毕业设计外文翻译89C51单片机.docx
- 文档编号:7559729
- 上传时间:2023-01-25
- 格式:DOCX
- 页数:9
- 大小:27.87KB
毕业设计外文翻译89C51单片机.docx
《毕业设计外文翻译89C51单片机.docx》由会员分享,可在线阅读,更多相关《毕业设计外文翻译89C51单片机.docx(9页珍藏版)》请在冰豆网上搜索。
毕业设计外文翻译89C51单片机
毕业设计外文翻译--89C51单片机
TheDescriptionofAT89S51
1GeneralDescription
TheAT89S51isalow-power,high-performanceCMOS8-bitmicrocontrollerwith4KbytesofIn-SystemProgrammableFlashmemory.ThedeviceismanufacturedusingAtmel’shigh-densitynonvolatilememorytechnologyandiscompatiblewiththeindustry-standard80C51instructionsetandpinout.Theon-chipFlashallowstheprogrammemorytobereprogrammedin-systemorbyaconventionalnonvolatilememoryprogrammer.Bycombiningaversatile8-bitCPUwithIn-SystemProgrammableFlashonamonolithicchip,theAtmelAT89S51isapowerfulmicrocontrollerwhichprovidesahighly-flexibleandcost-effectivesolutiontomanyembeddedcontrolapplications.
TheAT89S51providesthefollowingstandardfeatures:
4KbytesofFlash,128bytesofRAM,32I/Olines,Watchdogtimer,twodatapointers,two16-bittimer/counters,afive-vectortwo-levelinterruptarchitecture,afullduplexserialport,on-chiposcillator,andclockcircuitry.Inaddition,theAT89S51isdesignedwithstaticlogicforoperationdowntozerofrequencyandsupportstwosoftwareselectablepowersavingmodes.
TheIdleModestopstheCPUwhileallowingtheRAM,timer/counters,serialport,andinterruptsystemtocontinuefunctioning.ThePower-downmodesavestheRAMcontentsbutfreezestheoscillator,disablingallotherchipfunctionsuntilthenextexternalinterruptorhardwarereset.
2Ports
Port0isan8-bitopendrainbi-directionalI/Oport.Asanoutputport,eachpincansinkeightTTLinputs.When1sarewrittentoport0pins,thepinscanbeusedashigh-impedanceinputs.Port0canalsobeconfiguredtobethemultiplexedlow-orderaddress/databusduringaccessestoexternalprogramanddatamemory.Inthismode,P0hasinternalpull-ups.Port0alsoreceivesthecodebytesduringFlashprogrammingandoutputsthecodebytesduringprogramverification.Externalpull-upsarerequiredduringprogramverification.
Port1isan8-bitbi-directionalI/Oportwithinternalpull-ups.ThePort1outputbufferscansink/sourcefourTTLinputs.When1sarewrittentoPort1pins,theyarepulledhighbytheinternalpull-upsandcanbeusedasinputs.Asinputs,Port1pinsthatareexternallybeingpulledlowwillsourcecurrent(IIL)becauseoftheinternalpull-ups.
Port1alsoreceivesthelow-orderaddressbytesduringFlashprogrammingandverification.
PortPin
AlternateFunctions
P1.5
MOSI(usedforIn-SystemProgramming)
P1.6
MOSO(usedforIn-SystemProgramming)
P1.7
SCK(usedforIn-SystemProgramming)
Port2isan8-bitbi-directionalI/Oportwithinternalpull-ups.ThePort2outputbufferscansink/sourcefourTTLinputs.When1sarewrittentoPort2pins,theyarepulledhighbytheinternalpull-upsandcanbeusedasinputs.Asinputs,Port2pinsthatareexternallybeingpulledlowwillsourcecurrent(IIL)becauseoftheinternalpull-ups.Port2emitsthehigh-orderaddressbyteduringfetchesfromexternalprogrammemoryandduringaccessestoexternaldatamemorythatuse16-bitaddresses(MOVX@DPTR).Inthisapplication,Port2usesstronginternalpull-upswhenemitting1s.Duringaccessestoexternaldatamemorythatuse8-bitaddresses(MOVX@RI),Port2emitsthecontentsoftheP2SpecialFunctionRegister.Port2alsoreceivesthehigh-orderaddressbitsandsomecontrolsignalsduringFlashprogrammingandverification.
Port3isan8-bitbi-directionalI/Oportwithinternalpull-ups.ThePort3outputbufferscansink/sourcefourTTLinputs.When1sarewrittentoPort3pins,theyarepulledhighbytheinternalpull-upsandcanbeusedasinputs.Asinputs,Port3pinsthatareexternallybeingpulledlowwillsourcecurrent(IIL)becauseofthepull-ups.Port3receivessomecontrolsignalsforFlashprogrammingandverification.Port3alsoservesthefunctionsofvariousspecialfeaturesoftheAT89S51,asshowninthefollowingtable.
PortPin
AlternateFunctions
P3.0
RXD(serialinputport)
P3.1
TXD(serialoutputport)
P3.2
INT0(externalinterrupt0)
P3.3
INT1(externalinterrupt1)
P3.4
T0(timer0externalinput)
P3.5
T1(timer1externalinput)
P3.6
WR(externaldatamemorywritestrobe)
P3.7
RD(externaldatamemoryreadstrobe)
3MemoryOrganization
MCS-51deviceshaveaseparateaddressspaceforProgramandDataMemory.Upto64KbyteseachofexternalProgramandDataMemorycanbeaddressed.
3.1ProgramMemory
IftheEApinisconnectedtoGND,allprogramfetchesaredirectedtoexternalmemory.OntheAT89S51,ifEAisconnectedtoVCC,programfetchestoaddresses0000HthroughFFFHaredirectedtointernalmemoryandfetchestoaddresses1000HthroughFFFFHaredirectedtoexternalmemory.
3.2DataMemory
TheAT89S51implements128bytesofon-chipRAM.The128bytesareaccessibleviadirectandindirectaddressingmodes.Stackoperationsareexamplesofindirectaddressing,sothe128bytesofdataRAMareavailableasstackspace.
4WatchdogTimer(One-timeEnabledwithReset-out)
TheWDTisintendedasarecoverymethodinsituationswheretheCPUmaybesubjectedtosoftwareupsets.TheWDTconsistsofa14-bitcounterandtheWatchdogTimerReset(WDTRST)SFR.TheWDTisdefaultedtodisablefromexitingreset.ToenabletheWDT,ausermustwrite01EHand0E1HinsequencetotheWDTRSTregister(SFRlocation0A6H).WhentheWDTisenabled,itwillincrementeverymachinecyclewhiletheoscillatorisrunning.TheWDTtimeoutperiodisdependentontheexternalclockfrequency.ThereisnowaytodisabletheWDTexceptthroughreset(eitherhardwareresetorWDToverflowreset).WhenWDToverflows,itwilldriveanoutputRESETHIGHpulseattheRSTpin.
4.1UsingtheWDT
ToenabletheWDT,ausermustwrite01EHand0E1HinsequencetotheWDTRSTregister(SFRlocation0A6H).WhentheWDTisenabled,theuserneedstoserviceitbywriting01EHand0E1HtoWDTRSTtoavoidaWDToverflow.The14-bitcounteroverflowswhenitreaches16383(3FFFH),andthiswillresetthedevice.WhentheWDTisenabled,itwillincrementeverymachinecyclewhiletheoscillatorisrunning.ThismeanstheusermustresettheWDTatleastevery16383machinecycles.ToresettheWDTtheusermustwrite01EHand0E1HtoWDTRST.WDTRSTisawrite-onlyregister.TheWDTcountercannotbereadorwritten.WhenWDToverflows,itwillgenerateanoutputRESETpulseattheRSTpin.TheRESETpulsedurationis98xTOSC,whereTOSC=1/FOSC.TomakethebestuseoftheWDT,itshouldbeservicedinthosesectionsofcodethatwillperiodicallybeexecutedwithinthetimerequiredtopreventaWDTreset.
4.2WDTDURINGPower-downandIdle
InPower-downmodetheoscillatorstops,whichmeanstheWDTalsostops.WhileinPower-downmode,theuserdoesnotneedtoservicetheWDT.TherearetwomethodsofexitingPower-downmode:
byahardwareresetorviaalevel-activatedexternalinterrupt,whichisenabledpriortoenteringPower-downmode.WhenPower-downisexitedwithhardwarereset,servicingtheWDTshouldoccurasitnormallydoeswhenevertheAT89S51isreset.ExitingPower-downwithaninterruptissignificantlydifferent.Theinterruptisheldlowlongenoughfortheoscillatortostabilize.Whentheinterruptisbroughthigh,theinterruptisserviced.TopreventtheWDTfromresettingthedevicewhiletheinterruptpinisheldlow,theWDTisnotstarteduntiltheinterruptispulledhigh.ItissuggestedthattheWDTberesetduringtheinterruptservicefortheinterruptusedtoexitPower-downmode.ToensurethattheWDTdoesnotoverflowwithinafewstatesofexitingPower-down,itisbesttoresettheWDTjustbeforeenteringPower-downmode.BeforegoingintotheIDLEmode,theWDIDLEbitinSFRAUXRisusedtodeterminewhethertheWDTcontinuestocountifenabled.TheWDTkeepscountingduringIDLE(WDIDLEbit=0)asthedefaultstate.TopreventtheWDTfromresettingtheAT89S51whileinIDLEmode,theusershouldalwayssetupatimerthatwillperiodicallyexitIDLE,servicetheWDT,andreenterIDLEmode.
WithWDIDLEbitenabled,theWDTwillstoptocountinIDLEmodeandresumesthecountuponexitfromIDLE.
5.Interrupts
TheAT89S51hasatotaloffiveinterruptvectors:
twoexternalinterrupts(INT0andINT1),twotimerinterrupts(Timers0and1),andtheserialportinterrupt.TheseinterruptsareallshowninFigure6-1.EachoftheseinterruptsourcescanbeindividuallyenabledordisabledbysettingorclearingabitinSpecialFunctionRegisterIE.IEalsocontainsaglobaldisablebit,EA,whichdisablesallinterruptsatonce.
6OscillatorCharacteristics
XTAL1andXTAL2aretheinputandoutput,respectively,ofaninvertingamplifierthatcanbeconfiguredforuseasanon-chiposcillator,asshowninFigure7-1.Eitheraquartzcrystalorceramicresonatormaybeused.Todrivethedevicefromanexternalclocksource,XTAL2shouldbeleftunconnectedwhileXTAL1isdriven,asshowninFigure7-2.Therearenorequirementsonthedutycycleoftheexternalclocksignal,sincetheinputtotheinternalclockingcircuitryisthroughadivide-by-twoflip-flop,butminimumandmaximumvoltagehighandlowtimespecificationsmustbeobserved.
7IdleMode
Inidlemode,theCPUputsitselftosleepwhilealltheon-chipperipheralsremainactive.Themodeisinvokedbysoftware.Thecontentoftheon-chipRAMandallthespecialfunctionregistersremainunchangedduringthismode.Theidlemodecanbeterminatedbyanyenabledinterruptorbyahardwarereset.
Notethatwhenidlemodeisterminatedbyahardwarereset,thedevicenormallyresumespro-gramexecutionfromwhereitleftoff,uptotwomachinecyclesbeforetheinternalresetalgorithmtakescontrol.On-chiphardwareinhibitsaccesstointe
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 毕业设计 外文 翻译 89 C51 单片机
![提示](https://static.bdocx.com/images/bang_tan.gif)