`
`Programming
`Emb€dd€d
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`Systems in C and C++
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`1
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`LG 1021
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`WEMWIJEMEH
`by Michael Barr
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`Copyright 0 1999 G‘li‘deill}r 3r. Associates. Inc. M] rights reserved.
`Prhued in the United States of America.
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`Published In O'Reilly iii Associates. Inc“ 191 Morris Sheet. Sebastopol, Cal 954”.
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`HEW: find? Dram
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`m Elites Melanie Wang
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`mm
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`januar}r 1999:
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`First Edition.
`
`Nutshell Handbook. the Nutshell Handbook logo, and the D'Reflly logo are registered
`trademarks offl‘fleillyii Associates, Inc. 111e modatimtbetween the image offirJts and the
`topleofembeddedsystemsisauademarkoffi’fleifly&hssodafls Inch-Itartyofthe
`desigmtimts usedbynmnufaehreisuldseflersmdistmguishdleirpmductsmdalmedas
`trademarks. Where those designations appearlnthisboolt. andD‘Reflly&Assoe-iatee, [nowas
`awareofahadelrmk lullaim1 Ihedesignalionshavebeen pfintedineapsorirfllialeaps.
`
`While ell-«era.r precaution has been taken in the preparation oftlfis hook. the publisher assume:
`noreepocrlsihilinrforerrm Hermie-shone. orimdamgesrestfltingfiwnmeuseefthe
`infirm-ration oorrtained herein
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`ISBN: 1565923545
`[Ml
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`tum]
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`2
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`GermKnowwercessor
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`5!
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`evolutionary path. The most obvious example is lntel’s 80x86 family. which spans
`from the original 8086 to the Pentium ll—and beyond. in fact, the 80x86 family
`has been so successful that it has spawned an entire industry of imitators.
`
`As itisusedinthisbook. the tennpmcessorreferstoanyofthreetypesofdevices
`known as microprocessors, microcontrollers, and digital signal processors. The
`name microprocessor is usually reserved for a chip that contains a powerful CPU
`that has not been designed with any particular computation in mind. These chips
`are usually the foundation of personal computers and high-end workstations. The
`most common microprocessors are members of Motorola's 68k—found in older
`Macintosh computers—and the ubiquitous 80x86 families.
`
`A microcontroller is very much like a microprocessor. except that it has been
`designed specifically for use in embedded systems. Microcontrollers typically
`include a CPU, memory (a small amount of RAM, ROM. or both), and other
`peripherals in the same integrated circuit. if you purchase all of these items on a
`single chip, it is possible to reduce the cost of an embedded system substantially.
`Among the most popular microcontrollers are the 8051 and its many imitators and
`Motorola's 68HCxx series. It is also common to find microcontroller versions of
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`popular microprocessors. For example, Intel's 386EX is a microcontroller version
`of the very successful 80386 microprocessor.
`
`The final type of processor is a digital signal processor, or 08?. The CPU within a
`DSP is specially designed to perform discrete-time signal processing alculations—
`like those required for audio and video communications—extremely fast. Because
`DSPs can perform these types of calculations much faster than other processors,
`they offer a powerful,
`low-cost microprocessor alternative for designers of
`modems and other telecommunications and multimedia equipment. Two of the
`most common DSP families are the TMSSZOCxx and 5600x series from Ti and
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`Motorola, respectively.
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`Intel'5 80188EB Processor
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`The processor on the Arcom board is an Intel 8018888—a microcontroller version
`of the 80186. In addition to the CPU, the 8018888 contains an interrupt control
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`unit. two programmable [/0 ports. three timer/counters. two serial ports. a DRAM
`controller, and a chip-select unit. These extra hardware devices are located within
`the same chip and are referred to as on-chip peripherals. The CPU is able to com-
`municate with and control the on-chip peripherals directly, via internal buses.
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`Although the on-chip peripherals are distinct hardware devices. they act like little
`extensions of the 80186 CPU. The software can control them by reading and writ-
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`ing a 256—byte block of registers known as the peripheral control block (PCB).
`You may real] that we encountered this block when we first discussed the mem-
`ory and [/0 maps for the board. By default the PCB is located in the [/0 space,
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