AT89C51外文翻译毕业设计.docx
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AT89C51外文翻译毕业设计.docx
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AT89C51外文翻译毕业设计
AT89C51外文翻译毕业设计
AT89C51外文翻译
Description
TheAT89C51isalow-powerhigh-performanceCMOS8-bitmicrocomputerwith4KbytesofFlashProgrammableandErasableReadOnlyMemoryPEROMThedeviceismanufacturedusingAtmelshighdensitynonvolatilememorytechnologyandiscompatiblewiththeindustrystandardMCS-51instruction-setandpinoutTheon-chipFlashallowstheprogrammemorytobereprogrammedin-systemorbyaconventionalnonvolatilememoryprogrammerBycombiningaversatile8-bitCPUwithFlashonamonolithicchiptheAtmelAT89C51isapowerfulmicrocomputerwhichprovidesahighlyflexibleandcosteffectivesolutiontomanyembeddedcontrolapplications
Features
CompatiblewithMCS-51Products
4KBytesofIn-SystemReprogrammableFlashMemory
–Endurance1000WriteEraseCycles
FullyStaticOperation0Hzto24MHz
Three-LevelProgramMemoryLock
128x8-BitInternalRAM
32ProgrammableIOLines
Two16-BitTimerCounters
SixInterruptSources
ProgrammableSerialChannel
LowPowerIdleandPowerDownModes
TheAT89C51providesthefollowingstandardfeatures4KbytesofFlash128bytesofRAM32IOlinestwo16-bittimercountersafivevectortwo-levelinterruptarchitectureafullduplexserialporton-chiposcillatorandclockcircuitryInadditiontheAT89C51isdesignedwithstaticlogicforoperationdowntozerofrequencyandsupportstwosoftwareselectablepowersavingmodesTheIdleModestopstheCPUwhileallowingtheRAMtimercountersserialportandinterruptsystemtocontinuefunctioningThePower-downModesavestheRAMcontentsbutfreezestheoscillatordisablingallotherchipfunctionsuntilthenexthardwarereset
VCC
Supplyvoltage
GND
Ground
Port0
Port0isan8-bitopen-drainbi-directionalIOportAsanoutputporteachpincansinkeightTTLinputsWhen1sarewrittentoport0pinsthepinscanbeusedashigh-impedanceinputs
Port0mayalsobeconfiguredtobethemultiplexedlow-orderaddressdatabusduringaccessestoexternalprogramanddatamemoryInthismodeP0hasinternalpullups
Port0alsoreceivesthecodebytesduringFlashprogrammingandoutputsthecodebytesduringprogramverificationExternalpullupsarerequiredduringprogramverification
Port1
Port1isan8-bitbi-directionalIOportwithinternalpullupsThePort1outputbufferscansinksourcefourTTLinputsWhen1sarewrittentoPort1pinstheyarepulledhighbytheinternalpullupsandcanbeusedasinputsAsinputsPort1pinsthatareexternallybeingpulledlowwillsourcecurrentIILbecauseoftheinternalpullupsPort1alsoreceivesthelow-orderaddressbytesduringFlashprogrammingandverification
Port2
Port2isan8-bitbi-directionalIOportwithinternalpullupsThePort2outputbufferscansinksourcefourTTLinputsWhen1sarewrittentoPort2pinstheyarepulledhighbytheinternalpullupsandcanbeusedasinputsAsinputsPort2pinsthatareexternallybeingpulledlowwillsourcecurrentIILbecauseoftheinternalpullups
Port2emitsthehigh-orderaddressbyteduringfetchesfromexternalprogrammemoryandduringaccessestoexternaldatamemorythatuse16-bitaddressesMOVXDPTRInthisapplicationitusesstronginternalpullupswhenemitting1sDuringaccessestoexternaldatamemorythatuse8-bitaddressesMOVXRIPort2emitsthecontentsoftheP2SpecialFunctionRegisterPort2alsoreceivesthehigh-orderaddressbitsandsomecontrolsignalsduringFlashprogrammingandverification
Port3
Port3isan8-bitbi-directionalIOportwithinternalpullupsThePort3outputbufferscansinksourcefourTTLinputsWhen1sarewrittentoPort3pinstheyarepulledhighbytheinternalpullupsandcanbeusedasinputsAsinputsPort3pinsthatareexternallybeingpulledlowwillsourcecurrentIILbecauseofthepullupsPort3alsoservesthefunctionsofvariousspecialfeaturesoftheAT89C51aslistedbelow
Port3alsoreceivessomecontrolsignalsforFlashprogrammingandverification
RST
ResetinputAhighonthispinfortwomachinecycleswhiletheoscillatorisrunningresetsthedevice
ALEPROG
AddressLatchEnableoutputpulseforlatchingthelowbyteoftheaddressduringaccessestoexternalmemoryThispinisalsotheprogrampulseinputPROGduringFlashprogrammingInnormaloperationALEisemittedataconstantrateof16theoscillatorfrequencyandmaybeusedforexternaltimingorclockingpurposesNotehoweverthatoneALEpulseisskippedduringeachaccesstoexternalData
Memory
IfdesiredALEoperationcanbedisabledbysettingbit0ofSFRlocation8EHWiththebitsetALEisactiveonlyduringaMOVXorMOVCinstructionOtherwisethepinisweaklypulledhighSettingtheALE-disablebithasnoeffectifthemicrocontrollerisinexternalexecutionmode
PSEN
ProgramStoreEnableisthereadstrobetoexternalprogrammemoryWhentheAT89C51isexecutingcodefromexternalprogrammemoryPSENisactivatedtwiceeachmachinecycleexceptthattwoPSENactivationsareskippedduringeachaccesstoexternaldatamemory
EAVPP
ExternalAccessEnableEAmustbestrappedtoGNDinordertoenablethedevicetofetchcodefromexternalprogrammemorylocationsstartingat0000HuptoFFFFHNotehoweverthatiflockbit1isprogrammedEAwillbeinternallylatchedonresetEAshouldbestrappedtoVCCforinternalprogramexecutionsThispinalsoreceivesthe12-voltprogrammingenablevoltageVPPduringFlashprogrammingforpartsthatrequire12-voltVPP
XTAL1
Inputtotheinvertingoscillatoramplifierandinputtotheinternalclockoperatingcircuit
XTAL2
OutputfromtheinvertingoscillatoramplifierOscillatorCharacteristics
XTAL1andXTAL2aretheinputandoutputrespectivelyofaninvertingamplifierwhichcanbeconfiguredforuseasanon-chiposcillatorasshowninFigure1EitheraquartzcrystalorceramicresonatormaybeusedTodrivethedevicefromanexternalclocksourceXTAL2shouldbeleftunconnectedwhileXTAL1isdrivenasshowninFigure2Therearenorequirementsonthedutycycleoftheexternalclocksignalsincetheinputtotheinternalclockingcircuitryisthroughadivide-by-twoflip-flopbutminimumandimumvoltagehighandlowtimespecificationsmustbeobserved
IdleMode
InidlemodetheCPUputsitselftosleepwhilealltheon-chipperipheralsremainactiveThemodeisinvokedbysoftwareThecontentoftheon-chipRAMandallthespecialfunctionsregistersremainunchangedduringthismodeTheidlemodecanbeterminatedbyanyenabledinterruptorbyahardwareresetItshouldbenotedthatwhenidleisterminatedbyahardwareresetthedevicenormallyresumesprogramexecutionfromwhereitleftoffuptotwomachinecyclesbeforetheinternalresetalgorithmtakescontrolOn-chiphardwareinhibitsaccesstointernalRAMinthiseventbutaccesstotheportpinsisnotinhibitedToeliminatethepossibilityofanunexpectedwritetoaportpinwhenIdleisterminatedbyresettheinstructionfollowingtheonethatinvokesIdleshouldnotbeonethatwritestoaportpinortoexternalmemory
Figure1OscillatorConnections
NoteC1C230pF±10pFforCrystals40pF±10pFforCeramicResonators
Figure2ExternalClockDriveConfiguration
Power-downMode
Inthepower-downmodetheoscillatorisstoppedandtheinstructionthatinvokespower-downisthelastinstructionexecutedTheon-chipRAMandSpecialFunctionRegistersretaintheirvaluesuntilthepower-downmodeisterminatedTheonlyexitfrompower-downisahardwareresetResetredefinestheSFRsbutdoesnotchangetheon-chipRAMTheresetshouldnotbeactivatedbeforeVCCisrestoredtoitsnormaloperatinglevelandmustbeheldactivelongenoughtoallowtheoscillatortorestartandstabilize
ProgramMemoryLockBits
OnthechiparethreelockbitswhichcanbeleftunprogrammedUorcanbeprogrammedPtoobtaintheadditionalfeatureslistedinthetablebelowWhenlockbit1isprogrammedthelogiclevelattheEApinissampledandlatchedduringresetIfthedeviceispoweredupwithoutaresetthelatchinitializestoarandomvalueandholdsthatvalueuntilresetisactivatedItisnecessarythatthelatchedvalueofEAbeinagreementwiththecurrentlogiclevelatthatpininorderforthedevicetofunctionproperly
ProgrammingtheFlash
TheAT89C51isnormallyshippedwiththeon-chipFlashmemoryarrayintheerasedstatethatiscontentsFFHandreadytobeprogrammedTheprogramminginterfaceacceptseitherahigh-voltage12-voltoralow-voltageVCCprogramenablesignalThelow-voltageprogrammingmodeprovidesaconvenientwaytoprogramtheAT89C51insidetheuserssystemwhilethehigh-voltageprogrammingmodeiscompatiblewithconventionalthirdpartyFlashorEPROMprogrammersTheAT89C51isshippedwitheitherthehigh-voltageorlow-voltageprogrammingmodeenabledTherespectivetop-sidemarkinganddevicesignaturecodesarelistedinthefollowingtable
TheAT89C51codememoryarrayisprogrammedbyte-by-byteineitherprogrammingmodeToprogramanynon-blankbyteintheon-chipFlashMemorytheentirememorymustbeerasedusingtheChipEraseModeProgrammingAlgorithmBeforeprogrammingtheAT89C51theaddressdataandcontrolsignalsshouldbesetupaccordingtotheFlashprogrammingmodetableandFigures3and4ToprogramtheAT89C51takethefollowingsteps
1Inputthedesiredmemorylocationontheaddresslines
2Inputtheappropriatedatabyteonthedatalines
3Activatethecorrectcombinationofcontrolsignals
4RaiseEAVPPto12Vforthehigh-voltageprogrammingmode
5PulseALEPROGoncetoprogramabyteintheFlasharrayorthelockbitsThebyte-writecycleisself-timedandtypicallytakesnomorethan15msRepeatsteps1through5changingtheaddressanddatafor
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