individual bits set in the two control words energize relays to send control voltages to external equipment. Once again plugboards are used to increase system flexibility. Ready Analog (RA) Inputs Processing of synchro inputs (ready analog data) is performed by the synchro multiplexer and synchro converter logic (figure 13-11). The KCMX can accept inputs from 32 three-wire synchros. Six cables are used to connect the synchro inputs and reference voltages to the KCMX. Five cables carry 6 synchro inputs and the sixth carries 2 inputs and up to a maximum of 12 reference voltage inputs. The first 24 synchro channels require 400-Hz reference voltages, while the last 8 may use either 60-Hz or 400-Hz. The KCMX accepts either single- or dual-speed synchro system inputs. The synchro multiplexer provides the method for selecting a unique synchro address from the 32 possible synchro inputs. The KCMX, in response to a TDUC external function from the controlling computer, will convert the addressed synchro input into digital form and transmit the digitized angle (BAM) to the controlling computer. The digital logic in the KCMX allows a fixed time delay for a full conversion to take place. The conversion delay is 2 msec if a 400-Hz reference is used, or 10 msec if a 60-Hz reference is used. A time out of the conversion delay would cause a data word of all ONEs to be returned to the controlling computer. A single synchro-to-digital (S/D) converter processes the multiplexed synchro input. The S/D converter uses the sector method to derive the precise angle of the rotor in BAMs. The converter will perform two separate conversions, the first for the fine speed and the second for the coarse speed. The converter places the combined results as a single BAM word in its output register where the data is held until accepted by the TDUC circuits and inputted to the controlling computer. For single-speed synchros, both fine and coarse conversions are performed, but the results of the fine conversion are ignored. The bits in the BAM word that apply to the fine conversion are left blank (ZERO). Digital-to-Synchro (D/S) Conversion The KCMX does not have a built in D/S conversion capability. To provide this capability, one or more of the DOCs must be connected to DACs. 13-19

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Controls and Indicators (KCMX) The front panels of the KCMX (figs. 13-12 and 13-13) contain all the controls and indicators used by operating personnel. The chassis behind the front panels (A1, A2, A3, and A4) and the power supply chassis in the bottom unit (PS1) can be unlatched and run out like drawers for access to the logic board racks inside. Signals can be observed at the appropriate test points, which are given in the equipment prints. Power supply fuses appear on panel A5 (power control assembly); test points for the power supply can be found by extending chassis PS1 outward. Power Control Assembly (AS) The power control assembly at the top of the unit (figure 13-10) contains the BLOWER ON/OFF switch and indicator, main POWER ON/OFF switch and indicator, running time meter, 3-phase BLOWER POWER fuses, and a 1-amp fuse for the -26.5 vdc power supply. An amber TEST MODE indicator will light whenever the MODE SELECTOR switch (panel A2) is in any position except NORM. The A5 assembly also contains over-temperature warning indicators and bypass circuitry. The red Figure 13-12.—KCMX front panels (A1/A2). 13-20

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Figure 13-13.—KCMX front panels (A3/A4). OVER-TEMP WARNING light will come on and the Computer Input Data Register Panel (A1) horn will sound when the cabinet’s internal air temperature exceeds 115° F (46° C). The ALARM The upper half of the A1 panel (figure 13-12) BYPASS will inhibit the from if desired. The red OVER-TEMP SHUTDOWN indicator will light, and contains the 30-bit COMPUTER INPUT DATA REGISTER. The 30 pushbutton/indicators show thepower will be removed from everything except the blowers if the cabinet’s internal temperature exceeds contents of the computer input data register when the 140° F (60° C). The red OVER-TEMP BYPASS KCMX MODE SELECT switch (bottom of A2 panel) switch/indicator can be used to bypass the is in the NORM position. The pushbuttons can be used over-temperature circuits under EMERGENCY to simulate data from the KCMX to the computer when conditions. The OVER-TEMP RESET pushbutton can the MODE SELECT switch is not in the NORM be used to reset the horn and warning indicators. position. 13-21

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The lower half of the A1 panel (figure 13-12) contains the SIMULATED COMPUTER OUTPUT DATA switches and the DD/DDI SELECT switches and indicators. SIMULATED COMPUTER DATA OUTPUT SWITCHES. —These switches are used to simulate 30-bit computer external function and computer output data words from the controlling computer to the KCMX. DD/DDI SELECT SWITCHES/INDI- CATORS. —These switches and indicators are used to select DD or DDI mode for the group 1 DD devices. The top two indicator/pushbuttons identify the group mode (left DD/right DDI). The pushbuttons may be used to manually switch between DD and DDI modes. The eight individual device indicators show if there is an enter signal on the line from one of the group 1 devices (addresses 1 through 10). The eight ON/OFF switches are used to control the individual device DDI enter signals. The ON position enables the device DDI enter signal, the OFF position disables it. Individual devices will not enter DDI data with these switches OFF, even if group 1 is in the DDI mode. Digital Control Logic Panel (A2) The upper half of the A2 panel (figure 13-12) contains the DATA REGISTER and the CONTROL OUTPUT REGISTER. The data register pushbutton/indicators are lighted to indicate the presence of data for DOC equipments. The pushbuttons may be used to enter data bits into the register for offline operations. The control output register indicates the status of the external control signals. A lighted indicator means a control signal is being generated. The pushbuttons may be used to set individual control signals during offline operations. The lower half of the A2 panel contains the following controls and indicators: DUPLEX controls, KCMX mode controls/indicators, DOC interface controls/indicators, and KCMX interrupt controls/ indicators. DUPLEX CONTROLS. —The duplex controls (figure 13-12) are identical for both A and B computers; therefore, only the A controls/indicators are discussed. The DUPLEX A CONTROL pushbutton/indicator, when lighted, indicates that the A computer is in control. In other than normal operation, the pushbutton may be depressed to simulate that computer A is in control. The DUPLEX A RC, DUPLEX A IDR, and DUPLEX A ODR pushbutton/indicators are lighted to indicate that the KCMX has received the request control (RC), input data request (IDR), or output data request (ODR) signals. These pushbutton/indicators may be used to monitor or, in test mode, to simulate the indicated signals. KCMX MODE CONTROLS/INDICA- TORS.—The TDUC and RDUC pushbutton/indicators (figure 13-12) are lighted when the KCMX is in the associated mode. The pushbuttons may be used to simulate reception of the computer external function roles for that mode. The MODE SELECT rotary switch (bottom of A2 panel) selects one of four operating/test modes. The NORM position permits normal KCMX operation. The DOC position enables testing of the digital output channels. The MANUAL position enables the KCMX to simulate computer operations by the use of the front panel controls. The synchro-to-digital converter may be tested in the A/D CONV position. The MASTER CLEAR pushbutton resets all logic circuits. The INDICATORS ON/OFF toggle switch disables all indicators on the A1 A2, A3, and A4 panels. The CMPTR A EF, B EF, OA, and IA pushbuttons are used to simulate external functions, output acknowledges, and input acknowledges from the computer. The DATA pushbutton/indicator is lighted when the KCMX is in the RDUC mode and is prepared to transfer a data or control word. The pushbutton is used to enable the data transfer sequence when a simulated computer OA signal is present. The BFW indicator is lighted when the KCMX is in the RDUC mode and processing a computer buffer function word (BFW). The pushbutton is used to simulate reception of the RDUC BFW code from the computer. The CONTROL CHANNEL pushbutton/indicator is lighted when a control word transfer takes place. The pushbutton may be used to simulate a control word transfer. The six pushbutton/indicators labeled CURRENT ADDRESS (figure 13-12) display the octal KCMX address being interrogated by the TDUC mode. The pushbuttons may also be used to allow manual selection of a single address, or starting address of a set of addresses to be interrogated in a test mode. The FINAL ADDRESS pushbutton/indicators are used to select (test mode) or display (TDUC mode) the last KCMX address of a set of addresses being interrogated. The ADDRESS CLEAR pushbutton clears both the current and final address bit indicators. 13-22

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The KEYSET ERROR pushbutton/indicator is lighted to indicate that the KCMX is in the keyset error mode. It maybe manually set to indicate reception of the computer external function keyset error bit. DOC INTERFACE CONTROLS/INDI- CATORS. —In the RDUC mode, the pushbutton/ indicators labeled DOC 1, 2, 3, or 4 are lighted when the buffer function word specifies a DOC transfer (DOC1-DOC4). The pushbuttons may be used to simulate a buffer function word DOC input data (ID) code. Four toggle switches (DOC 4, 3, 2, 1 COMPUTER/PERIPHERAL) are used to manually select the DOC operational mode. KCMX INTERRUPT CONTROLS/INDICA- TORS. —In the interrupt indicators (A/B COMPUTER INTERRUPTS), CMPTR A INT and CMPTR B INT pushbutton/indicators are lighted when an interrupt signal is on the computer (A or B) input line. The buttons may be used to simulate an interrupt condition. The six interrupt pushbutton/indicators (INTERRUPTS) are left to right; ILL ADR, EIC, EEC, DIC REQ, DD, and ID ERR. The pushbuttons for the interrupt indicators may be used to simulate the associated interrupt condition. When an illegal address (octal 00 or 77) is detected in either the current or final address registers, the ILL ADR indicator is lighted. The EIC pushbutton/ indicator is lighted to indicate an end-f-input cycle. The EEC indicator is lighted to indicate when the KCMX has completed a keyset error transmission. The DIC REQ indicator is lighted when the digital input channel request interrupt is active. The DD indicator is lighted when an enter signal is received from a group 1 keyset and the group is in the interrupt mode. When the KCMX detects an error in the buffer function word ID codes, the ID ERR indicator is lighted. The EOC ENABLE/DISABLE toggle switch is used to enable or disable the sending of an end-of-output cycle (EOC) interrupt to the computer. The indicator above the toggle switch indicates the detection of an end-of-output cycle condition. The COMPUTER ACKNOWLEDGE (CA) push- button/indicator is lighted when a computer (A or B) has been granted control of the KCMX and the KCMX sends a control acknowledge interrupt to the computer. The pushbutton may be used to simulate the CA interrupt. Digital Input Channel (DIC) Logic Panel (A3) The A3 panel (figure 13-13) contains the registers, controls, and indicators for monitoring and testing DIC operations. There are four 30-bit registers labeled DIC 1 INPUT REGISTER through DIC 4 INPUT REGISTER. These registers are used to indicate the status of the bit positions for each channel. In KCMX operations other than the normal mode, each bit position may be set manually using the pushbutton/indicator. Each channel has its own toggle switch for computer or peripheral mode selection, two TEST pushbutton/indicators, and an INPUT ACTIVE pushbutton/indicator. The input active indicators are lighted when an interrogation for the associated channel is being performed. The two TEST pushbutton/indicators for each channel indicate the status of external functions or interrupts (EF/INT) and output acknowledges or input data requests (OA/IDR). The DIC mode selected determines which of the signals is being displayed. The DIC computer uses EF and OA, while the DIC peripheral uses INT and IDR. The lower portion of the A3 panel contains some pushbutton/indicators used with DOC operations. DOC EF/INT is a three-stage counter used to determine the number of DOC EF or INT words in an output buffer (maximum of 7). The DATA WORDS counter keeps track of the number of data words in an output buffer (maximum of 191). S/D Converter/Multiplexer Panel (A4) The controls and indicators for the synchro-to- digital converter and multiplexer are contained on the A4 panel (figure 13-13). There are 12 indicating fuses (F1-F12) for the 12 reference input transformers. An indicator lights on the fuseholder when the reference voltage is present and the associated fuse is open. The TEST indicator lights when the seven-position SELECTOR switch is in any position other than normal (NORM). The SELECTOR switch, in any position but normal generates a simulated single-speed synchro angle. The following is a summary of the switch positions and angles: 13-23

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Figure 13-14.—Manual switchboard. 13-24

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The SECTOR REGISTER consists of three pushbutton/indicators. The register displays the sector number of the 60-degree sector in which the rotor is located. The pushbuttons may be used to simulate a sector angle. The eight pushbutton/indicators of the RATIO REGISTER indicate or simulate the binary ratio angle. The +REF/OFF/-REF toggle switch allows selection of positive (+REF) or negative (-REF) reference voltage. The switch is set to the OFF position for normal operations. The OSCILLATOR potentiometer is used to vary the frequency of the S/D converter test circuits from 2 to 100 Hz. With the HIGH/LOW toggle switch in the HIGH position, the S/l) converter is enabled for continuous recycling when in the test mode. When the switch is in the LOW position, the recycling rate can be varied from 2 to 100 conversions a second using the OSCILLATOR potentiometer. The OUTPUT REGISTER has 15 pushbutton/ indicators and a clear pushbutton. The register indicates the 15-bit BAM output of the S/D converter. Each bit-position indicator equates to a degree value portion of the summed synchro-mechanical angle. TOPIC 3—SWITCHBOARDS Shipboard tactical data system devices are interconnected with each other and with equipments in other shipboard subsystems through switch- boards. Combat systems use two major types of switchboards: digital switchboards and analog switchboards. Digital switchboards primarily interconnect digital devices. These types of interfaces include computer-to- computer interfaces and computer-to-peripheral devices and other serial or parallel digital inter- faces. Analog switchboards provide the interconnection for analog devices and signals including control and status signals, synchro signals, and linear signals. In addition, analog switchboards provide supply and return voltages and reference voltages for analog signal exchanges. Most current shipboard combat direction systems use a combination of analog and digital switchboards to completely interface CDS equipments with each other and with other shipboard sub- systems. DIGITAL SWITCHBOARDS The two basic types of shipboard digital switchboards are manual switchboards and remotely Figure 13-15.—Sample manual switching configuration. controlled switchboards. Manual switchboards are made up of variable configurations of three-position or five-position switches (figure 13-14). Each switch must be manually positioned for the interconnection required by the current system configuration. At least two manual switches, one for input and one for output, are required for each I/O device or computer channel to allow for the complete range of system configuration requirements (figure 13-15). Manual switchboards are for the most part being replaced by remotely controlled switchboards. 13-25

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Remotely controlled switchboards (figure 13-16) allow for configuration changes to be controlled from one or two remote computer switching control panels (CSCPs) (figure 13-17). The actual switch configuration and data routing take place in the CDS digital fire control switchboard (DFCS). This greatly reduces the time required for configuration changes in the event of equipment casualties. As examples of DFCS and CSCP we are using the Mk 70 Mod ( ) DFCS and the Mk 328 Mod ( ) CSCP. The Mod numbers of the DFCS and CSCP will vary with the ship class on which they are installed. For training purposes we refer to the Mk 70 as the DFCS and the Mk 328 as the CSCP. DIGITAL FIRE CONTROL SWITCHBOARD (DFCS) The digital fire control switchboard (DFCS) (figure 13-16) provides data routing, power monitoring, action cutout (ACO) switching, and digital switching. To perform these functions, the switchboard uses remotely operated switches and other assemblies. The switches route digital signals through the switchboard during normal operation. The digital signals consist of groups of parallel bits, which form digital words. The digital words are transmitted between computers, associated peripheral equipment, and digital equipment in other subsystems as shown in figure 13-18. The switches also can be used to interrupt or redirect signal flow manually during maintenance operations. Control and status signals are normally used to initiate the switching action and monitor the status of the switch positions. The CSCP generates control signals to select the desired switch configuration on the switchboard. Status signals from the switchboard light indicators on the CSCP to display the current switching configuration. In a casualty situation, manual positioning of switches can be performed. The DFCS is composed of two or more switch- board sections (figure 13-16) covered with variable configurations of switch panels. Each panel type performs a specific function. The 24 panels per section are normally arranged in groups according to the functions performed by the panels. The front panel of each switchboard section is hinged on the left side to Figure 13-16.—Digital fire control switchboard (DFCS). 13-26

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Figure 13-17.—Computer switching and control panel (CSCP). Figure 13-18.—Equipment interconnection through the CDS DFCS. 13-27

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allow access to the interior of the switchboard. The interior of the switchboard (figure 13-19) contains a system of modules and terminal board connectors that allow ship’s wiring to be interconnected to the appropriate switch panels. The switchboard panel locations are numbered for identification purposes starting at the upper left corner of the switchboard. The numbering continues from top to bottom, left to right. Each panel is marked with a designation plate mounted on the upper-left corner of the panel assembly or with a blank plate. Power Distribution Panel The power distribution panel (figure 13-20) provides a visual indication of power supplied to the switchboard. Six indicators are mounted on the front of the panel and lighted when the appropriate power has been applied to the panel and distributed to the remainder of the switchboard. Linear Movement Switch Assemblies The majority of panel assemblies are linear movement switch assemblies. These assemblies route a specific number of circuits. The linear movement switch assemblies are normally positioned by control signals from the CSCP, but they may be manually positioned. There are two types of linear movement switch as- semblies, the R3DLSO-lB/R5DLSO-lB (figure 13-21) Figure 13-19.—DFCS interior. 13-28

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Figure 13-20.—Power distribution panel assembly. Figure 13-21.—R3DLSO-1B/R5DLSO-1B linear movement switch assembly. 13-29

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and the R3BLSO-lC/R5BLSO-lC (figure 13-22) assembly. The assemblies differ from each other in the front panel organization and in the wiring module capabilities. The panels provide different arrangements of 20-pin, 38-pin, 117-pin, and 120-pin connectors. Both types of linear switches have similar mechanism and contact assembly modules. The mechanism assembly module contains the drive motor, the control circuit module, and the control transformers for remote operation of the switch. The contact assembly module consists of a stationary control plate and a moveable plate to perform the switching functions. The linear switches perform either three-position (R3) or five-position (R5) switching functions. The three-position switches are used for NORMAL/ ALTERNATE configuration switching with an OFF position for circuit isolation. The five-position switches have an OFF position with the four other switch positions being used for circuit configuration or reconfiguration. For an example, see figure 13-23. One channel of a duplexed magnetic tape unit can be switched between four separate CDS IOC channels or isolated in the OFF position. The front panels of both types contain a REMOTE-MANUAL toggle switch. When the switch is in the REMOTE position, the CSCP has control of the switch position (normal operating mode). When the toggle switch is in MANUAL, the switch must be positioned using the switch handle. Switch Control and Potential Transformer ACO Assembly The switch control and potential transformer action cutout (ACO) assembly (figure 13-24) provides control voltages for bench testing of the linear movement switches. The control voltages are provided through test cables from the test jack to the linear switch assembly under test. Figure 13-22.—R3BLSO-1C/R5BLSO-1C linear movement switch assembly. 13-30

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Figure 13-23.—Magnetic tape interconnection through the DFCS. Figure 13-24.—Switch control and potential transformer ACO assembly. 13-31

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Figure 13-25.—Relay tester assembly. Relay Tester Assembly The relay tester assembly (figure 13-25) provides the facilities for testing each type of relay used in the DFCS and the CSCPs. Relay sockets are provided for 8-, 10-, and 16-pin relays. The rotary switch is used to select the appropriate relay coil voltage. The toggle switch is used to energize/deenergize the relay coil. The indicator lamps indicate the state of the relay under test (ENERGIZED/DEENERGIZED). Fuse Tester Assembly The fuse tester assembly (figure 13-26) is used to test fuses for continuity. The POWER ON PBI is used to apply power to the fuse tester. The POWER ON indicator will light when the tester is on. When a good fuse is placed across the contact strips, the CONTINUITY INDICATOR light will come on. A blown fuse placed across the contact strips will not light the indicator, since there is no current path through the fuse. Figure 13-26.—Fuse tester assembly (DFCS). 13-32

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Computer Switching and Control front panel (figure 13-27). The CSCP will generate a Panel (CSCP) control signal to the appropriate DFCS linear switch assembly, which will respond with a status signal when The two computer switching and control panels it is in the assigned position. The PBI will light when(CSCPs) are used to make switch assignments on the the switch is in the commanded position.DFCS (controlling CSCP front panel). Switch assignments are made by depressing the associated Four colors are used for PBI indicators: white, red, pushbutton/indicator (PBI) on the controlling CSCP green, and yellow. White indicates the linear slide Figure 13-27.—CSCP controls and indicators. 13-33

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switch position is in the ON position. Red indicates the switch is in the OFF position. Green indicates the switch is in the NORMAL position, while yellow indicates the switch is in the ALTERNATE position. Figure 13-27 shows an example of a typical CSCP configuration. The number and functional assignment of PBIs vary from ship to ship. The PBIs in the lower right comer of the CSCP front panel shown in figure 13-27 are used to apply power to the CSCP PBIs (ON), to indicate current CSCP control status (CSCP CONTROL or ALT CSCP CONTROL), and to transfer control from the controlling CSCP to the alternate CSCP (REQ CONTROL, HOLD, ACT CSCP REQ CONTROL, and ALT CSCP HOLD). Manual PBI actions are required at both CSCPs to transfer control between panels. At the requesting CSCP, depression of the REQ CONTROL PBI will cause the ALT CSCP REQ CONTROL indicator to light red on the controlling CSCP. The REQ CONTROL PBI will flash red on the requesting CSCP until the operator of the controlling CSCP depresses AT CSCP CONTROL PBI, giving control to the requesting CSCP. The CSCP CONTROL light will come on when the requesting CSCP is in control and the flashing light will go out. The HOLD PBIs are used to indicate refusal to transfer control. SHIP, SWITCHBOARD, AND COMPUTER SWITCHING CONTROL PANEL (CSCP) WIRING Switchboard and CSCP wires connect assemblies and components inside the switchboard and CSCP. Ship’s cables are individually plug-connected to panel connectors in the switchboard. Ship’s cables are identified by a cable group number and cable type. Ship’s cables, switchboard wires, and CSCP harness wires use plastic sleeves or metal tags for marking. Each ship wire has a marking bearing the ship’s wire number. When required, switchboard and CSCP wires have plastic marking sleeves at each end. The sleeves identify the terminals at both ends of the wire. Separate wiring codes are used for ship’s wires, switchboard wires, and CSCP wires. The ship’s wire marking codes are system oriented. They consist of an alphanumeric code that identifies the signal being carried by function number, circuit designation, and assigned wire number. A typical ship’s wire code number is shown in table 13-4. Table 13-4.—A Typical Ship’s Wire Code Number There are eight types of PANEL ASSEMBLY connectors used in the switchboard. These connectors are used for the linear movement switch assemblies, fuse tester assembly, relay tester assembly, and power distribution assembly. They consist of various types of 120-, 117-, 104-, 85-, 38-, 20-, 10-, and 3-pin connectors. For wiring and maintenance purposes, a common alphanumeric designation system is used to identify specific circuit connections, as shown in table 13-5. Table 13-5.—Panel Connection Cable Code Within the switchboard are what are known as matrix panels. The matrix panels interconnect the signal paths between the ship’s wiring and the assembly panels. The designation codes for matrix panel connections are shown in table 13-6. Table 13-6.—Matrix Panel Connection Code Intersection connectors are used to tie switchboard sections together. Intersection connector codes are identified in table 13-7. Table 13-7.—Intersection Connector Code The CSCP uses two types of connectors, a 10-pin connector and an 85-pin connector. The l0-pin connectors are designated JA, JB, JN, and JP. The 85-pin connectors are designated JC through JG, JH, and JK. The alphanumeric identification shown in table 13-8 is used for CSCP connectors. 13-34

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Table 13-8.—CSCP Connector Code ANALOG SWITCHBOARDS Analog switchboards are similar in design to the Mk 70 DFCS. The switchboard is made up of a variable number of switchboard sections. The number of sections required will vary with the analog interface requirements of the shipboard system. Each switchboard section consists of front and rear cabinets (figure 13-28). The front cabinet contains the panel assemblies. The rear cabinet contains removable modules on which are mounted the ship’s cable connectors. Each switchboard section contains 36 panels of various types mounted on the door of the front cabinet. The panels are numbered starting with panel 1 in the upper left-hand corner in section 1 and progressing consecutively downward in each column and successively to the right. The door in each switchboard section allows access to the section interior. Figure 13-28.—Analog switchboard. 13-35

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Figure 13-29.—Analog switchboard section, door open. Ship’s cables enter the switchboard through the rear cabinet and connect to the front of the module terminal boards (figure 13-29). From the panel assemblies, wiring is routed to the back side of the terminal boards on the modules via plug connectors. Wiring between switchboard sections is routed via inter-section connectors. The following panel assemblies are found on analog switchboards. Individual analog switchboard layouts and configurations will vary between ship classes. Indicator Panel Assembly The indicator panel assembly (figure 13-30) provides a visual indication of the active power being supplied to the switchboard. The panel assembly contains up to 10 indicators, all of which are mounted on the front panel. 13-36 Figure 13-30.—Indicator panel assembly.

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Figure 13-31.—Fuse panel assembly. Fuse Panel Assembly The fuse panel assembly (figure 13-31) contains overflow fuses for circuits located in an associated panel. Each panel may contain up to 10 dual indicator-type fuseholders. Fuse Tester Panel Assembly The fuse tester panel (figure 13-32) functions in the same manner as the Mk 70 DFCS fuse tester panel. Figure 13-32.—Fuse tester assembly (analog switchboard). Figure 13-33.—Meter panel assembly. Meter Panel Assembly Two meter panels (figure 13-33) are used: one panel type monitors 60-Hz and 400-Hz power buses and the other monitors dc buses. The panels contain an ac or dc meter and a rotary snap switch. The snap switch enables voltage measurements to be performed on the selected power bus. Flasher Panel Assembly The flasher panel (figure 13-34) produces pulsating (ON/OFF/ON and so forth) potentials to activate Figure 13-34.—Flasher panel assembly. 13-37

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Figure 13-35.—Snap switch panel assembly. flashing system indicators when a warning or emergency condition occurs. Motor-driven dual-cam and three-cam activated switches open and close control or status signal circuits to provide the flashing effect on indicator lamps. Snap Switch Panel Assembly The snap switch panel assembly (figure 13-35) provides manual control of switchboard power buses. An individual panel mat contains either one or two snap switches. The snap switch (figure 13-36) is a device that opens or closes a circuit with a quick motion. Rotary snap switches are used extensively in the distribution Figure 13-36.—Snap switch. 13-38 Figure 13-37.—Manually operated JR switch panel assembly. sections of switchboards to connect the shipboard power supplies to the various switchboard power buses. Manually Operated JR Switch Panel Assembly The manually operated JR switch panel assembly (figure 13-37) provides manual switching and action cutout (ACO) functions. The manually operated JR switch panel assembly uses either a 2JR or 4JR switch. Both switch types are similar in construction and differ only in the electrical application because of switching action. A JR switch as shown in figure 13-38 is made up of a variable number of waferlike sections. As the switch is manually positioned, one or more moveable contacts are positioned to each switch position on the wafer. The contacts may connect (bridge) two or more contacts on each wafer effectively opening or closing circuit paths as required to configure the system for normal or alternate operation. Remotely Operated JR Switch Panel Assembly The remotely operated JR switch panel (figure 13-39) provides remote and manual control of signal routing and ACO switching. The automatic junction rotary (AJR) switches used in these assemblies are driven by a motor and gear train servo system. The automatic switches allow control of switching functions from remote stations. Analog switchboards used with combat direction systems use control signals provided by the multiplexing data converter to activate the switches and provide status signals back to the converter to indicate switch position to the system.

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Figure 13-38.—JR switch (type 4). Each panel contains a REMOTE-MANUAL toggle switch. The servo system controls the position of the AJR switch when the toggle switch is in the REMOTE position. The toggle switch must be placed in MANUAL to allow personnel to rotate the switch. Linear Movement Switches In newer switchboards and upgrades to older switchboards, the rotary-type JR and AJR switches have been replaced by linear movement switches with the same electrical configurations as the JR switches. We covered linear movement switch panel assemblies in the Mk 70 DFCS. Figure 13-39.—Remotely operated JR switch panel assembly. END-AROUND-TEST (EAT) One of the functions provided by both analog and digital switchboards is the end-around-test (EAT). When switches are in the EAT position, switchboards take the output of a device and feed it back to the same or similar device as input data. For instance, a control signal generated by a device such as the KCMX can be routed end-around as a status signal input. The output of a digital-to-synchro (D/S) converter can be fed end- around to a synchro-to-digital (S/D) converter or the output channel of a computer can be end-around as an input channel for the same computer. EAT allows for offline testing and verification of the operability of digital and analog interfaces, both within the CDS and external to the CDS. SUMMARY-DATA CONVERSION DEVICES AND SWITCHBOARDS This chapter has introduced you to analog-to- digital (A/D), digital-to-analog (D/A), and digital-to- digital (D/D) conversion methods and some typical conversion devices. You were also introduced to data switchboards used in system configuration. The following information summarizes important points you should have learned. FUNDAMENTALS OF DATA CONVER- SION— The digital equipment that composes the combat direction system (CDS) uses information in analog form. To use this information, the analog signals must first be converted to digital signals. The amplitude, frequency, or phase of an analog signal may represent a value within a given set of limits (minimum 13-39

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limit to maximum limit). Binary codes of ONEs and ZEROs are used to represent digital values. Each bit position in a binary number represents a portion of the overall quantity being represented. The summation of the values of the set bits (ONEs) determines the value to be represented. ANALOG-TO-DIGITAL (A/D) AND DIGI- TAL-TO-ANALOG (D/A) CONVERSIONS— The analog-to-digital conversion process can be divided into three operations: sampling, quantization, and encoding. ANALOG AND DIGITAL QUANTITIES— An analog signal is sampled or tested repeatedly over a period of time to determine the characteristic that contains the analog quantity. The sampled analog value is converted to the nearest binary value or quantity. The binary value is then encoded into a code acceptable to the digital equipments that use the data. Standardized binary words called BAMs (binary angular measurement) are used to transmit angular, range, and height values between digital equipments in shipboard combat direction systems. Other coding systems such as Gray code or binary-coded decimal (BCD) are also used to transmit converted values. ANALOG-TO-DIGITAL CONVERTERS— An analog-to-digital converter is a device that receives an analog signal and converts it to a digital (binary) quantity with a given accuracy and resolution. SYNCHROS— One of the most common analog shipboard signals indicating angular position that requires conversion to binary is the 3-phase or 5-wire synchro signal. Synchro is the name given to a variety of rotary, electromechanical, position-sensing devices. A synchro system is made up of a combination of a synchro transmitter and one or more synchro receivers. There are two major classifications of synchro systems: torque systems and control systems. Most shipboard synchro systems operate on a supply or reference voltage of 115 vac at a frequency of 60 or 400 Hz. SYNCHRO ACCURACY— The accuracy of data transmitted by synchros is improved by using a multispeed synchro system such as a dual-speed system. A dual-speed synchro system uses two synchro transmissions, with a common reference voltage, called the coarse and fine transmissions. The coarse and fine transmissions are converted separately and the results are then combined into one BAM word. SYNCHRO SIGNAL CONVERSION— Two methods are currently in use to convert synchro signals to digital (BAM) words: the sector method and the octant method. SECTOR METHOD— The sector method first determines the 60-degree sector angle in which the rotor is positioned using the stator voltages. When the sector has been determined, two of the three stator voltages are sampled to determine the ratio angle within the sector. The sector angle and the ratio angle are then summed to determine the binary angle of the rotor position in BAMs. OCTANT METHOD— The octant method first determines the 45-degree octant by converting the synchro signal into two sine and cosine voltages. The remaining angle within the octant is determined by a process of successive approximations. THE DIGITAL-TO-ANALOG CONVERTER CV-2517B/UYK— The CV-2517B/UYK DAC is a multipurpose digital-to-analog converter. It is capable of accepting parallel digital data words (BAMs) and converting them into linear, scalar, or synchro output signals. Each DAC is divided into two channels, designated channels A and B. Each channel can output two linear voltages, a sine/cosine scalar signal, or a single-speed synchro signal. SHIPBOARD DIGITAL/ANALOG SYSTEM INTERFACES— Shipboard digital/analog system interfaces permit nominally independent shipboard systems or subsystems to communicate or interface with the combat direction system. MULTIPLEXING DATA CONVERTERS— Multiplexing data converters are computer-controlled multipurpose devices that operate between one or more digital computers and a variety of control, status, digital and analog devices located in remote shipboard subsystems. KEYSET CENTRAL MULTIPLEXER (KCMX)— The KCMX provides the means for exchanging data, control, and status information between either one of two computers and a variety of I/O devices. The KCMX duplexer allows two computers to alternately control operation of the KCMX. Three external function (EF) commands are used to control the duplexer operation: REQUEST CONTROL, RELEASE LOCAL, and RELEASE REMOTE. The KCMX can operate in one of seven modes, as specified by the controlling computer: NEUTRAL, DUPLEX, RDUC (receive data from unit computer), TDUC (transmit data to unit computer), TDUC and RDUC, INTERRUPT, and KEYSET ERROR. 13-40

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KCMX INPUT AND OUTPUT— The KCMX can receive ready digital (RD) data from up to eight radar azimuth converters (RACs). The ENTER signal indicates that the ready digital (RD) data is valid and may be sampled and sent to the controlling computer. The KCMX is capable of outputting data over four digital output channels (DOCs) and receiving data from four digital input channels (DICs). These channels can be manually set to computer (COMPUTE) or peripheral (PERIPH) formats. The KCMX can receive up to 60 status signals. The status signals’ conditions (0 or 1) are inputted to the computer as two 30-bit status words. The KCMX generates control signals based on individual bits set in two control words received from the controlling computer. KCMX CONVERSIONS— The KCMX can accept and convert inputs from up to 323-wire synchros using 12 reference voltages. Two separate conversions are performed for each input, one for the fine speed and one for the coarse speed. When converting single-speed synchro inputs, both conversions are performed. However, the fine conversion is ignored and the bits that apply to the fine conversion in the BAM word are zeroed. SWITCHBOARDS— Switchboards are used to interconnect a ship’s systems. There are two major types of switchboards: digital and analog. DIGITAL SWITCHBOARDS— Digital switch- boards primarily interconnect digital devices. There are two types of digital switchboards: manual switchboards and remotely controlled switchboards. MANUAL SWITCHBOARDS— Manual switch- boards are made up of variable configurations of manually operated three-position and five-position switches. REMOTELY CONTROLLED SWITCH- BOARDS— Remotely controlled switchboard configuration changes are accomplished from one of two computer switching control panels (CSCPs). The CSCP generates control signals to position the linear slide switches and receives status signals from the switches to indicate current switch position. DIGITAL FIRE CONTROL SWITCHBOARD (DFCS)— The digital fire control switchboard (DFCS) performs data routing, power monitoring, action cutout (ACO) switching, and digital switching. SHIP, SWITCHBOARD, AND CSCP WIRING— All cables and wires used aboard a ship are labeled with a specific code. Specific codes are used to identify ship’s wiring, switchboard wiring, and CSCP wiring. These codes are found on metal or plastic labels on each end of the cable. ANALOG SWITCHBOARDS— Analog switch- boards receive control signals from the multiplexing data converter to position the automatic junction rotary (AJR) switches and provide status signals to indicate switch status. END-AROUND-TEST (EAT)— One of the functions provided by both analog and digital switchboards is the end-around-test (EAT). When switches are set to the EAT position, the switchboard routes the output of a device back to the same or similar device as input data. 13-41

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APPENDIX I GLOSSARY OF TERMS AND ACRONYMS 2M— Miniature/Microminiature (2M) Electronic Repair. A/D— Analog-to-digital. AAC— Analog-to-analog converter. ABORT— To end the execution of a program before is it completed because of an irrecoverable error, mistake, or malfunction. ABT— Automatic bus transfer. ac— Alternate current. ACO SWITCHING— Action cutout switching. ADDRESS— A character or group of characters that defines a particular part of storage, some other data source, or destination. Nor- mally the location of a given storage cell in a memory. ADDRESS BUS— A bus carrying signals that define storage addresses. ADP— Automated data processing. ALGORITHM— The series of steps to solve a problem. ALS— Advanced low-power Schottky. Alt— Alternate. ALU— Arithmetic logic unit. amp— Amplifier. ANEW— Army-Navy Electronic Warfare. ANSI— American National Standards Institute. AS— Advanced Schottky. ASCII (American Standard Code for Information Interchange)— A standard 8-bit code for use with computers and data terminals. ASR— Active status register. ASW— Antisubmarine warfare. ASW SYSTEMS— Antisubmarine warfare systems. ASWOC— Antisubmarine Warfare Operations Cen- ter. ASWOC/HLT— Antisubmarine Warfare Operations Center/High-Level Terminal. Async— Asynchronous. AZIMUTH— An angular measurement in the hor- izontal plane in a clockwise direction. BAM— Binary angular movement or motion. BAP— Buffer address pointer. BASIC— Beginner’s All-purpose Symbolic Instruction Code. BBC-MTC CABLE— Buffered block channel/mag- netic tape controller cable. BBU— Battery back-up unit. BCD— Binary-coded decimal. BCH— Binary-coded hexadecimal. BCO— Binary-coded octal. BCW— Buffer control word. BEARING— An angular measurement of the direc- tion of an object from a reference direction, such as true north. AI-1

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BFW— Buffer function word. BIDFET— Highvoltage bipolar field-effect transistor. BIDMOS— High voltage DMOS FET. BIFET— Bipolar field-effect transistor. BIMOS— Bipolar metal-oxide semiconductor, com- bines bipolar and MOS technology. BIOS— Basic input/output system. BIPOLAR— A logical true input represented by an electric voltage polarity opposite to that re- presenting a logical false input. BIPOLAR ICs— Contain parts comparable to dis- crete bipolar transistors, diodes, capacitors, and resistors. Controlled by current applied to the control terminal (base). BIT— Built-in test. BOT— Beginning-of-tape mark. bpi— Bits per inch. bps— Bits per second. BREAKPOINTS— Location of a point in a program where program executing can be stopped to permit a visual test, printing, or a performance analysis. BUS— One or more conductors used to transmit signals. C/D— Control/data. CA— Computer acknowledge. CAP— Chain address pointer. CAS— Column address strobe. CD-ROM— Compact disc read-only memory. A high density optical storage medium. CHIP— An integrated circuit on a piece of semi- conductive material. CIS— Computer Interconnection System. CLCC— Ceramic leadless chip carrier. CLK— Clock signal. CML— Current mode logic. CMOS— Complementary metal-oxide semiconductor. Where both NMOS and PMOS transistors are integrated into the same gate circuit. CMPs— Control and maintenance panels. CMR— Code memory register. CNP CABLE— Communication network processor cable. COBOL— COmmon Business Oriented Language. COMPUTER WORD— A word stored in one computer memory location and capable of being treated as a unit. Synonymous with full word, machine word. CONTROL BUS— A bus carrying signals that regulate system operations. cpi— Characters per inch. CPU— Central processing unit. CS— Chip select. CSCP— Computer switching control panel. CSTOM— Combat systems operating manual. Ctrl— Control. CTS— Clear to send. CV-ASWM— Carrier-Antisubmarine Warfare Mod- ule. CD-I— Compact disc-interactive. CDS— Combat direction system. D/D— Digital-to-digital. D/A— Digital-to-analog. AI-2

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DAC— Digital-to-analog converter. DATA BUS— A bus used to communicate data internally and externally to and from a pro- cessing unit, or a storage or peripheral de- vice. DBCU— Data bus control unit. dc— Direct current. DCE— Data communications equipment. DCI— Defective card index. DCU— Display control unit. DD— Demand digital. DDI— Demand digital interrupt. DECODE— To convert data by reversing the effect of some previous encoding. Del— Delete. DEMON— Diagnostic environment monitor. DFCS— Digital fire control switchboard. DIBIT (dipole bit)— A form of data prerecorded on a disk pack during manufacture. Recorded only on servo tracks of standard disk packs. DIC— Digital input channel. DIM/DOM— Digital input multiplexer/digital output multiplexer. DIP— Dual-in-line package. DIP SWITCH— Dual-in-line switch. DMA— Direct memory access. DMI— Direct memory interface. DMOS— Diffused metal-oxide semiconductor. DMTU— Digital magnetic tape unit. DOC— Digital output channel. DOS— Disk operating system. DOT MATRIX— A matrix of rows and columns of dots used to generate characters or character images composed of dots. dpi— Dots per inch. DRAM— Dynamic random access memory. DSR— Data set ready. DTC— Desktop computer. DTE— Data terminal equipment. DTL— Diode-transistor logic. DTR— Data terminal ready. EA— Electronic attack. EAPROM— Electrically alterable programmable read-only memory. ECL— Emitter-coupled logic. EDIT— To prepare data for a later operation. Editing may include the rearrangement or addition of data, the deletion of unwanted data, or the addition/deletion of format control char- acters. EEPROM— Electrically erasable programmable read-only memory. EF— External function. EFA— External function acknowledge. EFM DATA— Eight-to-fourteen modulation data. Used with CD-ROM. EFR— External function request. EGA VIDEO— Enhanced graphics adapter video. EI— External interrupt. EIA— Electronks Industry Association. AI-3

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EIE— External interrupt enable. EIR— External interrupt request. EL— Electroluminescent. EMI— Electromagnetic interference. ENCODE— To convert information into coded form. EOT— End-of-tape mark. EPROM— Electrically programmable read-only memory. ESA— Externally specified address. ESD— Electrostatic discharge. ESDI— Enhanced small device interface. A fixed disk interface. ESI— Externally specified index. EVEN PARITY— A characteristic of a group of bits having an even number of binary ONEs. EW— Electronic warfare. FAT— File allocation table. FDDI— Fiber Distributed Data Interface. FERRITE— A powdered and compressed ferric oxide material that has both magnetic properties and light resistance to current flow. FET— Field-effect transistor. A voltage operated transistor. FF— Flip-flop. FHLT SYSTEMS— Force High-Level Terminal Sys- tems. FIBER OPTICS— Conductors or optical waveguides that readily pass light. FIFO— First-in, first-out. FILO— First-in, last-out. FIRMWARE— Program instructions stored in read- only memory (ROM) or programmable read- only memory (PROM). FIT— Fault isolation table. FLUX DENSITY— The number of magnetic lines of force passing through a given area. FLUX— In electrical or electromagnetic devices, a general term used to designate collectively all the electric or magnetic lines of force in a region. FM— Frequency modulation. FONT— A family or assortment of characters of a given size and style. FORMAT— The arrangement or layout of data in or on a data medium. FORTRAN— FORmula Translation programming language. fpi— Frames per inch. FREQUENCY— The number of complete cycles per second existing in any form of wave motion, such as the number of cycles per second of an alternating current. FTA— Fast-time analyzer. GAIN— Any increase or decrease in the strength of a signal. GPIB— General-Purpose Interface Bus. GRAY CODE— A binary code in which sequential numbers are represented by binary expressions, each of which differs from the preceding expression in one place only. Synonymous with reflected binary code. HARD COPY— A permanent copy of a display image that is portable and can be read by human beings. HARDWARE— Physical equipment as opposed to programs (software), procedures, rules, and documentation. AI-4

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HCMOS— High-speed complementary metal-oxide semiconductor. HEAD— A device that reads, writes, or erases data on a storage medium. HERTZ (Hz)— A unit of frequency equal to one cycle per second. HSP— High-speed printer. Hz— Hertz. I— Instruction. I/O— Input/output. I 2 L— Integrated injection logic (also IIL). IC— (1) Integrated circuit; (2) Intercomputer chan- nel. IC CHIPS— Integrated circuit chips ID— Input data. IDA—Input data acknowledge. IDC— (1) Integrated disk controller; (2) Insulation displacement connection. IDE— Integrated drive electronics. A fixed disk con- troller in which the controller is on the fixed disk drive electronics card. IDR— Input data request. IEEE— Institute for Electrical and Electronics En- gineers. IFF— Identification friend or foe. IIL— Integrated injection logic (also I 2 L). IMPACT PRINTER— A printer in which printing is the result of mechanical impacts. IN PHASE— The condition that exists when two or more signals of the same frequency pass through their minimum and maximum values of like polarity at the same instant. INDICATORS— Lights that show status of an operation or a selected item. INSTRUCTION— In a microprocessor or digital computer system, the information that tells the computer what to do. One step in a computer program. INT— Interrupt. INTELLIGENCE— In communications, any signal that conveys information. INTERFACE— The interconnecting devices, in- cluding wiring, data converters, switchboards, and so forth, that enable equipments to establish communication with other equipments or sys- tems. INTERRUPT— A method of stopping a process and identifying a certain condition exists. IOA— Input/output adapter. IOC— Input/output controller. IOCC— Input/output communications console. JFET— Junction field-effect transistor. JMP— Jump. JOTS— Joint Operation Tactical System. K— Kilobyte. KCMX (Keyset Central Multiplexer)— A data con- version and interface device. LAN— Local-area network. LANDS— Smooth areas of CD-ROM tracks that reflect the laser beam to a photodiode. LASER DIODE— A small laser beam generator employing a semiconductor junction as the active medium. LCC— Leadless chip carrier. LED— Light-emitting diode. AI-5

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LIFO— Last-in, first-out. LIGHT EMITTING DIODE (LED)— A diode that emits visible light when it is forward biased. Lin CMOS— Silicon gate metal-oxide semiconductor field-effect transistor (Trademark of Texas In- struments, Inc.). LINE PRINTER— A printer that prints data one line at a time. LP TTL-S— Low-power transistor-transistor logic- Schottky. LRU— Line replaceable unit. LSB— Least significant bit. LSI— Large scale integration. M— Megabyte. MAGNETIC INDUCTION— Generating a voltage in a circuit by the creation of relative motion between the magnetic field and the circuit. MAINTENANCE— Work done to correct, reduce, or to counteract wear, failure, and damage to equipment. MBR— Master boot record. MC— Master clear. MDD— Micro disk drive. MEMORY— Synonym for storage. MFM— Modified frequency modulation. A system of encoding data on a magnetic disk. MICROCONTROLLER— Synonym for microproc- essor. MICROELECTRONICS— The solid-state concept of electronics in which compact semiconductor materials are designed to function as an entire circuit or subassembly rather than as circuit components. MICROINSTRUCTION— An instruction of a microprogram. MICROPROCESSOR— An integrated circuit that accepts coded instructions at one or more terminals or ports, executes the instructions received, and delivers signals describing its progress. The instructions may be entered, integrated, or stored internally. MICROPROGRAM— A sequence of instructions executed by a microprocessor. MILITARY STANDARDS (MILSTD)— Standards of performance for components or equipment that must be met to be acceptable for military sys- tems. MIP— Maintenance index page. MIPS— Million instructions per second. MOS ICs— Contain parts comparable to discrete resistors (NMOS, PMOS, and FETS). Source acts as the emitter; gate acts as the base; and the drain acts as the collector. Controlled by voltage produced on the controlling terminal (gate). MOS— Metal-oxide semiconductor. Describes the structure in which this electric field is created—a metal gate, an oxide layer, and a semiconductor channel. MOSFET— MOS field-effect transistor. MPC— Microprogrammed controller. MRC— Maintenance requirement card. MS-DOS— Microsoft-Disk Operating System. MSB— Most significant bit. MSI— Medium-scale integration. MT— Main timing. MTIDC— Mass termination insulation displacement connection. MTI— Magnetic tape transport. AI-6

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MTU— Magnetic tape unit. N-FET— N-channel field-effect transistor. NDRO MEMORY— Nondestructive readout mem- ory. NEETS— Navy Electricity and Electronics Training Series. NIPS— Naval Intelligence Processing System. NLQ— Near letter quality. NMOS-N— channel metal-oxide semiconductor. NONIMPACT PRINTER— A printing device that does not mechanically impact the paper. NONVOLATILE STORAGE— A storage device whose contents are not lost when power is removed. NRZ— Non-return-to-zero recording method. NRZI— Non-return-to-zero indiscrete. NTDS— Naval Tactical Data System. NuBus— Simple 32-bit backplane bus (standard internal data bus). O— Operand. OA— Output acknowledge. OD— Output data. ODA— Output data acknowledge. ODR— Output data request. OFFLINE— Pertaining to the operation of a func- tional unit when not under the direct control of a computer. ONLINE— Pertaining to the operation of a funt- ional unit when under the direct control of a computer. OP CODE— Operation code. OP PROGRAM— Operational program. OTCIXS— Officer-in-Tactical-Command Information Exchange System. OUTPUT DATA— Data being delivered or to be delivered from a device or from a computer program. OUTPUT CHANNEL— A channel for conveying information from a device or logic element. P/TP— Power/temperature panel. PAGE PRINTER— A device that prints a whole page as an entity. PARITY CHECK— A check that tests whether the number of binary ONEs in an array of binary digits is odd or even. PBI— Pushbutton/indicator. PC— (1) Personal computer/microcomputer; (2) Printed circuit. PCB— Printed circuit board. PE— Phase encoding. PEAK VOLTAGE— The maximum value present in a varying or alternating voltage. This value may be positive or negative. PEFT— Peripheral equipment fictional test. PERIPHERAL DEVICE— With respect to a par- ticular processing unit, any equipment that can communicate directly with that unit. Synony- mous with peripheral unit. PGA— Pin grid array. PHOTODIODE— A diode that produces current by absorbing light. PI— Power interrupt. PITS— Depressions in a CD-ROM that causes the laser beam to defuse. PLCC— Plastic leadless chip carrier. AI-7

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PMOS— P-channel metal-oxide semiconductor. PMS— Planned Maintenance System. POFA— Programmed Operational Functional Anal- ysis. POST— Power-on self test. PPS— Primary power supply. PREVENTIVE MAINTENANCE— Maintenance performed specifically to prevent faults from occurring. PRF— Pulse-repetition frequency. PRINTER— An output device that produces a durable record of data in the form of a se- quence of discrete graphic characters belonging to a predetermined character set. PRO M— Programmable read-only memory. PRT— Pulse-repetition time. PS— Power supply. PW— Pulse width. QMOS— Quick metal-oxide semiconductor. RAC— Radar azimuth converter. RAM— Random access memory. RC— Resistance-capacitance. RC— Request control. RD— Read data. RDUC— Receive data from unit computer. RECORD— A set of related data or words treated as a unit. RAS— Refresh address strobe. REI— Requester extension interface. RFI— Radio frequency interference. RLL— Run length limited. A fixed disk controller and data encoding system that increases the density of data on the disk. ROCU— Remote operator control unit. ROM— Read-only memory. ROTOR— The rotating member of a synchro that consists of one or more coils of wires wound on a laminated core. Depending on the type of synchro, the rotor functions in a manner similar to the primary or secondary windings of a transformer. RS-232— Recommended standard 232. ANSI stand- ard serial interface. RS— Recommended standard. RTC— Real-time clock. RTS— Request to send. RZ— Return-to-zero recording method. S/D— Synchro-to-digital. SCSI— Small computer systems interface. SDC— Signal data converter. SEEK— To selectively position the access mechan- ism of a direct access device. SEM— Standard electronic module. SEM CHASSIS— Standard electronic module chassis. SERIAL— An occurrence of events, such as pulses, in a timed sequence rather than simultaneously. SERIAL PRINTER— Synonym for character printer; prints one character at a time. SERVO SYSTEM— An automatic feedback control system that compares a required condition with an actual condition and uses the difference to adjust a control device to achieve the desired condition. SIMMs— Single inline memory modules. AI-8

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SIPPs— Single inline pin package. SIPs— Single inline package SNAP I, II, AND III SYSTEMS— Shipboard Non- tactical ADP Program I, II and III Systems. SOFTWARE— Programs, procedures, rules, and documentation pertaining to the operation of a computer system. SOIC— Small-outline integrated circuit. SOM— System operating manual. SPS— Standby power supply. SRAM— Static random access memory. SSI— Small-scale integration. ST-506— A fixed disk interface system. SYNC— Synchronous. SYNCHRO— A small motorlike analog device that operates like a variable transformer and is used primarily for the transmission of data among analog equipments and stations. TDUC— Transmit data from unit computer. TFCC— Tactical Flag Command Center. TO— Transistor-outline. TRISTATE— Output configuration capable of as- suming three output states: high, low, and high impedance (open). TTL— Transistor-transistor logic. TTL-H— Transistor-transistor logic-high-speed. TTL-S— Transistor-transistor logic-Schottky. TTLC— Bipolar transistor-transistor logic series in CMOS technology. TTY— Teletype. TVM— Time volatile memory. UART— Universal asynchronous receiver/transmitter. UNIX— An operating system developed by AT&T (Trademark of AT&T). UPS— Uninterruptible power supply. USART— Universal synchronous/asynchronous receiver transmitter. USRT— Universal synchronous receiver transmitter. UV— Ultraviolet. UV EPROM— Ultraviolet-erasable PROM. VF— Vacuum fluorescent. VLSI— Very large-scale integration. VMB— Virtual memory board. VOS— Virtual operating system. WD— Write data. AI-9

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APPENDIX II REFERENCES USED TO DEVELOP THE TRAMAN NOTE: Although the following references were current when this TRAMAN was published, their continued currency cannot be assured. Therefore, you need to be sure that you are studying the latest revision. Chapter 1 Combat System Technical Operations Manual (CSTOM) for DDG-993 Class (U), Combat System Readiness, NAVSEA S9DDG-7C-CSM-050/(U), DDG-993, CL, Vol 3, Part 1, Naval Sea Systems Command, Washington, D.C., 1982. Computer Science Source Book, The McGraw-Hill Science Reference Series, McGraw-Hill, New York, N.Y., 1988. Data Processing Technician 2, NAVEDTRA 12511, Naval Education and Training Program Management Support Activity, Pensacola, Fla., 1991. Data Systems Technician 3 & 2, NAVEDTRA 10231, Naval Education and Training Program Management Support Activity, Pensacola, Fla., 1987. Department of the Navy Information and Personnel Security Program Regulation, OPNAVINST 5510.1, Chief of Naval Operations, Washington, D.C., 1991. Department of the Navy Security Program for Automatic Data Processing Systems, OPNAVINST 5239.1, Chief Naval Operations, Washington, D.C., 1985. Electronics Installation and Maintenance Books, Electromagnetic Interference Reduction, NAVSHIPS 0967-LP-000-0150, Naval Sea Systems Command, Washington, D.C., 1980. Electromagnetic Radiation Hazards (U), (Hazards to Ordnance, [U]) NAVSEA OP 3565, NAVAIR 16-l-529/NAVELEX 0967-LP-624-6010, Vol 1, Naval Sea Systems Command, Washington, D. C., 1979. Electromagnetic Radiation Hazards (U), (Hazards to Ordnance, [U]) NAVSEA OP 3565, NAVAIR 16-l-529/NAVELEX 0967-LP-624-6010, Vol 2, Naval Sea Systems Command, Washington, D.C., 1989. Electronics Technician, 1 & C, NAVEDTRA 10292-F, Naval Education and Training Program Management Support Activity, Pensacola, Fla., 1987. AII-1

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Handbook of Shipboard Electromagnetic Shielding Practices, S9407-AB- HBK-010, Naval Sea Systems Command, Washington, D.C., 1989. Levine, Sy, Integrated Circuits and Computer Concepts, Electro-Horizons Publications, Plainview, N.Y., 1989. Maintenance Manual for Computer Set AN/UYK-7(V), Vol 1, SE610-AW- MMA-010, Naval Sea Systems Command, Washington, D.C., 1990. Navy Electricity and Electronics Training Series, Introduction to Digital Computers, Module 22, NAVEDTRA B72-22-00-88, Naval Education and Training Program Management Support Activity, Pensacola, Fla., 1988. Shipboard Bonding, Grounding, and Other Techniques for Electromagnetic Compatibility and Safety, MIL-STD-1310E(NAVY), Naval Sea Systems Command, Washington, D. C., 1987. System Coordinator Manual, AN/UYK-62(V), SE610-GV-OPl-610/UYK- 62(V), Naval Sea Systems Command, Washington, D.C., 1985. Technical Manual, Design Data for Data Processing Set, AN/UYK-44V, SE610-PV-MMV-010, Naval Sea Systems Command, Washington, D.C., 1986. Technical Manual, Operation and Maintenance Instructions for Computer Set AN/UYK43/V, SE610-NV-MMO-010/UYK-43(V), Naval Sea Systems Command, Washington, D.C., 1990. Walker, Roger S., Understanding Computer Science, Howard W. Sams and Co., Indianapolis, Ind., 1984. Chapter 2 Baker, Charles H., John C. Bellamy, John L. Fike, George E. Friend, Under- standing Data Communications, Howard W. Sams and Co., Indianapolis, Ind., 1984. Connectors and Jacketed Cable, Electric, Selection Standard for Shipboard Use, MIL-STD-1683B, Naval Sea Systems Command, Washington, D.C., 1987. Derfler, Frank J., Jr., “Connectivity,” 2d ed, PC Magazine, Ziff Davis Press, Emeryville, Calif., 1992. Digital Time Division Command/Response Multiplex Data Base, MIL-STD- 1553B, Naval Sea Systems Command, Washington, D.C., 1986. Electronical Connectors, Plug-In Sockets and Associated Hardware Selections and Use of, MIL-STD-1353B, Naval Sea Systems Command, Washington, D.C., 1980. Electronics Installation and Maintenance Books, Installation Standard, NAVSEA 0967-LP-000-0110, Naval Sea Systems Command, Washington, D.C., 1977. AII-2

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General Requirements for Electrontic Equipment Specifications, MIL-STD-2036, Naval Sea Systems Command, Washington, D.C., 1991. Encyclopedia of Electronics, Stan Gibilisco and Neil Sclater, Eds., 2d ed., Tab Books, Blue Ridge Summit, Penn., 1990. Hecht, Jeff, Understanding Fiber Optics, Howard W. Sams and Co., Indianapolis, Ind., 1987. Input/Output Interfaces, Standard Digital Data, Navy Systems, MIL-STD 1397B (Navy), Naval Sea Systems Command, Washington, D.C., 1989. Maintenance Manual for Computer Set AN/UYK-7(V), VOl 1, SE610-AW- MMA-010, Naval Sea Systems Command, Washington, D.C., 1990. Maintenance Manual for Computer Set AN/UYK-7(V), Vol 2, SE610-AW- MMA-020, Naval Sea Systems Command, Washington, D.C., 1990. Microcomputer Software and Hardware Guidelines, MIL-HDBK-805(OM), Naval Sea Systems Command, Washington, D.C., 1990. Mueller, Scott, Upgrading and Repairing PCs, Que Corporation, Carmel, Ind., 1988. Naval Ships Technical Manual (NSTM), S9086-RQ-STM-000, Chapter 510, Ventilating Heating Cooling and Air Conditioning Systems for Surface Ships, Naval Sea Systems Command, Washington, D.C., 1977. Naval Ships Technical Manual (NSTM), S9086-SD-STM-000, Chapter 532, Liquid Cooling Systems for Electronic Equipment, Naval Sea Systems Command, Washington, D.C., 1978. Naval Shore Electronics Criteria, Digital Computer Systems, Vol 1 of 2, SPAWAR 0280-LP-900-9000, Naval Electronics Systems Command, Washington, D.C., 1972. Naval Shore Electronics Criteria, Digital Computer Systems, Vol 2 of 2, SPAWAR 0280-LP-901-3000, Naval Electronics Systems Command, Washington, D.C., 1972. Naval Shore Electronics Criteria, Naval Security Group Elements Design and Performance, SPAWAR 0280-LP-900-6000, Space and Naval Warfare System Command, Washington, D.C., 1973. Naval Shore Electronics Criteria, SPAWAR 0280-LP-900-8000, Installation Standard and Practices, Space and Naval Warfare System Command, Washington, D.C., 1977. Navy Electricity and Electronics Training Series, Introduction to Circuit Protection, Control, and Measurement, Module 3, NAVEDTRA 172-03-00-85, Naval Education and Training Program Development Center, Pensacola, Fla., 1985. AII-3

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Navy Electricity and Electronics Training Series, Introduction to Electrical Conductors, Wiring Techniques, and Schematic Reading, Module 4, NAVEDTRA 172-04-00-85, Naval Education and Training Program Development Center, Pensacola, Fla., 1984. Navy Electricity and Electronics Training Series, Technician’s Handbook, Module 19, NAVEDTRA 172-19-00-85, Naval Education and Training Program Development Center, Pensacola, Fla., 1985. Navy Electricity and Electronics Training Series, Introduction to Fiber Optics, Module 24, NAVEDTRA B72-24-00-92, Naval Education and Training Program Management Support Activity, Pensacola, Fla., 1992. Organizational Level Maintenance Manual, Vol 1, AN/UYK-62(V), SE610- GV-MMO-010/UYK-62(V), Naval Sea Systems Command, Washington, D.C., 1989. Organizational Level Maintenance Manual, Vo1 2, AN/UYK-62(V), SE610- GV-MMO-020/UYK-62(V), Naval Sea Systems Command, Washington, D.C., 1989. Servicing Tools for Electric Contacts and Connections, Selection and Use of, MIL-STD-1646, Naval Sea Systems Command, Washington, D.C., 1983. System Coordinator Manual, AN/UYK-62(V), SE610-GV-OP1-610/UYK- 62(V), Naval Sea Systems Command, Washington, D.C., 1985. Technical Manual, Design Data for Data Processing Set, AN/UYK-44V, SE610-PV-MMV-010, Naval Sea Systems Command, Washington, D.C., 1986. Technical Manual, Operation and Maintenance Instructions for Computer Set AN/UYK-43/V, SE610-NV-MMO-010/UYK-43(V), Naval Sea Systems Command, Washington, D.C., 1990. Technical Manual, Operation and Maintenance with Parts List, Data Processing Set, AN/UYK-20(V), Vol 1, Naval Sea Systems Command, Washington, D.C., 1990. Z-248 Maintenance, (Part 1), Navy Regional Data Automation Center, Norfolk, Va., 1989. Z248 Systems Administrator, Zenith Data Systems Corporation, St. Joseph, Mich., 1988. Chapter 3 Data Processing Technician 2, NAVEDTRA 12511, Naval Education and Training Program Management Support Activity, Pensacola, Fla., 1991. Maintenance Manual for Computer Set AN/UYK-7(V), Vol 1, SE610-AW- MMA-010, Naval Sea Systems Command, Washington, D.C., 1990. AII-4

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Maintenance Manual for Computer Set AN/UYK-7(V), “Circuit Diagrams,” Vol 3, Part 1, SE610-AW-MMA-030, Naval Sea Systems Command, Washington, D.C., 1990. Maintenance Manual for Computer Set AN/UYK-7(V), “Circuit Diagrams,” Vol 3, Part 2, SE610-AW-MMA-040, Naval Sea Systems Command, Washington, D.C., 1990. Organizational Level Maintenance Manual, Vol 1, AN/UYK-62(V), SE610- GV-MMO-010/UYK-62(V), Naval Sea Systems Command, Washington, D.C., 1989. Organizational Level Maintenance Manual, Vol 2, AN/UYK-62(V), SE610- GV-MMO-020/UYK-62(V), Naval Sea Systems Command, Washington, D.C., 1989. System Coordinator Manual, AN/UYK-62(V), SE610-GV-OPl-610/UYK- 62(V), Naval Sea Systems Command, Washington, D.C., 1985. Technical Manual, Design Data for Data Processing Set, AN/UYK-44V, SE610-PV-MMV-010, Naval Sea Systems Command, Washington, D.C., 1987. Technical Manual, Operation and Maintenance Instuctions for Computer Set AN/UYK-43/V, SE610-NV-MMO-010/UYK-43(V), Naval Sea Systems Command, Washington, D.C., 1990. Chapter 4 Cannon, Don L., Gerald Luecke, Understanding Microprocessors, Howard W. Sams and Co., Indianapolis, Ind., 1984. Electronics Installation and Maintenance Books, Test Methods and Practices, NAVSEA 0967-LP-000-130, Naval Sea Systems Command, Washington, D.C., 1980. IEEE Standard for Logic Circuit Diagram, ANSI/IEEE Std. 991-1986, The Institute of Electrical and Electronics Engineers, New York, N.Y., 1986. IEEE Standard Graphic Symbols for Logic Functions, ANSI/IEEE Std 91-1984, Institute of Electrical and Electronics Engineers, Inc., New York, N.Y., 1984. Interface Standards for Shipboard Systems, Electrical Power Alternating Current (Metric), Section 300A, MIL-STD-1399 (Navy), Naval Sea Systems Command, Washington, D.C., 1992. Lancaster, Don, TTL Cookbook, Howard W. Sams and Co., Indianapolis, Ind., 1974. Levine, Sy, Integrated Circuits and Computer Concepts, Electro-Horizons Publications, Plainview, N.Y., 1989. AII-5

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List of Standard Microcircuits, MIL-STD-1562C, Naval Sea Systems Com- mand, Washington, D.C., 1981. Maintenance Manual for Computer Set AN/UYK-7(V), “Circuit Diagrams,” Vol 3, Part 1, SE610-AW-MMA-030, Naval Sea Systems Command, Washington, D.C., 1990. Maintenance Manual for Computer Set AN/UYK-7(V), “Circuit Diagrams,” Vol 3, Part 2, SE610-AW-MMA-040, Naval Sea Systems Command, Washington, D.C., 1990. McWhorter, Gene, Understanding Digital Electronics, Howard W. Sams and Co., Indianapolis, Ind., 1984. Microcircuits, General Specifications For Military Specification, MIL-M-38510H, Rome Air Development Center, Griffis Air Force Base, N.Y., 1990. Navy Electricity and Electronics Training Series, Introduction to Generators and Motors, Module 5, NAVEDTRA 172-05-00-79, Naval Education and Training Program Development Center, Pensacola, Fla., 1979. Navy Electricity and Electronics Training Series, Introduction to Elec- tronic Emission, Tubes, and Power Supplies, Module 6, NAVEDTRA B72-06-00-92, Naval Education and Training Program Management Support Activity, Pensacola, Fla., 1992. Navy Electricity and Electronics Training Series, Introduction to Solid- State Devices and Power Supplies, Module 7, NAVEDTRA B72-07-00-92, Naval Education and Training Program Management Support Activity, Pensacola, Fla., 1992. Navy Electricity and Electronics Training Series, Introduction to Amplifiers, Module 8, NAVEDTRA 172-08-00-82, Naval Education and Training Program Development Center, Pensacola, Fla., 1982. Navy Electricity and Electronics Training Series, Introduction to Wave- Generation and Wave-Shaping Circuits, Module 9, NAVEDTRA 172-09-00-83, Naval Education and Training Program Development Center, Pensacola, Fla., 1983. Navy Electricity and Electronics Training Series, Introduction to Number Systems and Logic Circuits, Module 13, NAVEDTRA B72-13-00-86, Naval Education and Training Program Management Support Activity, Pensacola, Fla., 1986. Navy Electricity and Electronics Training Series, Introduction to Micro- electronics, Module 14, NAVEDTRA 172-14-00-84, Naval Education and Training Program Development Center, Pensacola, Fla., 1984. Navy Electricity and Electronics Training Series, Technician’s Handbook, Module 19, NAVEDTRA 172-19-00-85, Naval Education and Training Program Development Center, Pensacola, Fla., 1985. AII-6

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Seidman Arthur and Ivan Flores, eds., The Handbook of Computers and Computing, Van Nostrand Reinhold Co., New York, N.Y., 1984. Technical Manual, Operation and Maintenance Instructions for Computer Set AN/UK-43/V, SE610-NV-MMO-010/UYK-43(V), Naval Sea Systems Command, Washington, D.C., 1990. Tolkheim, Roger L., Digital Electronics, 2d ed, McGraw-Hill, New York, N.Y., 1984. Understanding Advanced Solid State Electronics, Howard W. Sams and Co., Indianapolis, Ind., 1986. Understanding Solid State Electrontics, 4th ed, Howard W. Sams and Co., Indianapolis, Ind., 1984. Walker, Roger S., Understanding Computer Science, Howard W. Sams and Co., Indianapolis, Ind., 1984. Z-248 Maintenance, (Part 1), Navy Regional Data Automation Center, Norfolk, Va., 1989. Z248 Systems Administrator, Zenith Data Systems Corporation, St. Joseph, Mich., 1988. Chapter 5 Cannon, Don L., Gerald Luecke, Understanding Microprocessor, Howard W. Sams and Co., Indianapolis, Ind., 1984. Chips, “Cache Memory, The Key to High Performance Personal Computers,” Department of the Navy, Washington, D.C., Jan 1992. Computer Science Source Book, The McGraw-Hill Science Reference Series, McGraw-Hill, New York, N.Y., 1988. Encyclopedia of Electronics, Stan Gibilisco and Neil Sclater, Eds., 2d cd., Tab Books, Blue Ridge Summit, Penn., 1990. Fink, Donald G., Donald Christiansen, eds., Electrons Engineers’Handbook, 3d cd., McGraw-Hill, New York, N.Y., 1989. Levine, Sy, Integrated Circuits and Computer Concepts, Electro-Horizons Publications, Plainview, N.Y., 1989. Maintenance Manual for Computer Set AN/UYK-7(V), Vol 1, SE610-AW- MMA-010, Naval Sea Systems Command, Washington, D.C., 1990. Maintenance Manual for Computer Set AN/UYK-7(V), “Circuit Diagrams,” Vol 3, Part 1, SE610-AW-MMA-030, Naval Sea Systems Command, Washington, D.C., 1990. Maintenance Manual for Computer Set AN/UYK-7(V), “Circuit Diagrams,” Vol 3, Part 2, SE610-AW-MMA-040, Naval Sea Systems Command, Washington, D.C., 1990. AII-7

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McWhorter, Gene, Understanding Digital Electronics, Howard W. Sams and Co., Indianapolis, Ind., 1984. Military Standard, General Requirements for Electrontic Equipment Specifica- tions, MIL-STD-2036, Naval Sea Systems Command, Washington, D.C., 1991. Minasi, Mark, The Complete PC Upgrade and Maintenance Guide, SYBEX, Inc., Alameda, Calif., 1991. Mueller, Scott, Upgrading and Repairing PCs, Que Corporation, Carmel, Ind., 1988. Navy Electricity and Electronics Training Series, Introduction to Solid-State Devices and Power Supplies, Module 7, NAVEDTRA B72-07-00-92, Naval Education and Training Program Management Support Activity, Pensacola, Fla., 1992. Navy Electricity and Electronics Training Series, Introduction to Amplifiers, Module 8, NAVEDTRA 172-08-00-82, Naval Education and Training Program Development Center, Pensacola, Fla., 1982. Navy Electricity and Electronics Training Series, Introduction to Wave- Generation and Wave-Shaping Circuits, Module 9, NAVEDTRA 172- 09-00-83, Naval Education and Training Program Development Center, Pensacola, Fla., 1983. Navy Electricity and Electronics Training Series, Introduction to Number Systems and Logic Circuits, Module 13, NAVEDTRA B72-13-00-86, Naval Education and Training Program Management Support Activity, Pensacola, Fla., 1986. Navy Electricity and Electronics Training Series, Introduction to Micro- electronics, Module 14, NAVEDTRA 172-14-00-84, Naval Education and Training Program Development Center, Pensacola, Fla., 1984. Navy Electricity and Electronics Training Series, Technician’s Handbook, Module 19, NAVEDTRA 172-19-00-85, Naval Education and Training Program Development Center, Pensacola, Fla., 1985. Navy Electricity and Electronics Training Series, Introduction to Digital Computers, Module 22, NAVEDTRA B72-22-00-88, Naval Education and Training Program Management Support Activity, Pensacola, Fla., 1988. Oganizational Level Maintenance Manual, Vol 1, AN/UYK-62(V), SE610- GV-MMO-010/UYK-62(V), Naval Sea Systems Command, Washington, D.C., 1989. Seidman Arthur and Ivan Flores, eds., The Handbook of Computers and Computing, Van Nostrand Reinhold Co., New York, N.Y., 1984. Technical Manual, Design Data for Data Processing Set, AN/UYK-44V, SE610-PV-MMV-010, Naval Sea Systems Command, Washington, D.C., 1987. AII-8

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Technical Manual, Operation and Maintenance Instructions for Computer Set AN/UYK-43/V, SE610-NV-MMO-010/UYK-43(V), Naval Sea Systems Command, Washington, D.C., 1990. Technical Manual, Operation and Maintenance with Parts List, Data Processing Set, AN/UYK-20(V), Vol 1, Naval Sea Systems Command, Washington, D.C., 1990. Understanding Computers, Computer Basics, Alexandria, Va., 1985. Walker, Roger S., Understanding Computer Science, Howard W. Sams and Co., Indianapolis, Ind., 1984. Z-248 Maintenance, (Part 1), Navy Regional Data Automation Center, Norfolk, Va., 1989. 2248 Systems Administrator, Zenith Data Systems Corporation, St. Joseph, Mich., 1988. Chapter 6 Cannon, Don L., Gerald Luecke, Understanding Microprocessors, Howard W. Sams and Co., Indianapolis, Ind., 1984. Computer Science Source Book, The McGraw-Hill Science Reference Series, McGraw-Hill, New York, N.Y., 1988. Data Systems Technician 3 & 2, NAVEDTRA 10231, Naval Education and Training Program Management Support Activity, Pensacola, Fla., 1987. Fink, Donald G., Donald Christiansen, eds., Electrons Engineers’Handbook, 3d cd., McGraw Hill, New York, N.Y., 1989. Gibilisco, Stan, Neil Sclater, Eds., Encyclopedia of Electrons, 2d cd., Tab Books, Blue Ridge Summit, Penn., 1990. Levine, Sy, Integrated Circuits and Computer Concepts, Electro-Horizons Publications, Plainview, N.Y., 1989. Maintenance Manual for Computer Set AN/UYK-7(V), Vol 1, SE610-AW- MMA-010, Naval Sea Systems Command, Washington, D.C., 1990. Maintenance Manual for Computer Set AN/UYK-7(V), “Circuit Diagrams,” Vol 3, Part 1, SE610-AW-MMA-030, Naval Sea Systems Command, Washington, D.C., 1990. Maintenance Manual for Computer Set AN/UYK7(V), “Circuit Diagrams,” Vol 3, Part 2, SE610-AW-MMA-040, Naval Sea Systems Command, Washington, D.C., 1990. McWhorter, Gene, Understanding Digital Electronics, Howard W. Sams and Co., Indianapolis, Ind., 1984. Microcomputer Software and Hardware Guidelines, MIL-HDBK-805(OM), Naval Sea Systems Command, Washington, D.C., 1990. AII-9

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Minasi, Mark, The Complete PC Upgrade and Maintenance Guide, SYBEX, Inc., Alameda, Calif., 1991. Minasi, Mark, The Complete PC Upgrade and Maintenance Guide, Fourth Edition, SYBEX, Inc., Alameda, Calif., 1995. Mueller, Scott, Upgrading and Repairing PCs, Que Corporation, Carmel, Ind., 1988. Mueller, Scott, Upgrading and Repairing PCs, Fifth Edition, Que Corporation, Carmel, Ind., 1995. Navy Electricity and Electronics Training Series, Introduction to Solid-State Devices and Power Supplies, Module 7, NAVEDTRA B72-07-00-92, Naval Education and Training Program Management Support Activity, Pensacola, Fla., 1992. Navy Electricity and Electronics Training Series, Introduction to Amplifiers, Module 8, NAVEDTRA 172-08-00-82, Naval Education and Training Program Development Center, Pensacola, Fla., 1982. Navy Electricity and Electronics Training Series, Introduction to Wave-Generation and Wave-Shaping Circuits, Module 9, NAVEDTRA 172-09-00-83, Naval Education and Training Program Development Center, Pensacola, Fla., 1983. Navy Electricity and Electronics Training Series, Introduction to Number Systems and Logic Circuits, Module 13, NAVEDTRA B72-13-00-86, Naval Education and Training Program Management Support Activity, Pensacola, Fla., 1986. Navy Electricity and Electronics Training Series, Introduction to Micro- electronics, Module 14, NAVEDTRA 172-14-00-84, Naval Education and Training Program Development Center, Pensacola, Fla., 1984. Navy Electricity and Electronics Training Series, Technician Handbook, Module 19, NAVEDTRA 172-19-00-85, Naval Education and Training Program Development Center, Pensacola, Fla., 1985. Organizational Level Maintenance Manual, Vol 1, AN/UYK-62(V), SE610- GV-MMO-010/UYK-62(V), Naval Sea Systems Command, Washington, D.C., 1989. Seidman Arthur and Ivan Flores, eds., The Handbook of Computers and Computing, Van Nostrand Reinhold Co., New York, N.Y., 1984. Technical Manual, Design Data for Data Processing Set, AN/UYK-44V, SE610-PV-MMV-010, Naval Sea Systems Command, Washington, D.C., 1987. Technical Manual, Operation and Maintenance Instuctions for Computer Set AN/UYK-43/V, SE610-NV-MMO-010/UYK-43(V), Naval Sea Systems Command, Washington, D.C., 1990. AII-10

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Technical Manual, Operation and Maintenance with Parts List, Data Processing Set, AN/UYK-20(V), Vol 1, Naval Sea Systems Command, Washington, D.C., 1990. Walker, Roger S., Understanding Computer Science, Howard W. Sams and Co., Indianapolis, Ind., 1984. Z-248 Maintenance, (Part 1), Navy Regional Data Automation Center, Norfolk, Va., 1989. Z248 Systems Administrator, Zenith Data Systems Corporation, St. Joseph, Mich., 1988. Chapter 7 Baker, Charles H., John C. Bellamy, John L. Fike, George E. Friend, Under- standing Data Communications, Howard W. Sams and Co., 1984. Cannon, Don L., Gerald Luecke, Understanding Microprocessors, Howard W. Sams and Co., Indianapolis, Ind., 1984. Computer Science Source Book, The McGraw-Hill Science Reference Series, McGraw-Hill, New York, N.Y., 1988. Derfler, Frank J., Jr., “Connectivity,” 2d ed, PC Magazine, Ziff Davis Press, Emeryville, Calif., 1992. Digital Time Division Command/Response Multiplex Data Base, MIL- STD-1553B, Naval Sea Systems Command, Washington, D.C., 1978. Electronical Connectors, Plug-In Sockets and Associated Hardware Selections and Use of, MIL-STD-1353B, Naval Sea Systems Command, Washington, D.C., 1980. Encyclopedia of Electronics, Stan Gibilisco and Neil Sclater, Eds., 2d cd., Tab Books, Blue Ridge Summit, Penn., 1990. Fink, Donald G., Donald Christiansen, eds., Electronics Engineers’ Handbook, 3d ed., McGraw-Hill, New York, N.Y., 1989. General Requirements for Electronic Equipment Specifications, MIL-STD-2036, Naval Sea Systems Command, Washington, D.C., 1991. Hecht, Jeff, Undemanding Fiber Optics, Howard W. Sams and Co., Indianapolis, Ind., 1987. Input/Output Interfaces, Standard Digital Data, Navy Systems, MIL-STD 1397B (Navy), Naval Sea Systems Command, Washington, D.C., 1989. Levine, Sy, Integrated Circuits and Computer Concepts, Electro-Horizons Publications, Plainview, N.Y., 1989. Maintenance Manual for Computer Set AN/UYK-7(V), Vol 1, SE610-AW- MMA-010, Naval Sea Systems Command, Washington, D.C., 1990. AII-11

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Maintenance Manual for Computer Set AN/UYK-7(V), “Circuit Diagrams,” Vol 3, Part 1, SE610-AW-MMA-030, Naval Sea Systems Command, Washington, D.C., 1990. Maintenance Manual for Computer Set AN/UYK-7(V), “Circuit Diagrams: Vol 3, Part 2, SE610-AW-MMA-040, Naval Sea Systems Command, Washington, D.C., 1990. McWhorter, Gene, Understanding Digital Electronics, Howard W. Sams and Co., Indianapolis, Ind., 1984. Microcomputer Software and Hardware Guidelines, MIL-HDBK-805(OM), Naval Sea Systems Command, Washington, D.C., 1990. Minasi, Mark, The Complete PC Upgrade and Maintenance Guide, SYBEX, Inc., Alameda, Calif., 1991. Minasi, Mark, The Complete PC Upgade and Maintenance Guide, Fourth Edition, SYBEX, Inc., Alameda, Calif., 1995. Mueller, Scott, Upgrading and Repairing PCs, Que Corporation, Carmel, Ind., 1988. Mueller, Scott, Upgrading and Repairing PCs, Fifth Edition, Que Corporation, Carmel, Ind., 1995. Navy Electricity and Electronics Training Series, Introduction to Solid- State Devices and Power Supplies, Module 7, NAVEDTRA B72-07-00-92, Naval Education and Training Program Management Support Activity, Pensacola, Fla., 1992. Navy Electricity and Electronics Training Series, Introduction to Amplifiers, Module 8, NAVEDTRA 172-08-00-82, Naval Education and Training Program Development Center, Pensacola, Fla., 1982. Navy Electricity and Electronics Training Series, Introduction to Wave- Generation and Wave-Shaping Circuits, Module 9, NAVEDTRA 172-09-00-83, Naval Education and Training Program Development Center, Pensacola, Fla., 1983. Navy Electricity and Electronics Training Series, Introduction to Number Systems and Logic Circuits, Module 13, NAVEDTRA B72-13-00-86, Naval Education and Training Program Management Support Activity, Pensacola, Fla., 1986. Navy Electricity and Electronics Training Series, Introduction to Micro- electronics, Module 14, NAVEDTRA 172-14-00-84, Naval Education and Training Program Development Center, Pensacola, Fla., 1984. Navy Electricity and Electronics Training Series, Technician’s Handbook, Module 19, NAVEDTRA 172-19-00-85, Naval Education and Training Program Development Center, Pensacola, Fla., 1985. AII-12

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Navy Electricity and Electronics Training Series, Introduction to Fiber Optics, Module 24, NAVEDTRA B72-24-00-92, Naval Education and Training Program Management Support Activity, Pensacola, Fla., 1992. Organizational Level Maintenance Manual, Vol 1, AN/UYK-62(V), SE610- GV-MMO-010/UYK-62(V), Naval Sea Systems Command, Washington, D.C., 1989. Seidman Arthur and Ivan Flores, eds., The Handbook of Computers and Computing, Van Nostrand Reinhold Co., New York, N.Y., 1984. Technical Manual, Design Data for Data Processing Set, AN/UYK-44V, SE610-PV-MMV-010, Naval Sea Systems Command, Washington, D.C., 1987. Technical Manual, Operation and Maintenance Instructions for Computer Set AN/UYK-43/V, SE610-NV-MMO-010/UYK-43(V), Naval Sea Systems Command, Washington, D.C., 1990. Technical Manual, Operation and Maintenance with Parts List, Data Processing Set, AN/UYK-20(V), Vol 1, Naval Sea Systems Command, Washington, D.C., 1990. Understanding Advanced Solid State Electronics, Howard W. Sams and Co., Indianapolis, Ind., 1986. UnderstandingSolid State Electrontics, Howard W. Sams and Co., Indianapolis, Ind., 1984. Walker, Roger S., Understanding Computer Science, Howard W. Sams and Co., Indianapolis, Ind., 1984. WHISPERNET User’s Guide, Document No. 10133538, Rev. 1, Fiber Com, Inc., Roanoke, Va., 1978. Z-248 Maintenance, (Part 1), Navy Regional Data Automation Center, Norfolk, Va., 1989. Z248 Systems Administrator, Zenith Data Systems Corporation, St. Joseph, Mich., 1988. Chapter 8 Cannon, Don L., Gerald Luecke, Understanding Microprocessor, Howard W. Sams and Co., Indianapolis, Ind., 1984. Computer Science Source Book, The McGraw-Hill Science Reference Series, McGraw-Hill, New York, N.Y., 1988. Data Processing Technician 2, NAVEDTRA 12511, Naval Education and Training Program Management Support Activity, Pensacola, Fla., 1991. Maintenance Manual for Computer Set AN/UYK-7(V), Vol 1, SE610-AW- MMA-010, Naval Sea Systems Command, Washington, D.C., 1990. AII-13

p. 376

Maintenance Manual for Computer Set AN/UYK-7(V), “Circuit Diagrams,” Vol 3, Part 1, SE610-AW-MMA-030, Naval Sea Systems Command, Washington, D.C., 1990. Maintenance Manual for Computer Set AN/UYK-7(V), “Circuit Diagrams,” Vol 3, Part 2, SE610-AW-MMA-040, Naval Sea Systems Command, Washington, D.C., 1990. Microcomputer Software and Hardware Guidelines, MIL-HDBK-805(OM), Naval Sea Systems Command, Washington, D.C., 1990. Operating Procedures for Computer Set AN/UYK-7(V) Diagnostic Program, Part 4, NAVSEA 0967-LP-024-5454, Naval Sea Systems Command, Washington, D.C., 1989. Navy Electricity and Electronics Training Series, Introduction to Amplifiers, Module 8, NAVEDTRA 172-08-00-82, Naval Education and Training Program Development Center, Pensacola, Fla., 1982. Navy Electricity and Electronics Training Series, Introduction to Wave- Generation and Wave-Shaping Circuits, Module 9, NAVEDTRA 172-09-00-83, Naval Education and Training Program Development Center, Pensacola, Fla., 1983. Navy Electricity and Electronics Training Series, Introduction to Number Systems and Logic Circuits, Module 13, NAVEDTRA B72-13-00-86, Naval Education and Training Program Management Support Activity, Pensacola, Fla., 1986. Operating Procedures for Computer Set AN/UYK-7(V) Diagnostic Programs, Parts 1-3, NAVSEA 0967-LP-024-5454, Naval Sea Systems Command, Washington, D.C., 1989. Organizational Level Maintenance Manual, Vol 1, AN/UYK-62(V), SE610- GV-MMO-020/UYK-62(V), Naval Sea Systems Command, Washington, D.C., 1989. Seidman Arthur and Ivan Flores, eds., The Handbook of Computers and Computing, Van Nostrand Reinhold Co., New York, N.Y., 1984. Technical Manual, Design Data for Data Processing Set, AN/UYK-44V, SE610-PV-MMV-010, Naval Sea Systems Command, Washington, D.C., 1987. Technical Manual, Operation and Maintenance Instructions for Computer Set AN/UYK-43/V, SE610-NV-MMO-010/UYK-43(V), Naval Sea Systems Command, Washington, D.C., 1990. Technical Summary Handbook, AN/UYK 7, NAVSEA 0967-LP-024-5800, Naval Sea Systems Command, Washington, D.C., 1986 UNISYS, AN/UYK-43, Abbreviated Reference Manual, Naval Sea Systems Command, Washington, D.C., 1986. AII-14

p. 377

Walker, Roger S., Understanding Computer Science, Howard W. Sams and Co., Indianapolis, Ind., 1984. Z-248 Maintenance, (Part 1), Navy Regional Data Automation Center, Norfolk, Va., 1989. Chapter 9 Data Processing Technician Third Class, NAVEDTRA 10263, Naval Education and Training Program Support Activity, Pensacola, Fla., 1987. Navy Electricity and Electronics Training Series, Magnetic Recording Mod- ule 23, NAVEDTRA B72-23-00-91, Naval Education and Training Program Management Support Activity, Pensacola, Fla., 1991. Technical Manual for Type 1840 Modified Magnetic Tape Subsystem, RD- 358(V)/UYK, NAVSEA 0967-LP-562-8020, Naval Sea Systems Command, Washington, D.C., 1983. Chapter 10 Minasi, Mark, The Complete PC Upgrade and Maintenance Guide, SYBEX Inc., Alameda, Calif., 1991. Minasi, Mark, The Complete PC Upgrade and Maintenance Guide, Fourth Edition, SYBEX, Inc., Alameda, Calif., 1995. Minasi, Mark, The Hard Disk Survival Guide, SYBEX Inc., Alameda, Calif., 1991. Mueller, Scott, Que’s Guide to Data Recovery, Que Corporation, Carmel, Ind., 1991. Mueller, Scott, Upgrading and Repairing PCs, Que Corporation, Carmel, Ind., 1988. Mueller, Scott, Upgrading and Repairing PCs, Fifth Edition, Que Corporation, Carmel, Ind., 1995. Navy Electricity and Electronics Training Series, Magnetic Recording, Mod- ule 23, NAVEDTRA B72-23-00-91, Naval Education and Training Program Management Support Activity, Pensacola, Fla., 1991. Navy Electricity and Electronics Training Series, Principles of Synchros, Servos, and Gyros, Module 15, NAVEDTRA 172-15-00-85, Naval Education and Training Program Management Support Activity, Pensacola, Fla., 1985. Operation and Maintenance Instructions for Recorder-Reproducer Set, Magnetic Disk AN/UYH-3(V), NAVSEA SE600-AA-MMM-010/AN/UYH-3(V), Naval Sea Systems Command, Washington, D.C., 1988. Programmer Reference Manual for Recorder-Reproducer Set, Magnetic Disk AN/UYH-3(V), NAVSEA SE600-AA-MMM-040/AN/UYH-3(V), Naval Sea Systems Command, Washington, D.C., 1985. AII-15

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Seidman Arthur and Ivan Flores, eds., The Handbook of Computers and Computing, Van Nostrand Reinhold Co., New York, N.Y., 1984. Technical Manual, Disk Memory Set, AN/UYH-2(V), Vol.1, NAVSEA SE600- CV-MMO-010/UYH-2(V), Naval Sea Systems Command, Washington, D.C., 1991. Chapter 11 Brewer, Bryan and Young Key, The Compact Disc Book, Harcourt Brace Jovanovich, Orlando, Fla., 1987. Budding, Laura and Elizabeth Young, The Brady Guide To CD-ROM, Prentice Hall Press, New York, N.Y., 1987. PC/Computing Magazine, “Safe and Speedy Storage,” Volume 6, Number 6, Ziff-Davis Publishing Co., New York, N.Y., June 1993. Chapter 12 Bigelow, Stephen J., Maintain & Repair Your Computer Printer and Save a Bundle, Windcrest Books, Blue Ridge Summit, Penn., 1992. LaBadie, Horace W. Jr., Build Your Own Postscript® Laser Printer and Save a Bundle, Windcrest Books, Blue Ridge Summit, Penn., 1991. Minasi, Mark, Maintaining Upgrading and Troubleshooting IBM PCs, Com- patibles, and PS/2 Personal Computers, COMPUTE! Publications Inc., Greensboro, N.C., 1990. Minasi, Mark, The Complete PC Upgrade and Maintenance Guide, SYBEX Inc., Alameda, Calif., 1991. Operation, Maintenance, and Installation Instructions for TT-624(V), SPAWAR EE161-NA-OMI-010/El10-TT624, Space and Naval Warfare Systems Command, Washington, D.C., 1991. Operation and Maintenance Manual with Parts List for Printer-Plotter PT549(V)1/U, NAVSEA SE630-AC-OMP-010~T549(V)1/U, Naval Sea Systems Command, Washington, D.C., 1990. Chapter 13 Digital Data Converter CV-2036/USQ-20(V) or Keyset Central Multiplexer (KCMX) Technical Manual, NAVSEA 0967-LP-051-5110, Naval Sea Systems Command, Washington, D.C., 1968. Navy Electricity and Electronics Training Series, Introduction to Matter, Energy and Direct Current, Module 1, NAVEDTRA 172-01-00-88, Naval Education and Training Program Management Support Activity, Pensacola, Fla., 1988. Navy Electricity and Electronics Training Series, Principles of Synchros, Servos, and Gyros, Module 15, NAVEDTRA 172-15-00-85, Naval Education and Training Program Management Support Activity, Pensacola, Fla., 1985. AII-16

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Signal Data Converter Group, CV-2953A (P)/UYK, Desctiption, Operation, and Maintenance, Vol. 1, NAVSEA 0967-LP-581-9010, Naval Sea Systems Command, Washington, D.C., Oct 1974. Technical Manual, Description, Operation and Maintenance Combat Direction System, Digital Fire Control Switchboard Mk-70 Mod 13 and Computer Switching Control Panels Mk-328 Mod 11 CG 16 Class, Vol. 1, NAV- SEA SC675-AG-MMO-010/CG, 16CL, Naval Sea Systems Command, Washington, D.C., Apr 1986; Vol. 2, NAVSEA SC675-AG-MMO- 020/CG, 16CL, Naval Sea Systems Command, Washington, D.C., Apr 1986. Technical Manual for Digital Data Signal Dhttiution Switchboard, SB-1299/ USQ-20(V), SB-1299A/USQ-20(V), and SB-1299B/USQ-20(V), NAV- SHIPS 0967-224-4010, Naval Sea Systems Command, Washington, D.C., Jan 1967. Technical Manual for Digital-to-Signal Distribution Switchboard, SB-1299/ USQ-20(V), SB-1299~SQ-20(V), and SB-1299B/USQ-20(V), NAV- SHIPS 0967-224-4010, Naval Sea Systems Command, Washington, D.C., Jan 1967. Technical Manual for Electronic Equipment Mounting Base MT-3574B USQ-20(V), NAVSHIPS 0967-306-8010, Naval Sea Systems Command, Washington, D.C., Nov 1980. AII-17

p. 380

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p. 381

INDEX A A/D converters, 4-20 ABT, 4-30 Access direct memory, 7-16 time, 6-2 Accumulator (register), 5-6 Acknowledge external function, 7-33 input data, 7-33 output data, 7-33 signal, 7-32 Adder and subtracter circuits, 4-12 Address bus, 5-24 pointers, buffer, 7-14 translation memory, 6-6 Addressing operands direct, 8-10 extended, 8-11 immediate, 8-11 implicit, 8-11 indexed, 8-11 indirect, 8-12 instruction, 8-10 relative, 8-12 task state instruction, 5-10 ADP security, 1-14 Alarms, audible, 3-2 ALU timing, 5-19 Amplifiers dc, 4-19 sense, 4-21, 6-13, 6-20 Analog signal conversion circuits, 4-19 to digital converters, 4-20, 13-3 Analog switchboards, 13-35 ANSI X3.131,7-23 Applications programs, 8-3 Architecture cable, 2-23 connector, 2-15 memory, 6-4 Arithmetic logic unit, 5-18 operations, 5-20 Arrays, 6-16 Assembly/chassis layout, 2-4 ASW systems, 1-8 Asynchronous data exchanges, 7-28 Automatic bus transfers, 4-30 B Backplane/motherboard layout, 2-6 Backup power, 4-29 BAP, 7-13 Basic input/output system, 5-18 Battery-protected storage, 8-17 Battle short mode operation, 1-13 BCW, 7-13 Binary angular measurement (BAM), 13-4 Binary-coded decimal, 13-4 BIOS, 5-18 Bipolar ICs, 4-7 Bit, 4-24 Boards, printed circuit, 2-13 Boolean algebra, 4-4 Boot/bootstrap procedure, 5-18 mainframe computer, 8-25 microcomputer, 8-19 minicomputer, 8-22 Breakers, circuit, 3-2 Buffer address pointers, 7-13 control words, 7-13 transmit, 7-21 Bus address, 5-24 computer interconnection system, 5-25 control, 5-24 data, 5-24 direct memory interface, 5-26 I/O MEM bus, 5-25 input/output controller, 5-25 instruction, 5-25 operand, 5-25 time multiplexed, 5-26 Buses, 5-1 INDEX-1

p. 382

operations, 5-26 types, 5-24 Busy signal, 7-32 Byte, 4-24 C Cabinets/frames (See frames/cabinets) Cables, 2-15 architecture, 2-25 coaxial, 2-25 connectors, 2-15 fiber optic, 2-25 flat, 2-24 input, 7-33 output, 7-33 ribbon, 2-24 single, 7-32 twisted/multiconductor, 2-25 Cache memory, 5-15 Cage/rack frames/cabinets, 2-10 Capabilities, operational, 1-13 Capacity, memory, 6-1 Card cage/rack layout, 2-4 Cartridge magnetic tape devices, 9-18 CD-ROM, 11-1 applications, 11-6 data storage structure, 11-2 physical characteristics, 11-2 CD-ROM drives, 11-4 CD controller, 11-6 interface section, 11-6 optical head, 11-4 turntable, 11-6 Central processing unit, 5-1 arithmetic and logic unit (ALU), 5-18 control section, 5-2 Centronics parallel, 7-27 Chain address pointer, 7-13 Chaining, daisy, 7-17 Chaining instructions, 7-10 Channel control, 7-14 Character-addressable instructions, 8-12 Character printers, 12-9 daisy wheel printers, 12-10 dot matrix printers, 12-9 Character sets, 12-2 alternate character sets, 12-3 ASCII character set, 12-2 Chassis/assembly frames/cabinets, 2-8 layout, 2-4 Check, parity, 6-7 Circuit analog signal conversion, 4-20 boards, printed, 2-13 breakers, 3-2 integrated, regulator, 4-20 line driver/receiver integrated, 4-21 read/write cycle, 6-20 regulator integrated, 4-20 Circuits, 4-1, 4-4, 4-5 adder/subtracter, 4-12 code converter, 4-11 data routing, 4-12 digital ICs, 4-7 digital logic, 4-4, 4-9, 4-10 driver integrated, 4-19 general linear, 4-19 I/O, 7-13 integrated (ICs), 4-5, 4-7 memory interface, 6-4 sequencing, 7-13 systems interface, 4-21 timing, 4-22,6-7,7-12 CIS, 5-25 Class I through IV interrupts, 5-12 Clear/set flag, 7-14 Clock master, 5-4 monitor, 5-5 multiple phase, 4-23 real-time, 5-5 single phase, 4-23 Coaxial cables, 2-25 Codes converter circuits, 4-11 Hamming, 6-8 interrupt, 5-13 operation, 8-7 Combinational digital logic circuits, 4-4, 4-9 Command instructions, 7-10 signals (enables), 4-13 Comparators, 4-13, 4-20 Compensators, 4-29 INDEX-2

p. 383

Components, 4-1 circuits, 4-4 interfacing, 7-19 number systems, 4-2 physical layouts, 2-3, 2-6 Computers central processing units and buses, 5-1 components and circuits, 4-1 configurations and hardware, 2-1 fundamentals and operations, 1-1 input/output and interfacing, 7-1 instructions and man/machine interfaces, 8-1 memories, 6-1 operator controls and controlling units, 3-1 types of, 1-3 Computer switching and control panel (CSCP), 13-33 Computer viruses, 10-29 Conditioners, line, 4-29 Configurations, 1-9, 2-1 block diagrams, 2-1 hardware, 1-10 layouts, 2-2, 2 -4, 2-6 mainframe computer, 8-23 microcomputer, 8-16 minicomputer, 8-20 software, 1-10 Connectors, 2-15 architectures, 2-15 cables, 2-15 external, 2-21 internal, 2-18 Consoles maintenance, 3-10 remote, 3-13 Control and maintenance panels, 3-8 Control memory, 5-15 operations, 7-15 Control section, 5-2 cache memory, 5-15 control memory, 5-15 instruction and control, 5-6 instruction operand addressing, 5-10 interrupts, 5-10 read-only memory, 5-17 timing, 5-3 Controlling units, 3-1, 3-4 display, 3-9 keyboards, 3-11 mainframe computer, 8-23 maintenance consoles, 3-10 microcomputer, 8-17 minicomputer, 8-21 panels, 3-7, 3-8, 3-10 power/temperature panels, 3-7 remote consoles, 3-13 teletypes, 3-12 Controls buffer, 7-21 bus, 5-24 channel, 7-14 circuits, 6-4, 7-13 data entry/display, 8-21 external, 1-10 function/command, 7-9 independent request, 7-18 mainframe computer, 8-23 memory, 7-13, 7-20 microcomputer, 8-17 minicomputer, 8-21 modem, 7-20 operator, 1-10 sequence, 5-5 transmit, 7-21 words, 7-9, 7-14 Converter analog to digital, 4-20, 13-3 Cooling systems, 2-26 Coprocessor, numeric data, 5-23 Core memory, 6-9 Correction/detection, error bit, 6-8 Counter, program, 5-6, 5-9 Counters, 4-15 CPU interface, direct, 7-14 Cycle core, 6-12 mated film, 6-18, 6-19 memory, 6-6, 6-7 read/write, 6-20 Cylinder addressing, disk, 10-4 D Daisy chaining, 7-17 Data asynchronous, 7-28 INDEX-3

p. 384

bus, 5-24 communications equipment, 7-1, 7-28 display, 1-3, 8-17, 8-21, 8-23 entry, 8-17, 8-21, 8-23 external function, 7-1 gathering, 1-2 input acknowledge, 7-33 input request, 7-33 lines, 7-33 message framed, 7-29 process, 1-2 routing circuits, 4-12 sequence of events, input, 7-33 strobe, 7-32 synchronous, 7-28 terminal equipment, 7-1,7-28 transfer, 7-36 types/formats, 4-24 words, 7-8 Data conversion devices, 13-1 Data encoding methods, disk, 10-25 frequency modulation, 10-26 modified frequency modulation (MFM), 10-26 run length limited (RLL), 10-26 Data organization CD-ROM, 11-2 disk, 10-3 tape, 9-8 DC amplifiers, 4-21 DCE/DTE serial I/O cable signals, 7-29 Decision-making functions, 4-11 Demultiplexer, 4-14 Designators, 8-7 Desktop systems, 1-9 Destructive readout, 6-2 Detection/correction, error bit, 6-8 Devices, protection, 3-2,4-29 Diagnostics mainframe computer, 8-24 microcomputer, 8-18, 8-19 minicomputer, 8-21 ROM, 8-18 tape, 9-20 testing, 5-18 Diagrams, functional block, 2-2 Digit drivers, 6-20 Digital ICs, 4-7 convention, 4-8 functional uses, 4-11 groups, 4-9 logic circuits, 4-9, 4-10 logic gates, 4-8,4-9 Digital fire control switchboard (DFCS), 13-26 Digital switchboards, 13-25 manual switchboards, 13-25 remotely controlled switchboards, 13-26 Digital-to-analog conversion, 13-7 converter, CV-25lB/UYK, 13-8 Digital-to-digital (D/D) conversion, 13-13 Digital-to-linear/scalar conversion, 13-8 DIP switches, 8-16 Direct interface, 7-14 memory access, 7-16 memory interface (DMI) bus, 5-26 operand addressing, 8-10 Directories, disk root directory, 10-5 subdirectories, 10-5 Disk magnetic— see magnetic disk INDEX-4 Display, 3-2 control units, 3-9 data, 1-3 drivers, 4-21 operator controls, 3-1 Disseminate data, 1-3 DIX, Ethernet, 7-25 Double-length instructions, 8-13 Double word, 4-25 DRAM, 6-24 Drivers digit, 6-20 display, 4-21 integrated circuits, 4-19 line, 7-21 memory, 4-21 peripheral, 4-21 Dual-channel operating mode, 7-11 Dynamic RAM (DRAM), 6-24 E EF sequence of events, 7-34 EFA, 7-33 EFR, 7-33

p. 385

EI data, 7-2 sequence of events, 7-34 EIA RS-232, 7-24 EIE, 7-33 EIR, 7-33 Electromagnetic interference, 1-14 Electronics, integrated drive, 7-27 Enables, sequence, 5-5 Encoding, 13-3 End-around-test (EAT), 13-39 Enhanced small device interface (ESDI), 7-27 Environmental inventory, 5-18 Equipment data communications, 7-1, 7-28 data terminal, 7-1, 7-28 Error bit detection/correction, 6-8 ESA, 7-11 Escape codes, printer, 12-3 ESDI, 7-28 ESI, 7-11 Ethernet DIX (IEEE 802.3), 7-25 Events external function sequence (normal), 7-34 external interrupt sequence, 7-34 input data sequence, 7-32 output data sequence, 7-34 single-cable sequence, 7-32 two-cable sequence, 7-33 Exchanges asynchronous data, 7-28 synchronous data, 7-28 Executive state, 5-10 instructions, 5-10 Extended operand addressing, 8-11 Extension interface, requestor, 5-25 External connectors, 2-21 controls, 1-10 single-cable equipment, 7-32 two-cable equipment, 7-33 External function data, 7-2 request/acknowledge, 7-33 sequence of events (normal), 7-34 External interrupt data, 7-2 requestionable, 7-33 sequence of events, 7-34 words, 7-9 Externally specified address/index (ESI) operating mode, 7-11 E Fault detection, memory, 6-7 Fetch (read) the instruction, 5-9 Fiber optic cables, 2-25 File allocation table, 10-6 Film mated, 6-17 memory, 6-13 Filter, power supply, 4-26 Filters, 2-12 5.25-inch floppy disk, 10-7 densities and coercivities, 10-10 Fixed disk care and handling, 10-30 Fixed disk interfaces, 10-27 Enhanced Integrated Drive Electronics Interface (EIDE), 10-28 Enhanced Small Device Interface (ESDI), 10-27 Integrated Drive Electronics (IDE) Interface, 10-27 Small Computer Systems Interface (SCSI), 10-28 ST-506/412 Interface, 10-27 Fixed hard disk systems, 10-23 Fixed-point operations, 5-20 Flag, set/clear, 7-14 Flat cables, 2-24 Flip-flops, 4-10 Floating-point operations, 5-20 Floppy disk drives, 10-8 configuration, 10-11 installation, 10-11 Floppy disks, 10-6 care and handling, 10-12 5.25-inch, 10-7 3.5-inch, 10-8 Format instructions, 8-7 interfacing, 7-21 parallel, 7-9 serial, 7-9 Formatting disk, 10-4 disk pack, 10-22 INDEX-5

p. 386

high-level format, 10-29 low-level format, 10-28 Formats, data, 4-24 Frames/cabinets, 2-7 cage/rack, 2-10 chassis/assembly, 2-8 modular, 2-8 motherboard/backplane, 2-11 safety/security features, 2-12 Full-word instructions, 8-12 Function commands control words, 7-8 external acknowledge, 7-33 external data, 7-2 external request, 7-33 external sequence of events, 7-34 Functional operation, 1-7 battle short mode, 1-13 block diagrams, 2-2 decision making, 4-11 layouts, 2-4 online and offline, 1-12 operational capabilities/limitations, 1-13 operational requirements, 1-14 operational uses, 1-7 Functions computer, 1-1 instruction/control, 5-6 memory, 4-15 G Gaskets, 2-12 Gates, digital logic, 4-9 Gateway, 7-2 Gather data, 1-2 General linear circuits, 4-19 Gray code, 13-4 Ground, 7-32 Guards, 3-2 H Half-word instructions, 8-12 Hamming code, 6-8 Handshaking, 7-2 Hexadecimal, 4-3 Hours (time totalizing meter), 3-2 Hub, 7-2 I I/O (See input/output) IC bipolar, 4-7 categories, 4-7 digital, 4-7 families, 4-7 linear, 4-18 metal-oxide semiconductor, 4-7 packaging, 4-5 size, 4-5 ID lines, 7-33 sequence of events, 7-33 IDA, 7-33 IDR, 7-33 IEEE 802.3 (Ethernet DIX), 7-25 802.5,7-24 Immediate operand addressing, 8-11 Impact printers, 12-7 chain and band printers, 12-8 character printers, 12-9 daisy wheel printers, 12-10 dot matrix printers, 12-9 drum printers, 12-7 line printers, 12-7 Implicit (implied) operand addressing, 8-11 Independent request control, 7-18 Index registers, 5-6 Indexed operand addressing, 8-12 Indicators, operator controls, 3-2 Indirect operand addressing, 8-12 Inhibit current regulator, 6-13 Initiate transfer, 7-14 Input cable, 7-33 data lines, 7-33 data request/acknowledge, 7-33 data sequence of events, 7-33 Input/output, 7-1 circuits, 7-11, 7-13 control memory, 7-13 data arrangement, 7-8 functions, 7-12 INDEX-6

p. 387

instructions, 7-9 intercomputer, 7-35 interrupt driven, 7-15 IOC/IOA interfacing, 7-4 IOC/IOA module, 7-3 MEM bus or input/output controller (IOC) bus, 5-25 memory reference, 7-13 operations, 7-11, 7-13, 7-14 organization, 7-2 parallel data operations, 7-31 pcb’s, 7-7 polled, 7-15 processor, 7-3 serial data operations, 7-28 terminology, 7-1 wait loop, 7-15 waveshapes, 4-8 Instruction(s), 5-19, 7-9, 8-1 bus, 5-25 character addressable, 8-12 double length, 8-13 execute, 5-9 fetch/read, 5-9 formats, 8-7, 8-8 full-word, 8-12 half-word, 8-12 language interpretation, 8-5 levels, 8-3 multiple-word, 8-13 operand addressing, 5-10, 8-10 operational levels, 5-10 programs/software, 8-2 register, 5-6 size, 8-12 translation, 5-9 types, 8-3 Instruction and control functions, 5-6 Integrated circuits, 4-5 categories, 4-7 digital, 4-7 families, 4-7 line driver/receiver, 4-21 linear, 4-18, 4-20 packaging, 4-5 receiver, 4-20 regulator, 4-20 size integration, 4-5 Integrated drive electronics (IDE), 7-27 Intercomputer channel operating mode, 7-11 I/O operations, 7-35 Interconnection system, 5-25 Interface circuits, memory, 6-4 circuits, systems, 4-21 direct, 7-14 enhanced small device, 7-27 man/machine, 8-1, (See also, man/machine interfaces) requestor extension, 5-25 small system, 7-23 Interfacing, 7-1, 7-14 components, 7-19 formats, 7-21 methods of connections, 7-17 parallel data operations, 7-31 serial data operations, 7-28 standards, 7-18 terminology, 7-1 Interference, electromagnetic, 1-14 Interleave, 6-7 Interleave factor, fixed disk, 10-26 Internal connectors, 2-18 Interrupt, 5-10 classes I-IV, 5-12 codes, 5-13 driven I/O, 7-15 external data, 7-2 external sequence of events, 7-34 external words, 7-9 handling process, 5-13 lockout, 5-12 request, external, 7-33 task state, 5-10 Inventory, environmental, 5-18 IOA, 7-4 IOC, 7-3 J Jumpers, 8-16 K Key switches, 3-2 INDEX-7

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Keyboards, 3-11 Keyset central multiplexer (KCMX), 13-15 L Language instructions, 8-5 Layouts assembly/chassis, 2-4 backplane/motherboard, 2-6 block diagrams, 2-2 card cage/rack, 2-4 Functional, 2-3 modular, 2-4 physical, 2-4,2-6 Levels of instruction, 8-3 Limitations, operational, 1-13 Line conditioners, 4-29 drivers/receivers, 4-20, 4-21, 7-21 Line printers, 12-7 chain and band printers, 12-8 drum printers, 12-7 Linear ICs, 4-18 family types, 4-18 fictional uses, 4-20 gates, 4-19 groups, 4-19 Lines data, 7-32 input data, 7-33 output data, 7-33 Load/write control memory, 7-14 Logic circuits, digital, 4-4, 4-9 gates, digital, 4-9 Logical operations, 5-23 M Main timing, 5-4 Mainframe computers, 1-3, 8-8, 8-23 bootstrap, 8-25 configuration, 8-23 controls, 8-23 data entry/display, 8-23 diagnostics, 8-25 initiate operational programs, 8-25 instruction format, 8-8 interrupt/lockout, 5-12, 5-14 power, apply, 8-23 revise/patch software, 8-26 Magnetic disk data encoding methods, 10-25 drive unit, 10-19 file unit controls and indicators, 10-15 fixed hard drive system, 10-23 floppy disks, 10-7 memory sets, 10-13 Magnetic disk packs, 10-14 data surfaces, 10-14 servo surface, 10-14 Magnetic disk storage, 10-1 data organization, 10-3 disks and disk drives, 10-2 Magnetic tape, 9-1 construction, 9-2 devices, 9-11 handling procedures, 9-2 maintenance, 9-3 recording methods, 9-7 storage, 9-6 transport, 9-15 Magnetic tape controller, 9-12 control unit, 9-13 control panel, 9-14 microprogrammed controller, 9-13 Magnetic tape unit operations, 9-12 offline operations, 9-13 programmed controller, 9-13 read/write, 9-12 rewind, 9-13 search, 9-12 space file, 9-12 Maintenance consoles, 3-10 Man/machine interfaces, 8-1,8-15 functions, 8-16 mainframe computer, 8-23 microcomputer, 8-16 minicomputer, 8-20 operating modes, 8-15 operations, 8-15 Mapped I/O memory, 7-14 Master clock, 5-4 Mated film, 6-17 Math pat, 5-23 Matrices, 6-16 INDEX-8

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Memory address translation, 6-6 architecture, 6-4 cache, 5-15 capacity, 6-1 control, 5-15 core, 6-9 cycle, 6-6 direct interface, 5-26 DRAM, 6-24 drivers, 4-21 fault detection, 6-7 film, 6-13 functions, 4-15 interface circuits, 6-4 load/write control, 7-14 mapped I/O, 7-l 4 modules, 6-2 non-destructive readout, 6-27 nonvolatile, 6-2 operations, 6-l, 6-4 organization, 6-2 pcb’s, 6-3 programmable ROM, 6-30 protection, 6-8 RAM chip, 6-3, 6-20 read-only (ROM), 5-17, 6-26 read/write, 6-11 ROM, 5-17, 6-26 semiconductor, 6-20 SRAM, 6-22 stack, 6-11, 6-18 store control, 7-15 terminology, 6-2 types, 6-8 volatile, 6-2 Memory-type functions, 4-15 Message framed data, 7-28 Metal-oxide-semiconductor ICs, 4-7 Meter, time totalizing, 3-2 Microcomputers, 1-6, 8-10 bootstrap, 8-19 configuration, 8-16 controls, 8-17 data entry/display, 8-17 diagnostics, 8-18, 8-19 initiate operational programs, 8-19 instruction formats, 8-7 interrupt, 5-11 power, 8-17 revise/patch software, 8-20 MIL-STD-188, 7-24 MIL-STD-1397, 4-22, 7-22 Minicomputers, 1-5, 8-20 bootstrap, 8-22 configuration, 8-20 controls, 8-21 data entry and display, 8-21 diagnostics, 8-21 initiate operational programs, 8-22 interrupt/lockout, 5-12 power, apply, 8-20 revise/patch software, 8-23 Modem control, 7-20 Modes dual-channel operating, 7-11 intercomputer channel operating, 7-11 online/offline, 1-12 phase, 8-15 run, 8-15 sequence, 8-15 single channel, 7-11 step, 8-15 stop, 8-15 Modular frames/cabinets, 2-7 layout, 2-4 Modules, memory, 6-2 Monitor clock, 5-5 sync/suppress, 7-14 words, 7-14 Motherboard/backplane, 2-11 layout, 2-6 Multiple-phase clock systems, 4-23 Multiple-word instructions, 8-13 Multiplexing data converters, 13-14 Multivibrators, 4-23 N NDRO memory, 6-27 Nibble, 4-24 NIPS, 1-8 Non-destructive readout memory, 5-17, 6-2, 6-27 INDEX-9

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Nonimpact printers, 12-10 electrothermal printers, 12-13 inkjet printers, 12-13 laser printers, 12-11 Nontactical systems, 1-8 Nonvolatile memory, 6-2 Number systems, 4-2 Numeric data coprocessor, 5-23 O Octal, 4-3 ODA, 7-33 ODR, 7-33 Online/offline operations, 1-12 Operand addressing direct, 8-10 extended, 8-11 immediate, 8-11 implicit, 8-11 indexed, 8-11 indirect, 8-12 instruction, 8-10 relative, 8-12 task state, 5-10 Operand bus, 5-25 Operands, 5-20, 8-9 addressing, 8-10 Operating modes battle short, 1-13 dual-channel, 7-11 externally specified index, 7-11 I/O operations, 7-35 intercomputer channel, 7-11 online/offline, 1-12 single channel, 7-11 Operating systems, 8-4 Operation code, 8-7 levels of instructions, 5-10 types, 5-20 Operational capabilities/limitations, 1-13 programs, 8-3 requirements of computer systems, 1-14 uses of computers, 1-7 Operations, 1-1, 1-7 control memory, 7-15 fixed point, 5-20 floating point, 5-20 functions, 1-1, 1-7 intercomputer I/O, 7-35 logical, 5-23 memory, 6-4 parallel, 7-13 Operator controls, 1-15,3-1 displays, 3-2 indicators, 3-2 potentiometer, 3-1 protective devices, 3-2 switches, 3-2 time totalizing meter, 3-2 Operator panels, 3-7 Organization, memory, 6-2 Orientation, print, 12-4 Oscillators, 4-23 Output cable, 7-33 Output data request/acknowledge, 7-33 sequence of events, 7-34 P Pat, math, 5-23 Packets, 6-14 Panels control/maintenance, 3-8 operator, 3-7 power/temperature, 3-7 Paper-feed assembles, 12-6 friction feed, 12-6 tractor feed, 12-6 Parallel . data interfacing, 7-31 format, 7-9 operations, 7-13 Parity check, 6-7 Parity checks, tape, 9-9 Pcb, 2-19,6-3 Peripheral drivers, 4-21 Personal systems, 1-9 Phase mode, 8-15 Physical layouts, 2-4,2-8 Pin description, RS-232, 7-30 Pointers, buffer address, 7-14 Polled I/O, 7-15 INDEX-10

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Position switches, 3-3 Potentiometer, 3-1 Power backup, 4-29 filter, 4-26 mainframe computer, 4-27 microcomputer, 4-28 minicomputer, 4-30 requirements, 2-22 standby, 4-30 uninterruptible, 4-30 Power supplies, 4-25 components, 4-26 controlling devices, 4-26 input, 4-25 mainframe/minicomputer, 4-27 microcomputer, 4-28 output, 4-27 protection, 4-27 protection devices, 4-29 Power/temperature panels, 3-7 Printed circuit boards, 2-13 Printer interfaces, 12-5 Centronics parallel interface, 12-5 RS-232 serial interface, 12-5 Printers, 12-1 character printers, 12-9 characteristics, 12-5 control codes, 12-3 impact printers, 12-7 nonimpact printers, 12-10 Printing character sets, 12-2 control codes, 12-3 line characteristics, 12-4 orientation, 12-4 Procedures, boot, 5-18 mainframe computer, 8-25 microcomputer, 8-19 minicomputer, 8-22 Process data, 1-2 interrupt handling, 5-13 Processor, I/O, 7-4 Program counter, 5-6, 5-9 Programmable interval timers, 5-5 read-only memory, 6-30 Programs, 8-2 applications, 8-3 instructions, 8-3 mainframe computer, 8-25 microcomputer, 8-19 minicomputer, 8-22 operational, 8-3 utility., 8-3 PROM, 6-30 Protection devices, 3-2, 4-29 memory, 6-10 Protocol, 7-2 Pushbutton switches, 3-3 Q Quantization, 13-3 Queue/stack, interrupt, 5-13 R Random access memory (RAM), 6-3 chip, 6-20 dynamic, 6-24 static, 6-22 Read cycle circuits, 6-20 core, 6-12 mated film, 6-18 memory, 6-7 Read/write control, 7-20 cycle circuits, 6-20 memories, 6-9 Read-only memory (ROM), 5-17,6-26 Readout, destructive, 6-2 Real-time clock, 5-5 Receive buffer/receive control, 7-21 Receivers line, 7-21 transmitters, universal, 7-19 Rectifier, 4-26 Reduced write current, 10-28 Registers, 4-11, 5-6, 5-22 accumulator, 5-6 index, 5-6 instruction, 5-6 INDEX-11

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shift, 4-18 status indicating, 5-7 storage, 4-17 Regulators, 4-26 inhibit current, 6-13 integrated circuits, 4-19 switching, 4-20 voltage, 4-20 REI, 5-25 Relative operand addressing, 8-14 Remote consoles, 3-13 operator control units, 3-13 Requestor extension interface (REI), 5-25 Requests independent control, 7-18 input data, 7-33 output data, 7-33 Requirements functional operations, 1-14 operational, 1-14 power, 2-21 Ribbon cables, 2-24 Ring, token, 7-24 ROM, 5-17, 6-26 ROM based diagnostics, 8-18 RS-232, 7-24 pin description, 7-30 RS-422, 7-24 RS-449, 7-23 RTC, 5-5 Run mode, 8-15 S Safety/security features of frames/cabinets, 2-12 Sampling, 13-3 Search for sync/set suppress/set monitor, 7-14 Sectors, disk, 10-3 Security, ADP, 1-14 Select signal, 7-32 Selectors, 4-14 Semiconductor memory, 6-20 DRAM, 6-24 SRAM, 6-22 Sense amplifiers, 4-21,6-13,6-20 Sequence enables and control, 5-5 mode, 8-15 Sequence of events external function, 7-34 external interrupt, 7-34 input data, 7-33 output data, 7-33 single cable, 7-32 two cable, 7-33 Sequencing circuits, 7-13 Sequential digital logic circuits, 4-10 Serial, 7-14 data operations, 7-28 format, 7-9 Set/clear flag, 7-14 Shift registers, 4-18 Ship, switchboard, and computer switching control panel (CSCP) wiring, 13-34 Signals acknowledge, 7-32 audible alarms, 3-2 busy, 7-32 command, 4-13 DCE/DTE, 7-29 enable, 4-13 select, 7-32 Single-cables, 7-32 sequence of events, 7-32 Single-channel operating mode, 7-11 Single-phase clock systems, 4-23 Size instructions, 8-12 Small computer system interface, 7-23 SNAP systems, 1-9 Software, 1-10, 8-4 Software revisions mainframe computer, 8-26 microcomputer, 8-20 minicomputer, 8-23 SPS, 4-30 SRAM, 6-22 ST-506/412, 7-27 Stack memory, 6-11, 6-16 queue, interrupt, 5-13 Standards, interfacing, 7-18 Standby power supply (SPS), 4-30 State, executive, 5-10 State, task INDEX-12

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instruction operand addressing, 5-10 interrupts, 5-10 Static RAM (SRAM), 6-22 Status-indicating registers, 5-7 Step mode, 8-15 Stop mode, 8-15 Storage battery protected, 8-17 registers, 4-17 Store control memory, 7-14 data, 1-2 Strobe, data, 7-32 Subassemblies, 2-13 Support systems, tactical, 1-8 Suppress sync monitor, 7-14 word, 7-14 Surge protectors, 4-29 Switchboards, 13-1 analog, 13-35 digital, 13-25 Switches, 3-2 DIP, 8-16 key, 3-3 position, 3-3 pushbutton, 3-3 toggle, 3-4 two position, 3-4 Switching regulators, 4-20 Sync/suppress monitor, 7-14 Synchro signals, 13-6 Synchro-to-digital (S/D) conversion, 13-7 octant conversion, 13-7 sector conversion, 13-7 single-speed/dual-speed synchro conversions, 13-7 Synchros, 13-5 control synchro systems, 13-5 multispeed synchro systems, 13-5 torque systems, 13-5 Synchronous data exchanges, 7-28 Systems ASW, 1-8 basic input/output, 5-18 cooling, 2-26 interconnection, 5-25 interface circuits, 4-21 nontactical, 1-8 number, 4-2 operating, 8-4 operational requirements, 1-14 personal/desktop, 1-9 single-phase clock, 4-23 SNAP, 1-9 tactical, 1-7 tactical support, 1-8 T Tactical support systems, 1-7 Tactical systems, 1-7 Tape, magnetic— see magnetic tape Task state, 5-10 instruction operand addressing, 5-10 instructions, 5-10 interrupts, 5-10 Teletypes, 3-12 Testing, diagnostic, 5-18 3.5-inch floppy disk construction, 10-8 densities and coercivities, 10-10 Time access, 6-2 multiplexed bus, 5-26 totalizing meter, 3-2 Timers, 4-21 programmable interval, 5-5 Timing, 5-2 ALU, 5-19 circuits, 4-22,4-23 components, 4-23 control section, 5-3 I/O, 7-12 main, 5-3 memory, 6-5 Toggle switches, 3-4 Token ring (IEEE 802.5), 7-24 Tracks, disk, 10-3 Transformer, 4-26 Translate instructions, 5-9 Translators, 4-14 Transmit buffer/transmit control, 7-21 Transmitters, universal receiver, 7-19 Twisted component/multiconductor cables, 2-25 Two-cable sequence of events, 7-33 Two-position switches, 3-4 INDEX-13

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U Uninterruptible power supply (UPS), 4-30 Universal receiver transmitters, 7-19 Update the program counter, 5-9 UPS, 4-30 Uses, operational, 1-7 Utility programs, 8-3 V Viruses, 10-29 Volatile memories, 6-2 Voltage regulators, 4-20 W Waveshapes, 4-8 Word, 4-24 control, 7-8 data, 7-8 double, 4-25 external interrupt, 7-9 function (command) control, 7-9 monitor, 7-14 suppress, 7-14 Write cycle core, 6-13 mated film, 6-19 memory, 6-7 Write precompensation, 10-28 INDEX-14

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Assignment Questions Information: The text pages that you are to study are provided at the beginning of the assignment questions.

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ASSIGNMENT 1 Textbook Assignment: “Fundamentals and Operations of Computers,” chapter 1, p[ages 1-1 through 1-17; and “Computer Configurations and Hardware,” chapter 2, pages 2-1 through 2-12. 1-1. 1-2. 1-3. 1-4. 1-5. All computers have which of the following components in common? 1. Modem, memory, and floppy drives 2. Math coprocessor, microchips, and central processing unit 3. Central processing unit, memory, and input/output section 4. Analog processing unit, input/ output section, and microchips The amount of computing power a computer has is determined by which of the following factors? 1. Physical size 2. Size of drives 3. Number of drives 4. Technology used All computers must be capable of which of the following functions? 1. Processing and storing data 2. Retaining data on compact disks 3. Interfacing with mainframe computers 4. Interfacing with desktop publishing equipment Computers can gather data by which of the following methods? 1. Manually only 2. Automatically only 3. Both manually and automatically 4. Local-area networks A computer automatically gathers data by which of the following means? 1. 2. 3. 4. From another system, subsystem, or equipment From specific software By a local terminal user By a remote terminal user 1-6. Which of the following tasks is the main purpose of a computer? 1. 2. 3. 4. Storing data Gathering data Processing data Disseminating data 1-7. Computers can externally store data on which of the following types of media? 1. Magnetic disks only 2. Magnetic tape only 3. Paper tape only 4. Magnetic disks, magnetic tape, and paper tape 1-8. Computers can disseminate data to which of the following types of equipment? 1. A display subsystem only 2. A magnetic tape or disk unit only 3. A printer only 4. A display subsystem, magnetic tape or disk unit, and a printer 1-9. Computer systems display which of the following general types of data/information? 1. 2. 3. 4. Hardware performance information only Data related to the system’s mission only Status information related to the system’s operation only Data related to the system’s mission and status information related to the system’s operation, and hardware performance information 1-10. In addition to display units, a computer relies on what other equipment to display processed data? 1. Floppy disks 2. Processors 3. Printers 4. Modems 1

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1-11. What are the three general types of computers? 1. Mini, macro, and laptop 2. Personal, mini, and macro 3. Mainframe, mini, and micro 4. Technological, mainframe, and desktop 1-12. The mainframe computers you will maintain in the 1-13. 1-14. 1-15. 1-16. Navy are categorized by which of the following terms? 1. Wordprocessing 2. General purpose 3. Specialized 4. Graphical The Navy adapts a specific program to fit its needs and does not deviate once this program is installed into the computer. 1. True 2. False What type of computer is housed in a large, rugged frame or cabinet? 1. Minicomputer 2. Microcomputer 3. Macrocomputer 4. Mainframe computer What types of computers use operator console and maintenance console panel/display control units to perform maintenance? 1. Mainframe computers 2. Microcomputers and minicomputers 3. Minicomputers and microcomputers 4. Microcomputers and local-area network computers Although a computer maybe used for many types of operations, which of the following computers are considered the heart of the tactical and tactical support data systems? 1. 2. 3. 4. Minicomputers Microcomputers Mainframe computers Minicomputers or microcomputers, depending on the system 2 1-17. The SNAP I and II systems use as their host computers which of the following equipment? 1. Minicomputers 2. Microcomputers 3. Mainframe computers 4. Local-area network computers 1-18. Some of the newer microcomputers maybe even more powerful than older, larger mainframe computers. 1. True 2. False 1-19. What type of computer has the CPU contained on a single integrated chip? 1. Microcomputer 2. Macrocomputer 3. Minicomputer 4. Mainframe computer 1-20. Which of the following elements is generally considered an optional equipment for microcomputers? 1. Display monitor 2. Keyboard 3. Printer 4. Modem 1-21. Training for which of the following types of computers is NOT NEC producing? 1. Minicomputer 2. Microcomputer 3. Mainframe computer 4. Microcomputer 1-22. What is the heart of every data system? 1. Software 2. Operator 3. Computer 4. Peripherals

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1-23. How do computer systems exchange data? 1. Through local-area networks 2. Through transfer of software 3. Through a knowledgeable and competent operator 4. Through a series of interrupts, requests, and acknowledges 1-24. Which of the following types of data do computers 1-25. 1-26. 1-27. 1-28. exchange? 1. Data words only 2. Status signals only 3. Control signals only 4. Data words, status signals, and control signals How is interfacing between computers and peripherals accomplished? 1. Cables and connectors 2. Electronic emissions 3. Output devices 4. External disk drives What are the three operational uses of computers by the Navy? 1. Graphical, database, and tactical 2. Nontactical, tactical, and tactical support 3. Tactical support, graphical, and database 4. Word processing, tactical support, and nontactical The number of computers used in a tactical data system depends on which of the following factors? 1. Size of ship 2. Class of ship 3. Mission of ship 4. Length of ship deployment Tactical support platforms include a variety of systems and normally use which of the following types of computers in their operations? 1. Minicomputers only 2. Microcomputers only 3. Mainframe computers only 4. Microcomputers and mainframe computers 1-29. ASW systems use what means as the central point of operation? 1. A single computer only 2. A data processing subsystem 3. A video processing subsystem 4. Multiple computers 1-30. In a JMCIS system, informational data is provided 1-31. 1-32. 1-33. 1-34. to designated - flagships for what purpose? 1. Logistical inventories 2. Flight orders of shipboard planes 3. Mobilization and documentation of personnel 4. Battle management of tactical situations In the JMCIS system, how do desktop computers in the data processing and video processing subsystems communicate? 1. By coaxial cable 2. By fiber-optic LANs 3. By disk exchange 4. By modems The naval intelligence processing system uses which of the following types of specially modified computers in a LAN configuration as its operational computers? 1. Unisys 44 2. Unisys 101 3. Zenith 150 4. DTC/TAC-n personal computers The naval intelligence processing system uses which of the following operating systems? 1. OS-2 and UNIX 2. OS-2 and MS-DOS 3. MS-DOS® and UNIX™ 4. DR-DOS and INIX Nontactical systems normally use which of the following types of computers? 1. Minicomputers and microcomputers 2. Mainframes and minicomputers 3. Microcomputers and mainframes 4. Desktop and mainframes 3

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1-35. What are BASIC, FORTRAN, COBOL, PASCAL, and C? 1. Computer programs 2. Computer languages 3. Computer processing units 4. Computer operating systems 1-36. 1-37. 1-38. On a LAN, personal computers can share which of the following resources? 1. Software only 2. Data files only 3. Data files and peripherals only 4. Data files, peripherals, and software The type and number of computers that makeup a system have a direct bearing on which of the following elements? 1. Hardware and software 2. Configuration and setup 3. Operating system and location 4. Number of operators and types of software Hardware setup includes what three things? 1. Physical design, ease of maintenance, and operator controls 2. Operator controls, external controls, and physical design 3. External controls, ease of maintenance, and physical design 4. Maintenance availability, operator controls, and external controls 1-39. In software setup, what must you specify to the software? 1. The resources to use 2. The number of operators 3. The climate of the location 4. The purpose of the software 1-40. 1-41. 1-42. 1-43. Your involvement with software is directly dependent on which of the following factors? 1. Type of mission 2. Type of computer 3. Type of peripherals 4. Type of organization Who designs the software for mainframes used in tactical and tactical support applications? 1. Outside support activities 2. Commercial software designers 3. Shipboard computer programmers 4. MOTUs When configuring and setting up software for a microcomputer, you must keep in mind which of the following factors? 1. You must know how to correct operational program discrepancies 2. You must use only software that was designed by an outside support activity 3. The computer system must be connected to the nearest mainframe computer 4. The operating system must be customized to the hardware of the computer system When using applications software with your microcomputer, you must ensure that the software is compatible with which of the following elements? 1. Coprocessor 2. Operating system 3. Memory unit 4. Mainframe computers 1-44. When the computer is on line, which of the following factors cause it to function correctly? 1. Software 2. Peripherals 3. RAM capacity 4. Modems 4

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1-45. 1-46. 1-47. 1-48. 1-49. In the offline mode of operation, a computer is limited to performing which of the following operations? 1. Tactical 2. Nontactical 3. Maintenance 4. Tactical support The battle short mode of operation is used when the computer must run continuously under which of the following conditions? 1. When software is being loaded 2. When maintenance is being performed 3. When an overtemperature condition exists 4. When an under-temperature condition exists An overtemperature condition can be a result of which of the following conditions? 1. Too many software programs loaded into ROM 2. A failed assembly situation only 3. An inadequate cooling condition only 4. Either a failed assembly situation or an inadequate cooling situation The operational capabilities and limitations of a computer system can be controlled by all except which of the following devices? 1. Switchboards 2. Telephone hookups 3. Software commands 4. Control panels To reconfigure a computer system to a reduced capability, which of the following devices can be used? 1. Peripherals only 2. Switchboards only 3. Control panels only 4. Switchboards, control panels, and I/O devices 1-50. A computer’s effective operation and security may be seriously jeopardized by which of the following factors? 1. Electromagnetic interference and lack of ADP security 2. Electromagnetic interference and physical location of equipment 3. Operator knowledge of mission and lack of ADP security 4. Both 2 and 3 above 1-51. The Navy ensures that only authorized users gain 1-52. 1-53. 1-54. access to computer nontactical systems (SNAP) by which of the following means? 1. Locking the computer when it is not in authorized use 2. Authorizing the use of only certain software 3. Storing the software in a secure place 4. Using passwords to identify authorized users To learn more about computer security, which of the following instructions should you study? 1. OPNAVINST 5239.1 only 2. OPNAVINST 5510.1 only 3. Both OPNAVINSTS 5239.1 and 5510.1 4. MIL-STD-1355 What type of electromagnetic interference (EMI) causes the majority of EMI problems in digital data equipment? 1. Narrowband 2. Broadband 3. Inherent 4. Natural Aboard ship, which of the following conditions does NOT have a significant effect in EMI? 1. 2. 3. 4. Grounding of equipment Interconnecting cables Location of equipment Software in use 5

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1-55. 1-56. 1-57. 1-58. 1-59. 1-60. At a shore-based installation, control of EMI involves the same factors as for a shipboard computer system, but with the addition of which of the following other considerations? 1. Terminal operators 2. Site location only 3. Soil quality only 4. Both site location and soil quality To assist in avoiding or reducing the effects of EMI, you may find guidelines for the proper construction of bonding straps and grounding cables in which of the following publications? 1. OPNAVINST 5510.1 2. NAVSEA OP 3556 3. NAVSEA S9507 4. MIL-STD 1310 The functional units of a computer are always consistent regardless of the computer’s type. 1. True 2. False To obtain the most reliable and effective instructions for maintaining a computer, you should refer to which of the following current references? 1. 2. 3. 4. OPNAVINST 5239.1 SECNAVINST 5230.7 The computer’s technical manual Local instructions A computer’s functional block diagram should provide you with all of the following information except which one? 1. Operational principles 2. Software compatibility 3. Signal types and flows 4. Major functional areas What are the three major functional areas of a computer? 1. CPU, I/O, and modem 2. Memory, I/O, and CPU 3. Hard disk, modem, and memory 4. Monitor, memory, and hard disk 1-61. 1-62. 1-63. 1-64. 1-65. 1-66. 6 The physical layout diagram gives you a picture of all of the following locations or types of computer elements except which one? 1. Module 2. Console 3. Assembly 4. Signal flow What are the four types of physical layouts for computers? 1. Backplane, assembly, cage, and LAN 2. Cage, motherboard, modular, and desktop 3. Assembly, rack, backplane, and modular 4. Chassis, motherboard, mainframe, and desktop For modular data systems that use multiple configurations, both minimum and full physical layout configurations will be shown on a physical layout. 1. True 2. False In a chassis or assembly type computer, which of the following methods is/are usually used to mount the chassis or assembly? 1. Door mounted only 2. Slide mounted only 3. Both door and slide mounted 4. Backplane mounted A cage or rack type computer’s major functional areas are always contained on one pcb. 1. True 2. False Computers that use motherboards usually have a total of how many backplanes or motherboards to contain assemblies and pcb’s? 1. One 2. Two 3. Three 4. Four

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1-67. What layout gives you information on subassemblies or printed circuit boards in each assembly, chassis, or module? 1. 2. 3. 4. Overall physical layout Overall functional layout Individual physical layout Individual functional layout 1-68. 1-69. 1-70. You do not have a need for an individual physical layout diagram in which of the following situations? 1. When you have the overall physical layout diagram 2. When you have the overall functional layout diagram 3. When you have the repair memorized 4. When you never repair the unit The configuration of a particular computer is normally dictated by which of the following criteria? 1. 2. 3. 4. Type of computer and data system platform Available power supply and programming needs Data system platform and projected use of computer Type of computer and anticipated software installation A computer’s frame usually contains which of the 1. 2. following hardware? 1. The computer only 2. The power supply only 3. The computer and the power supply only 4. The computer, power supply, and cooling hardware 1-71. When compared to other types of computer cabinets, what is the largest single advantage of modular frames in addition to mobility? 1-72. 1-73. Pcb’s are arranged in which of the following ways inside a chassis? 1. In close proximity and in square blocks 2. In close proximity and in rows 3. Spread out and in rows 4. Spread out and on opposite sides of the cabinet Motherboard-designed computers have which of the following features as their primary design feature? 1. Portability 2. Ruggedness 3. Shipboard use 4. Tactical use 1-74. It is easier to maintain computers that have motherboards for which of the follow reasons? 1. The cabinet need not be removed 2. The power need not be secured 3. The computer’s small size and ease of component accessibility 4. All of the above 1-75. What two features used in or on a cabinet provide limited protection for a computer? 3. 4. Gaskets and filters Surge protectors and shock reducers Insulating material and grounding wires External power source and RF interference adapters 1. 2. 3. 4. Ruggedness Adaptability Ease of installation Access to control panels NOTE: MS-DOS is a registered trademark of Microsoft Corporation. UNIX is a trademark of AT&T. 7

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ASSIGNMENT 2 Textbook Assignment: “Computer Configurations and Hardware,” chapter 2, pages 2-13 to 2-27; and “Computer Operator Controls and Controlling Units,” pages 3-1 through 3-15. 2-1. 2-2. 2-3. 2-4. 2-5. How do manufacturers key subassemblies to avoid incorrect installation? 1 2 3 4 They tag the subassembly with the correct location They write the location on the part with indelible ink They make the designation very clear in the technical manual They cut a slot in the side of the pcb or put plastic sheeting on one or more connector pins All subassemblies are repairable at the work station. 1. True 2. False The majority of a computer’s functional areas consists of which of the following components? 1. Motherboards 2. Power drivers 3. Random access memories 4. Printed circuit boards What factor determines the number of printed circuit boards required for a particular computer? 1. Type of computer 2. Portability of computer 3. Accessibility of one computer to another computer 4. Danger of electronic emissions near the work station The arrangement of pcb’s in a computer is dictated by which of the following factors? 1. Type of computer 2. Purpose of the computer 3. Location of the computer 4. Software programs to be used 2-6. 2-7. 2-8. 2-9. 8 Keying pcb’s is done for which of the following reasons? 1. To ensure that the pcb is inserted correctly only 2. To ensure that a different card type is not inserted into an incorrect slot only 3. To ensure that the pcb is inserted correctly and to ensure that a different card type is not inserted into an incorrect slot 4. To facilitate ease of location in an emergency situation You should know the color codes of pcb’s. You will find these color codes explained in which of the following publications? 1. NEETS, Module 3 2. NEETS, Module 4 3. NEETS, Module 19 4. NEETS, Module 21 LEDs are used for which of the following maintenance functions on pcb’s? 1. To test voltage levels 2. To test waveforms 3. To tell when equipment is operating abnormally 4. All of the above Which of the following publications provides a listing for standard external interfaces? 1. MIL-STD-2000 2. MIL-STD-2036 3. NEETS, Module 4 4. NEETS, Module 24

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2-10. Which of the following documents provide(s) maintenance information on connectors and cables? 1. Computer technical manuals 2. EIMB, Installation Standards, NA VSEA 0967-LP-000-0110 3. Both 1 and 2 above 4. MIL-STD-2036 2-11. Connector receptacles are also known as what? 1. Printed circuit boards 2. Subassemblies 3. Modules 4. Jacks 2-12. Mating of a connection only includes electrical pins and contacts or pcb card-edge? 1. True 2. False 2-13. A rectangular connector’s electrical contacts or pins may have which of the following characteristics? 1. Be male or female, flat or oval 2. Be male or female, round or flat 3. Be male or female, round or oval 4. Be oval, round, or rectangular A. Single-piece pcb or card edge B. Two-piece plug and receptable pcb C. Rectangular multipin D. Circular multipin E. Coaxial F. Component Figure 2A.—Connector architecture. IN ANSWERING QUESTIONS 2-14 THROUGH 2-19, SELECT FROM FIGURE 2A THE TYPE OF CONNECTOR ARCHITECTURE DESCRIBED IN THE QUESTION. 2-14. Which item can contain more than 100 pins and contacts? 1. A 2. B 3. C 4. E 2-15. MTIDC or IDC are included in all except which of the following connectors? 1. A 2. B 3. C 4. F 2-16. Telephone jack connectors can be used to connect a conductor to which connector? 1. A 2. C 3. D 4. F 2-17. Contacts or pins on plugs or receptacles are male or female except on which of the following connectors? 1. B 2. C 3. D 4. F 2-18. Provisions for shielding against shock and vibration can be on all except which of the following connectors? 1. A 2. C 3. D 4. E 2-19. Hardware is used to secure which of the following connections and provide stability against shock and vibration? 1. C 2. D 3. E 4. F 9

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2-20. 2-21. Internal connectors are used inside the computer for which of the following reasons? 1. To connect the computer to a display system 2. To provide power to the computer only 3. To interconnect major individual units inside the computer only 4. To interconnect major individual units inside the computer and provide power to the computer What precaution should you use when making connections for pcb’s, modules, or subassemblies? 1. 2. 3. Secure the power to the computer and ensure the receptacle and plug match Ensure that the receptacle or plug has guide pins Force the connection Both 2 and 3 above4. 2-22. Which of the following documents can be used to find the signal names used by a computer? 1. The wire listings only 2. The computer’s prints only 3. The description of a pcb only 4. The computer’s wire listings, prints, and/or a description of each pcb 2-23. Internal conductors can only take mass data and route it for distribution throughout the computer. 1. True 2. False 2-24. To make effective use of limited space, which of the following items are used to neatly organize conductor bundles internally? 1. Lacings 2. Spot ties 3. Wiring harnesses 4. Self-cliching straps 2-25. To secure the wires contained in a wire harness, which of the following items may be used? 1. Lacings only 2. Spot tying only 3. Self-clinching straps only 4. Lacings, spot tying, and self-clinching straps 2-26. If a conductor is partially replaced or completely replaced, a different grade (AWG) and type of conductor can be used. 1. True 2. False 2-27. In addition to securing power to the computer,— what other precaution, if any, should you exercise 2-28. 2-29. when you are disconnecting and reconnecting power and data connections? 1. Follow the proper tag-out procedures 2. Document your actions in the computer room pass down log 3. Backup the data to a floppy or hard drive 4. None; no precautions are needed The power requirements for all computers are identical regardless of where the computers are used. 1. True 2. False To help mate connector receptacles and plugs properly, which of the following methods maybe used? 1. Keying only 2. Physical shape only 3. Keying and physical shape A. Flat B. Ribbon C. Twisted component or multiconductor D. Coaxial E. Fiber optic Figure 2B.—Cable architecture. IN ANSWERING QUESTIONS 2-30 THROUGH 2-34, SELECT FROM FIGURE 2B THE TYPE OF CABLE ARCHITECTURE THAT BEST MATCHES THE DESCRIPTION IN EACH QUESTION. 10

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2-30. Conductors are separated by the dielectric core. 1. A 2. B 3. C 4. D 2-31. Can be terminated with card-edge connectors or IDCs. 1. B 2. C 3. D 4. E 2-32. Can have up to 120 conductors. 1. A 2. B 3. C 4. D 2-33. Capable of transmitting a 20-Mhz signal with minimum loss and no distortion. 1. A 2. B 3. C 4. D 2-34. Used for serial transfer of data only. 1. D only 2. E only 3. D and E 4. A, B, and C 2-35. What is the most critical piece of equipment in any data system? 1. Memory 2. Computer 3. Connector 4. Disk drive 2-36. In cooling systems, what four methods of cooling are used? 1. Convection, forced air, air-to-air, and air-to-liquid 2. Forced air, air-to-air, microwaved, and convection 3. Air-to-liquid, air-to-air, microwaved, and forced air 4. Air-to-air, forced air, external fan-blown, and convection 2-37. What type of operator control is used to alter the speed of an internal computer clock or vary the intensity of indicators? 1. Thumbwheel switch 2. Potentiometer 3. Pushbutton 4. Mouse 2-38. To provide status information to the computer operator, which of the following devices may be used? 1. Dot matrix display only 2. Light-emitting diodes only 3. Dot matrix display and light-emitting diodes 4. Mouse devices 2-39. What is the simplest way to show the status of an operation or the selection of an item? 1. Send a message to a printer 2. Send a message to disk 3. Turn on a light 4. Sound an alarm 2-40. All of the following are types of indicators except which one? 1. Backlit 2. Opaque 3. Clear 4. Color 2-41. Protective devices can serve as controls. 1. True 2. False 11

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2-42. To protect from accidental activation of selected keys and switches, what device is used with selected keys and switches? 1. Horn 2. Guard 3. Circuit breaker 4. Light-emitting diode 2-43. Switches have which of the following functions? 1. To activate a function 2. To turn a unit on/off 3. To set a parameter 4. Each of the above 2-44. A key switch you depress to activate a function 2-45. 2-46. and depress again to deactivate the function is called a/an 1. momentary-action key switch 2. alternate-action key switch 3. three-position key switch 4. on/off key switch A key that repeats the function continuously while being held down is which of the following types of keys? 1. Momentary-action key 2. Alternate-action key 3. Toggle key 4. On/off key Switches that have several positions the operator can select by turning a knob are which of the following types of switches? 1. Rotary switches 2. Pushbutton switches 3. Alternate-action toggle switches 4. Momentary-action toggle switches 2-47. All of the following are characteristics of thumbwheel switches except which one? 1. They have alphanumeric characters built in 2. Each position is locked until another position is selected 3. The position values are usually marked on the controlling unit cover 4. The positions are selected by dialing the switch 2-48. Pushbutton switches may not have indicators. 1. True 2. False 2-49. On toggle switches, which of the following can be 2-50. 2-51. 2-52. a use of the neutral position? 1. To interact with software 2. To set a parameter 3. To disable a locked up/down position 4. All of the above Alternate-action toggle switches may have which of the following positions? 1. Permanent up and return to neutral only 2. Permanent up and down only 3. Either permanent up and return to neutral or permanent up and down, depending on design 4. On and off Momentary-action/contact, two-position toggle switches are normally used for which of the following purposes? 1. To turn the unit on 2. To initiate an operation 3. To provide status information 4. To turn the unit off On a three-position toggle switch, the center position may be used for which of the following purposes? 1. To set a parameter only 2. To disable the locked up/down position only 3. Either to set a parameter or to disable the locked up/down position, depending on the function 4. To provide status information 12

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2-53. 2-54. 2-55. You should expect to find all of the following types of information about controlling units in the technical manuals and owner’s manuals of your system except which one? 1. 2. 3. 4. General description of the unit Tables and figures to describe each control and indicator Circuit diagrams with information for maintenance Manufacturing specifications and design requirements In addition to operational programs, what other type of programs will you be using to perform preventive maintenance? 1. Diagnostic programs 2. Applications programs 3. Word processing programs 4. Database management programs Information about each control and indicator will include all except which of the following information? 1. Name 2. Type 3. Date installed 4. Function and use 2-56. In addition to providing power indicators, which of the following other important functions do power/temperature panels provide? 1. 2. 3. 4. Notify you of an overtemperature condition Enable you to modify the temperature setting for efficient operation Both 2 and 3 above Shut down the system automatically when an overtemperature condition is reached 2-57. From the operator panel you can perform all of the following functions except which one? 1. 2. 3. 4. Initiate computer operations Monitor computer operations Put the computer in battle short condition Power up/down individual designated modules 2-58. Built-in test (BIT) controls and indicators are included on which of the following panels? 1. Operator panel 2. Power/temperature panel 3. Control and maintenance panel 4. Each of the above 2-59. During operation and maintenance, all of the following are computer monitoring capabilities from a control and maintenance panel (CMP) except which one? 1. Software availability 2. Hardware availability 3. Switch settings 4. Jump stops 2-60. The ac plasma part of a display control unit has which of the following functions? 1. Provides you operational information 2. Provides you corrective maintenance information 3. Interfaces with the CPU/IOC and memory 4. Both 2 and 3 above 2-61. A built-in microprocessor with five levels of controls and indications for loading and initiating operations, monitoring operations, status indications, operator interfacing, and self-testing is part of what type of controlling unit? 1. Maintenance console unit 2. Computer control panel 3. Display control unit 4. Operator panel 2-62. To perform diagnostics on a computer, what type of controlling unit enables you to use a data terminal and diagnostics stored on a magnetic tape? 1. 2. 3. 4. Operator panel Maintenance console Display control unit Computer control panel 13

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2-63. From a computer control panel, you can perform which of the following types of monitoring? 1. Operational program status only 2. Display registers only 3. Switch settings only 4. Switch settings, display registers, and computer operations 2-64. What controlling unit enables you to operate the computer set under expanded and varied conditions, at various operating speeds, and in various operating modes? 1. Operator panel 2. Maintenance console 3. Power/temperature panel 4. Computer control unit 2-65. When you manually interface with the CPU and IOC for software enhancement, what is the name of the function you are performing? 1. Diagnostic programming 2. Operator programming 3. Inspect and change 4. Casualty control 2-66. A keyboard will be your primary device for controlling what type of computer, if any? 1. Mainframe 2. Minicomputer 3. Microcomputer 4. None; keyboards are not used to control computers 2-67. On a microcomputer, what is the primary method used to provide information to you? 1. 2. 3. 4. Printer Monitor Light-emitting diodes Indicator lights on the keyboard 2-68. The meanings of function keys and control keys can be assigned in which of the following ways? 1. By the computer hardware manufacturer only 2. By the computer program only 3. By the operating system only 4. By both the computer program and the operating system 2-69. In addition to the keyboard, what other device may 2-70. 2-71. 2-72. you use as a controlling device with the monitor to control the operations of a microcomputer? 1. Mouse 2. Key switch 3. Rotary switch 4. Toggle switch Of the following devices, which one can provide both input to a computer and output from a computer? 1. Mouse 2. Printer 3. Teletype 4. Keyboard A teletype is composed of which of the following components? 1. Printer only 2. Keyboard only 3. Printer and keyboard only 4. Printer, keyboard, and monitor From remote consoles and remote operator control units, you may be able to perform all except which of the following functions? 1. 2. 3. 4. Power the computer set up/down Initiate computer operations Monitor computer status Perform self-testing 14

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ASSIGNMENT 3 Textbook assignment: “Computer Components and Circuits,” chapter 4, pages, 4-1 through 4-23. 3-1. 3-2. 3-3. 3-4. 3-5. A computer has a total of how many states in its binary system? 1. One only 2. Two only 3. Three only 4. Four The digital functions and operations of a computer are based upon what mathematical concept? 1. Calculus 2. Trigonometry 3. Logic algebra 4. Plane geometry You have been assigned to maintain a set of computers. What must you understand about the computers to successfully accomplish your assignment? 1. What comprises the computer’s components 2. How the components make up the computer’s fictional areas 3. How to determine if a particular component is malfunctioning 4. All of the above On input data, a computer performs which of the following types of general functions? 1. Calculus only 2. Geometric only 3. Trigonometric and geometric only 4. Arithmetic and logical What basis is used to determine the logic circuits to be used in a particular computer? 1. The computer’s requirements 3. The computer’s location 4. The software to be used 3-6. Which of the following publications lists standard microcircuits? 1. NEETS, Module 7 2. NEETS, Module 14 3. ANSI/IEEE 91-1984 4. MIL-STD-1562 3-7. Which of the following publications discusses Boolean algebra? 1. NEETS, Module 9 2. NEETS, Module 13 3. NEETS, Module 19 4. MIL-M-38510 3-8. To study wave-generation, you should refer to which of the following publications? 1. NEETS, Module 9 2. NEETS, Module 19 3. ANSI/IEEE 91-1984 4. ANSI/IEEE 991-198 3-9. Standard graphic symbols for logic functions are found in which of the following publications? 1. NEETS, Module 7 2. NEETS, Module 14 3. ANSI/IEEE 91-1984 4. MIL-M-38510 3-10. The octal and hexadecimal number systems are the most popular derivatives used today by digital computers. From what number system are they derived? 1. Roman 2. Arabic 3. Decimal 4. Binary 2. The skills of the operator 15

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IN ANSWERING QUESTIONS 3-11 AND 3-12, REFER TO FIGURE 4-1 ON PAGE 4-3 IN THE TRAMAN. 3-11. The octal number 14 is what in (a) decimal, (b) binary, and (c) hexadecimal? 1. (a) 12 (b) 01110 (c) 14 2. (a) 12 (b) 01100 (c) C 3. (a) 14 (b) 01100 (c) 14 4. (a) 14 (b) 01110 (c) E 3-12. The decimal number 16 is what in (a) binary, (b) octal, and (c) hexadecimal? 1. (a) 1000 (b) 18 (c) F 2. (a) 1000 (b) 20 (c) 10 3. (a) 10000 (b) 16 (c) 16 4. (a) 10000 (b) 20 (c) 10 3-13. In Boolean algebra, what are the two logic levels? 1. 1 and 0 2. 1 and 2 3. 2 and 0 4. 2 and 3 3-14. Which of the following combinations represents the three basic logic gates used in building the combinational and sequential digital logic circuits? 1. OR, BUT, ALSO 2. AND, OR, NOT 3. NOT, NEITHER, NOR 4. AND, BUT, OR 3-15. Modern computers rely on what type of circuits? 1. Balanced 2. Monophase 3. Integrated 4. Multipoint 3-16. Integrated circuits provide what three major advantages? 1. 2. 3. 4. High reliability, low cost, and accessibility Low cost, small size, and high reliability Portability, accessibility, and reliability Small size, low cost, and portability 3-17. For which of the following reasons are integrated circuits packaged in various sizes? 1. Number of leads 2. Color coding 3. Size of chip 4. Key coding 3-18. What scale of integration has 10 to 100 gates? 1. Small scale 2. Medium scale 3. Large scale 4. Very large scale 3-19. What factor determines the integration size of an integrated circuit package? 1. The number of chips 2. The types of leads 3. The number of gates 4. The types of keying 3-20. Integrated circuits that combine the technology of bipolar and metal-oxide semiconductors are referred to as what type of circuit? 1. Unipolar 2. Bipolar 3. BIMOS 4. MOS 3-21. Most of a computer’s integrated circuits are digital. 1. True 2. False 3-22. To process and store information in a computer’s memory, what category of circuit is used? 1. MOS only 2. Bipolar only 3. Digital 4. Linear 16

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3-23. Bipolar integrated circuits include all of the following components except which one? 1. ECL 2. ALS 3. TTL 4. TTLC 3-24. Which of the following components is NOT a part of a MOS integrated circuit? 1. DTL 2. TTLC 3. CMOS 4. HCMOS 3-25. In the determination of whether a computer’s logic level is negative or positive, what is the relationship of the two voltages? 1. 2. 3. 4. They are relative to each other They are independent of each other They intermesh with each other One is dominant; the other subordinate IN ANSWERING QUESTIONS 3-26 THROUGH 3-28, SELECT FROM THE FOLLOWING LIST THE TERM DESCRIBED IN EACH QUESTION. 1. Pulse width 2. Pulse-repetition time 3. Pulse-duration modulation 4. Pulse-repetition frequency 3-26. The time period from a repeating waveshape’s starting point until the next starting point. 3-27. The time interval between specified reference points on the leading and trailing edges of a waveform. 3-28. The number of times per second that a signal’s complete cycle occurs. GIVEN: A DIGITAL WAVESHAPE HAS A PRT OF 25 µsec AND A NEGATIVE PW OF 15 µsec. Figure 3A.—Example statement. IN ANSWERING QUESTIONS 3-29 AND 3-30, REFER TO FIGURE 3A. 3-29. What is the value of the positive PW? 1. 6 µsec 2. 8 µsec 3. 10 µsec 4. 12 µsec 3-30. What is the value of the PRF? 1. 37 kHz 2. 40 kHz 3. 43.5 kHz 4. 47.5 kHz 3-31. What is the basic building block for combinational digital circuits? 1. Diode 2. Capacitor 3. Flip-flop 4. Logic gate 3-32. What is the basic building block for sequential circuits? 1. Resistor 2. Conductor 3. Flip-flop 4. Logic gate 3-33. Logic gates perform decision-making functions throughout the computer. 1. True 2. False 3-34. Which of the following is another term for flip-flops? 1. Unistable multivibrators only 2. Bistable multivibrators only 3. Tristable multivibrators only 4. Multivibrators 17

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3-35. What are the four types of flip-flops? 1. J-K, set, open, closed 2. Toggle, data, reset-set, J-K 3. Reset-set, data, continuous, open 4. Open, continuous, closed, toggle 3-36. Decision-making functions are composed primarily of which of the following components? 1. Combinational gates 2. Bistable multivibrators 3. Sequential digital circuits 4. Independent linear circuits IN ANSWERING QUESTIONS 3-37 THROUGH 3-44, SELECT FROM FIGURE 3-B THE DATA ROUTING CIRCUIT DESCRIBED IN THE QUESTION, A. Adder and subtracter circuits B. Command signal circuits C. Comparator circuits D. Demultiplexer circuits E. Selector circuits F. Translator circuits Figure 3B.—Data routing circuits. 3-37. Which circuits provide the enable to route data between circuits? 1. A 2. B 3. E 4. F 3-38. Which circuits are used with shift registers and holding registers to perform hyperbolic and trigonometric functions? 1. A 2. B 3. C 4. D 3-39. 3-40. 3-41. 3-42. 3-43. 3-44. Which circuits can change machine octal codes into function codes? 1. C 2. D 3. E 4. F Which circuits expand the number of input data paths to a register? 1. A 2. C 3. E 4. F Which circuits are capable of performing square root when used with shift and holding registers? 1. A 2. C 3. D 4. F Which circuits can select an address? 1. B 2. D 3. E 4. F Which circuits can be used to compare incoming binary numbers after mathematical operations have been performed? 1. B 2. C 3. D 4. F Which circuits route data from one input to any one of several outputs? 1. A 2. D 3. E 4. F 18

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3-45. 3-46. 3-47. 3-48. 3-49. 3-50. Memory-type functions are accomplished by what type of circuit? 1. Linear 2. Bipolar 3. Sequential 4. Combinational Counters can only be used in parallel operations. 1. True 2. False Counters are used for which of the following functions? 1. 2. 3. 4. For counting operations and quantities only For counting periods of time only For addressing information in storage only For counting operations, quantities, and periods of time; and for addressing information in storage What items constitute a register? 1. Numbers of circuits 2. Groups of flip-flops 3. Numbers of logic gates 4. All of the above The length of a register is determined by what factor? 1. 2. 3. 4. The function it performs The type of logic the computer uses The number of bits (flip-flops) grouped together The number system the computer uses: octal or hexadecimal There are two types of registers most commonly used in computers. Which of the following terms refer to these registers? 1. 2. 3. 4. Memory and backup Storage and shift Backup and memory Storage and backup 3-51. 3-52. 3-53. 3-54. 3-55. 3-56. What type of storage register, if any, does NOT alter the contents? 1. General 2. Specialized 3. Subject-specific 4. None; all storage registers can alter their contents In what transfer method is the receiving register cleared of its contents before a transfer occurs? 1. Single-line parallel 2. Double-1ine parallel 3. Complement 4. Displaced Of the following transfer methods used with registers, which one is the fastest? 1. Complement method 2. Displaced method 3. Direct method 4. Forced method What register can handle information in serial and parallel form? 1. Complement 2. Storage 3. Backup 4. Shift In linear circuits, the graph of output versus input approximates which of the following types of lines? 1. Wavy 2. Arced 3. Zigzag 4. Straight DMOS and bipolar technology is known by what acronym? 1. BIFET 2. BIDFET 3. BIDMOS 4. MOSFET 19

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3-57. The basic gate for a linear integrated circuit is a/an 1. operational amplifier 2. diffuser 3. catalyst 4. conductor 3-58. An inverting input of an op amp provides what degree of phase shift at the output? 1. 150 2. 180 3.210 4.315 3-59. All of the following types of circuits are part of a computer’s linear integrated circuits except which one? 1. Digital circuits 2. Driver integrated circuits 3. Regulator integrated circuits 4. Analog signal conversion circuits 3-60. Which of the following circuits detect overtemperature conditions? 1. Timers 2. Analog converters 3. Digital converters 4. Comparators, voltage regulators, and switching regulators 3-61. Which of the following circuits can be used to produce an astable multivibrator? 1. 2. 3. 4. Timers Comparators Switching regulators Analog to digital converters 3-62. All of the following are classifications of systems interface circuits of a computer except which one? 1. 2. 3. 4. Line drivers, receivers Sense amplifiers, memory drivers Peripheral and display drivers Timers and analog-to-digital converters 3-63. Information is written into magnetic memories by which of the following drivers? 1. Line 2. Memory 3. Display 4. Peripheral 3-64. Display drivers use what type of input and output application? 1. Single 2. Dual 3. Trifold 4. Multiple 3-65. In the transmission of digital signals over short distances, which of the following types of line drivers and receivers are used? 1. 2. 3. 4. Peripheral Differential only Single-ended only Either differential or single-ended, depending on the design 3-66. For high-speed, long distance communications, which of the following types of drivers is/are used? 1. Single-ended only 2. Differential only 3. Both single-ended and differential 4. Basic wire cables 3-67. Timing circuits are used in a computer for which of the following reasons? 1. To keep track of calendar and clock times 2. To automatically make backup copies of data 3. To properly enable and disable circuits at specific times 4. To automatically disengage the computer if it becomes too hot 20

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3-68. Aprogram has been installed and the computer is operating. The enabling and disabling circuits will stop operating under each of the following conditions except which one? 1. Fault condition occurs 2. Programmed stop is reached 3. Program completion is reached 4. Instructions are executing 3-69. The master clock in a computer is the key to the computer’s timing circuits. Master clocks usually operate at a frequency or pulse-repetition rate determined by which of the following factors? 1. The maximum speed of the operator 2. The minimum speed of the operator 3. The minimum rate the computer can handle data 4. The maximum rate the computer can handle data 3-70. In computer timing circuits, what is the most important reason for using oscillators? 1. Their output characteristics 2. Their frequency stability 3. Their phase processing 4. Their speed IN ANSWERING QUESTIONS 3-71 THROUGH 3-74, SELECT FROM THE FOLLOWING LIST THE TYPE OF MULTIVIBRATOR DESCRIBED BY THE PHRASE IN EACH QUESTION. 1. Monostable 2. Bistable 3. Astable 3-71. The multivibrator that is also referred to as a one-shot multivibrator. 3-72. The multivibrator that counts clock pulses. 3-73. The multivibrator also known as a free-running multivibrator. 3-74. The multivibrator used to enable logic gates. 3-75. A single-phase clock system has what types of multivibrators? 1. 2. 3. 4. Monostable and bistable Bistable and astable Monostable and astable Astable and multistable 21

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ASSIGNMENT 4 Textbook Assignment: “Computer Components and Circuits,” chapter 4, pages 4-24 through 4-31; and “Central Processing Units and Buses,” chapter 5, pages 5-1 through 5-10. 4-1. Which of the following are the types of data elements that can be processed by a computer? 1. Bits and bytes only 2. Bytes and single words only 3. Bits, bytes, and single words only 4. Nibbles, words, double words, bytes, and bits 4-2. What data element is normally the same size as the computer’s registers? 1. Bit 2. Nibble 3. Word 4. Double word 4-3. What is the purpose of a computer’s power supply? 1. To supply dc voltage 2. To convert ac voltage from a source to useable dc voltage(s) 3. To convert dc voltage(s) from a source to useable ac voltage(s) 4. To supply ac voltage 4-4. Characteristics of a power supply include all of the following except which one? 1. 2. 3. 4. Provide precision voltages Protect the computer from serious damage Supply regulated ac voltages Sense irregular inputs and outputs 4-5. What are the major sections of a computer’s power supply? 1. Amplifier, rectifier, filter, and regulator 2. Transformer, generator, filter, and regulator 3. Transformer, rectifier, filter, and regulator 4. Transformer, rectifier, filter, and transmitter 4-6. 4-7. 4-8. 4-9. The computer can only handle one specified input voltage and frequency. 1. True 2. False Aboard ship, distribution of computer input power is via which of the following means? 1. 2. 3. 4. Outlets only Load centers only Power panels only Outlets, load centers, and power panels Mainframe and minicomputers aboard ship and ashore are preset to only receive the specific input line voltage needed. 1. True 2. False Aboard ship, what document provides the specific voltage and frequency values as well as the location of your computer’s power? 1. MIL-STD-1399 2. MIL-HDBK-411 3. Ship’s electronics doctrine 4. MIL-HDBK-263 4-10. For referencing input power ashore, which of the following documents should you use? 1. 2. 3. 4. MIL-STD-1399, Section 300A MIL-STD-480 MIL-HDBK-411 Each of the above 22

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4-11. For referencing input power aboard ship, which of the following documents should you use? 1. MIL-STD-1399, Section 300A 2. MIL-STD-480 3. MIL-HDBK-411 4. Each of the above 4-12. Where does the input line voltage go before it is received by the transformer section of the computer’s power supply? 1. To the rectifier section 2. To the ON/OFF switch 3. To the blower fan 4. To the filter section IN ANSWERING QUESTIONS 4-13 THROUGH 4-20, SELECT THE POWER SUPPLY SECTION THAT MATCHES THE CHARACTERISTIC DESCRIBED IN EACH QUESTION. 1. Regulator 2. Rectifier 3. Filter 4. Transformer 4-13. Isolates the power supply from the input line voltage. 4-14. Provides regulated power to additional circuits for further filtering and/or conversion. 4-15. Converts an ac input signal to pulsating dc voltage or ripple. 4-16. Steps up the input line voltage. 4-17. Maintains the output of the power supply at a constant level. 4-18. Provides the necessary power for the bus system terminating resistors. 4-19. Removes pulsating dc ripple and produces a useable dc voltage. 4-20. Provides dc power to the backplane wire harness, and to remote, operator, and maintenance consoles. 4-21. The voltage levels and logic convention for mainframe and minicomputers are identical. 1. True 2. False 4-22. The output of the computer’s power supply can be distributed by which of the following sections? 1. Rectifier only 2. Regulator only 3. Both rectifier and regulator 4. Filter 4-23. The power supply must protect the computer from which of the following elements? 1. Incoming power 2. Distributed power 3. Internal cabinet and/or module temperature 4. All of the above 4-24. A power supply will shut off while the computer is running under what condition(s), if any? 1. A low overtemperature condition 2. A high overtemperature condition only 3. A high overtemperature condition and an overcurrent condition 4. None IN ANSWERING QUESTIONS 4-25 THROUGH 4-31, SELECT FROM THE FOLLOWING LIST THE SIGNAL GENERATED UNDER THE SPECIFIC CONDITION DESCRIBED IN EACH QUESTION. 1. POWER INTERRUPT (PI) 2. MASTER CLEAR (MC), AUTOMATIC 3. STOP 4-25. Used for computer initialization after power has been applied. 4-26. Source power falls below specifications and returns to normal. 4-27. Generates a class I interrupt. 4-28. Logic power goes out of tolerance. 23

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4-29. Source power is lost or the computer cabinet is shut off. 4-30. Generated a specific period after a PI occurs. 4-31. Prevents loss of memory data if logic power is lost faster than normal the turn-off sequence can occur. 4-32. To indicate that power requirements have been met, what digital active signals are generated by a microcomputer’s power supply? 1. LEDs only 2. Ac only 3. Dc only 4. Ac and dc 4-33. To provide protection to the computer, which of the following devices are placed in line with the power source? 1. Compensators only 2. Line conditioners only 3. Surge protectors only 4. Compensators, line conditioners, and surge protectors 4-34. Which of the following protective devices provide protection against brownouts? 1. ABTs 2. Surge protectors 3. Line conditioners only 4. Compensators and line conditioners 4-35. Line conditioners can provide all of the following protection except which one? 1. Suppress over-voltage 2. Filter input power 3. Bridge brownouts 4. Provide ac input voltage 4-36. Surge protectors retain their effectiveness with successive surges. 1. True 2. False 4-37. What device allows the computer to execute software during power absences up to 100 ms during transfer of primary power source? 1 G UPS 2. Compensator 3. ABT 4. SPS 4-38. SPSs and UPSs are constructed in much the same way except for which feature? 1. Switching circuitry 2. Power loss is detected 3. Ac line current is sensed 4. Power is transferred from one primary source to another 4-39. What are the three major functional areas of a computer? 1. CPU, I/O, buses 2. CPU, memory, power supply 3. CPU, memory, I/O 4. CPU, I/O, power supply 4-40. Information concerning the logic implementation and interpretation of a specific digital computer would be found in which of the following references? 1. Technical manual 2. Technical manual and MRC 3. MRC only 4. NEETS, Module 13 4-41. Which of the following documents should contain the functional schematics of a digital computer? 1. Technical manual only 2. Owner’s manual only 3. Either the technical manual or the owner’s manual 4. NEETS, Module 13 24

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4-42. 4-43. 4-44. 4-45. 4-46. 4-47. Which of the following references contains the test documentation and procedures, test equipment, and tools required to perform corrective maintenance on a specific computer? 1. Technical manual/owner’s manual 2. MRC 3. Ship’s electronics equipment doctrine 4. CSOSS documentation Which of the following functional areas provide(s) the means for the CPU, memory, and I/O to communicate with each other? 1. System cables 2. System buses 3. System modem 4. Wire bundles What two interacting sections compose the CPU? 1. Control and memory 2. ALU and memory 3. Control and ALU 4. ALU and I/O All of the following are characteristics of the CPU’s control section except which one? 1. Whereto store information and who to talk with 2. How to compute logical solutions 3. When to start and stop 4. What to do The control section may provide the computer with the ability to function under which of the following conditions? 1. Manual control only 2. Program control only 3. Manual and program control 4. Interface control The control section includes all the following logically designed areas except which one? 1. Timing, and instruction and control 2. Fixed- and floating-point operations 3. Memories-control, cache, and read-only 4. Addressing and interrupts 4-48. What logically designed area in the control section regulates the operation of the computer? 1. Instruction and control 2. Addressing 3. Interrupts 4. Timing 4-49. What type of timing is used for the execution of instructions stored sequentially in memory? 1. Arithmetic timing 2. Synchronous operations 3. Master clock events 4. Asynchronous operations IN ANSWERING QUESTIONS 4-50 THROUGH 4-55, SELECT FROM THE FOLLOWING LIST THE LOGICALLY DESIGNED AREA THAT PERFORMS THE OPERATION DESCRIBED IN EACH QUESTION. 4-50. 4-51. 4-52. 4-53. 4-54. 4-55. 1. Master clock 2. Main timing chain 3. Main timing signals 4. Timing sequences Used to trigger a single-shot to enable and disable circuits in the sequence necessary to execute computer operations. Flip-flops are arranged in a ring counter to count master clock phases. Used to generate a command enable for sending data from one register to another. Taps on a delay line oscillator can be used to provide additional phases. Used to issue a series of commands to perform a particular instruction or operation. Used to start arithmetic timing and generate command enables used for arithmetic operations. 25

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4-56. To keep track of time intervals, which of the following types of timing circuitry can be used? 1. Monitor clock only 2. Programmable internal timer only 3. Monitor clock and programmable internal timer 4. Real-time clock (RTC) A. Accumulator B. Index register C. Instruction register D. Program counter E. Status indicating register Figure 4A.—Memory type circuits. 4-57. To keep track of real time, which of the following timing circuits can be used? 1. 2. 3. 4. RTC only Monitor clock only RTC and monitor clock RTC and programmable interval timer 4-58. Which of the following timing circuits are 4-59. 4-60. 4-61. software/machine instruction controlled? 1. RTC only 2. Monitor clock only 3. Programmable interval timer only 4. RTC, monitor clock, and programmable interval timer To channel data inside the computer, what type of circuits are primarily used with registers for instruction and control operations? 1. Analog conversion 2. Data routing circuits 3. Code converter circuits 4. Interface circuits A general-purpose register is also known by what name? 1. Instruction 2. Accumulator 3. Program counter 4. Status indicating General-purpose registers are generally the same size as the computer’s memory word. 1. True 2. False IN ANSWERING QUESTIONS 4-62 THROUGH 4-68, SELECT FROM FIGURE 4A THE MEMORY TYPE CIRCUIT THAT APPLIES TO THE FUNCTION DESCRIBED IN EACH QUESTION. 4-62. Used for address modification and counting. 1. A 2. B 3. C 4. D 4-63. Holds the address of the next instruction to be executed. 1. B 2. C 3. D 4. E 4-64. Can be used to indicate the status of operations in the computer. 1. B 2. C 3. D 4. E 4-65. Outputs of this register are translated into commands for CPU execution. 1. B 2. C 3. D 4. E 26

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4-66. 4-67. 4-68. 4-69. 4-70. Used for temporary storage of data or memory addresses. 1. A 2. B 3. C 4. D These registers are used with branching condition instructions to change the sequence of instruction execution. 1. A 2. B 3. D 4. E Enables a single instruction to be used to specify a large number of operands indirectly. 1. A 2. B 3. C 4. D In the general process of executing a machine instruction, what are the major steps? 1. 2. 3. 4. Write the instruction to memory, update the program counter, translate the instruction, and execute the instruction Encode the instruction, execute the instruction, update the program counter, and read the instruction from memory Increment the instruction register, update the program counter, decode the instruction, and execute the instruction Read the instruction from memory, update the program counter, translate the instruction, and execute the instruction Which of the following methods can be used to change the sequence of program execution? 1. Stop and jump switches only 2. Program instructions only 3. Stop and jump switches and program instructions 4-71 Command enables are generated by which of the following parts of the general process of machine instruction execution? 1. Fetch the instruction 2. Update the program counter 3. Translate the instruction 4. Execute the instruction 4-72. The computer executes instructions at two levels or states. Data bits in what register are used to select the instruction operating levels? 1. The index register 2. The program counter 3. The instruction register 4. The status indicating register 4-73. Interrupt processing instructions can be included in which of the following types of programs? 1. Executive function programs 2. Application programs to solve a fire control solution 3. Application programs to compute a sonobuoy pattern 4. Both 2 and 3 above 4-74. Which of the following instructions can only be performed in the executive state? 1. Add instructions 2. Subtract instructions 3. Privileged instructions that are part of interrupts 4. Read instructions 4-75. What is the purpose of instruction operand addressing? 1. To specify the location of the operand 2. To tell when to perform the instruction 3. To tell whereto obtain the instruction 4. To tell how to obtain the memory address of the instruction 27

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ASSIGNMENT 5 Textbook Assignment: “Central Processing Units and Buses,” chapter 5, pages 5-13 through 5-23. 5-1 5-2 5-3 5-4 The interrupt that occurs with the actual event that caused the interrupt is (a) what type and (b) what will be the status of the condition of the process or program after the interrupt is processed? 1. (a) Asynchronous (b) Different conditions will exist 2. (a) Asynchronous (b) The exact same conditions will exist 3. (a) Synchronous (b) Different conditions will exist 4. (a) Synchronous (b) The exact same conditions will exist What type of interrupt occurs (a) when there is an error in a peripheral device and (b) when I/O operations are terminated? 1. (a) External (b) internal 2. (a) External (b) external 3. (a) Internal (b) internal 4. (a) Internal (b) external In a microcomputer, an interrupt from an internal hard disk can be masked out by the computer. 1. True 2. False In microcomputers, which of the following methods can be used to direct the processor to the address of the interrupt of a maskable interrupt? 1. An interrupt code only 2. A ROM lookup table only 3. A ROM/PROM lookup table only 4. An interrupt code and a ROM/PROM lookup table IN ANSWERING QUESTIONS 5-5 THROUGH 5-11, SELECT FROM THE FOLLOWING LIST THE INTERRUPT CLASS THAT MATCHES THE CONDITION OR PRIORITY DESCRIBED IN EACH QUESTION. 5-5. 5-6. 5-7. 5-8. 5-9. 5-10. 5-11. 5-12. 5-13. 1. Class I 2. Class II 3. Class III 4. Class IV An RTC overflow has occurred. An intercomputer timeout has occurred. The highest priority interrupt that can occur in the computer. A power out of tolerance has occurred. The computer will execute a power failure processing routine. An input chain interrupt has occurred, An illegal op code has been executed in the CPU. Lower level interrupts can be disarmed and/or armed by software. 1. True 2. False Which of the following interrupts can usually be locked out by software? 1. Power fault 2. External interrupt 3. CPU instruction fault 4. IOC instruction fault interrupt 28

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5-14. In newer computers, which of the following methods can be used to retain multiple interrupt codes of the same class? 1. Interrupt stack only 2. Interrupt queue only 3. Both interrupt stack and queue 4. Index registers 5-15. For an interrupt signal in a particular class to be indicated to the CPU, what minimum number of interrupts must be present? 1. One 2. Two 3. Three 4. Four A. Terminate current program execution B. Lock out all interrupts C. Store program and register data D. Retrieve interrupt processor data E. Enter executive state and enable desired interrupts F. Execute interrupt processor program G. Return to original process Figure 5-A.--Interrupt handling process steps. IN ANSWERING QUESTIONS 5-16 THROUGH 5-23, REFER TO FIGURE 5-A ABOVE AND FIGURE 5-9 ON PAGE 5-13 OF THE TRAMAN. SELECT THE MOST APPROPRIATE INTERRUPT HANDLING PROCESS STEP FOR THE PROCESS DESCRIBED IN EACH QUESTION. 5-16. New interrupts are locked out to protect the integrity of the process that ensures returning to the same conditions after processing the interrupt. 5-17. 5-18. 5-19. 5-20. 5-21. The step in which the interrupt process will be initiated. 1. A 2. B 3. C 4. D In newer computers, a separate register set for each task and executive state is used, and these registers are disabled and the contents protected until the appropriate state is entered. 1. A 2. B 3. C 4. D The computer enters the required executive state and enables the interrupts that in turn interrupt the interrupt processor after the status registers are loaded. 1. B 2. C 3. D 4. E The new executive state registers are loaded with the interrupt processor program data after the register data is saved. 1. B 2. C 3. D 4. E The current process’s register data is stored with at least the contents of the program counter and status register(s). 1. A 2. B 3. C 4. D 1. A 2. B 3. C 4. D 29

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5-22. The first instruction of an interrupt routine is executed after the interrupt code words are sampled. 1. D 2. E 3. F 4. G 5-23. The program counter and status register(s) is/are reloaded with the saved data. The next instruction, prior to the interrupt (instruction 4), is called up by the program counter. 1. D 2. E 3. F 4. G 5-24. Less time is required to access control memory than to access main memory. 1. True 2. False 5-25. Where is cache memory usually located in a computer? 1. In main memory 2. In the I/O section 3. Between the CPU’s control and ALU sections 4. Between main memory and the CPU 5-26. For rapid data transfers, what two types of semiconductor devices are usually used by cache memories? 1. Bipolar DRAMs and MOS SRAMs 2. Bipolar SRAMs and bipolar DRAMs 3. MOS SRAMs and MOS DRAMs 4. MOS DRAMs and bipolar SRAMs 5-27. 5-28. 5-29. 5-30. 5-31 In terms of access and capacity of a cache memory, a cache memory is usually on the order of one magnitude (a) than main (slower; faster) memory and its capacity is two orders of magnitude (b) than main memory. (less; more) 1. (a) Slower (b) less 2. (a) Slower (b) more 3. (a) Faster (b) less 4. (a) Faster (b) more Which of the following methods can be used by a cache memory to indicate which entries of main memory have been copied into it? 1. A hit 2. A tag store 3. An identifier 4. Both 2 and 3 above Which of the following properties pertain(s) to cache memory? 1. 2. 3. 4. A high-speed memory A logical network and an old entries replacement method Timing and control All of the above To indicate that data from the requested address is present, which, if any, of the following terms is used? 1. Hit 2. Miss 3. Tag 4. None of the above What area of cache memory writes only to the directories? 1. Updates 2. Invalidates 3. Searches 4. Tags 30

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5-32. What cache process is performed by a requestor other than the CPU within? 1. Main 2. Mapping 3. Eavesdrop 4. Searching IN ANSWERING QUESTIONS 5-33 THROUGH 5-36, SELECT FROM THE FOLLOWING LIST THE CACHE MAPPING TECHNIQUE DESCRIBED IN EACH QUESTION. 5-33. 5-34. 5-35. 5-36. 5-37. 5-38. 5-39. 1. Direct mapping 2. Fully associative mapping 3. Set associative mapping Is the most flexible cache mapping technique with regards to where data can reside. Combines the best cache mapping techniques. Main memory locations can only be copied into one location in cache. If cache is full, a replacement algorithm is used to decide which block gets replaced by new data. What cache read method can be used to present the cache and main memory with the reference simultaneously? 1. Look-aside, serial read 2. Look-aside, parallel read 3. Look-through, serial read 4. Look-through, parallel read In a look-through read, the cache is checked last. 1. True 2. False Optimum cache replacement would be psychic and have perfect knowledge of the future. What cache replacement policy, if any, comes closest to the optimum cache replacement? 1. LRU 2. FIFO 3. Random 4. None, all are very different 5-40. Instruction routines in a ROM are considered to have which of the following characteristics? 1. Permanent and volatile 2. Permanent and nonvolatile 3. Temporary and volatile 4. Temporary and nonvolatile 5-41. Permanent software loaded as firmware is the process known by which of the following terms? 1. Boot 2. Bootstrap 3. Boot up 4. Each of the above 5-42. An NDRO in a militarized mainframe or minicomputer is usually located in which of the following places? 1. In the CPU module 2. In the chassis that contains CPU’s pcbs 3. Either 1 or 2 above, depending on whether it is a mini or mainframe computer 4. On one or more IC chips of a CPU/memory pcb 5-43. Diagnostics programs on an NDRO include all of the following items except which one? 1. Test the timer 2. Load failure analysis 3. Memory and interface tests 4. Computer interconnection system IN ANSWERING QUESTIONS 5-44 THROUGH 5-47, SELECT FROM THE FOLLOWING LIST THE AREA OF A BIOS DESCRIBED IN EACH QUESTION 5-44. 5-45. 5-46. 1. Diagnostic testing 2. Environmental inventory 3. Boot procedure Testing the video, interrupt controller, CPU register and flags, or the keyboard. A prompt is displayed to let you know the microcomputer is ready to use. The ROM chip program searches for the operating system files. 31

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5-47. The number of printers and serial ports is determined. 5-48. The ALU obtains the data required to perform arithmetic and logical calculations from which of the following places? 1. Timing circuits 2. Operands only 3. Designated CPU registers only 4. Operands and designated CPU registers 5-49. To perform computations, which of the following methods is/are used in addition and subtraction operations? 1. Radix minus one only 2. Radix minus two only 3. Conversion only 4. Radix minus one, radix minus two, and conversion 5-50. The destination of the results of ALU operations may include which of the following places? 1. Timing circuits 2. Registers only 3. Operands only 4. Registers and operands 5-51. Computers can be designed to use which of the following word-length operands to carry out arithmetic operations? 1. Whole-word, half-word, and quarter-word operands only 2. Single-length word operands only 3. Double-length word operands only 4. Whole-word, half-word, quarter-word, single-length word, and double-length word operands 5-52. Double-length memory word operands will be used for mathematical operations when the size of the result would be (a) than the (less; greater) length of either of the registers used to provide inputs to the ALU or the operands being input to the ALU are (b) than a single word. (larger; smaller) 1. (a) Less (b) larger 2. (a) Less (b) smaller 3. (a) Greater (b) larger 4. (a) Greater (b) smaller IN ANSWERING QUESTIONS 5-53 THROUGH 5-56, SELECT FROM THE FOLLOWING LIST THE ITEM USED BY THE ALU IN ARITHMETIC OR LOGICAL CALCULATIONS DESCRIBED IN EACH QUESTION. 5-53. 5-54. 5-55. 5-56. 5-57. 5-58. 1. Flags 2. Selectors 3. Counters Used to keep track of shifts. A carry or borrow condition is indicated. Used to transfer data between various registers in the ALU. Used to indicate the status of the last logical calculation. What method is used to represent a integer number? 1. R’s minus 1 2. R’s minus 2 3. Fixed-point 4. Floating-point For whole numbers, what is the maximum absolute decimal value that can be contained in a 6-bit register? 1. 31 2. 32 3. 63 4. 64 32

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5-59. 5-60. 5-61. 5-62. 5-63. A zero in what (a) position indicates a positive number and a one in what (b) position indicates a negative number? 1. (a) msb (b) lsb 2. (a) msb (b) msb 3. (a) lsb (b) lsb 4. (a) lsb (b) msb In a 6-bit register, the largest positive value that can be contained is what decimal number? 1. 31 2. 32 3. 63 4. 64 When floating-point operations are performed, the radix point must be aligned properly. The alignment of the radix point takes place at which of the following times? 1. During arithmetic operations only 2. After arithmetic operations only 3. Either during or after arithmetic operations, depending on the type of operation 4. Before arithmetic operations In floating-point operations, what is the fractional portion of the number called? 1. Characteristic 2. Mantissa 3. Radix 4. Sign In a number, the radix point is usually placed in what location? 1. Between the sign bit and the msb of the characteristic 2. Between the sign bit and the lsb of the characteristic 3. Between the sign bit and the lsb of the mantissa 4. Between the sign bit and the msb of the mantissa IN ANSWERING QUESTION 5-64, REFER TO FIGURE 5-15, FRAME A, ON PAGE 5-21 IN THE TRAMAN. 5-64. 5-65. 5-66. 5-67. 5-68. For which of the following reasons is zero extended through the most significant 16 bits of the word that contains the characteristic? 1. The integer is a positive number 2. The integer is a negative number 3. The mantissa is a positive number 4. The mantissa is a negative number Where the most accuracy is required during floating-point operations, (a) what format is used with two 32-bit words and (b) what is the relationship of the characteristic to the mantissa? 1. (a) Single-precision (b) Characteristic is smaller 2. (a) Single-precision (b) Characteristic is larger 3. (a) Double-precision (b) Characteristic is smaller 4. (a) Double-precision (b) Characteristic is larger Under which of the following conditions are the mantissa’s results rounded up? 1. When the mantissa is less than one-half of one only 2. When the mantissa is greater than one-half of one only 3. When the mantissa is equal to or less than one-half of one 4. When the mantissa is equal to or greater than one-half of one What type of floating-point interrupt condition, if any, exists when there is a positive excess? 1. Overflow 2. Underflow 3. Divisor 4. None, there is no floating point interrupt What method does the ALU use to perform arithmetic and logical instructions? 1. Logical quotients of the logic gates 2. Logical products of the logic gates 3. Logical sums of the logic gates 4. Logical differences of the logic gates 33

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5-69. 5-70. The ALU portion of a computer can be designed to perform a wide variety of arithmetic operations. Which of the following are the only arithmetic capabilities that computers can have to perform all arithmetic operations? 1. 2. 3. 4. Addition and multiplication Addition and subtraction Subtraction and multiplication Subtraction and division A computer has no dedicated square root instruction. Which of the following instructions could be used to perform the square root function? 1. Addition and subtraction only 2. Addition and comparison only 3. Subtraction and comparison only 4. Addition, subtraction, and comparison 34 5-71. Logical ALU functions include all of the following except which one? 1. AND and OR 2. NOT 3. Compare 4. BAM 5-72. A numeric data coprocessor operates in (a) what manner with the CPU and independent of the CPU using (b) which of the following buses? 1. (a) Parallel (b) Different buses from the CPU 2. (a) Parallel (b) The same buses as the CPU 3. (a) Serial (b) Different buses from the CPU 4. (a) Serial (b) The same buses as the CPU

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ASSIGNMENT 6 Textbook Assignment: “Central Processing Units and Buses,” chapter 5, pages 5-24 through 5-29; and “Computer Memories,” chapter 6, pages 6-1 through 6-20. 6-1. 6-2. 6-3. 6-4. The buses in a computer are controlled by (a) what functional area and (b) what type of communication path is used? 1. (a) CPU (b) serial 2. (a) CPU (b) parallel 3. (a) Memory (b) serial 4. (a) Memory (b) parallel All the following types of information are transferred over buses except which type? 1. Power 2. Data 3. Commands 4. Instructions The preferred method of transfer for data/information between system components is which of the following? 1. Control bus 2. Common data bus 3. Operand bus 4. Address bus What IEEE standard is used for a simple 32-bit backplane bus? 1. 1196 2. 1296 3. 896.1 4. 1014 A. Control bus B. Address bus C. Data bus D. Instruction (I) bus E. Operand (C) bus F. I/O mem bus or IOC bus G. Time multiplexed bus H. DMI bus Figure 6-A.—Buses. IN ANSWERING QUESTIONS 6-5 THROUGH 6-11, REFER TO FIGURE 6-A. SELECT THE NAME(S) OF THE BUS OR BUSES THAT IS/ARE DESCRIBED IN EACH QUESTION. 6-5. 6-6. 6-7. Has all the signals necessary to define any of the possible memory address locations within the computer or a module. 1. A 2. B 3. C 4. D Can be used to transfer instructions from memory to the CPU. 1. A 2. B 3. C only 4. Both C and D Allows communication between the CPU and memory or the CPU and the IOC. 1. C 2. D 3. E 4. F 35

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6-8. 6-9. 6-10. 6-11. (b) source (b) destination6-12. 6-13. Controlled by the IOC; responds to the CPU by using the O bus. 1. E 2. F 3. G 4. H Transmits individual signals to control and coordinate the operations of the computer. 1. A 2. B 3. C 4. D Transmits addresses and data by using clock cycles. 1. E 2. F 3. G 4. H Acts as a requester; sends requests from other computers. 1. E 2. F 3. G 4. H What device accepts requests and uses a priority network to determine the order in which it is to respond to the requesters? 1. Operand bus extender 2. REI bus extender 3. CPU 4. DMI Regardless of whether a computer has an IOC or not, the CPU will control all buses. 1. True 2. False 6-14. 6-15. 6-16. 6-17. 6-18. 36 In bus communications, which of the following factors relating to the data being transferred must be considered? 1. Source only 2. Destination only 3. Transfer priority only 4. Source, destination, and transfer priority Bus requests may be made by all of the following parts except which one? 1. CPU 2. IOC 3. Memory 4. DMI Holding registers are used by source and destination sections to prevent data loss and to help coordinate data exchange. 1. True 2. False In the exchange of data on the buses, (a) what logic generates a ready signal when data is in the holding register and on the bus and (b) what logic sends an accept signal? 1. (a) Source (b) source 2. (a) Source (b) destination 3. (a) Destination 4. (a) Destination Which of the following items is/are stored in main memory? 1. Data and programs only 2. Calculations and operands only 3. Data, programs, and PROMS 4. Data, programs, calculations, and operands

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A. Memory address B. Capacity C. Access time D. Destructive readout E. Non-destructive readout F. Volatile memory G. Nonvolatile memory Figure 6-B.—Terminology. IN ANSWERING QUESTIONS 6-19 THROUGH 6-24, REFER TO FIGURE 6-B. SELECT THE TERM THAT MATCHES THE DESCRIPTION IN EACH QUESTION. 6-19. 6-20. 6-21. 6-22. Time interval from the instant a request for data is initiated until the data is available for use. 1. A 2. B 3. C 4. D The output side of a flip-flop is read from memory without having to be rewritten. 1. D 2. E 3. F 4. G The power to the computer is turned off and the contents of memory are retained. 1. D 2. E 3. F 4. G The particular location of a larger memory array where a packet of information is located. 1. A 2. B 3. C 4. D 6-23. 6-24. 6-25. 6-26. 6-27. 6-28. Power is shut off to the computer and the contents of the semi-conductor memory are lost. 1. D 2. E 3. F 4. G The data is lost when it is read from memory. 1. A 2. B 3. C 4. D A memory unit that can receive requests from more than one CPU or I/O section is known as which of the following types of memories? 1. Memory pcb 2. Single-inline memory module 3. Multiported memory module 4. Dual-action memory module Pcb type memories are usually composed of which of the following memory types? 1. 2. 3. 4. Semiconductor Core Film Both 2 and 3 above In a typical square form memory, the intersection of an x row and y column is called a 1. memory word address 2. memory word 3. memory module 4. memory cell The x rows and y columns of a typical memory will be equal in number. 1. True 2. False 37

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6-29. 6-30. 6-31. 6-32. 6-33. 6-34. Memory operations in most computers usually include which of the following items? 1. Control circuits 2. Timing circuits 3. Memory cycle 4. All of the above Memory interface circuits include which of the following items? 1. Address register 2. Communication lines 3. Interfacing register 4. Both 2 and 3 above A word is read from memory, then rerouted back through the Z register to be rewritten. This is what type of memory? 1. Non-destructive readout 2. Destructive readout 3. Hardwired 4. ROM The priority of a memory request is evaluated by which of the following devices? 1. Control circuits 2. Address register 3. Z register 4. C P U Memory read/write enables are provided by which of the following devices? 1. Control circuits 2. Timing circuits 3. CPU 4. I/O control During a complete memory cycle, which of the following actions occurs first? 1. Registers used for read/write operations are cleared 2. Enables are generated to gate memory address into registers used for read/write operations 3. Memory address translation is accomplished 4. Interface logic acknowledges reading data from memory 6-35. To locate a memory address word, the computer uses which of the following items in memory? 1. Timing circuits 2. Control circuits 3. Interface circuits 4. Memory logic 6-36, 6-37. 6-38. 6-39. 6-40. 38 The conversion from a logical to a physical memory address is a function of which of the following items in memory? 1. Memory logic 2. Timing circuits 3. Control circuits 4. Interface circuits In all computers, for every read operation there will always be a corresponding write operation. 1. True 2. False Increasing memory speed using interleaving requires which of the following items? 1. Memory modules of 32 bits 2. A minimum of 8 memory modules 3. More complex CPU and memory control circuitry 4. All of the above When odd parity is used for memory fault detection, all words stored in memory will have which of the following bits? 1. A logic 1 parity bit 2. A logic 0 parity bit 3. An even number of set bits stored at each memory location 4. An odd number of set bits stored at each memory location The memory protection register set is used for which of the following purposes? 1. To restrict read/write operations in portions of memory 2. To protect memory from unplanned power loss 3. To protect against erroneous write instructions 4. To limit access of memory to authorized users

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6-41. In a memory segment within the protected area with all three bits of the memory protection control register set, which of the following operations are allowed? 1. Execute protected 2. Write protected 3. Read protected 4. All of the above 6-42. Memory lockout is used by larger computers to prevent access to particular areas of memory by task state instructions. Which of the following statements describes the lockout function? 1. It is disabled when the CPU enters a particular executive or interrupt state and enabled when the CPU enters the task state 2. It is enabled when the CPU enters a particular executive or interrupt state and enabled when the CPU enters the task state 3. It is enabled when the CPU enters a particular executive or interrupt state and disabled when the CPU enters the task state 4. It is disabled when the CPU enters a particular executive or interrupt state and disabled when the CPU enters the task state 6-43. Compared with semiconductor memories, magnetic memories have which of the following advantages? 1. They cost less 2. They are faster in terms of storage and access 3. They require less power and they are volatile 4. They require less power and they are nonvolatile 6-44. The state of a core or film is changed by which of the following conditions? 1. Current flow in the opposite direction of sufficient magnitude to overcome the magnetic field and to magnetize in the new direction 2. Current flow in the same direction of sufficient magnitude to match the magnetic field and to magnetize in the old direction 3. Voltage amplitude of a sufficient magnitude to overcome the magnetic field and to magnetize in the new direction 4. Current flow in the opposite direction of sufficient magnitude to overcome the magnetic field and to magnetize in the old direction 6-45. Compared with core memory, film memory has which of the following advantages? 1. Increased speed of read/write operations and less power required 2. More compact and durable 3. Twice as many memory cells can be put in the same space for the same amount of power 4. All of the above 6-46. Each ferrite core can store what total number of bits? 1. One 2. Two 3. Three 4. Four 6-47. In a four-wire core winding, what is the physical make up of the windings that are strung through each and every core? 1. 1 drive line, 1 sense line, and 1 inhibit line 2. 2 drive lines, 1 sense line, and 2 inhibit lines 3. 2 drives lines, 1 sense line, and 1 inhibit line 4. 2 drive lines, 2 sense lines, and 1 inhibit line IN ANSWERING QUESTIONS 6-48 THROUGH 6-51, SELECT THE CORE LINE THAT MATCHES THE DESCRIPTION IN EACH QUESTION. 1. Drive line 2. Sense line 3. Inhibit line 39

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6-48. 6-49. 6-50. 6-51. 6-52. 6-53. 6-54. 6-55. Detects the change in state of the core from one to zero. Each line provides 1/2 of the current necessary to change the state of the core. Prevents changing the core from a zero to a one. In a three-wire core, this line performs the same function as in the four-wire core. To simplify addressing, reading, and writing operations, magnetic cores are arranged in which of the following ways? 1. In hierarchical patterns 2. In matrices 3. In planes 4. In stacks Which core in an array will be switched from one state to another? 1. A core with a full read or write current passing through it 2. A core with a half read current passing through it 3. A core with a half write current passing through it 4. A core with a half read or write passing through it In a core array the inhibit line is threaded in (a) with the x or y drives lines (series, parallel) and the sense line is threaded through (b) core. (each, every other) 1. (a) Series (b) each 2. (a) Parallel (b) each 3. (a) Series (b) every other 4. (a) Parallel (b) every other What is the basic building block of the memory stack? 1. Matrix 2. Array 3. Plane 4. Quadrant 40 6-56. 6-57. 6-58. 6-59. 6-60. The address register bits are used to translate the bits to make which of the following bit selections? 1. Stack only 2. Inhibit upper and lower stack only 3. X and Y primary, secondary, and diode only 4. X and Y primary, secondary, and diode; stack; and inhibit upper and lower stack Which selectors are activated only when writing zeros? 1. Inhibit 2. X and Y primary 3. X and Y secondary 4. X and Y read/write diode In a core read/write cycle, the read current is designed to change the state of the core(s) to (a) what value; and the write current is designed to change the state of the core(s) from (b) what value to (c) what value? 1. (a) Zero (b) zero 2. (a) Zero (b) one 3. (a) One (b) zero 4. (a) One (b) one (c) one (c) one (c) one (c) one The process of reading cores to the zero state is known as which of the following types of readout? 1. 2. 3. 4. Destructive readout Non-destructive readout Volatile readout Nonvolatile readout In a core memory, a restore cycle is necessary after data has been read from memory for what reason, if any? 1. To change the state of each selected core from zero to one 2. To change the state of all the cores from one to zero 3. To sense the state of each core 4. None, a restore cycle is not needed

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6-61. During a restore operation of zeros in a three-wire core, the absence of write current on which of the following lines will leave the cores in the zero state? 1. Digit 2. Word 3. X drive 4. Y drive 6-62. What specific number of paired film spots is used for each bit position? 1. One 2. Two 3. Three 4. Four 6-63. Current flow through which of the following lines will magnetize a film spot? 1. Drive 2. Word only 3. Sense/digit only 4. Word or sense/digit, depending on the function 6-64. In the application of external fields, the longitudinal fields are produced by passing the current (a) in which of the following ways and the transverse fields are produced by passing the current (b) in which of the following ways? 1. (a) Down the word line (b) In the proper direction along the sense/digit line 2. (a) In the proper direction along the word line (b) Down the sense/digit line 3. (a) In the proper direction along the sense/digit line (b) Down the word line 4. (a) In the proper direction along the sense/digit line (b) Down the drive line 6-65. In a film memory, a packet stores what specific number of bits of data? 1. One 2. Two 3. Three 4. Four 6-66. Which, if any, of the following devices makes the mated film cells less susceptible to the disturbance from other cells in close proximity to them? 1. Ground plane 2. Insulator 3. Keeper 4. None of the above 6-67. How is mated film memory structured? 1. Bit organized 2. Stack organized 3. Word organized 4. Array organized 6-68. What item is the basic building block of the film memory stack? 1. Matrix 2. Array 3. Packet 4. Plane 6-69. The memory capacity of a film core storage device is determined by which of the following factors? 1. Size of the computer 2. Number of packets only 3. Size of the array in the memory stack only 4. Number of packets and the size of the array in the memory stack 6-70. In film storage, up to how many words can be selected at each memory location? 1. One 2. Two 3. Three 4. Four 41

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6-71. 6-72. 6-73. The address register bits used to translate the bits to make selections are processed in which of the following sequences? 1. Word at the address location, memory location, and stack 2. Stack, word at th eaddress location, memory location 3. Word at the address location, stack, and memory location 4. Stack, memory location, and word at the address location A mated film memory cell is read by which of the following methods? 1. A current is generated along the digit line and a transverse field is applied to the thin film cell 2. A current is generated along the sense line and a transverse field is applied to the thin film cell 3. A current is generated along the word line and a transverse field is applied to the thin film cell 4. A current is generated along the word line and a longitudinal field is applied to the thin film cell What factor will determine the recorded state of the film? 1. The direction of the cell vector rotation induced film signal on the sense/digit line 2. The direction of the cell vector rotation induced film signal on the word line 3. The magnitude of the cell vector rotation induced film signal on the digit line 4. The direction of the cell vector rotation 6-74. 6-75. When a one is to be stored, (a) what is the direction of the bit current in relationship to that used to store a zero and (b) what field steers the vector to the one state? 1. (a) The same (b) Transverse 2. (a) The same (b) Longitudinal 3. (a) Reversed (b) Transverse 4. (a) Reversed (b) Longitudinal In a restore operation of a film memory, what factor determines the direction of the digit current on the sense/digit line? 1. Binary value of the data register 2. Direction of current on the word line 3. The easy axis 4. The hard axis induced film signal on the sense line 42

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ASSIGNMENT 7 Textbook Assignment: “Computer Memories,” chapter 6, pages 6-20 through 6-32; and “Input/Output (I/O) and Interfacing,” chapter 7, pages 7-1 through 7-20. 7-1. Semiconductor memories are known by all of the following terms except which one? 1. Read/write memory 2. Scratch-pad memory 3. Random access memory 4. Read-only memory 7-2. Semiconductor memories have which of the following characteristics? 1. Destructive readout and volatile 2. Destructive readout and nonvolatile 3. Non-destructive readout and volatile 4. Non-destructive readout and nonvolatile 7-3. Each RAM chip contains which of the following items? 1. One memory cell only 2. One memory cell and the logic to support it only 3. Large numbers of memory cells only 4. Large numbers of memory cells and the logic to support them 7-4. On RAM chips, memory cells are organized based on which of the following factors? 1. Number of memory words only 2. Number of bits per word only 3. Number of memory words and number of bits per word 4. Number of gate arrays 7-5. The transistors used in flip-flops of static RAM may be MOS or bipolar. Compared to MOS, bipolar has what advantage, if any? 1. Higher density 2. Higher access speed 3. Requires less space 4. None, they both have the same advantages 7-6. In a static RAM, the address lines are used to enable the addressed memory cell flip-flop circuit by row and column number. 1. True 2. False IN ANSWERING QUESTION 7-7, REFER TO FIGURE 6-31 ON PAGE 6-24 OF THE TRAMAN. 7-7. Data is stored into, or read from, the memory cells of SRAM via a total of how many lines? 1. O n e 2. Two 3. Three 4. Four 7-8. The (a) address lines and the (b) I/O data lines are usually tied to what buses? 1. (a) Computer or memory system bus (b) Computer or memory system bus 2. (a) Computer or memory system bus (b) Data bus 3. (a) Data bus (b) Computer or memory system bus 4. (a) Data bus (b) Data bus 7-9. During a SRAM read cycle, what is (a) the status of the write enable and (b) the mode of the data buffers? 1. (a) True (b) input 2. (a) True (b) output 3. (a) False (b) input 4. (a) False (b) output IN ANSWERING QUESTION 7-10, REFER TO FIGURE 6-32 ON PAGE 6-25 OF THE TRAMAN. 43

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7-10. Each dynamic RAM cell consists of which of the following devices? 1. 2. 3. 4. One MOS transistor only One tiny capacitor only One MOS transistor and one tiny capacitor only Many MOS transistors and several tiny capacitors 7-11. DRAM cells do not retain their charged state for 7-12. 7-13. 7-14. more than a few milliseconds. This degradation is due to which of the following factors? 1. Time only 2. Temperature only 3. Time and temperature 4. Temperature and power To retain their charged state, DRAMs must be refreshed. Of the following methods, which one is (a) more cost effective because it uses what (b) device? 1. (a) (b) 2. (a) (b) 3. (a) (b) 4. (a) (b) Internal Battery backup Internal Single refresh address generator External Battery backup External Single refresh address generator In DRAM organization, the data input and data output lines may be tied together in what type of application, if any? 1. 2. 3. One that uses a unidirectional data bus One that uses a bidirectional data bus None, they are never tied together Compared to a SRAM, a DRAM has all except which of the following advantages? 1. It retains its charged state 2. It has lower power consumption 3. It has higher density 4. It is less complex 44 7-15. 7-16. Programs stored on ROM are often referred to as firmware for which of the following reasons? 1. They are software only 2. They are hardware only 3. They are more hardware than software 4. They write data into the ROM address Compared to RAM, ROM has all of the same operational characteristics except which of the following? 1. Allows random access 2. Uses a row/column arrangement 3. Can be read by normal computer accessing methods 4. Can be written to by normal computer accessing methods 7-17. ROM has what primary use? 1. 2. 3. 4. Stores data addresses for recovery purposes Allows the computer to perform I/O operations Provides a user interface through a panel Stores the content of the computer registers for interrupt processing — 7-18. The acronym BIOS stands for what term? 1. Basic input/output system 2. Bipolar input/output status 3. Binary input/output status 4. Bidirectional input/output system 7-19. The acronym NDRO stands for what term? 1. 2. 3. 4. Non-destructive readover Non-destructive readout Non-dynamic readover Non-dynamic readout IN ANSWERING QUESTION 7-20, REFER TO FIGURE 6-35 ON PAGE 6-28 OF THE TRAMAN.

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7-20. In the example, the ROM chip memory array has a total of (a) how many decoders and (b) how many lines are input to these decoders? 1. (a) 2 (b) 12 2. (a) 2 (b) 13 3. (a) 4 (b) 12 4. (a) 4 (b) 13 7-21. ROMs may be made of which of the following materials? 1. Hardwired and magnetic only 2. Fusible links only 3. MOS and bipolar transistors only 4. Hardwired, magnetic, fusible links, and MOS and bipolar transistors 7-22. To perform ROM operations, which of the following circuits are used? 1. Timing and control signals only 2. Registers, flip-flops, and internal buses only 3. Internal buses, timing, and control signals only 4. Timing, control signals, registers, flip-flops, and internal buses 7-23. Compared to PROM, an erasable PROM has what additional advantage, if any? 1. It can be used over and over again without reprogramming 2. It can be erased and reprogrammed 3. It can be field programmed by an authorized technician 4. None, there is no additional advantage 7-24. While still in the circuit, which of the following PROMS can (a) be programmed and (b) erased? 1. (a) EAPROM/EEPROM (b) EAPROM/EEPROM 2. (a) EAPROM/EEPROM (b) UV EPROM 3. (a) UV EPROM (b) EAPROM/EEPROM 4. (a) UV PROM (b) UV PROM 7-25. 7-26. 7-27. 7-28. 7-29. A device that serves as a shared entry point from a local-area network into a larger information resource is which of the following? 1. Gateway 2. Input/output adapter (IOA) 3. Input/output controller (IOC) 4. Data terminal equipment (DTE) A function that transfers status by using the appropriate control signals from a transmitting device to the receiving computer is which of the following? 1. Input data (ID) 2. Output data (OD) 3. External function (EF) 4. External interrupt (EI) The I/O processor controls which of the following transfers? 1. The transfer of data between registers 2. The transfer of information between main memory and the CPU 3. The transfer of timing signals between the ALU and the CPU 4. The transfer of information between main memory and the external equipments Establishing, directing, and monitoring transfers with external equipments are the functions of which of the following devices? 1. C P U 2. IOA 3. IOC 4. Bidirectional bus Changes to input and output control and data signal voltages are functions of which of the following devices? 1. CPU 2. IOA 3. IOC 4. Bidirectional bus 45

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7-30. The type of connectors for the I/O channels or ports will be dictated by which of the following factors? 1. Interfacing 2. Serial I/O 3. Parallel I/O 4. Voltage levels 7-31. The driver circuits are used for which of the following tasks? 1. To pass data to the IOC 2. To set/clear output registers 3. To pass interface signals to the IOC 4. To pass interface and data signals to the external equipments 7-32. External microcomputer I/O operations are usually 7-33< handled by which of the following devices? - 1. A single serial port 2. A single parallel port 3. A single printed circuit board 4. Multiple printed circuit boards Examples of consistencies found in the architecture of a computer’s I/O section include which of the following? 1. Types of external equipments 2. The arrangement and format of the information exchanged 3. The type and number of interfaces possible 4. The type of circuits used to process I/O information 7-34. If a printer senses a paper jam during a print operation, which of the following actions should occur? 1. A control word should be sent by the computer specifying an error condition 2. A control word should be sent to the computer specifying an error condition 3. A data word should be sent by the computer specifying a special condition 4. A data word should be sent to the computer specifying a special condition 7-35. Handshaking is also known by which of the following terms? 1. Function control word 2. External interrupt words 3. Both 1 and 2 above 4. Alphabetic and numeric data exchange 7-36. The type of interface used when all bits of 7-37. 7-38. 7-39. 7-40. 46 information represented by a byte or word are input or output simultaneously is known as which of the following formats? 1. Serial format 2. Parallel format 3. 8-bit word format 4. 32-bit word format Command instructions provide control over which of the following areas/operations? 1. 2. 3. 4. Main memory CPU operations IOC single and dual channel operations Interrupt driven I/O operations The I/O command start instruction accomplishes which of the following actions? 1. Specifies an IOC, then halts further CPU processing 2. References specific main memory addresses 3. Executes a previously stored IOC command 4. Indicates to the CPU that the command has been processed The CPU will delay processing while waiting for an I/O operation only during which of the following actions? 1. 2. 3. 4. Execution of input chain operations Execution of output chain operations Actual data transfer operations Executions of an I/O command start instruction The actual execution of chaining instructions is independent of the CPU. 1. True 2. False

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7-41. Input and output chains deal primarily with which of the following activities? 1. The processing of IOC control words 2. Specification of the locations of external status words 3. Transfer of blocks of information 4. Addresses provided by the load control memory command 7-42. Data transfer between the computer and external equipments will take place when which of the following conditions is/are met? 1. The memory areas for the data have been specified by the computer programs 2. The external equipment is ready to send or receive data and has sent a request signal 3. Initiate input/output or equivalent instruction is executed by the CPU 4. All of the above 7-43. Which of the following is one of the constants in all I/O operations? 1. Data words will always be limited to 16 bits 2. When the data transfer will begin 3. The circuitry required to connect external equipments 4. A serial data interface between the computer and external equipments 7-44. In I/O operations, communications with the external equipment require which of the following devices/operating modes? 1. An IOC 2. A single channel operating mode 3. Circuitry that specifies a sequence of events 4. A dual channel operating mode 7-45. When an index address in main memory is specified by an external equipment during an I/O operation, the computer is operating in which of the following modes? 1. Intercomputer channel mode 2. Externally specified index mode 3. Externally specified address mode 4. Dual channel mode 7-46. In I/O operations, which of the following is one of the primary uses of registers? 1. To enable and route data information only 2. To enable and route control information only 3. To enable and route both control and data information 4. To provide timing circuitry for I/O interfacing 7-47. Decoder circuits are used for which of the following purposes? 1. Main timing 2. I/O processors 3. Address translation 4. Data buffers 7-48. Status registers are used for which of the following purposes? 1. To enable and route data using the internal bus system 2. To hold or buffer data during interchanges between the very fast CPU and slower external equipments 3. To hold control data generated by main memory or the CPU when operating with very fast external equipments 4. To hold information for the CPU that indicates the operating condition and current activities of the external equipments 7-49. In computers with an IOC, once started the master clock can be stopped when which of the following actions occurs? 1. Computer master clear 2. External interrupt 3. Input data request 4. Output data request 7-50. In computers with an IOC, the master clock is started when which of the following actions occurs? 1. The computer is initially powered on 2. The computer is auto restarted 3. Both 1 and 2 above 4. An execute master clear is issued 47

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7-51. The I/O control circuits are controlled by which of 7-56. I/O control memory words are set aside in main the following means? 1. The CPU 2. The IOC 3. The I/O master clock 4. The computer program 7-52. A sequential set of memory locations that contains data to be sent out or an area that is set aside for data to be received is known by which of the following items? 1. An input register 2. An output register 3. Both 1 and 2 above 4. A buffer 7-53. Which of the following operations is/are unbuffered? 1. 2. 3. 4. Data is transferred between the computer and the external devices Data is exchanged between the CPU and the various parts of the computer Both 1 and 2 above Data is exchanged between external devices offline 7-54. The I/O processor’s sequencing circuits control which of the following actions? 1. The order in which events will be executed based upon the translated function code 2. The order in which memory addresses of data to be retrieved or stored will be acted on 3. The order in which external equipment output requests will be acknowledged 4. The order in which external interrupts will be acted on by the computer 7-55. The CPU interfaces with the I/O processor through which of the following means? 1. Special interface circuits 2. The CPU’s I/O instructions 3. The sequencing circuitry 4. The maintenance console memory to control which of the following actions? 1. Data transfers for I/O buffer functions 2. The sequence of I/O operations 3. Parallel operations 4. Serial operations 7-57. In parallel operations, each I/O channel has its own block of memory addresses for which of the following operations? 1. Input and output only 2. External function only 3. External interrupt operations only 4. Input, output, external function, and external interrupt operations 7-58. Serial operations are affected by which of the following factors? 1. 2. 3. 4. Character size, parity selection, and asynchronous interfacing only Parity selection, baud rate, and synchronous interfacing only Character size, parity selection, and synchronous and asynchronous interfacing only Character size, parity selection, baud rate, and synchronous and asynchronous interfacing 7-59. Monitor words are used for which of the following purposes? 1. To monitor external equipment status 2. To monitor bytes that are to be transferred by the pending operation 3. To store characters for comparison with received data characters 4. To monitor main memory for the next available address for chaining instructions 7-60. Another term for accumulator based I/O is which of the following? 1 Direct CPU interface 2. Direct memory access 3. Interrupt driven I/O 4. Memory mapped I/O 48

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7-61. The CPU handles all I/O transactions by executing one or more instructions for each word of information transferred. This process is known by which of the following terms? 1. Polled I/O 2. Memory mapped I/O 3. Interrupt driven I/O 4. Accumulator based I/O 7-62. In memory mapped I/O, the CPU accesses the I/O device by which of the following means? 1. Tieing peripheral devices directly into the communication bus 2. Placing appropriate addressing information on the bus 3. Checking each channel or port to determine if it has data for input or is ready to accept output data 4. Using an I/O processor for interface between memory and the external equipments 7-63. During direct CPU interface operations, the CPU continuously tests the status register. This technique is known by which of the following terms? 1. Memory mapped I/O 2. Accumulator based I/O 3. Interrupt driven I/O 4. Polled I/O 7-64. The main advantage of direct memory access is which of the following? 1. Speed 2. Reliability 3. Less complicated circuity 4. Maximum utilization of memory 7-65. When the CPU and the DMA attempt to access main memory simultaneously, the CPU has priority. 1. True 2. False 7-66. When a high speed disk drive is used, output data will be in which of the following forms? 1. Octal 2. Binary 3. Octal coded decimal 4. Various; form is dependent on type of interface used 7-67. The technique used when more than one peripheral device is connected to a single port/channel is known by which of the following terms? 1. Daisy chaining 2. Independent request control 3. External interrupt control method 4. Request/acknowledge control method 7-68. When more than one peripheral device is connected to a single port/channel, the priority of a device is determined by which of the following factors? 1. The CPU 2. The I/O controller 3. The computer program 4. The order of connection 7-69. When using a request and acknowledge system, the priority of the functions and channels is determined by which of the following factors? 1. The CPU 2. The I/O controller 3. The computer program 4. The order of connection 7-70. Communication formats are governed by which of the following items? 1. The type of external equipment 2. The speed of the external equipment 3. The interfacing standard 4. The speed of the computer 49

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7-71. 7-72. The compatibility of voltage levels between the 7-74. computer and external equipments is ensured by which of the following means? 1. The CPU 2. The I/O processor 3. The I/O interfacing components 4. The type and number of pins in the cable connectors 7-75. Transfer of data within a digital computer is accomplished internally using which of the following means? 1. Standard I/O interfaces 2. Serial format 3. Parallel format 4. Serial interface board 7-73. The conversion of data for transmission over a serial channel is accomplished by which of the following means? 1. A serial interface board 2. A standard format interface 3. A universal receiver-transmitter 4. I/O control printed circuit board 50 When a universal synchronous-asynchronous receiver transmitter is used, it functions as which of the following devices? 1. A microprocessor 2. An I/O serial interface board 3. An I/O parallel interface board 4. A peripheral device to the microprocessor The universal synchronous-asynchronous receiver transmitter’s specific asynchronous interfacing is controlled by which of the following means? 1. The bidirectional tristate data bus 2. The I/O control printed circuit board 3. The read/write control logic 4. The CPU

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ASSIGNMENT 8 Textbook Assignment: “Input/Output (I/O) and Interfacing,” chapter 7, pages 7-20 through 7-38. 8-1. 8-2. 8-3. 8-4. The read/write control logic accepts control signals from which of the following devices? 1. The data bus 2. The control bus 3. The master clock 4. The USART To program the USART for the applicable interface when it is in an idle state, which of the following signals/words is required? 1. A reset signal 2. A clock signal 3. A new set of data words 4. A new set of control words The universal synchronous-asynchronous receiver transmitter is enabled for reading/writing operations when which of the following signals is true? 1. The WRITE DATA 2. The CHIP SELECT 3. The CONTROL DATA 4. The DATA SET READY When the WRITE DATA (WD) signal is true, it means which of the following things? 1. It indicates the microprocessor is placing data on the data bus 2. It indicates the microprocessor is ready to receive data or control words 3. It identifies the write operation as a data or control word 4. It enables the universal synchronous/asynchronous receiver transmitter for writing operations 8-5. 8-6. 8-7. 8-8. 8-9. When the READ DATA (RD) signal is true, the microprocessor is ready for which of the following activities? 1. To receive data only 2. To receive status words only 3. To receive data and status words 4. To receive clock signals The transmit control logic converts the data bytes stored in the transmit buffer into which of the following forms? 1. An asynchronous bit stream 2. Start bits 3. Stop bits 4. Parity bits A start bit is used for which of the following purposes? 1. To initiate data transfer 2. To alert the output device 3. To control transmit logic 4. To program protocol A parity bit is used for which of the following purposes? 1. To regulate signal flow 2. To specify data type 3. To detect errors 4. Each of the above The receive buffer stores which of the following information? 1. The output bit stream 2. The protocol signals 3. Serial bytes 4. Parallel bytes 51

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8-10. 8-11. 8-12. 8-13. 8-14. The voltage and current characteristics of line drivers/receivers are dictated by which of the following factors? 1. The format 2. The interface 3. Channel/port configurations 4. Type of circuitry (TTL or MOS) The Type A (NTDS) Slow interface format is able to transmit what type(s) of bit groupings? 1. 16 only 2. 30 only 3. 32 only 4. 16,30, or 32, depending on the type of computer The data transmission rate for the Type A (NTDS) Slow format is limited by which of the following factors? 1. The requirement to convert data from serial to parallel 2. The type of equipment used 3. The large voltage change between logic states 4. The long distance the transmission must cover In the Type D (NTDS SERIAL) interface format, information frames are made up of what total number of bits? 1. 32 bits 2. 16 bits 3. 3 bits 4. 8 bits The Type D (NTDS SERIAL) interface format can transmit digital signals up to which of the following lengths? 1. 300 feet 2. 1000 feet 3. 1500 feet 4. The total length of the cable used regardless of its length 8-15. 8-16. 8-17. 8-18. 8-19. 8-20. 52 The Type E (NATO SERIAL) format requires which of the following I/O cables? 1. Coaxial 2. Triaxial 3. Dual coaxial 4. Twisted pairs The Type E (NATO SERIAL) format is most frequently used with which of the following equipment? 1. Mainframe computers 2. Minicomputers 3. Microcomputers The Type F (aircraft internal time division multiplex [TDM] bus) interface format transmits bit groupings consisting of what total number of bits? 1. 16 2. 20 3. 30 4. 32 The Type F (aircraft internal time division multiplex [TDM] bus) interface format can handle which of the following numbers of external devices on one channel? 1. 16 2. 30 3. 32 (including a bus controller) 4. 34 (including a bus controller) The Type G (RS-449) interface format primarily uses which of the following protocols? 1. Request acknowledge 2. Command and response 3. SIS/SOS 4. Interrupt/request The Small Computer System Interface (ANSI X3.131) using one controller can daisy chain up to what maximum number of units? 1. 8 2. 16 3. 30 4. 32

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8-21. The RS-232 interface can be used for which of 8-22. 8-23. 8-24. 8-25. the following types of transfers? 1. Asynchronous parallel only 2. Synchronous parallel only 3. Asynchronous and synchronous parallel 4. Asynchronous and synchronous serial The RS-232 interface can be used with which of the following types of computers? 1. Micros only 2. Mainframes only 3. Minis and mainframes only 4. Micros, minis, and mainframes The RS-232 interface limits cable transfers to what maximum number of feet? 1. 50 2. 100 3. 300 4. 1000 In the RS-232 interface, most peripherals control configuration parameters using which of the following methods? 1. A controller card 2. Dip switches 3. Software 4. VACALES The higher transmission rate of the RS-422 interface is made possible by which of the following techniques? 1. Two separate wires are used 2. The receiver transition period is narrower 3. The grounding requirements are less critical 4. All of the above 8-26. In a token ring network, a station with a message waits until it receives a free token, it then changes the free token to a busy token, and transmits a block of data following the busy token. What term is used for the block of data? 1. Record 2. Server 3. Frame 4. File 8-27. The Ethernet interface is used to transfer which of the following types of data in what format? 1. Serial I/O data in packet format 2. Serial data in string format 3. Parallel I/O data in packet format 4. Parallel I/O data in string format 8-28. The type of cable used for the Ethernet interface is which of the following? 1. Twisted pairs 2. Unshielded coaxial 3. Shielded coaxial 4. Triaxial 8-29. Thin Ethernet interface used in smaller systems can have a maximum cable length of which of the following? 1. 500 feet 2. 600 feet 3. 1000 feet 4. 1500 feet 8-30. The Centronics Compatible Parallel interface uses which of the following types of protocol? 1. Command/acknowledge 2. Interrupt driven 3. Asynchronous 4. Synchronous 8-31. Most floppy disk drives today are controlled by which of the following interfaces? 1. Enhanced small device interface 2. ST-506/412 interface 3. Integrated drive electronics interface 4. RS-422 interface 53

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8-32. 8-33. 8-34. 8-35. 8-36. 8-37. When the ST-506/412 interface is used, the controller card performs which of the following functions for disk drives? 1. Moves the magnetic head 2. Spins the magnetic disk 3. Strips off formatting and control words 4. All of the above When the ST-506/412 is used to interface a hard disk drive, which of the following cabling is required? 1. A 34-pin control cable 2. A 20-pin data cable 3. Both 1 and 2 above 4. A shielded coaxial cable When the ST-506/4 12 is used to interface a floppy disk drive, which of the following cabling is required? 1. A 34-pin control cable 2. A 20-pin data cable 3. Both 1 and 2 above 4. A shielded coaxial cable The enhanced small device interface can transfer data at up to which of the following rates? 1. 5 megabits per second 2. 24 megabits per second 3. 125 megabits per second 4. 1.2 gigabytes per second When the enhanced small device interface is used with a floppy disk drive, which of the following cabling is required? 1. A 34-pin control cable 2. A 20-pin data cable 3. Both 1 and 2 above 4. A shielded coaxial cable All electronics used for the integrated drive electronics interface are located in which of the following areas? 1. The computer motherboard 2. The controller card 3. The integrated CPU 4. The hard drive 8-38. The integrated drive electronics interface can handle disk drives with what maximum capacity? 1. 1 MB 2. 80 MB 3. 180MB 4. 300 MB 8-39. What is the minimum number of conductors 8-40. 8-41. 8-42. 8-43. 54 required for I/O serial data operations? 1. 1 2. 2 3. 37 4. 4 During asynchronous data exchange, a frame of data must include which of the following bits at a minimum? 1. One start bit 2. One stop bit 3. Seven character bits 4. All of the above During asynchronous data exchange, what is the maximum number of bits for one frame of data? 1. 8 2. 9 3. 10 4. 11 Compared to asynchronous data exchange, synchronous data exchange has which of the following advantages? 1. Faster speed 2. More reliability 3. Less electronics required 4. Fewer bits required for each character The generally accepted standard connector for implementing an RS-232 connection has what total number of pins? 1. 12 2. 25 3. 26 4. 32

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8-44. The protective ground, pin 1, of the RS-232 8-45. 8-46. 8-47. 8-48. interface connector in the DTE/DCE mode should always be connected to the shielded cable shield at both ends. 1. True 2. False Pin 7 of the RS-232 interface connector in the DTE/DCE mode should always be connected at both ends for which of the following reasons? 1. 2. 3. 4. To complete the path for control signals only To provide a complete path for the data signals only To provide timing signals to the peripheral device only To provide a common reference for all signals Pin 3 of the RS-232 interface connector in the DTE/DCE mode is used for which of the following purposes? 1. To send data signals 2. To send control signals 3. To receive data signals 4. To receive control signals Pins 4,5,6, and 20 are used in the DTE/DCE mode using the RS-232 interface connector for which of the following purposes? 1. To send and receive data signals 2. To send and receive control signals 3. To send and receive timing signals 4. To establish the communications link In parallel data operations, the IOA or line driver/receiver provides the means to accomplish which of the following tasks? 1. Convert the byte or word to a sequential bit stream 2. Drive or detect the digital signals 3. Convert serial data to parallel data 4. Provide constant timing signals at the specified voltage levels 8-49. 8-50. 8-51. 8-52. 8-53. In parallel data operations, one I/O channel could consist of which of the following devices? 1. 2. 3. 4. Two cables, one for input and one for output or a single cable to handle both input and output Eight or more data lines A number of control lines All of the above The data strobe in single parallel cable operations is used for which of the following purposes? 1. 2. 3. 4. To check for data on the data lines To ensure that the data on the data lines is stable To signal the external device that data is ready to be read from the data lines All of the above In single parallel cable operations, a busy signal is sent under which of the following conditions? 1. The computer output buffer is full 2. The external equipment is not energized 3. The external equipment input buffer is full 4. The computer is involved in internal operations In two-cable parallel operations, an external interrupt enable can be described as which of the following signals? 1. A signal sent from the external device on the input line 2. A signal sent from the computer on the output line 3. A signal sent from the external device on the output line 4. A signal sent from the computer on the input line When an external interrupt code is placed on the data lines, it is accompanied by which of the following signals? 1. An external interrupt request 2. An input data acknowledge 3. An input data request 4. All of the above 55

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8-54. When the computer samples an interrupt code, which of the following signals will occur? 1. An external interrupt acknowledge 2. An external interrupt enable 3. An input data acknowledge 4. All of the above 8-55. In a two-cable sequence of events for input data, which of the following events occurs first? 1. The external equipment sets the IDR line 2. The external equipment places a word of data on the ID lines 3. The computer sets the input data request line 4. The computer clears the IDA line 8-56. In the two-cable sequence of events for input data, the computer has sampled the data on the ID lines. Which of the following events must occur before the computer will accept more data? 1. The IDR must be cleared 2. A new data word must be placed on the I/O lines 3. The IDR must be reset 4. All of the above 8-57. During a normal external function sequence of events, the computer places an EF code word on the OD lines. The next event to take place is which of the following? 1. The EFR line is set 2. The ODA line is set 3. The EFR line is cleared 4. The EFA line is set 8-58. During forced external functions, the computer does not require which of the following signals? 1. An EFR 2. An EFA 3. An ODR 4. An ODA 8-59. During the external interrupt sequence of events, what is the first event that must occur before a computer will accept an external interrupt? 1. The EI code word must be placed on the ID lines 2. The EIE line must be set 3. The EIR line must be set 4. The IDA line must be set 8-60. During the external interrupt sequence of events, the computer samples the EI code word on the ID lines and clears the EIE line for data to continue to transfer. Which of the following events must occur? 1. The computer must set the IDA line only 2. The external equipment must detect the setting of IDA line only 3. The computer must clear the IDA line only 4. The computer sets the IDA line, the external equipment must detect the setting of the IDA line, and the computer must clear the IDA line 8-61. All computers used by the Navy have EIE lines. 1. True 2. False 8-62. In intercomputer I/O operations when parallel channels are used, the input and output cables will have which of the following characteristics? 1. The input and output cables can be uneven in number 2. An ODA signal becomes a resume signal 3. An ODR signal becomes a ready signal 4. The input and output cables will be identical 8-63. During intercomputer I/O operations, command words include which of the following data? 1. External functions only 2. Forced external functions only 3. External function buffer words only 4. External functions, forced external functions, and external function buffer words 56

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8-64. During intercomputer I/O operations, command word functions are identified by use of which of the following techniques? 1. Flag words 2. Setting ODA lines 3. Additional interface signals 4. All of the above 8-65. During intercomputer I/O operations, for a buffered command word transfer to be possible, (a) the transmitting computer must have what line and (b) the receiving computer must have what line? 1. (a) EFR (b) EIE 2. (a) EFR (b) EFR 3. (a) EIE (b) EIE 4. (a) EIE (b) ERF 8-66. For an intercomputer command word buffered transfer, the receiving computer is ready to accept an external function command word. This is signaled by which of the following means? 1. The external function request line is set 2. The external interrupt enable line is set 3. The external function acknowledge is set 4. The input data request line is set 8-67. During an intercomputer command word buffered transfer, before putting the EF code on the data lines, the transmitting computer recognizes which of the following signals? 1. An EFR 2. An EFA 3. An ODA 4. All of the above 8-68. In intercomputer command word transfers when the transmitting computer does not have an EFR line, the command word will be transferred in what way, if any? 1. As a data word 2. As a buffered command word 3. As a forced command word 4. None, data cannot be transferred without an EFR line 8-69. In intercomputer I/O operations, all command words specified by the receiving computer’s EF buffer control words will be transferred one command word at a time. 1. True 2. False 8-70. Before the intercomputer data transfer sequence of events can begin, which of the following events must have occurred on the same channel? 1. An OD buffer must have been established on the transmitting computer 2. An ID buffer must have been established on the receiving computer 3. Both 1 and 2 above 4. An IDA must have been established 8-71. In intercomputer data transfers, the data word is held on the OD lines until the receiving computer performs which of the following tasks? 1. Sets the IDR line 2. Clears the IDR line 3. Sets the resume line 4. Clears the resume line 8-72. In intercomputer data transfer, the receiving computer recognizes the ready line of the transmitting computer as what line? 1. The IDR line 2. The ODR line 3. The ODA line 4. The resume line 8-73. In intercomputer data transfer, the transmitting computer recognizes the IDA line of the receiving computer as what line? 1. The IDR line 2. The ODR line 3. The ODA line 4. The resume line 57

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8-74. In intercomputer data transfer, after one data word has been transferred and before the next data word is placed on the data OD lines, which of the following events occurs? 1. The receiving computer sets the IDA line 2. The transmitting computer clears the ready line 3. Both 1 and 2 above 4. The receiving computer clears the EFR line

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ASSIGNMENT 9 Textbook Assignment: “Computer Instructions and Man/Machine Interfaces” chapter 8, pages 8-1 through 8-26. 9-1. 9-2. 9-3. 9-4. 9-5. Various programming languages and types of languages are used to write computer programs. Which of the following are examples of procedural-type languages? 1. 2. 3. 4. COBOL and FORTRAN COBOL and BASIC FORTRAN and BASIC BASIC and Ada For embedded applications, which of the following languages could be used? 1. BASIC 2. FORTRAN 3. COBOL 4. Ada Which of the following languages is considered an interactive language? 1. Ada 2. BASIC 3. COBOL 4. FORTRAN Before a program can be executed on a computer, it may need to be translated. Which of the following types of languages need to be translated? 1. High level only 2. Assembly only 3. High level and assembly 4. Machine code Computer instructions to perform designated operations are contained in an instruction set. Which of the following is another name for instruction set? 1. Operation set 2. Repertoire of instructions 3. Operating system instructions 4. Instruction formats 9-6. 9-7. 9-8. 9-9. 9-10. Other names for the plan used to write a program include which of the following terms? 1. Algorithm 2. Formula 3. Utility 4. Application Some programs are stored in ROM or PROM. Which of the following is another name used for these read-only programs? 1. Operating systems 2. Utilities 3. Hardwired 4. Applications What type of program provides the link between the computer hardware and the user and enables. the execution of operational programs? 1. Operating system 2. Application 3. Utility 4. User interface Operating systems are a collection of many programs used by a computer to manage its own resources and operations. All of the following are types of operating systems except which one? 1. 2. 3. 4. Programmed operational and functional Single tasking Multitasking Real-time Which of the following are names commonly used to describe the programs for tactical, tactical support, and/or nontactical applications? 1. Application programs only 2. Operational programs only 3. Operational and processing programs only 4. Application, operational, and processing programs 59

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9-11. Commercially available programs designed to solve specific classes of problems are often called by which of the following terms? 1. Packaged software only 2. Off-the-shelf software only 3. Packaged and off-the-shelf software 4. On-the-shelf software 9-12. All of the following are considered utility programs except which one? 1. POFA 2. Operating system 3. Online diagnostic test 4. General routine to copy a disk 9-13. A predetermined and installed set of microinstruction is called what type of instruction? 1. Multiple instruction 2. Microinstruction 3. Mini-instruction 4. Controlled instruction 9-14. Which of the following types of instructions are classified by the function they perform? 1. Transfer of control only 2. Movement and transfer of control, only 3. Movement, transfer of control and arithmetic only 4. Movement, transfer of control, arithmetic, and logical 9-15. Data assignment instructions are normally held in which of the following types of registers? 1. Flag registers only 2. Memory address registers only 3. Memory address registers and active status registers 4. Flag registers and active status registers 9-16. All of the following are examples of data assignment instructions except which one? 1. 2. 3. 4. Branch instruction address Fixed point overflow Interrupt lockouts Compare designators 9-17. 9-18. 9-19. 9-20. 9-21. What type of instruction makes it possible to change the sequence in which a computer performs instructions? 1. Data assignment 2. Arithmetic 3. Logical 4. Branch What type of instruction will change the sequence of instructions only if a condition is met? 1. Conditional branch 2. Unconditional branch 3. Logical branch 4. Automatic branch What type of instructions include and, or, not, exclusive or/nor, compare, and shift instructions? 1. Data assignment 2. Arithmetic 3. Logical 4. Branch In addition to being classified by their functions, instructions may be classified by their action on operands. 1. True 2. False Instructions are the same on all computers. 1. True 2. False 9-22. All instructions include at least which of the following parts? 1. An operation code 2. An operand address 3. A modifier code 4. A register name IN ANSWERING QUESTION 9-23, REFER TO FIGURE 8-3 ON PAGE 8-7 OF THE RAMAN. 60

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9-23. In a 16-bit microcomputer instruction, in what positions is the operation code located? 1. Bits 2 5 and 2 4 2. Bits 2 11 and 2 10 3. Bits 2 15 through 2 13 4. Bits 2 16 through 2 13 9-24. The formats of instructions on mainframe computers vary greatly for all of the following reasons except which one? 1. Manufacturer of the computer 2. Generation of the computer 3. Memory size of the computer 4. Type of computer QUESTIONS 9-25 THROUGH 9-33 PERTAIN TO THE EXAMPLE INSTRUCTION FORMATS FOR A MAINFRAME COMPUTER WITH 32-BIT INSTRUCTIONS ON PAGES 8-8 THROUGH 8-10 IN THE TRAMAN. 9-25. A total of how many basic instruction formats is given? 1. One 2. Five 3. Seven 4. Nine 9-26. Which of the following fields is/are consistent in all the instruction formats? 1. Designator field (a) only 2. Function code (f) only 3. Designator field (a) and function code (f) 4. Function code (f) and subfunction code (f 2) 9-27. The “a” field is used to identify all except which of the following registers? 1. Stack pointer 2. Accumulator 3. Memory 4. Index 9-28. Basic load, store, replace, and simple mathematical operations are performed using what instruction format? 1. I 2. II 3. IV-B 4. V 9-29, 9-30, 9-31. 9-32. 9-33. Format II instructions perform all except which of the following types of operations? 1. Interrupt 2. I/O commands 3. Single precision mathematics 4. Program sequence control jumps What is the maximum value of a subfunction code of (a) two bits and (b) three bits? 1. (a) 2 (b) 3 2. (a) 2 (b) 7 3. (a) 3 (b) 5 4. (a) 3 (b) 7 Formats IV-A and IV-B are half-word instructions and two of them may be stored in one memory word. Which of the following methods is used to keep track of upper/lower instruction execution? 1. Active status register 2. Indirect addressing mode 3. Monitor clock 4. Accumulator For operations such as setting, clearing, or testing an individual bit, what instruction format is used? 1. IV-B 2. IV-C 3. III 4. II For single- and double-precision floating-point math operations, what instruction format should be used? 1. I 2. II 3. III 4. V 61

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9-34. Which of the following are types of operand addressing? 1. Direct and indirect only 2. Extended, immediate, and implicit only 3. Indexed and relative only 4. Direct, indirect, extended, immediate, implicit, indexed, and relative 9-35. In which addressing mode is the operand itself contained in the instruction? 1. Extended 2. Immediate 3. Implicit 4. Relative 9-36. An instruction in which no operand address needs to be specified because the operation code contains all the information needed uses what addressing mode? 1. Extended 2. Immediate 3. Implicit 4. Indexed 9-37. Which addressing mode requires the operand address to be generated when the instruction is being prepared for execution? 1. Indexed operand 2. Immediate 3. Indirect 4. Direct 9-38. In relative addressing, what two items must be added together to obtain the correct instruction or operand address? 1. Base address and offset 2. Base address and memory register 3. Offset and index register 4. Memory word and memory register 9-39. Instruction sizes vary among types and generations of computers. They include which of the following sizes? 1. Character and full-word only 2. Full-word and half-word only 3. Full-word and double-length word only 4. Character, half-word, full-word, double- length word, and multiple word 9-40. Microcomputers commonly use instructions of what word lengths? 1. Multiple 2. Double 3. Full 4. Half 9-41. Man-machine interfaces have at least data entry and data display capabilities. 1. True 2. False 9-42. The data entry function of a man-machine interface is used to enter commands or set parameters for which of the following activities? 1. Test activities only 2. Computer operations only 3. Status and computer operations only 4. Computer operations, status, and test activities 9-43. When a computer is continually executing instructions one after another as directed by its logic circuits and software, it is in what operating mode? 1. Run 2. Step 3. Phase 4. Sequence 9-44. When you want to put the computer in the stop mode, which of the following methods can you use? 1. Manual action using STOP pushbutton 2. Program control using a STOP instruction 3. Both 1 and 2 above 4. Timing clock circuits 62

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9-45. What mode of - operation enables a technician to test the contents of registers and memory locations at the end of each instruction execution? 1. Run 2. Step 3. Phase 4. Sequence 9-46. Which of the following operating modes enable a technician to test conditions during the execution of an instruction? 1. Phase and sequence 2. Step and stop 3. Run and phase 4. Run and step 9-47. The purpose of master clear is to clear which of the following areas? 1. All I/O registers only 2. All CPU registers only 3. All I/O and CPU registers only 4. All memory locations only QUESTIONS 9-48 THROUGH 9-65 PERTAIN TO MICROCOMPUTERS. 9-48. With a microcomputer, all of the following methods are commonly used to inform the processor of the system configuration except which one? 1. Battery protected storage 2. Switchboard panels 3. DIP switches 4. Jumpers 9-49. Each switch in a dual-inline package (DIP) indicates ON/OFF status. DIP switches can be used in which of the following ways? 1. Each single switch indicates the status of a component only 2. Each single switch indicates a requirement of the system operator only 3. Single and/or combinations of switches indicate the status of a component or the requirements of the system operator 4. Two switches must be used together to indicate any operational status 9-50. Board mounted DIP switches are designed so you can manually set them during which of the following tasks? 1. Component installation only 2. Component removal only 3. Initial configuration only 4. Component installation and removal, and initial configuration 9-51. Jumpers have which of the following characteristics? 1. Jumper settings are considered temporary 2. Jumpers must be physically removed and reinserted 3. Jumpers can only be manually positioned during component installation 4. Only a single jumper maybe used to specify a configuration option 9-52. A jumper connector consists of which of the following parts? 1. A receptacle only 2. A plug only 3. A receptacle and a plug 4. A set of switches 9-53. Jumpers have what purpose? 1. To define the configuration of each pcb 2. To connect the communications cables from a computer to an external device 3. To bridge a loose connection inside a computer chassis 4. To set a series of conditions to affect data flow within external devices 9-54. Which of the following are examples of functions affected by jumpers? 1. Mode of operation 2. Clock speed and wait states 3. I/O connections 4. All of the above 9-55. Newer microcomputers have a hardware/configuration program stored as firmware. 1. True 2. False 63

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9-56. In newer microcomputers, configuration data may be stored in which of the following ways? 1. In ROM 2. In EPROM protected by a rechargeable battery 3. In RAM protected by a rechargeable battery 4. On disk or tape, depending on the microcomputer’s design 9-57. In microcomputers with battery protected storage, where is the battery located? 1. In the keyboard 2. On the backplane/motherboard 3. In an external battery pack 4. In the surge protector 9-58. DIP switches and battery protected storage provide different basic configuration data to the microcomputer. 1. True 2. False 9-59. All of the following are examples of system setup/configuration options except which one? 1. Date and time data 2. Floppy disk drive identifiers 3. Type of video display and refresh time period 4. ROM content 9-60. Microcomputers usually have which of the following types of power? 1. Ac only 2. Fixed time period rechargeable battery only 3. Ac and fixed time period rechargeable battery 4. Ac and variable time period rechargeable battery 9-61. A voltage or line select switch allows a microcomputer to operate in which of the following voltage ranges? 1. 100 to 130 only 2. 200 to 230 only 3. 100 to 130 and 200 to 230 only 4. 100 to 230 9-62. The keyboard and the monitor of a microcomputer provide for all except which of the following functions? 1. Control cooling and battle short conditions 2. Running software programs 3. Performing tests 4. Viewing results 9-63. Internal diagnostics are performed in the power on sequence. The computer notifies you (a) of errors in what way and (b) that everything is correct in what way? 1. (a) Displays an error message if possible (b) Displays a message telling you to load the disk operating system 2. (a) Displays a menu to enable you to run external diagnostics (b) Displays a message telling you to load the DOS 3. (a) Displays an error message if possible (b) Loads DOS and displays an appropriate DOS display 4. (a) Displays an error message always (b) Loads DOS and displays an appropriate DOS display 9-64. Compared to internal diagnostics, LEDs provide which of the following advantages? 1. They simplify diagnostic software 2. They are easier to read than displayed messages 3. They save random access memory space 4. They enable the operator to select tests 9-65. Under DOS, you can also use disk based diagnostics with test selection menus. These menus usually provide which of the information on the monitor? 1. Test selection only 2. Test status only 3. Test status and error indications only 4. Test selection, test status, and error indications 64

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9-66. In addition to providing information on the operating system and software programs, panels on some minicomputers provide which of following controls and indicators? 1. Power only 2. Temperature only 3. Power and temperature 9-67. Internal diagnostics, called built-in tests (BITs), are designed to perform tests on which of the following devices? 1. CPUs only 2. IOCs only 3. CPUs and IOCs only 4. CPUs, IOCs, and any optional circuits 9-68. The pass/fail results of BITs will be displayed on the front panel. To decipher an error code from a failed test result and find the location of the module that may fix the problem, you should take which of the following actions? 1. Ask the senior DS 2. Look at the fault isolation table 3. Write down the error code and submit it to the trouble-shooting desk 4. Write down the error code and submit it to your supervisor 9-69. To configure a mainframe computer for reduced capability, you need to know which of the following information? 1. The capabilities and limitations of the system only 2. How to set the controls and switches on the computer and the switchboard only 3. How to set the controls and switches on the switchboard panels and the display and communications subsystems 4. The capabilities and limitations of the system, and how to set the switches on the computer, the switchboard panels, and the communications subsystems 9-70. Power to a mainframe computer is critical. Which of the following methods may be used to ensure there is stable power? 1. Circuit breaker protection 2. Indicators for blower and logic to show if there is stable power 3. Interrupts to indicate power fluctuations 4. Each of the above 9-71. In addition to controls, switches, and pushbutton indicators, newer mainframe computers use which of the following devices to display status information and address the contents of registers? 1. Displays only 2. Keyboards only 3. Displays and keyboards 4. Keyboards and voice generated messages 9-72. On mainframe computers, internal diagnostics to test hardware and return pass/fail results may include which of the following types? 1. Diagnostics on tape or disk 2. Built-in tests (BITs) 3. Tests on NDRO 4. Both 2 and 3 above 9-73. To perform bootstrap on a minicomputer or mainframe computer, what type of memory is used? 1. DRAM 2. SRAM 3. CMOS RAM 4. NDRO 9-74. Inspect and change routines are used on minicomputers and mainframe computers for which of the following purposes? 1. To ensure the software is operating properly 2. To patch or revise software 3. To change hardware configurations 4. To change software/hardware interfaces 65

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9-75. In a mainframe or minicomputer, what determines which peripheral device will be used to execute bootstrap? 1. The positions of the jumpers 2. The position of the bootstrap switch 3. The position on a DIP switch 4. The position of the step switch 66

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ASSIGNMENT 10 Textbook Asignment: “Magnetic Tape Storage,” chapter 9, pages 9-1 through 9-21. 10-1. 10-2. 10-3. 10-4. 10-5. Which of the following types of storage is used to store large amounts of data that are not required by the computer on a regular basis? 1. Main memory storage 2. Secondary memory storage 3. Tertiary memory storage 4. Thin film memory storage Magnetic tape can be used to store large amounts of data in a variety of convenient package sizes. 1. True 2. False Which of the following materials can be used as a base for magnetic tape? 1. Plastic 2. Iron oxide 3. Rubber 4. Paper Which of the following materials can be used to form the oxide coating of a magnetic tape? 1. Gamma ferric oxide only 2. Chromium dioxide only 3. Gamma ferric oxide and chromium dioxide 4. Plastic Which of the following procedures should NOT be used when magnetic tapes are handled? 1. 2. 3. 4. Keep unused tapes in dustproof containers Keep containers free of dust and contaminants Store tapes in electromagnetically shielded cabinets Store tapes on the top of equipment 10-6. To identify magnetic tapes, use adhesive labels with which of the following characteristics? 1. Easily erasable 2. Adhere permanently to tape containers 3. Both 1 and 2 above 4. Easily removable without leaving a residue 10-7. You should store tapes in the same room where they are to be used for which of the following reasons? 1. To reduce handling only 2. To prevent variations in environmental conditions only 3. To reduce handling and to prevent variations in environmental conditions 4. To decrease the time needed to find the tape 10-8. When you receive a new tape, which of the following actions, if any, should you take? 1. Immediately mount the tape on a drive to read the information 2. Condition the tape to the environment in which it is to be used 3. Copy the tape as soon as you receive it 4. None; no special action is required 10-9. What effect, if any, may result if you touch the magnetic oxide of a tape? 1. 2. 3. The oils and acids from your skin could damage the tape Your fingers could turn brown from picking up bits of the oxide None; no effect 67

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10-10. A tape cleaner performs which of the following 10-15. What area of a magnetic tape tends to show the actions? greatest amount of wear? 1. It shaves the oxide of the tape only 1. The area just after BOT 2. It wipes down both sides of the tape with a 2. The area just before EOT cleaning solution only 3. The interrecord gap area 3. It first shaves the oxide side of the tape, then 4. The file mark it wipes down both sides of the tape with a cleaning solution 10-16. To correct a tape’s worn or damaged areas, which 4. It alters the flux patterns on the tape of the following actions should you take? 10-11. Which of the following maintenance actions 1. Degaussing reduces the static buildup on open reel magnetic 2. Cleaning tapes? 3. Stripping 4. Splicing 1. Degaussing 2. Cleaning 10-17. After stripping a magnetic tape, what is the 3. Certifying minimum length of tape you should leave on the 4. Stripping reel? 10-12. A tape certifier performs all of the following tasks except which one? 1. Cleans the tape 2. Erases the tape 3. Checks the tape’s ability to record high density data, to retain magnetic flux patterns, and to be demagnetized 4. Restores the original data to the tape 10-13. For a tape that cannot be certified, what action, if any, should you take? 1. Destroy it 2. Keep it for use as a scratch tape only 3. Put it into general use because the standards of a tape certifier are higher than they need to be 4. None; no action is required 10-14. To nullify all the magnetic flux patterns is the sole purpose of which of the following machines? 1. 500 feet 2. 400 feet 3. 300 feet 4. 200 feet 10-18. You should NOT splice a tape for which of the following reasons? 1. Tape splices are generally the weakest point on the tape 2. Read and write operations may not perform properly in the area of the splice 3. Splicing a broken tape usually will not save the data 4. All of the above 10-19. All tape media used in a system must be accounted for in which of the following ways? 1. Listed 2. Labeled only 3. Numbered only 4. Labeled and numbered 1. A cleaner 10-20. An operational program tape being delivered to a 2. A stripper system is considered which of the following types 3. A degausser of tape? 4. A certifier 1. New 2. Used 3. Master 4. Scratch 68

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10-21. 10-22. 10-23. A tape containing data that maybe written over is called what type of tape? 1. New 2. Used 3. Master 4. Scratch Master tapes must be protected from which of the following operations? 1. Read 2. Write 3. Copy 4. Duplication Tapes generated from a master tape are referred to by which of the following terms? 1. New 2. Used 3. Working copies 4. Scratch A. Submit the tape for stripping or cleaning/ certifying. B. Make a new working copy from the master. C. Remove the tape from the unit and clean the transport. D. Attempt to read or write the tape on different transport. E. Align the magnetic tape transport. Figure 10-A—Magnetic tape maintenance actions. IN ANSWERING QUESTIONS 10-24 THROUGH 10-26, SELECT FROM FIGURE 10-A THE PROPER MAINTENANCE ACTION TO CORRECT THE PROBLEM DESCRIBED IN THE QUESTION. 10-24. A working copy receives read errors from several tape transports. 1. A 2. B 3. C 4. D 10-25. 10-26. 10-27. 10-28. 10-29. 10-30. The tape has visible damage. 1. A 2. B 3. D 4. E A tape reads properly from all transports except one. 1. A 2. B 3. D 4. E What is the form taken by a tape after it has been wound on a reel? 1. Tape 2. Tape deck 3. Tape roll 4. Tape pack What winding error causes steps to be observed in the tape pack? 1. Windowing 2. Spoking 3. Pack slip 4. Cinching What tape condition is caused when a loosely wound tape is exposed to extreme heat or humidity? 1. Windowing 2. Spoking 3. Pack slip 4. Cinching What tape condition is caused when tension is increased toward the end of the winding operation? 1. Windowing 2. Spoking 3. Pack slip 4. Cinching 69

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10-31. 10-32. 10-33. 10-34. 10-35. Storage of data using a magnetic tape unit is based on which of the following principles? 1. 2. 3. 4. Current flow in a conductor can be generated by a change in the magnetic lines of force that cut through a conductor Changing the current flow in a conductor creates a change in the magnetic lines of force radiating from the conductor Both 1 and 2 above Current flow cannot be created by moving a conductor through a magnetic field - The electromagnetic-type conductor used to create a magnetic spot on a magnetic tape is called a 1. read head 2. write head 3. flux pattern 4. magnetic oxide A magnetic spot recorded on a magnetic surface may be sensed by an electromagnetic-type conductor called a 1. read head 2. write head 3. flux pattern 4. magnetic oxide Data stored on a magnetic surface may only be read once. 1. True 2. False A flux pattern magnetized in one direction to indicate a binary ONE and the opposite direction to indicate a binary ZERO is a characteristic of which of the following recording techniques? 1. Return-to-zero 2. Non-return-to-zero 3. Phase encoding 10-36. 10-37. 10-38. 10-39. 10-40. 10-41. 70 Using narrow current spikes to write small flux patterns is a characteristic of which of the following recording techniques? 1. Return-to-zero 2. Non-return-to-zero 3. Phase encoding A binary ONE indicated by a change in flux direction is a characteristic of which of the following recording techniques? 1. Return-to-zero 2. Non-return-to-zero 3. Phase encoding What recording technique, if any, provides for the highest data density? 1. Return-to-zero 2. Non-return-to-zero 3. Phase encoding 4. None; they all provide the same density An invisible line on a tape where data is written or read a bit at a time is called a 1. file 2. frame 3. record 4. track Data bits written concurrently across the width of the tape are called a 1. file 2. frame 3. record 4. track Which of the following terms indicates the density of data stored on multitrack tape? 1. Bits per inch 2. Characters per inch 3. Frames per inch 4. Records per inch

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10-42. A nine-track magnetic tape contains (a) what number of data bits and (b) what number of parity bits? 1. (a) 7 (b) 2 2. (a) 8 (b) 1 3. (a) 9 (b) 1 4. (a) 9 (b) O 10-43. In which of the following recording techniques is the presence of a frame indicated by the detection of a binary ONE? 1. Return-to-zero 2. Phase encoding 3. Non-return-to-zero 4. Non-return-to-zero indiscrete 10-44. When writing or searching for data, which of the following tape markings is a common starting point used by a system? 1. BOT 2. EOT 3. Both 1 and 2 above 4. IRG 10-45. Data cannot be written or read under which of the following conditions? 1. The tape is stopped 2. The tape is just starting to move 3. The tape is stopping movement 4. All of the above 10-46. The start/stop effect creates a blank spot on the tape until which of the following conditions is met? 1. The tape is up to speed 2. The tape is stopped 3. The tape is starting to move 4. The tape is stopping movement 10-47. A group of contiguous frames is called a 10-48. Record length is fixed by the magnetic tape device. 1. True 2. False 10-49. A file can be defined as a group of 1. bits 2. characters 3. frames 4. records 10-50. Every file on a tape ends with a 1. file mark 2. interrecord gap 3. parity bit 4. record 10-51. Which of the following parity checks uses each frame’s parity bit? 1. Odd 2. Even 3. Lateral 4. Longitudinal 10-52. The parity bit in a seven-track frame consisting of 011101 is a ONE for which of the following parity formats? 1. Odd 2. Even 3. Lateral 4. Longitudinal 10-53. Odd parity is commonly used with non-return-to-zero indiscrete recording for what purpose? 1. File mark 2. Frame identification 3. Interrecord timing 4. Tape speed 1. file 2. record 3. software 4. track 71

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10-54. Which of the following parity checks uses a check frame? 1. Odd 2. Even 3. Lateral 4. Longitudinal 10-55. Each bit in the check frame contains the parity bit for all the ONEs in a particular 1. file 2. frame 3. record 4. track 10-56. Which of the following is NOT a function of the magnetic tape controller? 1. Receives data and commands from the computer 2. Reformats data into frame-size bytes 3. Detects BOT 4. Checks parity 10-57. What is the tape speed for all read, write, and search operations, in inches per second? 1. 100 2. 120 3. 180 4. 200 10-58. Tapes without a write-enabling ring are protected from the write operation. 1. True 2. False 10-59. What MTU operation compares the first word of each record to a specified key? 1. Read 2. Search 3. Space file 4. Write 10-60. During a rewind operation, what signal will cause tape motion to stop? 1. BOT 2. EOT 3. Low tape 4. Start of file tape mark 10-61. MTU operations that can be performed offline using the microprogrammed controller (MPC) are determined by the MPC program installed by the 1. operator 2. computer 3. manufacturer 4. maintenance technician 10-62. What functional area of a magnetic tape unit decodes external function words from the computer? 1. System control panel 2. Maintenance panel 3. Magnetic tape transport 4. Control unit 10-63. The MPC transmits data via which of the following data buses? 1. Source bus only 2. Destination bus only 3. Source and destination buses 4. ROM bus only 10-64. Which of the following control unit functions is NOT performed by the MPC? 1. Frame count checking for lost frames 2. Start/stop delay initiation 3. Read/write signal amplification 4. Search operations comparisons 10-65. Which of the following components contains controls and indicators for manual offline operations? 1. The maintenance panel 2. The system control panel 3. The magnetic tape transport 4. The microprogrammed controller 72

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10-66. 10-67. 10-68. 10-69. 10-70. Which of the following components contains the controls and indicators for primary power and tape transport manual control? 1. The maintenance panel 2. The system control panel 3. The magnetic tape transport 4. The microprogrammed controller Of the following operations, which one is NOT performed by the magnetic tape transport (MTT) control section? 1. Providing control signals for manual operations of the MTT 2. Acting as an interface for MTU control signals and status responses 3. Sending signals to light the MTT switch panel indicators 4. Providing timing pulses and a servo-movement control signal to the capstan The direction and speed of the supply and take-up servo motors are controlled by which of the following factors? 1. 2. 3. 4. The size of the tape loop in the vacuum column The direction and speed of the capstan motor The capstan tachometer The function being performed Which of the following MTT sections controls the speed and direction of tape movement? 1. Air control solenoids 2. Capstan servo-control 3. Supply reel servo-control 4. Take-up reel servo-control The supply and take-up reel servo-driven hubs attempt to maintain the tape loops in which of the following positions as shown in figure 10-20? 1. Above sensor A 2. Below sensor D 3. Between sensors B and C 10-71. 10-72. 10-73. 10-74. 10-75. The speed and direction of the servo-driven hubs are controlled by all of the following conditions except which one? 1. 2. 3. 4. Capstan direction and velocity Reel tachometer input Vacuum/pressure sensors in the buffer columns Read or write operation being performed Which of the following diagnostic programs is/are controlled by the MPC ROM? 1. POFA 2. PEFT 3. Internal diagnostics 4. All of the above Which of the following diagnostic programs is/are run under the control of the operational program? 1. 2. 3. 4. POFA PEFT Internal diagnostics All of the above Which of the following POFA tests checks the ability of the MTU to respond to computer commands and to provide status and error condition information to the computer? 1. The duplex test 2. The extended operation test 3. The function and format test 4. The transport compatibility test Which of the following POFA tests checks the MTU’s ability to read the same tape on several MTTs? 2. The extended operations test 3. The function and format test 4. The transport compatibility test 1. The duplex test 4. Between sensors A and D 73

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ASSIGNMENT 11 Textbook Assignment: “Magnetic Disk Storage,” chapter 10, pages 10-1 through 10-21. 11-1. Magnetic disks are generally used as which of the following types of storage? 1. 2. 3. Main memory Secondary storage Tertiary storage 11-2. The original fixed disk had what maximum capacity? 1. 5 megabytes 2. 10 megabytes 3. 20 megabytes 4. 50 megabytes 11-3. The first floppy disks had (a) what diameter and (b) maximum storage capacity? 1. (a) 5 in. (b) 180K 2. (a) 5 in. (b) 360K 3. (a) 8 in. (b) 180K 4. (a) 8 in. (b) 360K 11-4. The top and bottom surfaces of a removable disk pack are usually used for what purpose? 1. Data storage 2. Protection 3. Servo data 4. Indexing 11-5. Fixed disks have which of the following characteristics? 1. They are small sealed units with one or more platters 2. They are easily removed from the computer 3. They are only used with mainframe computers 4. They are not broken 11-6. 11-7. 11-8. 11-9. The 5.25-inch floppy disk is available with which of the following densities? 1. 360K only 2. 720K only 3. 1.2M only 4. 360K, 720K, and 1.2M The 3.5-inch floppy disk is available with which of the following densities? 1. 360K only 2. 720K only 3. 1.44M only 4. 720K and 1.44M Formatting a disk performs which of the following operations? 1. Writes tracks only 2. Writes sectors only 3. Writes cylinders only 4. Writes tracks and sectors Concentric rings used to store data on disk are called 1. bytes 2. tracks 3. records 4. cylinders 11-10. Track 00 is physically located on a disk’s recording surface in which of the following places? 1. Top track 2. Bottom track 3. Innermost track 4. Outermost track 74

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11-11. A cylinder address number is composed of which of the following numbers? 1. Cylinder number only 2. Track number only 3. Sector number only 4. Cylinder number, sector number, and head number 11-12. In a personal computer, which of the following data management areas is NOT created by the DOS 1 format program? 1. Root directory 2. Subdirectory 3. Disk boot sector 4. File allocation table 11-13. A new fixed disk installed in a personal computer needs to have what operation(s), if any, run before it is ready to store data? 1. Format only 2. High-level format only 3. Format and high-level format 4. None; new disks are ready to run 11-14. In a personal computer using DOS version 5, the root directory of a 40-megabyte fixed disk can have what maximum number of entries? 1. 128 2. 256 3. 512 4. 640 11-15. The DOS directory system is a file system that enables DOS to manage files. 1. True 2. False 11-17. In DOS, the maximum number of characters in a file extension is 1. one 2. two 3. three 4. four 11-18. When DOS is used on a personal computer, a directory entry is composed of how many bytes? 1. 32 2. 48 3. 64 4. 80 11-19. Which of the following parameters is NOT part of the DOS file allocation table (FAT) entry? 1. A bad cluster code written during formatting 2. A DOS cluster available for storage 3. The file name stored in that DOS cluster 4. An end of the file code 11-20. On a 5.25-inch floppy disk, which of the following materials is used as the magnetic coating? 1. Chromium dioxide 2. Iron oxide only 3. Cobalt only 4. Iron oxide or cobalt, depending on the density of the disk 11-21. The index hole on a 5.25-inch soft-sectored floppy disk is used to indicate the 1. start of sector 1 of each track 2. start of track 1 3. start of each sector 4. end of the data storage area of the disk 11-16. In DOS, the maximum number of characters in a file name is 1. 8 2. 9 3. 10 4. 11 75

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11-22. 11-23. 11-24. 11-25. 11-26. To protect a 5.25-inch floppy disk from being written on, which of the following actions should you take? 1. 2. 3. 4. Ensure the write enable notch is not obstructed Cover the write enable notch with a piece of tape Format the disk as read only Disable the write circuitry on the disk drive To allow for greater densities on a 3.5-inch floppy disk, the plastic cover provides what function, if any? 1. It stabilizes the disk as the disk spins 2. It makes it harder to damage the disk 3. It allows for greater disk speeds 4. None; it serves no function in increasing disk density When you handle a 3.5-inch floppy disk, what feature, if any, eliminates the need for you to keep the disk in a disk jacket? 1. 2. 3 4. The rigid plastic case The spring-loaded metal shutter The exposed media access hole None; you should always store a 3.5-inch disk in-a jacket What action, if any, is necessary to write data on a 3.5-inch disk? 1. 2. 3. 4. Ensure the write enable slide is positioned so you can see a hole in the disk case Ensure the write enable slide is positioned so that no hole is visible through the disk case Ensure the disk has not been formatted None; no action is necessary to write on a 3.5-inch disk The presence of a media indicator hole in a 3.5-inch disk case indicates what about the disk? 1. It has been properly inserted in the drive 2. It can be formatted as a 720K disk only 3. It can be formatted as a 1.44M disk 4. It has been preformatted 11-27. 11-28. 11-29. 11-30. 11-31. The drive motor in a 5.25-inch, 1.2M disk drive spins at what speed? 1. 200 rpm 2. 260 rpm 3. 300 rpm 4. 360 rpm The drive motor on most half-height floppy disk drives is what type of motors? 1. Gear box drive 2. Direct drive 3. Servo drive 4. Belt-drive To adjust the speed of some older full-height, belt-driven floppy disk drives, which of the following actions should you perform? 1. Replace the drive belt only 2. Observe the data on the floppy disk with an oscilloscope and adjust for maximum signal 3. Observe the drive speed frequency with an oscilloscope and adjust for proper speed 4. Observe the strobo-disk under a fluorescent light and adjust the speed until the strobo-disk spokes appear to be stationary Which of the following is NOT a function of the drive electronic circuit board? 1. To control the electromechanical parts of the disk drive 2. To control the operation of the read/write heads 3. To interface the disk drive to the computer 4. To interface the disk drive to the disk controller A 4-pin, in-line connector on the drive electronic circuit board of a floppy disk drive serves which of the following functions? 1. Provides power to the drive 2. Provides control signals to the drive 3. Transfers serial data from the heads to the. drive controller 4. Transfers serial data from the disk controller to the write head 76

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11-32. 11-33. 11-34. 11-35. 11-36. The head actuator assembly in a floppy disk drive has what purpose? 1. To retract the heads so the disk can be removed from the drive only 2. To move the heads to the proper position on the disk 3. To enable the write heads 4. To enable the read heads The two read/write heads in a floppy disk drive move independently of one another. 1. True 2. False Which of the following is a description of the construction of the read/write heads in a floppy disk drive? 1. 2. 3. 4. They are made of a hard ferrous material with electromagnetic coils for reading and writing They are made of a soft ferrous material with electromagnetic coils for reading and writing They are made of plastic with electromagnetic coils for reading and writing They are made of a hard ferrous material only and do not need any coils The write head is centered between two erase heads for which of the following reasons? 1. To erase the previous data before new data is written 2. To cancel the write current when a read operation is performed 3. To ensure that data being written does not spill over to adjacent tracks 4. To erase the previous data after the new data is written The number of tracks per inch that can be reliably written on a disk is called the 1. linear coercivity 2. longitudinal coercivity 3. linear density 4. longitudinal density 11-37. 11-38. 11-39. 11-40. 11-41. 11-42. The number of bits per inch that can be reliably written on a track is called the 1. linear coercivity 2. longitudinal coercivity 3. linear density 4. longitudinal density The strength of the magnetic field required to properly record data on a magnetic medium is referred to by which of the following terms? 1. Coercivity 2. Oersteds 3. Density 4. Ferrous Oersteds are used to make what type of measurements? 1. 2. 3. 4. Magnetic field strength Permeability of a ferrous material Magnetic density Magnetic polarity A 5.25-inch floppy disk that is labeled as DSDD has a maximum data capacity of 1. 180 kilobytes 2. 360 kilobytes 3. 720 kilobytes 4. 1.2 megabytes The track width of a 3.5-inch floppy disk is 1. 0.l15 mm 2. 0.16 mm 3. 0.33 mm 4. 0.45 mm Reading a 5.25-inch, 360K disk in a 1.2M disk drive will cause what problem, if any? 1. The disk drive will read the disk with massive read errors 2. The disk drive will be unable to read the disk at all 3. The 360K disk will not fit into a 1.2M disk drive 4. No problem; the disk drive will read the disk normally 77

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11-43. 11-44. Using a 1.2M, 5.25-inch drive to write data on a 5.25-inch, 360K disk that was originally created in a 360K disk drive will result in what problem, if any? 1. The 1.2M drive will not write on the 360K disk 2. The 360K disk will not fit into the 1.2M drive 3. The 1.2M drive will write a narrow track through the wider track on the 360K disk, which could result in read errors 4. None; no problem will be encountered Formatting a 5.25-inch, 360K DSDD disk as a 1.2M HD disk will result in what problem, if any? 1. The disk will not format because the DOS format program will check the media indicator on the disk and not permit the operation 2. The disk will appear to format correctly, but will be unreliable because of the increased write current required for high density disks 3. The disk will appear to format correctly, but will be unreliable because of the decreased write current required for high density disks 4. None; no problem will be encountered 11-45. Formatting a 720K DSDD, 3.5-inch floppy disk as a 1.44M will result in what problem, if any? 1. The disk will not format because the DOS format program will check the media indicator on the disk and not permit the operation 2. The disk will appear to format correctly, but will be unreliable because of the increased write current required for high density disks 3. The disk will appear to format correctly, but will be unreliable because of the decreased write current required for high density disks 4. None; no problem will be encountered 11-46. A high-density disk can be used in a low- density drive with no problems. 1. True 2. False 11.-47. 11-48. 11-49. 11-50. 11-51. The drive select jumper on a floppy disk drive’s electronics card is used to select which of the following functions? 1. Drive type 2. Drive density 3. Drive address 4. Drive operating speed When installing a floppy drive with a straight two-drive daisy chain cable, you should (a) connect Drive A to what connector and (b) set the drive select jumper to what drive? 1. (a) End (b) DS0 2. (a) End (b) DS1 3. (a) Middle (b) DS0 4. (a) Middle (b) DS1 The twist in a floppy disk cable was designed for which of the following reasons? 1. To ease floppy drive installation by setting all drives to DS1 2. To ease floppy drive installation by setting all drives to DS0 3. To ease floppy drive installation by setting drive A to DS0 and drive B to DS1 The twist in a floppy drive cable cross connects which of the following pins? 1. 10 through 16 only 2. 10 through 20 3. 20 through 26 only 4. 20 through 30 The terminating resistor on a floppy drive (a) is used to supply the proper load to what device and (b) should be connected on the floppy disk at what point on the cable? 1. (a) Computer (b) middle 2. (a) Computer (b) end 3. (a) Disk controller (b) middle 4. (a) Disk controller (b) end 78

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11-52. The media sensor detects a hole for which of the following disks? 1. 5.25-inch, 360K disks 2. 5.25-inch, 1.2M disks 3. 3.5-inch, 720K disks 4. 3.5-inch, 1.44M disks 11-53. It is impossible to recover data on a disk that has been damaged. 1. True 2. False 11-54. Large magnetic disk memory sets are generally used with which of the following computers? 1. Mainframe computers 2. Minicomputers 3. Personal computers only 4. Microcomputers 11-55. What is the diameter of most magnetic disk packs? 1. 10 inches 2. 12 inches 3. 14 inches 4. 16 inches 11-56. The top and bottom platters of most disk packs are used for which of the following functions? 1. To store data 2. To provide position data 3. Both 1 and 2 above 4. To provide protection to the pack 11-57. The servo surface of a disk pack is used for which of the following functions? 1. To control the movement of the read/write heads 2. To maintain alignment of the read/write heads over the proper track 3. Both 1 and 2 above 4. To provide additional data storage area 11-58. When the summing of dipole bits on the disk servo surface is equal to zero volts, which of the following conditions exists? 1. The heads are on an odd numbered track only 2. The heads are on an even numbered track only 3. The heads are between tracks 4. The heads are centered on a track 11-59. On a typical disk memory set’s operator panel, which of the following conditions is NOT indicated by the READY indicator? 1. The disk drive address 2. The disk is up to operating speed 3. The heads are properly loaded 4. No-fault conditions are present 11-60. On a disk memory set’s status/maintenance panel, a fault code of 5 indicates what fault condition? 1. Voltage fault 2. Seek error 3. Multiple heads selected fault 4. No heads selected fault 11-61. The FORMAT WRITE PROTECT switch on a disk memory unit’s status panel protects the disk from being inadvertently formatted by which of the following format commands? 1. Commands from the computer only 2. Commands from the status/maintenance panel only 3. Commands from the computer and the status/maintenance panel 11-62. The functions performed by the disk memory set’s controller microprocessor are governed by which of the following methods? 1. The firmware stored in a ROM 2. The software in the CDS computer 3. The firmware stored in the RAM 4. The software stored in the RAM 79

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11-63. 11-64. 11-65. 11-66. 11-67. The buffer memory in the disk memory set’s computer is used for which of the following functions? 1. 2. 3. 4. To prevent data from being read from the disk during a write operation To prevent data from being written on the disk during a read operation To prevent the loss of data during a reading or writing operation To hold the external function from the computer A disk memory set is capable of reading and writing data on the same disk at the same time. 1. True 2. False A single disk memory set controller is capable of controlling a total of how many drives? 1. One 2. Two 3. Three 4. Four In a disk memory set’s controller to disk drive interface, each drive is connected to the controller by which of the following means? 1. 2. 3. 4. A daisy chained A cable only A daisy chained B cable only Both a daisy chained A and a daisy chained B cable A daisy chained A cable and a unique B cable The A cable in a disk memory set’s controller-to- drive interface is used for which of the following functions? 1. 2. 3. 4. Interrupt signal processing only Send timing signals for read/write operations only Microprocessor control of the drives Data interface between the drive and controller 80 11-68. 11-69. 11-70. 11-71. 11-72. In a disk memory set, converting 16-bit parallel data into a serial NRZ pulse train is a function of which of the following areas? 1. Controller microprocessor 2. Controller buffer memory 3. Data bus control unit 4. Disk control logic In a disk memory set, the data bus control unit gives the highest priority to which of the following transfer requests? 1. Disk control logic and buffer memory 2. Processor input and output holding register 3. Input/output channel 4. Computer generated input data In a disk memory set, data is written on the disk using which of the following encoding methods? 1. 2. 3. 4. Phase encoding Non-return-to-zero Non-return-to-zero-indiscrete Modified frequency modulation What is the minimum speed required for the heads of a disk memory set to load? 1. 3,000 rpm 2. 3,100 rpm 3. 3,200 rpm 4. 3,600 rpm In a disk memory set, if the disk drive motor’s speed drops below 3,100, which of the following events will occur? 1. 2. 3. 4. The heads will crash into the disk The heads will automatically unload or retract The disk memory set will automatically turn off power The disk memory set will continue to operate normally

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11-73. 11-74. The speed of the drive motor in a disk memory set is sensed by which of the following devices? 1. A tachometer 2. A magnetic switch 3. An optical switch 4. A laser switch The static ground spring mounted on the lower end of the spindle assembly serves which of the following functions? 1. 2. 3. Protects the disk from a buildup of static electricity Provides power to the spindle Maintains proper pressure of the spindle and the disk Provides a static charge to the spindle 11-75. Which of the following assemblies are NOT part of the actuator assembly? 1. Carriage and voice coil assembly 2. Rail bracket assembly 3. Head/arm assemblies 4. Magnet assembly 4. 1 References to DOS refer to Microsoft® Disk Operating Systems (MS-DOS®). 81

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ASSIGNMENT 12 Textbook Assignment: “Magnetic Disk Storage”, chapter 10, pages 10-21 through 10-33; and “CD-ROM Storage”, chapter 11, pages 11-1 through 11-7. 12-1. 12-2. 12-3. 12-4. The velocity transducer in a disk memory set drive unit helps control the acceleration and deceleration of which of the following parts? 1. The drive motor 2. The spindle assembly 3. The carriage assembly 4. The operating frequency of the system clock The polarity and amplitude of the voltage induced into the velocity transducer coil by the transducer core indicate which of the following movement characteristics? 1. The speed the disk is rotating 2. The speed of the carriage assembly only 3. The direction of travel of the carriage assembly only 4. The speed and direction of the carriage assembly movement The servo circuit used to position the read/write heads in a disk memory set is centered on the right track when the error voltage is equal to 1. -1 volt 2. 0 volts 3. +1 volt 4. +5 volts The feedback signal in the velocity transducer servo circuit performs which of the following functions? 1. It is used to move the carriage faster 2. It tells the servo circuit when the desired location is reached 3. It opposes the position error and dampens carriage movement 4. It moves the heads by one track 12-5. 12-6. 12-7. 12-8. If a disk has an error on its servo surface, it is possible to rewrite the servo surface. 1. True 2. False The number of sectors per track that will be written on a disk memory set disk pack is selectable by what means, if any? 1. 2. 3. 4. The sector select switch only A set sector size command from the computer only Either the sector select switch or a set sector size command from the computer; the result is the same None; the number of sectors per track is fixed When a disk pack is formatted, the locations of the tracks are controlled by which of the following factors? 1. 2. 3. 4. The prerecorded tracks on the servo disk surface The smallest increment the actuator assembly can move the heads An operator controlled entry of number of tracks A computer command designating number of tracks per inch When a magnetic disk set is operating normally, what is the relationship, if any, between the position of the heads and the disk’s surface? 1. 2. 3. 4. The heads physically contact the disk The heads are held above the disk surface by the head arm springs The heads float above the surface of the disk on a cushion of air None; the position of the heads does not affect disk operation 82

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12-9. Which of the following actions will help prevent damage to the disk pack? 1. 2. 3. 4. Store the disk pack on its side Store the disk pack in an area where large magnetic fields exist Never reassemble the disk pack canister if it is empty Never touch the disk pack’s recording surfaces 12-10. The term “fixed hard disk system” refers to which of the following devices? 1. 2. 3. 4. A hard disk system that is not broken A hard disk system in which the disk is in a sealed case and inaccessible to the user A hard disk system in which the hard disk is contained in a removable cartridge A hard disk system that cannot be used with a microcomputer 12-11. The head disk assembly of a fixed disk system usually contains all of the following parts except which one? 1. The heads 2. The disk platters 3. The head actuator 4. The disk controller 12-12. What is the maximum number of platters that a half-height, fixed disk system may contain? 1. Five 2. Six 3. Seven 4. Eight 12-13. In the manufacture of a fixed hard disk, which of the following processes for applying the magnetic material is similar to the process used in creating semiconductors? 1. Sputtering 2. Platting 3. Electroplating 4. Coating 12-14. 12-15. 12-16. 12-17. 12-18. Which of the following materials is most commonly used as a base for fixed hard disk platters? 1. Polyester film 2. Aluminum alloy 3. Iron alloy 4. Plastic Having the thinnest magnetic media applied to the disk platters has which of the following advantages? 1. 2. 3. 4. A smaller space on the disk is required to reliably store data The head can fly closer to the disk A smaller magnetic field strength is required to reliably store data All of the above In a magnetic disk system, reducing the flying height of the heads has which of the following advantages? 1. 2. 3. 4. Requires a stronger current to accurately write on the disk Reduces the signal to noise ratio, increasing the accuracy of the disk Increases the signal to noise ratio, increasing the accuracy of the disk Increases the physical space on the disk required to store data The U-shaped groove in the bottom of a thin film head is used for what function? 1. 2. 3. 4. To regulate the air pressure and control the flying height of the head To direct the magnetic field from the head onto the disk when writing To channel the magnetic field from the disk to the head when reading To hold the erase head The mechanical system that moves the heads across the disk surface is known as the 1. head drive system 2. head arm 3. head actuator 4. disk drive motor 83

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12-19. A motor that moves imprecise detents when a drive signal is applied is known as a 1. voice coil motor 2. stepper motor 3. servo motor 4. synchro 12-20. Which of the following actuators could suffer a loss of data because of variations in temperature? 1. Voice coil 2. Stepper motor 3. Servo motor 4. Synchro 12-21. For proper positioning of the heads, which of the following actuators requires a dedicated servo surface or servo signal embedded in the sector gaps? 1. Voice coil 2. Stepper motor 3. Servo motor 4. Synchro 12-22. The speed of the spindle motor in a fixed disk is controlled by which of the following devices? 1. An optical sensor 2. A tachometer only 3. A feedback loop only 4. A tachometer and feedback loop 12-23. Timing and synchronization between a fixed disk drive and the drive controller are accomplished by which of the following means? 1. A clock on the controller 2. A clock on the disk drive logic board 3. Special timing signals on the disk 4. Data and flux reversal pulses 12-24. Which of the following data encoding methods is NOT used with fixed disk drives? 1. Modified frequency modulation 2. Frequency modulation 3. Run length limited 4. Non-return-to-zero indiscrete 12-25. A fixed disk system that uses frequency modulation to encode data will store the byte 1010 0001 as which of the following codes (P=pulse, N=no pulse)? 1. PPPPNPNPNPPPPPNP 2. PPPNPPPNPNPNPNPP 3. NPPPNPPPPPPPPPNP 4. NPNPNPNPNPNPNPNP 12-26. Which of the following data encoding methods groups bits together and uses a table to determine what code is written on the disk? 1. Non-return-to-zero 2. Frequency modulation 3. Modified frequency modulation 4. Run length limited 12-27. A fixed disk system using modified frequency modulation will encode a logic ZERO that is preceded by a logic ONE in which of the following ways? 1. No pulse followed by a pulse 2. A pulse followed by no pulse 3. Two no-pulse periods 4. Two pulses 12-28. Which of the following encoding methods will increase by 50 percent the data density and transfer rate of a fixed disk system? 1. Run length limited 2. Non-return-to-zero 3. Frequency modulation 4. Modified frequency modulation 12-29. The encoding method used to write data on a fixed disk is determined by which of the following means? 1. The application software installed in the computer 2. The disk operating system (DOS) installed in the computer 3. The disk controller 4. The manufacturer of the disk drive 84

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12-30. 12-31. 12-32. 12-33. 12-34. 12-35. The run length limited encoding method can be used with any fixed disk drive. 1. True 2. False A fixed disk’s interleave factor is the relationship between what two items? 1. The physical sectors and the logical sectors of a track 2. The disk drive and the disk controller 3. The disk drive and the encoding method used to store data 4. The disk drive and the computer Interleaving a fixed disk has which of the following effects? 1. Increases data density on the disk 2. Decreases data density on the disk 3. Increases data retrieval and transfer time 4. Decreases data retrieval and transfer time On a fixed disk with nine sectors per track and an interleave factor of 4:1, what is the physical sector numbering? 1. 1, 9, 7, 5, 3, 2, 8, 6, 4 2. 1, 8, 6, 4, 2, 9, 7, 5, 3 3. 1, 2, 3, 4, 5, 6, 7, 8, 9 4. 1, 4, 8, 3, 7, 2, 6, 5, 9 Which of the following interleave factors will provide the fastest data transfer rate? 1. 4:1 2. 3:1 3. 2:1 4. 1:1 Which of the following drive interfaces is a smart interface that can disconnect itself from the computer while it processes computer requests? 1. ST-506/412 2. IDE 3. ESDI 4. SCSI 12-36. 12-37. 12-38. 12-39. 12-40. 12-41. Which of the following interfaces requires that a set-up program in the computer be run to describe the fixed disk drive’s characteristics? 1. ST-506/412 2. IDE 3. ESDI 4. SCSI Which of the following interfaces has the data encoder/decoder on the controller card? 1. ST-506/412 2. IDE 3. ESDI 4. SCSI Which of the following interfaces could damage a disk if a low-level format is attempted? 1. ST-506/412 2. IDE 3. ESDI 4. SCSI Which of the following interfaces is actually a host adapter, capable of interfacing up to eight devices? 1. ST-506/412 2. IDE 3. ESDI 4. SCSI Which of the following interfaces is capable of formatting a drive up to 60 sectors per track and can support a 1:1 interleave? 1. ST-506/412 2. IDE 3. ESDI 4. SCSI Which of the following interfaces is manufactured on the motherboards of personal computers? 1. ST-506/412 2. IDE 3. ESDI 4. SCSI 85

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12-42. 12-43. 12-44. 12-45. Which of the following actions does the format program take while performing a low-level format on a fixed disk system? 1. Checks for bad tracks and marks them with a checksum code 2. Writes the sectors and tracks on the disk 3. Both 1 and 2 above 4. Divides the disk into DOS partitions Write precompensation helps eliminate data errors by what method, if any? 1. 2. 3. 4. Increasing the number of bytes per sector as the heads move toward the inner tracks of the disk Decreasing the number of bytes per sector as the heads move toward the inner tracks of the disk Changing the spacing of the magnetic fields as the heads move toward the inner tracks of the disk None; write precompensation does not help eliminate data errors Decreasing the amount of current used to write data on the inner tracks of the disk is known as 1. write precompensation 2. reduced write current 3. low-level disk format 4. disk partitioning Write precompensation and reduced write current are necessary for which of the following reasons? 1. 2. 3. 4. The inner tracks of the disk are larger than the outer tracks The inner tracks of the disk are smaller than the outer tracks The disk spins faster when reading the inner tracks The disk spins slower when reading the inner tracks 12-46. 12-47. 12-48. 12-49. 12-50. Runnmg the DOS FDISK program on a fixed disk in a personal computer performs which of the following functions? 1. Prepares the DOS boot sector on the disk 2. Creates the file allocation table on the disk 3. Writes the sectors on the disk 4. Creates the root directory When you erase a file on a disk in a personal computer, which of the following operations does DOS perform? 1. 2. 3. 4. Finds the file and writes all ZEROS to the sectors on the disk that the file occupied Finds the file and writes all ONES to the sectors on the disk that the file occupied Changes the code in the FAT to indicate that the clusters the file occupied are available for data storage Changes the code in the root directory to indicate that the file is erased A virus may only infect your personal computer if it loaded into which of the following types of files? 1. 2. 3. 4. A .COM or .EXE file only A data file only The master boot record only Any file loaded when doing a low-level disk format Which of the following viruses embeds itself into other programs and may contain other types of. viruses? 1. Worm 2. Trojan horse 3. Logic bomb Which of the following viruses tries to endlessly copy itself on a fixed disk, tying up the computer and eventually overloading the disk? 1. Worm 2. Trojan horse 3. Logic bomb 86

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12-51. 12-52. 12-53. 12-54. 12-55. 12-56. Which of the following viruses only executes itself if a certain set of conditions is met? 1. Worm 2. Trojan horse 3. Logic bomb Which of the following viruses is generally the most destructive to a system? 1. Worm 2. Trojan horse 3. Logic bomb Which of the following is NOT a precaution in preventing virus infections? 1. Making regular back-ups 2. Using only authorized software 3. Periodically checking the size of the COMMAND.COM file 4. Using software from an unauthorized source It is usually possible to recover some data from a fixed disk even after a severe head crash. 1. True 2. False In caring for a fixed disk, which of the following actions NOT recommended? 1. 2. 3. 4. Limit the number of times the system is turned on and off Avoid eating, drinking, and smoking around computer systems Clean the fixed disk on a regular basis Perform the low-level format of a fixed disk in the position and temperature that the disk will be used A multimedia CD-ROM is a disc that contains which of the following types of information? 1. 2. 3. 4. Data files only Digitized audio only Digitized video only Data files, digitized audio, and digitized video 12-57. 12-58. 12-59. 12-60. 12-61. Data is stored on a CD-ROM by which of the following methods? 1. Magnetizing spots on the disc 2. Etching tiny ones and zeros on the disc 3. Punching tiny holes through the disc 4. Etching pits between lands on the disc What is the diameter of a compact disc? 1. 120mm 2. 130 mm 3. 140 mm 4. 150 mm The data area of a CD-ROM consists of which of the following sections? 1. 2. 3. 4. The table of contents, the lead-out area, and the clamping area The table of contents and the program area only The table of contents, the program area, and the lead-out area The lead-out area and the clamping area CD-ROM storage has all of the following advantages except which one? 1. 2. 3. 4. Fast access time Storage capacity of over 540 megabytes of information Extremely durable Can store a mixture of digital information Data is stored on a CD-ROM disc in which of the following ways? 1. 2. 3. 4. In a series of separate tracks only In a series of separate tracks divided into sectors In a continuous spiral track divided into sectors In a continuous spiral sector divided into tracks 87

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12-62. 12-63. 12-64. 12-65. 12-66. Which of the following is a description of the operation of a drive that uses constant linear velocity? 1. 2. 3. 4. The speed of the disc decreases as the read head moves toward the outer edge of the disc The speed of the disc increases as the read head moves toward the outer edge of the disc The speed of the disc remains constant throughout the range of the read head The physical sizes of the sectors on the spiral track increase toward the outer edge of the disc Sectors on a CD-ROM are accessed by which of the following address forms? 1. Track:sector:head 2. Minute:second:sector 3. Hour:minute:sector 4. Cylinder:sector When a CD-ROM disc is manufactured, the data is written on the disc in which of the following formats? 1. Eight-to-fourteen modulation 2. Modified frequency modulation 3. Run length limited 2, 7 4. Non-return-to-zero The laser used in the optical head of a CD-ROM drive emits light in which of the following bands? 1. Ultraviolet 2. Visible spectrum 3. Infrared 4. White The collimating lens in a CD-ROM drive’s optical head is used to perform which of the following functions? 1. To focus the laser beam on the disc 2. To reduce the divergence of the laser beam 3. To focus the laser beam on the photodector circuit 4. To reduce the intensity of the laser beam 12-67. 12-68. 12-69. 12-70. 12-71. The final step in focusing the laser beam on the disc is accomplished by which of the following items? 1. Optical head 2. Objective lens 3. Collimating lens 4. Plastic coating on the disc Splitting the reflected laser beam and directing the split beams to a set of photodiodes is used in which of the following functions? 1. Ensuring the disc is rotating at the proper speed 2. Maintaining proper tracking and focus 3. Detecting data on the disc 4. Both 2 and 3 above The control section decodes the eight-to-fourteen data read from a disc using what method, if any? 1. 2. 3. 4. Checking the data for parity errors Using the data to address a ROM for the proper byte Adding the data to a set value to find the proper byte None; the data does not need to be decoded The turntable must rotate so that the data track passes over the optical head at what speed? 1. 1.3 meters per second 2. 1.5 meters per second 3. 1.7 meters per second 4. 1.9 meters per second The interface section provides control for which of the following functions? 1. 2. 3. 4. The transfer of data from the CD-ROM drive to the computer The receipt of data from the computer to be written on the disc Both 1 and 2 above The transfer of data from the disc to the control section of the drive 88

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12-72. Storing information on a large database on CD- ROM has which of the following advantages? 1. 2. 3. 4. Reduces the amount of paper storage required Enables the information to be quickly retrieved Allows the information to be quickly cross- referenced All of the above 12-73. In a multimedia or CD-I application, the different types of data are distinguished by which of the following methods? 1. 2. 3. 4. The control section analyzes the data to determine what it is All data is sent to the computer and the computer determines what it is A code is written at the start of each sector to identify the type of data The disc is divided into specific areas to store audio, video, and program information 89

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ASSIGNMENT 13 Textbook Assignment: “Printers,” chapter 12, pages 12-1 through 12-15; and “Data Conversion Devices and Switchboards,” chapter 13, pages 13-1 through 13-5. 13-1. Printers that use pins or hammers to strike an 13-2. 13-3. 13-4. inked ribbon to transfer characters to paper are classified as what type? 1. Impact 2. Nonimpact 3. Thermal 4. Laser A predefine table of characters that can be printed by a printer is known as the 1. print head 2. character set 3. printer code 4. character library The 8-bit printer codes that define the alphanumeric characters of the standard English alphabet are contained in which of the following character sets? 1. American National Standards Institute (ANSI) character set 2. Computer Institute character set 3. Institute of Electrical and Electronics Engineers (IEEE) standard character set 4. American National Standard Code for Information Interchange (ASCII) character set Standard printer character codes contain a total of how many data bits? 1. Five 2. Six 3. Seven 4. Eight 13-5. 13-6. 13-7. 13-8. 13-9. 90 The ASCII decimal value 66 represents which of the following characters? 1. A 2. a 3. B 4. b The ASCII decimal values 128 through 255 are used for which, if any, of the following characteristics or codes? 1. 2. 3. 4. Alternate character set Control codes Lowercase letters of the main character set None of the above; they are undefined and have no meaning The type of characters that a printer can print depends on which of the following factors? 1. The type of printer only 2. The software only 3. The type of printer and the software 4. The type of computer A printer driver is a software routine that performs which of the following functions? 1. 2. 3. 4. Defines the printer capabilities to the software Defines the character set to the printer Defines the graphics capability of the printer All of the above A separate printer driver is required for each type of printer that a software program will support. 1. True 2. False

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13-10. The original ASCII codes contained what total number of control codes? 1. 16 2. 32 3. 48 4. 54 13-11. Which of the following ASCII codes (in decimal) will result in the printer performing a carriage return? 1. 10 2. 12 3. 13 4. 27 13-12. The ASCII ESCAPE code (27) when combined with other characters and sent to a printer is used for which of the following functions? 1. To tell the printer to start printing 2. To initiate enhanced features of many printers 3. To stop all printer operations 4. To change the printer driver of the software 13-13. Printing each letter or character on a line based on the character’s actual size is known as which of the following printer spacing methods? 1. Proportional spacing 2. Prearranged spacing 3. Relative spacing 4. Fixed spacing 13-14. A font describes which of the following characteristics of the type? 1. Style of the typeface only 2. Size of the typeface only 3. Both the style and size of the typeface 4. All the characters a printer is capable of printing 13-15. The printer measure that is equal to 1/72 inch is known by what term? 13-16. Which of the following print modes is used to print text across the length of a standard size sheet of paper? 1. Landscape mode 2. Portrait mode 3. Picture mode 4. Graphics mode 13-17. What is the most widely used serial interface between a personal computer and a printer? 1. EIA interface 2. Centronics® interface 3. RS-232 interface 4. RS-323 interface 13-18. Parallel-to-serial data conversion for use in serial interfaces of personal computers is accomplished by which of the following circuits? 1. RS-232 interface 2. Universal asynchronous receiver/transmitter (UART) 3. Centronics interface 4. Serial converter 13-19. In a serial interface that uses software handshaking, what minimum number of pins must be connected? 1. Five 2. Two 3. Three 4. Four 13-20. The Centronics parallel interface uses what (a) connector at the computer end of the cable and (b) connector at the printer end of the cable? 1. (a) 36-pin Centronics (b) 36-pin Centronics 2. (a) 36-pin Centronics (b) DB-25 subminiature 3. (a) DB-25 subminiature (b) DB-25 subminiature 4. (a) DB-25 subminiature (b) 36-pin Centronics 1. Elite 2. Pica 3. Pitch 4. Point 91

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13-21. The Centronics parallel interface is which of the 13-22. 13-23. 13-24. 13-25. 13-26. following types of interface between the computer and the printer? 1. 8-bit, one-way 2. 8-bit, two-way 3. 16-bit, one-way 4. 16-bit, two-way Which of the following is NOT a function of the control panel on a printer? 1. Activating the print head 2. Providing operator selectable fonts 3. Initiating the self-test function 4. Controlling whether the printer is online or offline Continuous paper with perforated holes on each side is designed to be used with which of the following paper-feed methods? 1. Friction feed 2. Tractor feed 3. Sheet feeder 4. Pressure feed The paper-feed motor in a tractor-feed printer is usually what type of motor? 1. Stepper 2. Synchro 3. Servo 4. Reduction Which of the following paper-feed methods uses one or more pressure rollers to move paper through the printer? 1. Tractor feed 2. Friction feed 3. Sheet feeder 4. Both 2 and 3 above Which of the follow lists includes only impact printers? 1. Chain, band, and laser 2. Drum, dot matrix, and inkjet 3. Inkjet, laser, and daisy wheel 4. Chain, band, drum, dot matrix, and daisy wheel 13-27. 13-28. 13-29. 13-30. 13-31. 92 The maximum number of characters that a drum printer can print on one line is determined by which of the following factors? 1. The type of software being used 2. The number of rows on the drum 3. The number of columns on the drum 4. The type of computer being used A drum printer has which of the following numbers of hammers? 1. One for each column on the drum 2. One for each line the printer is capable of printing 3. One for each letter of the alphabet and seven for special characters 4. Two for each letter of the alphabet (one for uppercase and one for lowercase) and seven for special characters The quality of print produced by a dot matrix printer is directly related to which of the following factors? 1. The number of print wires in the print head 2. The number of characters being printed 3. The size of the print head 4. The type of font being printed The print wires in a dot matrix print head are driven by which of the following devices? 1. A relay 2. One solenoid that drives all the print wires 3. An individual solenoid for each print wire 4. A hi-stable multivibrator A dot matrix print head is mounted on a heat sink for 1. 2. 3. 4. which of the following reasons? To dissipate heat generated by the moving print wires To dissipate heat generated by the solenoid drivers To dissipate heat generated by the printer’s power supply To heat up the print wires to the proper operating temperature

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13-32. A nine-pin dot matrix print head prints in near letter quality mode by making two passes for each line, advancing the paper what distance before the second pass? 1. One-half line 2. One-half letter space 3. One-half dot space 4. One dot space 13-33. A 24-pin print head prints near letter quality faster and with greater resolution than a 9-pin print head for which of the following reasons? 1. It prints two characters at a time 2. It prints larger dots 3. It prints more dots per character only 4. It has two columns of offset print wires and prints smaller dots 13-34. The print head of a dot matrix printer is moved across the length of the platen by a wire, belt, or chain that is connected to which of the following devices? 1. Paper motor 2. Platen motor 3. Print head motor 4. Carriage motor 13-35. The daisy wheel printer has which of the following advantages over the dot matrix printer? 1. It prints letter quality 2. It can print carbon copies 3. Both 1 and 2 above 4. It prints faster than a dot matrix printer 13-36. The laser printer is what type of printer? 1. Electrostatic 2. Electrosensitive 3. Electrothermal 4. Impact 13-37. Laser printers are classified as what class of printer? 1. Character 2. Line 3. Daisy 4. Page 13-38. The photosensitive aluminum cylinder in a laser printer is known as the 1. primary corona 2. laser source 3. toner drum 4. print drum 13-39. The laser diode generates a single wavelength light in bursts of one-millionth of a second or less. 1. True 2. False 13-40. The erase lamps have which of the following effects on the print drum? 1. They apply a positive charge to the drum 2. They apply a negative charge to the drum 3. They neutralize any charge on the drum 4. They neutralize any toner on the drum 13-41. During a laser printer’s print cycle, a charge of -600V is applied to the print drum by what device? 1. Erase lamps 2. Primary corona wire 3. Secondary corona wire 4. Laser beam 13-42. The laser beam’s horizontal scan across the drum is developed by what device? 1. Rotating hexagon mirror 2. Laser diode carriage motor 3. Laser beam lens assembly 4. Laser beam shutter 13-43. What effect, if any, does the laser beam striking the print drum have on the print drum? 1. The area of the print drum becomes positively charged 2. The area of the print drum becomes negatively charged 3. Any charge on the print drum becomes neutralized 4. None 93

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13-44. The toner used in a laser printer consists of a fine powder containing metal, dyes, and 1. ink 2. sand 3. glass 4. plastic 13-45. As the print drum rotates past the toner reservoir, which of the following events occurs? 1. The excess toner on the drum is deposited into the reservoir 2. The toner is attracted to the positively charged areas of the drum 3. The toner is attracted to the negatively charged areas of the drum 4. The toner coats the entire drum 13-46. The transfer corona is used for which of the following functions? 1. It charges the toner to enable the toner to be transferred from the reservoir to the drum 2. It charges the drum to enable the toner to be transferred from the reservoir to the drum 3. It charges the drum to enable the transfer of toner from the drum to the paper 4. It charges the paper to enable the transfer of toner from the drum to the paper 13-47. The toner is permanently bonded to the paper by which of the following means? 1. The registration rollers apply pressure to the paper 2. The fusing rollers apply heat and pressure to the paper 3. The transfer corona applies heat to the paper 4. The primary corona applies heat to the paper 13-48. On a laser printer, a printout has blotches evenly spaced every 1.75 inches. This problem is probably caused by a defect in which of the following components? 1. Upper registration roller 2. Lower registration roller 3. Transfer roller 4. Lower fusing roller 13-49. A laser printer with a scratched print drum can be repaired by which of the following actions? 1. Removing the print drum and polishing the scratch out 2. Replacing the print drum only 3. Replacing the cartridge 4. Replacing the laser diode 13-50. To print a font using a Hewlett-Packard or compatible laser printer, the font definition bit map provides the printer with which of the following information? 1. Whereto place the dots to print the characters 2. Whereon the page to print the character 3. Whereon a line to print the character 4. Whereon the page to print graphic pictures 13-51. Soft fonts are font bit maps that are handled in which of the following ways? 1. They are loaded into the computer’s memory and transferred to the printer when needed 2. They are resident in the printer’s ROM 3. They are contained in ROM cartridges that plug into the computer 4. They are contained in RAM cartridges that plug into the printer 13-52. PostScript® printers are capable of printing a typeface in different sizes by using which of the following methods? 1. A different bit map for each size of character to be printed 2. A mathematical definition for each typeface and mathematically scaling the characters to the desired size 3. A mathematical definition for each size character 4. A bit map for one typeface that is mathematically scaled to change the size 13-53. Electrothermal printers use the heat of wires or pins to burn images onto plain paper. 1. True 2. False 94

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13-54. 13-55. 13-56. 13-57. Ink jet printers form images on the paper by which of the following methods? 1. 2. 3. 4. Spraying ink on the paper through a stencil to form the character Spraying ink on the paper with the print head moving to form each character Spraying ink on the paper in a series of dots to form the characters similar to those of a dot matrix printer Electrostatically charging the paper to attract the ink to the proper position to form the character The ink in an ink jet printer is sprayed onto the paper by which of the following methods? 1. 2. 3. 4. By using a pneumatic pump By using piezoelectric crystals to squeeze a nozzle tube By using small heaters to expand an air bubble and force the ink out of the nozzle Either 2 or 3 above, depending on the printer An analog signal has which of the following characteristics? 1. It varies continuously with time 2. Each bit position represents a portion of the overall quantity 3. The codes of ONEs and ZEROs indicate a value at a particular instant of time 4. The summation of the set bits is normally the quantity to be represented Analog signals representing analog quantities and binary numbers representing digital quantities have which of the following characteristics in common? 1. They both vary continuously with time 2. They both can express an infinitely large quantity 3. They both express values as a summation of set bits 4. They both express values within a given set of limits IN ANSWERING QUESTIONS 13-58 THROUGH 13-60, REFER TO FIGURE 13-1 ON PAGE 13-2 OF THE TEXT. 13-58. 13-59. 13-60. 13-61. 13-62. To indicate a range of values of 10 miles, what should the amplitude of the analog signal be, in volts peak to peak? 1. 7 2. 11 3. 12 4. 20 What should the digital quantity bit pattern contain to indicate a range of 12 miles? 1. 00011 2. 01100 3. 10010 4. 11000 To indicate a range of 25 miles, (a) the analog signal will be how many volts peak to peak while (b) the digital quantity bit pattern will contain what bit pattern? 1. (a) 25 (b) 11001 2. (a) 25 (b) 11100 3. (a) 27 (b) 11001 4. (a) 27 (b) 11100 The reference signal for an analog-to-digital conversion is normally equal to which of the following values? 1. The average value of the analog signal 2. The minimum value of the analog signal 3. The maximum value of the analog signal 4. The maximum value of the transmitted data In which of the following conversion operations is the input analog signal tested repeatedly over a period of time? 1. Encoding 2. Sampling 3. Decoding 4. Quantization 95

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13-63. 13-64. 13-65. 13-66. 13-67. 13-68. Which of the following conversion operations reduces the result of the conversion to a binary code acceptable to digital equipments? 1. Encoding 2. Sampling 3. Decoding 4. Quantization Which of the following conversion operations rounds out the conversion to the value of the LSB? 1. Encoding 2. Sampling 3. Decoding 4. Quantization Which of the following conversion operations is performed only when a conversion is required? 1. Encoding 2. Sampling 3. Decoding 4. Quantization In natural binary code, which of the following bit positions has the greatest weight or represents the largest value? 1. BAM 2. LSB 3. MSB Binary angular measurement uses what binary code? 1. Natural binary code 2. Hexadecimal 3. Gray code 4. BCD BAM data words are designed to indicate what maximum number of degrees of angular measurement? 1. 45 2. 90 3. 180 4. 360 13-69. 13-70. 13-71. 13-72. 13-73. When only the MSB of a BAM word used to transmit a non-angular value is set, what is the quantity indicated? 1. 2. 3. 4. The minimum value that can be transmitted The maximum value that can be transmitted One half of the minimum value that can be transmitted One-half of the maximum value that can be transmitted Binary-coded decimal uses what total number of bit positions to represent a single decimal digit? 1. One 2. Two 3. Eight 4. Four Which of the following binary codes is designed to change from one value to the next with only one bit change? 1. Hexadecimal 2. BCD 3. Gray code 4. Natural binary code A torque system has which of the following characteristics? 1. It provides a turning force to drive light loads 2. It provides an electrical output used to control the power that performs mechanical work 3. It is the combination of a synchro transmitter and synchro receivers 4. It is a variety of rotary, electromechanical, position sensing devices A synchro system has which of the following characteristics? 1. It provides a turning force to drive light loads 2. It provides an electrical output used to control the power that performs mechanical work 3. It is the combination of a synchro transmitter and synchro receivers 4. It is a variety of rotary, electromechanical, position sensing devices 96

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13-74. Which of the following is the primary characteristic of a control synchro system? 1. It provides a turning force to drive light loads 2. It provides an electrical output used to control the power that performs mechanical work 3. It is the combination of a synchro transmitter and synchro receivers 4. It is a variety of rotary, electromechanical, position sensing devices 13-75. The term “synchro” has which of the following meanings? 1. It provides a turning force to drive light loads 2. It provides an electrical output used to control the power that performs mechanical work 3. It is the combination of a synchro transmitter and synchro receivers 4. It is a variety of rotary, electromechanical, position sensing devices 97

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ASSIGNMENT 14 Textbook Assignment: “Data Conversion Devices and Switchboards,” chapter 13, pages 13-5 through 13-41. IN ANSWERING QUESTIONS 14-1 THROUGH 14-4, SELECT FROM THE FOLLOWING LIST THE SYNCHRO SYSTEM DESCRIBED BY THE QUESTION. ANSWERS MAY BE USED MORE THAN ONCE. 14-1. 14-2. 14-3. 14-4. 14-5. 14-6. 1. Single-speed synchro 2. Multispeed synchro 3. Dual-speed synchro Allows for a coarse value and a fine value to be sent at the same time. Uses more than one speed of data transmission. Uses a single synchro transmitter to transmit the entire range of data. Is the least accurate synchro system. In a dual-speed synchro system, which of the following values is/are sent by the synchro with (a) the highest ratio and (b) the lowest ratio? 1. (a) Coarse only (b) Fine only 2. (a) Fine only (b) Coarse only 3. (a) Coarse only (b) Fine and coarse 4. (a) Fine and coarse (b) Fine and coarse At any instant, the amplitude and polarity of the stator voltages, when compared to the supply or reference voltage, indicate the angular position of the rotor. 1. True 2. False 14-7. The sector conversion method divides the 360° of rotation into what total number of sectors? 1. 6 2. 8 3. 45 4. 60 IN ANSWERING QUESTIONS 14-8 AND 14-9, REFER TO TABLE 13-2 ON PAGE 13-7 OF THE TEXT. 14-8. 14-9. 14-10. 98 When the stator voltages S1 and S3 are in phase with the reference and S2 is out of phase, what sector is selected? 1. 30° to 90° 2. 90° to 150° 3. 150° to 210° 4. 330° to 30° When the stator voltages S1 and S2 are in phase with the reference and S3 is out of phase, what sector is selected? 1. 30° to 90° 2. 90° to 150° 3. 150° to 210° 4. 270° to 330° What is the total number of stator voltages required to determine the ratio angle once the sector has been determined? 1. One 2. Two 3. Three 4. Four

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14-11. During the octant conversion process, the 14-12. 14-13. 14-14. 14-15. 45-degree octant is determined by which of the following means? 1. The polarity and amplitude of two of the stator voltages 2. The polarity and amplitude of the sine and cosine voltages 3. The phase difference between two of the stator voltages 4. The phase difference between the sine and cosine voltages Once the octant has been determined during the octant conversion process, the remaining bit positions of the BAM word are determined by a trial and error approximation of a test binary angle against a ratio angle. 1. True 2. False How many synchro-to-digital conversions are required to generate a single BAM word from a dual-speed synchro input? 1. One 2. Two 3. Eight 4. Four Linear signals normally represent a quantity based on which of the following characteristics? 1. Signal amplitude 2. Signal frequency 3. Signal phase relationship 4. All of the above Scalar or resolver outputs are composed of which of the following signals? 1. A single linear waveform 2. A single waveform representing the sine of an angle 3. A single waveform representing the cosine of an angle 4. Two waveforms representing the sine and cosine of an angle 14-16. 14-17. 14-18. 14-19. 14-20. 14-21. The binary input to digital-to-analog converters is normally in which of the following binary forms? 1. Binary-coded decimal 2. Gray code 3. Binary angular measurement word 4. Natural binary A single digital-to-analog converter outputs what maximum number of proportional voltage signals? 1. One 2. Two 3. Three 4. Four What maximum number of DACs can be mounted on a mounting base? 1. One 2. Two 3. Three 4. Four Which of the following functions is/are performed by the BASE? 1. Selects the DAC operating mode 2. Provides all electrical interfaces for the DACs 3. Provides simulated digital data for test purposes 4. All of the above Each channel of a DAC can output which of the following signals? 1. Two linear voltages 2. A single-speed synchro 3. A sine/cosine resolver 4. All of the above, depending on the operational mode selected Which of the following functions is NOT performed by the EF and control address words? 1. 2. 3. 4. Master clear the DAC Initiate RDUC operations Set the individual DAC’s control address Define the control address of the DAC to receive the data words 99

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14-22. What is the maximum number of data words that can be sent in an output buffer to the DAC/BASE? 1. 8 2. 10 3. 12 4. 16 14-23. Individual DAC channels are identified by what code? 1. The A channel code 2. The B channel code 3. The data address code 4. The control address code IN ANSWERING QUESTIONS 14-24 THROUGH 14-27, SELECT FROM THE FOLLOWING LIST THE FUNCTIONAL SECTION OF THE DAC FUNCTION DESCRIBED IN THE QUESTION. ANSWERS MAY BE USED MORE THAN ONCE. 14-24. 14-25. 14-26. 14-27. 14-28. 1. Analog section 2. Digital section 3. Power supply section Generates the ODR signal to the computer to start the data word processing. Contains resistive ladder networks. Provides five regulated dc voltages. Converts the output of the holding registers to proportional voltages. Which of the following DAC sub-channels outputs the SINE waveform when in the TRIG mode? 1. A 2. B 3. A1 4. A2 14-29. 14-30. Which of the following DAC sub-channels outputs linear waveforms when in the LINEAR mode? 1. A 2. A1 only 3. A2 only 4. A1 and A2 Which of the following BASE controls allows for the selection of simulated test data from the BASE switches? 1. Mode control 2. Digital input 3. Channel A mode 4. Channel A data address 14-31. The selection of synchro or resolver output is performed by which of the following DAC/BASE controls? 1. Mode control only 2. Channel A mode only 3. Both mode control and channel A mode 4. Channel A data address 14-32. The digital-to-synchro converter in the DAC 14-33, 14-34. converts BAM data words to which of the following types of outputs? 1. Linear voltages 2. Sine and cosine voltages 3. Dual-speed synchro signals 4. Single-speed synchro signals The KCMX can accept demand digital from what maximum number of devices? 1. 8 2. 16 3. 24 4. 32 Multiplexing data converters allow the CDS computer to communicate with a variety of analog and digital equipments. 1. True 2. False 100

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IN ANSWERING QUESTIONS 14-35 THROUGH 14-37, SELECT FROM THE FOLLOWING LIST THE DEMAND DIGITAL CONTROL SIGNAL FOR THE FUNCTION DESCRIBED IN THE QUESTION. NOT ALL ANSWERS ARE USED. 1. Enter signal 2. Read signal 3. Error signal 4. Demand digital interrupt 14-35. A program controlled function signal. 14-36. Generated when a data entry device has input ready for transmission to the controlling computer. 14-37. Activates the DD device data lines. 14-38. The KCMX can accept ready digital data from what maximum number of inputs? 1. 8 2. 16 3. 24 4. 32 14-39. The KCMX is capable of communicating with digital devices over what total number of DIC/DOC channels? 1. One 2. Two 3. Three 4. Four 14-40. The KCMX can receive what maximum number of status signals? 1. 60 2. 45 3. 30 4. 15 14-41. On KCMX ready analog inputs, which of the following types of conversion is performed? 14-42. 14-43. 14-44. 14-45 14-46 The KCMX uses what maximum number of reference voltages to perform synchro-to-digital conversions on ready analog inputs? 1. 8 2. 12 3. 16 4. 20 The computer input data register is located on which of the following KCMX panels? 1. A1 2. A2 3. A3 4. A4 The DD/DDI select ON/OFF switches on the KCMX perform which of the following functions? 1. They identify the group mode 2. They indicate if an ENTER signal is on the line 3. They enable or disable the individual device DDI enter signals 4. All of the above Which of the following KCMX controls/ indicators indicates the status of individual external signals? 1. Data register 2. Output register 3. Control output register 4. Computer input data register DOC equipment output data maybe viewed using which of the following registers? 1. 2. 3. 4. Data register Output register Control output register Computer input data register 1. Digital-to-linear 2. Digital-to-synchro 3. Linear-to-digital 4. Synchro-to-digital 101

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14-47. 14-48. 14-49. 14-50. 14-51. Which of the following duplex controls/ indicators is/are lighted to indicate that computer A is in control of the KCMX and has received an input data request from computer A? 1. The A ODR 2. The A IDR only 3. The A IN CONTROL only 4. Both the A IDR and the A IN CONTROL Which of the following MODE SELECT switch positions enables the KCMX to simulate computer operations by use of the front panel controls? 1. DOC 2. MANUAL 3. NORM 4. A/D CONV Which of the following KCMX pushbuttons is used to reset all logic circuits? 1. BFE 2. DATA 3. MASTER CLEAR 4. ADDRESS CLEAR Which of the following KCMX indicators maybe used to display the starting address of a set of addresses to be interrogated in test mode? 1. INTERRUPTS 2. FINAL ADDRESS 3. ADDRESS CLEAR 4. CURRENT ADDRESS Which of the following operations is indicated by a lighted CONTROL CHANNEL indicator? 1. A simulated DOC input 2. An external function 3. The KCMX is in test mode 4. A control word transfer 14-52. 14-53. 14-54. 14-55. 14-56. 14-57. When address 77 is detected in the FINAL ADDRESS, which of the following interrupt indicators is lighted? 1. ID ERR 2. DIC REQ 3. ILL ADR 4. Each of the above When the KCMX has granted control to computer A or B, which of the following KCMX indicators is lighted? 1. DATA 2. INCONTROL 3. EOC ENABLE 4. COMPUTER ACKNOWLEDGE When in the DIC computer mode, the DIC channel EF/INT and OA/IDR indicators light for interrupts and input data requests. 1. True 2. False Which of the following positions should the SELECTOR switch be into simulate a 120-degree angle? 1. 1 2. 2 3. 3 4. 4 On digital switchboards, what is the minimum number of manual switches required for each I/O device or computer channel? 1. One 2. Two 3. Three 4. Four Control signals used to initiate switching action are generated by which of the following devices? 1. DFCS only 2. CSCP only 3. Both DFCS and CSCP 102

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14-58. 14-59. 14-60. 14-61. 14-62. 14-63. Each DFCS section contains what maximum number of switch panels? 1. 12 2. 18 3. 24 4. 32 Linear movement switch panels contain assemblies that can be switched to which of the following number of positions? 1. Six 2. Five only 3. Three only 4. Either three or five, depending on the type of assembly The switch control and potential transformer ACO assembly is used to provide voltages for bench testing which of the following DFCS panels? 1. Relay tester assemblies 2. Power distribution panels 3. Linear movement switches 4. All of the above What color CSCP pushbutton/indicator (PBI) will be lighted when the associated DFCS linear slide switch is in the ALTERNATE position? 1. Red 2. White 3. Green 4. Yellow What color CSCP PBI will be lighted when the associated DFCS linear slide switch is in the OFF position? 1. Red 2. White 3. Green 4. Yellow The DFCS can be controlled from two or more CSCPs at the same time. 1. True 2. False 14-64, 14-65. Ship’s cables are identified by which of the following markings? 1. Wire number 2. Cable type only 3. Cable group number only 4. Cable type and group number A ship’s wire has a plastic number with the following markings” “65 PD 632.” The number 632 indicates what designation? 1. Cable number 2. Function number 3. Circuit designator 4. Assigned wire number 14-66. Which of the following designations maybe used to identify a CSCP 85-pin connector? 1. JA 2. JB 3. JK 4. JP 14-67. Each analog switchboard section contains what maximum number of panels? 1. 2 2. 12 3. 24 4. 36 IN ANSWERING QUESTIONS 14-68 THROUGH 14-72, SELECT FROM THE FOLLOWING LIST THE ANALOG SWITCHBOARD PANEL WHOSE FUNCTION IS DESCRIBED IN THE QUESTION. ANSWERS MAY BE USED MORE THAN ONCE. 1. 2. 3. 4. Indicator panel assembly Fuse panel assembly Meter panel assembly Flasher panel assembly 14-68. Contains overflow fuses for associated switch panels. 14-69. Monitors ac or dc power busses. 14-70. Uses a motor driven cam to open or close control or status signal circuits. 103

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14-71. 14-72. 14-73. 14-74. Provides a visual indication of the active power being supplied to the switchboard. Indicates a warning or emergency condition. Which of the following switches are used to connect shipboard power supplies to the switchboard power busses? 1. Snap switches 2. Linear slide switches 3. Manually operated JR switches 4. Remotely operated JR switches What type of switches are found in a remotely operated JR switch assembly? 1. JR 2. AJR 3. Snap 4. Linear movement 104 14-75. When a control signal is fed back to the KCMX as a status signal input by the switchboard for test purposes, the switchboard is in which of the following configurations? 1. OFF 2. EAT 3. NORMAL 4. ALTERNATE

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