at89c51单片机外文资料.docx
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at89c51单片机外文资料.docx
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at89c51单片机外文资料
AT89C51的介绍
(原文出处:
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ThedeviceismanufacturedusingAtmel’shigh-densitynonvolatilememorytechnologyandiscompatiblewiththeindustry-standardMCS-51instructionsetandpinout.Theon-chipFlashallowstheprogrammemorytobereprogrammedin-systemorbyaconventionalnonvolatilememoryprogrammer.Bycombiningaversatile8-bitCPUwithFlashonamonolithicchip,theAtmelAT89C51isapowerfulmicrocomputerwhichprovidesahighly-flexibleandcost-effectivesolutiontomanyembeddedcontrolapplications.
Functioncharacteristic
TheAT89C51providesthefollowingstandardfeatures:
4KbytesofFlash,128bytesofRAM,32I/Olines,two16-bittimer/counters,afivevectortwo-levelinterruptarchitecture,afullduplexserialport,on-chiposcillatorandclockcircuitry.Inaddition,theAT89C51isdesignedwithstaticlogicforoperationdowntozerofrequencyandsupportstwosoftwareselectablepowersavingmodes.TheIdleModestopstheCPUwhileallowingtheRAM,timer/counters,serialportandinterruptsystemtocontinuefunctioning.ThePower-downModesavestheRAMcontentsbutfreezestheoscillatordisablingallotherchipfunctionsuntilthenexthardwarereset.
PinDescription
VCC:
Supplyvoltage.
GND:
Ground.
Port0:
Port0isan8-bitopen-drainbi-directionalI/Oport.Asanoutputport,eachpincansinkeightTTLinputs.When1sarewrittentoport0pins,thepinscanbeusedashighimpedance0mayalsobeconfiguredtobethemultiplexedloworderaddress/databusduringaccessestoexternalprogramanddatamemory.InthismodeP0hasinternal0alsoreceivesthecodebytesduringFlashprogramming,andoutputsthecodebytesduringprogramverification.Externalpullupsarerequiredduringprogramverification.
Port1
Port1isan8-bitbi-directionalI/OportwithinternalPort1outputbufferscansink/sourcefourTTL1sarewrittentoPort1pinstheyarepulledhighbytheinternalpullupsandcanbeusedasinputs.Asinputs,Port1pinsthatareexternallybeingpulledlowwillsourcecurrent(IIL)becauseoftheinternal1alsoreceivesthelow-orderaddressbytesduringFlashprogrammingandverification.
Port2
Port2isan8-bitbi-directionalI/OportwithinternalPort2outputbufferscansink/sourcefourTTL1sarewrittentoPort2pinstheyarepulledhighbytheinternalpullupsandcanbeusedasinputs.Asinputs,Port2pinsthatareexternallybeingpulledlowwillsourcecurrent,becauseoftheinternal2emitsthehigh-orderaddressbyteduringfetchesfromexternalprogrammemoryandduringaccessestoexternaldatamemorythatuse16-bitaddresses.Inthisapplication,itusesstronginternalpullupswhenemitting1s.Duringaccessestoexternaldatamemorythatuse8-bitaddresses,Port2emitsthecontentsoftheP2SpecialFunction2alsoreceivesthehigh-orderaddressbitsandsomecontrolsignalsduringFlashprogrammingandverification.
Port3
Port3isan8-bitbi-directionalI/OportwithinternalPort3outputbufferscansink/sourcefourTTL1sarewrittentoPort3pinstheyarepulledhighbytheinternalpullupsandcanbeusedasinputs.Asinputs,Port3pinsthatareexternallybeingpulledlowwillsourcecurrent(IIL)becauseofthe3alsoservesthefunctionsofvariousspecialfeaturesoftheAT89C51aslistedbelow:
Port3alsoreceivessomecontrolsignalsforFlashprogrammingandverification.
RST
Resetinput.Ahighonthispinfortwomachinecycleswhiletheoscillatorisrunningresetsthedevice.
ALE/PROG
AddressLatchEnableoutputpulseforlatchingthelowbyteoftheaddressduringaccessestoexternalmemory.Thispinisalsotheprogrampulseinput(PROG)duringFlashnormaloperationALEisemittedataconstantrateof1/6theoscillatorfrequency,andmaybeusedforexternaltimingorclockingpurposes.Note,however,thatoneALEpulseisskippedduringeachaccesstoexternalDataMemory.
Ifdesired,ALEoperationcanbedisabledbysettingbit0ofSFRlocation8EH.Withthebitset,ALEisactiveonlyduringaMOVXorMOVCinstruction.Otherwise,thepinisweaklypulledhigh.SettingtheALE-disablebithasnoeffectifthemicrocontrollerisinexternalexecutionmode.
PSEN
ProgramStoreEnableisthereadstrobetoexternalprogramtheAT89C51isexecutingcodefromexternalprogrammemory,PSENisactivatedtwiceeachmachinecycle,exceptthattwoPSENactivationsareskippedduringeachaccesstoexternaldatamemory.
EA/VPP
ExternalAccessEnable.EAmustbestrappedtoGNDinordertoenablethedevicetofetchcodefromexternalprogrammemorylocationsstartingat0000HuptoFFFFH.Note,however,thatiflockbit1isprogrammed,EAwillbeinternallylatchedonshouldbestrappedtoVCCforinternalprogrampinalsoreceivesthe12-voltprogrammingenablevoltage(VPP)duringFlashprogramming,forpartsthatrequire12-voltVPP.
XTAL1
Inputtotheinvertingoscillatoramplifierandinputtotheinternalclockoperatingcircuit.
XTAL2
Outputfromtheinvertingoscillatoramplifier.
OscillatorCharacteristics
XTAL1andXTAL2aretheinputandoutput,respectively,ofaninvertingamplifierwhichcanbeconfiguredforuseasanon-chiposcillator,asshowninFigureaquartzcrystalorceramicresonatormaybeused.Todrivethedevicefromanexternalclocksource,XTAL2shouldbeleftunconnectedwhileXTAL1isdrivenasshowninFigurearenorequirementsonthedutycycleoftheexternalclocksignal,sincetheinputtotheinternalclockingcircuitryisthroughadivide-by-twoflip-flop,butminimumandmaximumvoltagehighandlowtimespecificationsmustbeobserved.
Figure1.OscillatorConnectionsFigure2.ExternalClockDriveConfiguration
IdleMode
Inidlemode,theCPUputsitselftosleepwhilealltheonchipperipheralsremainactive.Themodeisinvokedbysoftware.Thecontentoftheon-chipRAMandallthespecialfunctionsregistersremainunchangedduringthismode.Theidlemodecanbeterminatedbyanyenabledinterruptorbyahardwareshouldbenotedthatwhenidleisterminatedbyahardwarereset,thedevicenormallyresumesprogramexecution,fromwhereitleftoff,uptotwomachinecyclesbeforetheinternalresetalgorithmtakescontrol.On-chiphardwareinhibitsaccesstointernalRAMinthisevent,butaccesstotheportpinsisnotinhibited.ToeliminatethepossibilityofanunexpectedwritetoaportpinwhenIdleisterminatedbyreset,theinstructionfollowingtheonethatinvokesIdleshouldnotbeonethatwritestoaportpinortoexternalmemory.
Power-downMode
Inthepower-downmode,theoscillatorisstopped,andtheinstructionthatinvokespower-downisthelastinstructionexecuted.Theon-chipRAMandSpecialFunctionRegistersretaintheirvaluesuntilthepower-downmodeisterminated.Theonlyexitfrompower-downisahardwarereset.ResetredefinestheSFRsbutdoesnotchangetheon-chipRAM.TheresetshouldnotbeactivatedbeforeVCCisrestoredtoitsnormaloperatinglevelandmustbeheldactivelongenoughtoallowtheoscillatortorestartandstabilize.
ProgramMemoryLockBits
Onthechiparethreelockbitswhichcanbeleftunprogrammed(U)orcanbeprogrammed(P)toobtaintheadditionalfeatureslistedinthetablebelow.
Whenlockbit1isprogrammed,thelogiclevelattheEApinissampledandlatchedduringreset.Ifthedeviceispoweredupwithoutareset,thelatchinitializestoarandomvalue,andholdsthatvalueuntilresetisactivated.ItisnecessarythatthelatchedvalueofEAbeinagreementwiththecurrentlogiclevelatthatpininorderforthedevicetofunctionproperly.
Synthesisofan8051-LikeMicro-ControllerToleranttoTransientFaults
Thispaperpresentstheimplementationofafaultdetectionandcorrectiontechniqueusedtodesignarobust8051micro-controllerwithrespecttoaparticulartransientfaultcalledSingleEventUpset(SEU).AspecificstudyregardingtheeffectsofaSEUinthemicro-controllerbehaviorwasperformed.Furthermore,afaulttoleranttechniquewasimplementedinaversionofthe8051.TheVHDLdescriptionofthefault-tolerantmicroprocessorwasprototypedinaFPGAenvironmentandresultsintermsofareaoverhead,levelofprotectionandperformancepenaltiesarediscussed.
1.Introduction
Theconstantimprovementsachievedinthemicroelectronicstechnologyallowthemanufacturingofverycomplexcircuits,substitutingboardsorevencomputersofthepast80’s.Nowadays,becauseofthemicroelectronicsadvances,traditionalapplicationsbecomecheaperandmorereliable,whilealargerangeofnewapplicationscantakeadvantageofintegrateddevicesbyusingtheso-calledembeddedsystems.Inallcases,architecturesarestronglybasedonsomekindofdataprocessor,suchasamicro-controlleroraDSPprocessingunit,forexample.
Thecontinuousdecreaseinthesemiconductordimensionsandinelectricalfeatures,leadstoanincreasingsensitivitytosomeeffectsoftheenvironment(ionizationduetoradiation,magneticperturbations,thermal,...)consideredminorornegligibleinthetechnologiesofthepast.Particularly,digitalcircuitsoperatinginspacearesubjecttodifferentkindsofradiation.However,someproblemshavealsobeenreportedforsomeEarthapplications,likeavionicssystems.
Radiationeffectscanbepermanentortransient.Permanentfaultsresultfromparticlestrappedatthesilicon/oxideinterfacesandappearonlyafterlongexposuretoradiation(TotalIonizationDose).Transientfaults(SingleEventEffects,SEE)maybecausedbytheimpact
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