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. 6.In the registers of the RTC.This section of circuitry is normallystored in the integrated peripheral controller on the systemboard.For more information, see the section titled Real-TimeClock. 7.Eight.For more information, see the section titled SystemBoard Evolution. 8.The maximum external clock frequency for the 286-12 is 24MHz.For more information, see the section titled The 80286Microprocessor. 9.At the system board s keyboard controller chip.This IRQ chan-nel is activated when the keyboard buffer becomes full.For moreinformation, see the section titled Interrupt Controllers. 10.A total of 1,048,576 bytes (1MB) of memory addresses.Formore information, see the section titled 8088 Pin Assign-ments. 11.Fifteen.(One of the 16 channels is used to cascade the firstcontroller to the second.) For more information, see the sec-tion titled Interrupt Controllers. 12.It drives the system s time-of-day clock.For more information,the section titled section System Board Evolution. 13.Four.For more information, see the section titled SystemBoard Evolution. 14.It provides the system s FDD DMA channel.For more informa-tion, see the section titled System Board Evolution. 15.When the DMA controller receives a DMA request, it issues ahold request to the system s microprocessor.The microproces-sor responds by finishing its current instruction andplacing its bus pins in a high-impedance state (effectively dis-connecting them from the bus).It follows this by notifying theDMA controller that it can use the buses to conduct high-speeddata transfers.For more information, see the section titled ATypical DMA Operation. A+ Certification Training Guide47416.It is unused in PC- and PC/XT-compatible systems.In AT-com-patible systems, it is the cascaded IRQ input for the secondaryPIC device.For more information, see the section titled SystemBoard Evolution. 17.IRQ-6 is dedicated to the FDD.For more information, see thesection titled System Board Evolution. 18.The terminal count (T/C) signal from the DMA controller oran end-of-process (EOP) count from the FDC controller can begenerated.If the transfer is correct, both signals will be generat-ed at the same time.For more information, see the sectiontitled A Typical DMA Operation. 19.I/O channel check and parity check errors can generate NMIfailures.For more information, see the section titled Non-Maskable Interrupts (NMI). 20.System time-of-day clock, DRAM refresh generator, and tonegenerator for the system speaker.For more information, see thesection titled section Timer/Counter Channels. 21.Its data bus is 16 bits wide (as opposed to 8 in the 8088), it sup-ports multiuser and multitasking operations, and it can performprotected-mode addressing to access up to 16MB of physicalmemory addresses.For more information, see the section titled The 80286 Microprocessor. 22.The interrupt controller, the DMA controller, the three-chan-nel timer/counter, and the system clock circuits.For more in-formation, see the section titled Integrated Peripheral Control-lers (IPC). 23.The 80486 brings an improved 80386DX microprocessor, ahigh-performance 80387 coprocessor, and an 82385 cachememory controller together in a single package.For more in-formation, see the section titled The 80486 Microprocessor. 24.The 80486 has no internal division factor to arrive at the chip sspeed rating.An 80486-33 microprocessor must operate from a33-MHz clock input signal.For more information, see the sec-tion titled The 80486 Microprocessor. 25.Decreased size and decreased production costs.For more infor-mation, see the section titled Chip Sets. Chapter 7 Input/Output475C h a p t e r7Input/Output 7After completing this chapter and its related lab procedures, youshould be able to meet the following objectives:.Define the overall function of the computer s input/Objectivesoutput units.Describe differences between parallel and serial ports.Identify the various port connectors used in PC-compatible systems.Given a block diagram of a parallel printer interface, iden-tify its major components
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