公交车报站单片机外文资料中文.docx
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公交车报站单片机外文资料中文.docx
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公交车报站单片机外文资料中文
山 东 轻 工 业 学 院
外文资料及中文译文
院系名称理学院
学生姓名吴秀
学生学号__200803021005
专业班级_信息08-1
指导教师贺爱玲
二○一二年五月七日
外文资料
出处:
AT89C51Microcomputer
Atpresent,asabuspassenger'slargestpublictransport,safetyandcomforthasabearingonthevitalinterestsofthemajorityofthepeople.However,themanagementandbusserviceshavebeenanumberofloopholes.Inadditiontothedrivertodrive,beresponsibleformanuallystopandopenthedoor,attentionhasbeendistributed,easytotrafficaccidents.Thedriverwhiledrivingshouldberoadobservation,thenumberofpassengersofthebuscannotbereal-timemonitoring.Atthesametime,thecompanyprovidespublictransportationbusdrivercannotrefuse,toworkthepeakofthehighaspirationsofthepassengerbus,busoverloadsituationoccursfromtimetotime,togetherwiththenormsandgetoffonthelowawareness,theaccidentprone,verydangerous.Inamovingbus,thebuscompaniesitisdifficultforthebusinreal-timemanagement,whichishardtoavoidtheoccurrenceofspeedingbus,aseriousthreattothesafetyofthepassengers.Stationpassengersknowthedifficultiesintravelduetotheeasywayanddonotseetoomanypassengersstandorgetoffonthestrangepointandmissedthestation,timeisnotclearandin-bustemperature,mayalsocousestolenwhenthepassengertakeoutthecellphonetoseewhattimeisit.Everythingaboveledtoalowcomfortofthebus.Inviewofthis,basedonRFIDtechnology,multi-functionalautomaticstopsystemdesignmethodshavebeenputforward.RFID(RadioFrequencyIdentification,thatis,radiofrequencyidentificationtechnology)automaticallystopMulti-functionalsystemfeaturesinclude:
automaticidentificationbusstations,auto-stopvoice,LEDdotmatrixscreenshowedreal-timeinformation,directionshowupanddown,showtime,temperatureShowedthatthebusstationautomaticallyopenthedoor,showthespeed,speedwarning,thebusshowthatthenumberofpassengerstogetoffonthenormsofmanagement,suchasoverloadingwarningfunctionofhumannature,therealdrivertoreducetheburdenofincreasedtrafficsafety.Thesystemiscost-effectiveandcanimprovethepublictransportoperator'sservicequality,withacertaindegreeofmarketapplications.
TheimprotantpartforbusisradiofrequencyidentificationanditisusedAT89C51microcomputertofillitsfunctions.TheoutlineoftheAT89C51aslistedbelow.
1、Description
TheAT89C51isalow-power,high-performanceCMOS8-bitmicrocomputerwith4KbytesofFlashprogrammableanderasablereadonlymemory(PEROM).ThedeviceismanufacturedusingAtmel’shigh-densitynonvolatilememorytechnologyandiscompatiblewiththeindustry-standardMCS-51instructionsetandpinout.Theon-chipFlashallowstheprogrammemorytobereprogrammedin-systemorbyaconventionalnonvolatilememoryprogrammer.Bycombiningaversatile8-bitCPUwithFlashonamonolithicchip,theAtmelAT89C51isapowerfulmicrocomputerwhichprovidesahighly-flexibleandcost-effectivesolutiontomanyembeddedcontrolapplications.
2、Functioncharacteristic
TheAT89C51providesthefollowingstandardfeatures:
4KbytesofFlash,128bytesofRAM,32I/Olines,two16-bittimer/counters,afivevectortwo-levelinterruptarchitecture,afullduplexserialport,on-chiposcillatorandclockcircuitry.Inaddition,theAT89C51isdesignedwithstaticlogicforoperationdowntozerofrequencyandsupportstwosoftwareselectablepowersavingmodes.TheIdleModestopstheCPUwhileallowingtheRAM,timer/counters,serialportandinterruptsystemtocontinuefunctioning.ThePower-downModesavestheRAMcontentsbutfreezestheoscillatordisablingallotherchipfunctionsuntilthenexthardwarereset.
3、引脚描述PinDescription
VCC:
Supplyvoltage.
GND:
Ground.
Port0:
Port0isan8-bitopen-drainbi-directionalI/Oport.Asanoutputport,eachpincansinkeightTTLinputs.When1sarewrittentoport0pins,thepinscanbeusedashighimpedanceinputs.Port0mayalsobeconfiguredtobethemultiplexedloworderaddress/databusduringaccessestoexternalprogramanddatamemory.InthismodeP0hasinternalpullups.Port0alsoreceivesthecodebytesduringFlashprogramming,andoutputsthecodebytesduringprogramverification.Externalpullupsarerequiredduringprogramverification.
Port1:
Port1isan8-bitbi-directionalI/Oportwithinternalpullups.ThePort1outputbufferscansink/sourcefourTTLinputs.When1sarewrittentoPort1pinstheyarepulledhighbytheinternalpullupsandcanbeusedasinputs.Asinputs,Port1pinsthatareexternallybeingpulledlowwillsourcecurrent(IIL)becauseoftheinternalpullups.Port1alsoreceivesthelow-orderaddressbytesduringFlashprogrammingandverification.
Port2:
Port2isan8-bitbi-directionalI/Oportwithinternalpullups.ThePort2outputbufferscansink/sourcefourTTLinputs.When1sarewrittentoPort2pinstheyarepulledhighbytheinternalpullupsandcanbeusedasinputs.Asinputs,Port2pinsthatareexternallybeingpulledlowwillsourcecurrent,becauseoftheinternalpullups.Port2emitsthehigh-orderaddressbyteduringfetchesfromexternalprogrammemoryandduringaccessestoexternaldatamemorythatuse16-bitaddresses.Inthisapplication,itusesstronginternalpullupswhenemitting1s.Duringaccessestoexternaldatamemorythatuse8-bitaddresses,Port2emitsthecontentsoftheP2SpecialFunctionRegister.Port2alsoreceivesthehigh-orderaddressbitsandsomecontrolsignalsduringFlashprogrammingandverification.
Port3:
Port3isan8-bitbi-directionalI/Oportwithinternalpullups.ThePort3outputbufferscansink/sourcefourTTLinputs.When1sarewrittentoPort3pinstheyarepulledhighbytheinternalpullupsandcanbeusedasinputs.Asinputs,Port3pinsthatareexternallybeingpulledlowwillsourcecurrent(IIL)becauseofthepullups.
Port3alsoservesthefunctionsofvariousspecialfeaturesoftheAT89C51aslistedbelow:
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.
EA/VPP:
ExternalAccessEnable.EAmustbestrappedtoGNDinordertoenablethedevicetofetchcodefromexternalprogrammemorylocationsstartingat0000HuptoFFFFH.Note,however,thatiflockbit1isprogrammed,EAwillbeinternallylatchedonreset.EAshouldbestrappedtoVCCforinternalprogramexecutions.Thispinalsoreceivesthe12-voltprogrammingenablevoltage(VPP)duringFlashprogramming,forpartsthatrequire12-voltVPP.
XTAL1:
Inputtotheinvertingoscillatoramplifierandinputtotheinternalclockoperatingcircuit.
XTAL2:
Outputfromtheinvertingoscillatoramplifier.
4、OscillatorCharacteristics
XTAL1andXTAL2aretheinputandoutput,respectively,ofaninvertingamplifierwhichcanbeconfiguredforuseasanon-chiposcillator,asshowninFigure1.Eitheraquartzcrystalorceramicresonatormaybeused.Todrivethedevicefromanexternalclocksource,XTAL2shouldbeleftunconnectedwhileXTAL1isdrivenasshowninFigure2.Therearenorequirementsonthedutycycleoftheexternalclocksignal,sincetheinputtotheinternalclockingcircuitryisthroughadivide-by-twoflip-flop,butminimumandmaximumvoltagehighandlowtimespecificationsmustbeobserved.
5、IdleMode
Inidlemode,theCPUputsitselftosleepwhilealltheonchipperipheralsremainactive.Themodeisinvokedbysoftware.Thecontentoftheon-chipRAMandallthespecialfunctionsregistersremainunchangedduringthismode.Theidlemodecanbeterminatedbyanyenabledinterruptorbyahardwarereset.Itshouldbenotedthatwhenidleisterminatedbyahardwarereset,thedevicenormallyresumesprogramexecution,fromwhereitleftoff,uptotwomachinecyclesbeforetheinternalresetalgorithmtakescontrol.On-chiphardwareinhibitsaccesstointernalRAMinthisevent,butaccesstotheportpinsisnotinhibited.ToeliminatethepossibilityofanunexpectedwritetoaportpinwhenIdleisterminatedbyreset,theinstructionfollowingtheonethatinvokesIdleshouldnotbeonethatwritestoaportpinortoexternalmemory.
6、Power-downMode
Inthepower-downmode,theoscillatorisstopped,andtheinstructionthatinvokespower-downisthelastinstructionexecuted.Theon-chipRAMandSpecialFunctionRegistersretaintheirvaluesuntilthepower-downmodeisterminated.Theonlyexitfrompower-downisahardwarereset.ResetredefinestheSFRsbutdoesnotchangetheon-chipRAM.TheresetshouldnotbeactivatedbeforeVCCisrestoredtoitsnormaloperatinglevela
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