搜索
外文翻译（原文）1TheGeneralSituationofAT89C51TheAT89C51isalow-power,high-performanceCMOS8-bitmicrocomputerwith4KbytesofFlashProgrammableandErasableReadOnlyMemory(PEROM)and128bytesRAM.ThedeviceismanufacturedusingAtmel’shighdensitynonvolatilememorytechnologyandiscompatiblewiththeindustrystandardMCS-51™instructionsetandpinout.Thechipcombinesaversatile8-bitCPUwithFlashonamonolithicchip;theAtmelAT89C51isapowerfulmicrocomputerwhichprovidesahighlyflexibleandcosteffectivesolutiontomanyembeddedcontrolapplications.Features:•CompatiblewithMCS-51™Products•4KBytesofIn-SystemReprogrammableFlashMemory•Endurance:1,000Write/EraseCycles•FullyStaticOperation:0Hzto24MHz•Three-LevelProgramMemoryLock•128x8-BitInternalRAM•32ProgrammableI/OLines•Two16-BitTimer/Counters•SixInterruptSources•ProgrammableSerialChannel•LowPowerIdleandPowerDownModesTheAT89C51providesthefollowingstandardfeatures:4KbytesofFlash,128bytesofRAM,32I/Olines,two16-bittimer/counters,afivevectortwo-levelinterruptarchitecture,afullduplexserialport,on-chiposcillatorandclockcircuitry.Inaddition,theAT89C51isdesignedwithstaticlogicforoperationdowntozerofrequencyandsupportstwosoftwareselectablepowersavingmodes.外文翻译（原文）2TheIdleModestopstheCPUwhileallowingtheRAM,timer/counters,serialportandinterruptsystemtocontinuefunctioning.ThePowerDownModesavestheRAMcontentsbutfreezestheoscillatordisablingallotherchipfunctionsuntilthenexthardwarereset.BlockDiagramPinDescription:VCCSupplyvoltage.GNDGround.Port0：Port0isan8-bitopendrainbidirectionalI/Oport.AsanoutputporteachpincansinkeightTTLinputs.When1sarewrittentoport0pins,thepinscanbeusedashighimpedanceinputs.(Sink/flow)Port0mayalsobeconfiguredtobethemultiplexedloworderaddress/databusduringaccessestoexternalprogramanddatamemory.InthismodeP0has外文翻译（原文）3internalpull-ups.Port0alsoreceivesthecodebytesduringFlashprogramming,andoutputsthecodebytesduringprogramverification.Externalpull-upsarerequiredduringprogramverification.Port1：Port1isan8-bitbidirectionalI/Oportwithinternalpull-ups.ThePort1outputbufferscansink/sourcefourTTLinputs.When1sarewrittentoPort1pinstheyarepulledhighbytheinternalpull-upsandcanbeusedasinputs.Asinputs,Port1pinsthatareexternallybeingpulledlowwillsourcecurrent(IIL)becauseoftheinternalpull-ups.Port1alsoreceivesthelow-orderaddressbytesduringFlashprogrammingandverification.Port2：Port2isan8-bitbidirectionalI/Oportwithinternalpull-ups.ThePort2outputbufferscansink/sourcefourTTLinputs.When1sarewrittentoPort2pinstheyarepulledhighbytheinternalpull-upsandcanbeusedasinputs.Asinputs,Port2pinsthatareexternallybeingpulledlowwillsourcecurrent(IIL)becauseoftheinternalpull-ups.Port2emitsthehigh-orderaddressbyteduringfetchesfromexternalprogrammemoryandduringaccessestoexternaldatamemorythatuses16-bitaddresses(MOVX@DPTR).Inthisapplicationitusesstronginternalpull-upswhenemitting1s.Duringaccessestoexternaldatamemoriesthatuse8-bitaddresses(MOVX@RI),Port2emitsthecontentsoftheP2SpecialFunctionRegister.Port2alsoreceivesthehigh-orderaddressbitsandsomecontrolsignalsduringFlashprogrammingandverification.Port3：Port3isan8-bitbidirectionalI/Oportwithinternalpull-ups.ThePort3outputbufferscansink/sourcefourTTLinputs.When1sarewrittentoPort3pinstheyarepulledhighbytheinternalpull-upsandcanbeusedasinputs.Asinputs,Port3pinsthatareexternallybeingpulledlowwillsourcecurrent(IIL)becauseofthepull-ups.外文翻译（原文）4Port3alsoservesthefunctionsofvariousspecialfeaturesoftheAT89C51aslistedbelow:Port3alsoreceivessomecontrolsignalsforFlashprogrammingandverification.RST：Resetinput.Ahighonthispinfortwomachinecycleswhiletheoscillatorisrunningresetsthedevice.ALE/PROG：AddressLatchEnableoutputpulseforlatchingthelowbyteoftheaddressduringaccessestoexternalmemory.Thispinisalsotheprogrampulseinput(PROG)duringFlashprogramming.InnormaloperationALEisemittedataconstantrateof1/6theoscillatorfrequency,andmaybeusedforexternaltimingorclockingpurposes.Note,however,thatoneALEpulseisskippedduringeachaccesstoexternalDataMemory.Ifdesired,ALEoperationcanbedisabledbysettingbit0ofSFRlocation8EH.Withthebitset,ALEisactiveonlyduringaMOVXorMOVCinstruction.Otherwise,thepinisweaklypulledhigh.SettingtheALE-disablebithasnoeffectifthemicrocontrollerisinexternalexecutionmode.PSEN：ProgramStoreEnableisthereadstrobetoexternalprogrammemory.WhentheAT89C51isexecutingcodefromexternalprogrammemory,PSENisactivatedtwiceeachmachinecycle,exceptthattwoPSENactivationsareskippedduringeachaccesstoexternaldatamemory.PortpinalternatefunctionsP3.0rxd(serialinputport)P3.1txd(serialoutputport)P3.2^int0(externalinterrupt0)P3.3^int1(externalinterrupt1)P3.4t0(timer0externalinput)P3.5t1(timer1externalinput)P3.6^WR(externaldatamemorywritestrobe)P3.7^rd(externaldatamemoryreadstrobe)外文翻译（原文）5EA/VPP：ExternalAccessEnable.EAmustbestrappedtoGNDinordertoenablethedevicetofetchcodefromexternalprogrammemorylocationsstartingat0000HuptoFFFFH.Note,however,thatiflockbit1(LB1)isprogrammed,EAwillbeinternallylatched(fastenwithalatch)onreset.EAshouldbestrappedtoVCCforinternalprogramexecutions.Thispinalsoreceivesthe12-voltprogrammingenablevoltage（VPP)duringFla