电子信息工程-微处理器[外文翻译]

1外文资料所译外文资料：1.作者G..Bouwhuis,J.Braat,A.Huijser2.书名：PrinciplesofOpticalDiskSystems3.出版时间：1991年9月4.所译章节：Session2/Chapter9,Session2/Chapter11原文：MicroprocessorOneofthekeyinventionsinthehistoryofelectronics,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,2subtract,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.TelltheAregistertolatchthevaluecurrentlyonthedatabus2.TelltheBregistertolatchthevaluecurrentlyonthedatabus3.TelltheCregistertolatchthevaluecurrentlyonthedatabus4.Telltheprogramcounterregistertolatchthevaluecurrentlyonthedatabus5.Telltheaddressregistertolatchthevaluecurrentlyonthedatabus6.Telltheinstructionregistertolatchthevaluecurrentlyonthedatabus7.Telltheprogramcountertoincrement8.Telltheprogramcountertoresettozero9.Activateanyofthesixtri-statebuffers(sixseparatelines)10.TelltheALUwhatoperationtoperform11.TellthetestregistertolatchtheALU’stestbits12.ActivatetheRDline13.ActivatetheWRlineComingintotheinstructiondecoderarethebitsfromthebestregisterandclockline,aswellasthebitsfromtheinstructionregister.RAMandROMTheaddressanddatabuses,aswellastheRDandWRlinesconnecteithertoRAMorROM—generallyboth.Inoursamplemicroprocessor,wehaveanaddressbus8bitswideandadatabus8bitswide.Thatmeansthatthemicroprocessoranaddress(2n)256bytesofthememoryanditcanreadorwrite8bitsofthememoryatatime.Let’sassumethatthissimplemicroprocessorhas128bytesofROMstartingataddress0and128bytesofRAMstartingataddress128.3ROMstandsforread-onlymemory.AROMchipisprogrammedwithapermanentcollectionofpre-setbytes.TheaddressbustellstheROMchipwhichbytetogetandplaceonthedatabus.WhentheRDlinechangesstate,theROMchippresentstheselectedbyteontothedatabus.RAMstandsforrandom-accessmemory.RAMcontainsbytesofinformation,andthemicroprocessorcanreadorwritetothosebytesdependingonwhethertheRDorWRlineissignaled.Oneproblemwithtoday’sRAMchipsisthattheyforgeteverythingoncethepowergoesoff.ThatiswhythecomputerneedsROM.Bytheway,nearlyallcomputerscontainsomeamountofROM(itispossibletocreateasimplecomputerthatcontainsnoRAM—manymicrocontrollersdothisbyplacingahandfulofRAMbytesontheprocessorchipitself—butgenerallyimpossibletocreateonethatcontainsnoROM).OnaPC,theROMiscalledtheBIOS(BasicInput/OutputSystem).Whenthemicroprocessorstarts,itbeginsexecutinginstructionsitfindsintheBIOS.TheBIOSinstructionsdothingsliketestthehardwareinthemachine,andthenitgoestotheharddisktofetchthebootsector.Thisbootsectorisanothersmallprogram,andtheBIOSstoreitinRAMafterreadingitoffthedisk.Themicroprocessorthenbeginsexecutingthebootsector’sinstructionsfromRAM.ThebootsectorprogramwilltellthemicroprocessortofetchsomethingelsefromtheharddiskintoRAM,whichthemicroprocessorthenexecutes,andsoon.Thisishowthemicroprocessorloadsandexecutesentireoperatingsystem.Mic