电子信息工程微处理器外文翻译Word格式文档下载.docx

电子信息工程微处理器外文翻译Word格式文档下载.docx

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2.书名：

PrinciplesofOpticalDiskSystems

3.出版时间：

1991年9月

4.所译章节：

Session2/Chapter9,Session2/Chapter11

原文：

Microprocessor

Oneofthekeyinventionsinthehistoryofelectronics,andinfactoneofthemostimportantinventionseverperiod,wasthetransistor.AstimeprogressedaftertheinventionofLSIintegratedcircuits,thetechnologyimprovedandchipsbecamesmaller,fasterandcheaper.Thefunctionsperformedbyaprocessorwereimplementedusingseveraldifferentlogicchips.Intelwasthefirstcompanytoincorporatealloftheselogiccomponentsintoasinglechip,thiswasthefirstmicroprocessor.Amicroprocessorisacompletecomputationenginethatisfabricatedonasinglechip.Amicroprocessorexecutesacollectionofmachineinstructionsthattelltheprocessorwhattodo.Basedontheinstructions,amicroprocessordoesthreebasicthings:

1.UsingtheALU（Arithmetic/LogicUnit）,amicroprocessorcanperformmathematicaloperationslikeaddition,subtraction,multiplicationanddivision;

2.Amicroprocessorcanmovedatafromonememorylocationtoanother;

3.Amicroprocessorcanmakedecisionsandjumptoanewsetofinstructionsbasedonthosedecisions.

Theremaybeverysophisticatedthingsthatamicroprocessordoes,butthoseareitsthreebasicactivities.Microprocessorhasanaddressbusthatsendsanaddresstomemory,adatabusthatcansenddatatomemoryorreceivedatafrommemory,anRD（read）andWR（write）linethatletsaclockpulsesequencetheprocessorandaresetlinethatresetstheprogramcountertozero（orwhatever）andrestartsexecution.Andlet’sassumethatboththeaddressanddatabusesare8bitswidehere.

Herearethecomponentsofthissimplemicroprocessor:

1.RegistersA,BandCaresimplylatchesmadeoutofflip-flops.

2.TheaddresslatchisjustlikeregistersA,BandC.

3.Theprogramcounterisalatchwiththeextraabilitytoincrementby1whentoldtodoso,andalsotoresettozerowhentoldtodoso.

4.TheALUcouldbeassimpleasan8-bitadder,oritmightbeabletoadd,subtract,multiplyanddivide8-bitvalues.Let’sassumethelatterhere.

5.ThetestregisterisaspeciallatchthatcanholdvaluesfromcomparisonsperformedintheALU.AnALUcannormallycomparetwonumberssenddetermineiftheyareequal,ifoneisgreaterthantheother,etc.Thetestregistercanalsonormallyholdacarrybitfromthelaststageoftheadder.Itstoresthesevaluesinflip-flopsandthentheinstructiondecodercanusethevaluestomakedecisions.

6.Therearesixboxesmarked“3-State”.Thesearetri-statebuffers.Atri-statebuffercanpassa1,a0oritcanessentiallydisconnectitsoutput.Atri-statebufferallowsmultipleoutputstoconnecttoawire,butonlyoneofthentoactuallydrivea1ora0ontotheline.

7.Theinstructionregisterandinstructiondecoderareresponsibleforcontrollingalloftheothercomponents.

Althoughtheyarenotshowninthisdiagram,therewouldbecontrollinesfromtheinstructiondecoderthatwould:

1.TelltheAregistertolatchthevaluecurrentlyonthedatabus

2.TelltheBregistertolatchthevaluecurrentlyonthedatabus

3.TelltheCregistertolatchthevaluecurrentlyonthedatabus

4.Telltheprogramcounterregistertolatchthevaluecurrentlyonthedatabus

5.Telltheaddressregistertolatchthevaluecurrentlyonthedatabus

6.Telltheinstructionregistertolatchthevaluecurrentlyonthedatabus

7.Telltheprogramcountertoincrement

8.Telltheprogramcountertoresettozero

9.Activateanyofthesixtri-statebuffers（sixseparatelines）

10.TelltheALUwhatoperationtoperform

11.TellthetestregistertolatchtheALU’stestbits

12.ActivatetheRDline

13.ActivatetheWRline

Comingintotheinstructiondecoderarethebitsfromthebestregisterandclockline,aswellasthebitsfromtheinstructionregister.

RAMandROMTheaddressanddatabuses,aswellastheRDandWRlinesconnecteithertoRAMorROM—generallyboth.Inoursamplemicroprocessor,wehaveanaddressbus8bitswideandadatabus8bitswide.Thatmeansthatthemicroprocessoranaddress（2n）256bytesofthememoryanditcanreadorwrite8bitsofthememoryatatime.Let’sassumethatthissimplemicroprocessorhas128bytesofROMstartingataddress0and128bytesofRAMstartingataddress128.

ROMstandsforread-onlymemory.AROMchipisprogrammedwithapermanentcollectionofpre-setbytes.TheaddressbustellstheROMchipwhichbytetogetandplaceonthedatabus.WhentheRDlinechangesstate,theROMchippresentstheselectedbyteontothedatabus.

RAMstandsforrandom-accessmemory.RAMcontainsbytesofinformation,andthemicroprocessorcanreadorwritetothosebytesdependingonwhethertheRDorWRlineissignaled.Oneproblem