2023年全國碩士研究生考試考研英語一試題真題（含答案詳解+作文范文）_第1頁
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1、一、英文原文一、英文原文TheHardwareOverviewThe8051familyofmicrocontrollersisbasedonanarchitecturewhichishighlyoptimizedfembeddedontrolsystems.ItisusedinawidevarietyofapplicationsfrommilitaryequipmenttoautomobilestothekeyboardonyourP

2、C.SecondonlytotheMotola68HC11ineightbitprocessssalesthe8051familyofmicrocontrollersisavailableinawidearrayofvariationsfrommanufacturerssuchasIntelPhilipsSiemens.Thesemanufacturershaveaddednumerousfeaturesperipheralstothe

3、8051suchasI2Cinterfacesanalogtodigitalconverterswatchdogtimerspulsewidthmodulatedoutputs.Variationsofthe8051withclockspeedsupto40MHzvoltagerequirementsdownto1.5voltsareavailable.Thiswiderangeofpartsbasedononecemakesthe80

4、51familyanexcellentchoiceasthebasearchitecturefacompanysentirelineofproductssinceitcanperfmmanyfunctionsdeveloperswillonlyhavetoearnthisoneplatfm.Thebasicarchitectureconsistsofthefollowingfeatures:1、aneightbitALU2、32desc

5、reteIOpins(4groupsof8)whichcanbeindividuallyaccessed3、two16bittimercounters4、fullduplexUART.5、6interruptsourceswith2priitylevels.6、128bytesofonboardRAM.7、separate64KbyteaddressspacesfDATACODEmemy.One8051processcycleconsi

6、stsoftwelveoscillatperiods.Eachofthetwelveoscillatperiodsisusedfaspecialfunctionbythe8051cesuchasopcodefetchessamplesoftheinterruptdaisychainfpendinginterrupts.Thetimerequiredfany8051instructioncanbecomputedbydividingthe

7、clockfrequencyby12invertingthatresultmultiplyingitbythenumberofprocesscyclesrequiredbytheinstructioninquestion.Therefeifyouhaveasystemwhichisusingan11.059MHzclockyoucancomputethenumberofinstructionspersecondbydividingthi

8、svalueby12.Thisgivesaninstructionfrequencyof921583instructionspersecond.Invertingthiswillprovidetheamountoftimetakenbyeachinstructioncycle(1.085microseconds).MemyganizationThe8051architectureprovidestheuserwiththreephysi

9、callydistinctmemyspaceswhichcanbeseeninFigureA1.EachmemyspaceconsistsofcontiguousThesecondmemyspaceisthe128bytesofinternalRAMonthe8051thefirst128bytesofinternalRAMonthe8052.ThissegmentistypicallyreferredtoastheDATAsegmen

10、t.TheRAMlocationsinthissegmentareaccessedinonetwocyclesdependingontheinstruction.ThisaccesstimeismuchquickerthanaccesstotheXDATAsegmentbecausememyisaddresseddirectlyratherthanviaamemypointersuchasDPTRwhichmustfirstbeinit

11、ialized.TherefefrequentlyusedvariablestemparyscratchvariablesareusuallyassignedtotheDATAsegment.Suchallocationmustbedonewithcarehoweverduetothelimitedamountofmemyinthissegment.VariablesstedintheDATAsegmentcanalsobeaccess

12、edindirectlyviaR0R1.Theregisterbeingusedasthememypointermustcontaintheaddressofthebytetoberetrievedaltered.Theseinstructionscantakeonetwoprocesscyclesdependingonthesourcedestinationdatabyte.TheDATAsegmentcontainstwosmall

13、ersegmentsofinterest.Thefirstsubsegmentconsistsofthefoursetsofregisterbankswhichcomposethefirst32bytesofRAM.The8051canuseanyofthesefourgroupsofeightbytesasitsdefaultregisterbank.Theionofregisterbanksischangeableatanytime

14、viatheRS1theRS0bitsintheProcessStatusWd(PSW).Thesetwobitscombineintoanumberfrom0to3(withRS1beingthemostsignificantbit)whichindicatestheregisterbanktobeused.Registerbankswitchingallowsnotonlyfquickparameterpassingbutalsoo

15、pensthedofsimplifyingtaskswitchingonthe8051.ThesecondsubsegmentintheDATAspaceisabitaddressablesegmentinwhicheachbitcanbeindividuallyaccessed.ThissegmentisreferredtoastheBDATAsegment.Thebitaddressablesegmentconsistsof16by

16、tes(128bits)abovethefourregisterbanksinmemy.The8051containsseveralsinglebitinstructionswhichareoftenveryusefulincontrolapplicationsaidinreplacingexternalcombinatiallogicwithsoftwareinthe8051thusreducingpartscountonthetar

17、getsystem.Itshouldbenotedthatthese16bytescanalsobeaccessedona“bytewide“basisjustlikeanyotherbyteintheDATAspace.SpecialFunctionRegistersControlregistersftheinterruptsystemtheperipheralsonthe8051arecontainedininternalRAMat

18、locations80hexabove.Theseregistersarereferredtoasspecialfunctionregisters(SFRsfsht).Manyofthemarebitaddressable.ThebitsinthebitaddressableSFRscaneitherbeaccessedbynameindexbitaddress.ThusyoucanrefertotheEAbitoftheInterru

19、ptEnableSFRasEAIE.70AFH.TheSFRscontrolthingssuchasthefunctionofthetimercounterstheUARTtheinterruptsourcesaswellastheirpriities.TheseregistersareaccessedbythesamesetofinstructionsasthebytesbitsintheDATAsegment.Amemymapoft

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