机械工程系车辆工程1301034224王博文外文翻译.docx
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机械工程系车辆工程1301034224王博文外文翻译
中北大学信息商务学院
毕业设计说明书
外文文献原文及译文
学生姓名:
王博文
学号:
1301034224
系名:
机械工程系
专业:
车辆工程
论文题目:
汽车防撞预警系统设计
指导教师:
罗佳
2017年5月19日
AT89C2051MicrocontrollerInstructions
1.1Features
∙CompatiblewithMCS-51Products
∙2KbytesofReprogrammableFlashMemory
Endurance:
1,000Write/EraseCycles
∙2.7Vto6VOperatingRange
∙FullyStaticOperation:
0Hzto24MHz
∙Two-LevelProgramMemoryLock
∙128x8-BitInternalRAM
∙15ProgrammableI/OLines
∙Two16-BitTimer/Counters
∙SixInterruptSources
∙ProgrammableSerialUARTChannel
∙DirectLEDDriveOutputs
∙On-ChipAnalogComparator
∙LowPowerIdleandPowerDownModes
1.2Description
TheAT89C2051isalow-voltage,high-performanceCMOS8-bitmicrocomputerwith2KbytesofFlashprogrammableanderasablereadonlymemory(PEROM).ThedeviceismanufacturedusingAtmel’shighdensitynonvolatilememorytechnologyandiscompatiblewiththeindustrystandardMCS-51instructionsetandpinout.Bycombiningaversatile8-bitCPUwithFlashonamonolithicchip,theAtmelAT89C2051isapowerfulmicrocomputerwhichprovidesahighlyflexibleandcosteffectivesolutiontomanyembeddedcontrolapplications.
TheAT89C2051providesthefollowingstandardfeatures:
2KbytesofFlash,128bytesofRAM,15I/Olines,two16-bittimer/counters,afivevectortwo-levelinterruptarchitecture,afullduplexserialport,aprecisionanalogcomparator,on-chiposcillatorandclockcircuitry.Inaddition,theAT89C2051isdesignedwithstaticlogicforoperationdowntozerofrequencyandsupportstwosoftwareselectablepowersavingmodes.TheIdleModestopstheCPUwhileallowingtheRAM,timer/counters,serialportandinterruptsystemtocontinuefunctioning.ThePowerDownModesavestheRAMcontentsbutfreezestheoscillatordisablingallotherchipfunctionsuntilthenexthardwarereset.
1.3PinConfiguration
1.4PinDescription
VCCSupplyvoltage.
GNDGround.
Port1
Port1isan8-bitbidirectionalI/Oport.PortpinsP1.2toP1.7provideinternalpullups.P1.0andP1.1requireexternalpullups.P1.0andP1.1alsoserveasthepositiveinput(AIN0)andthenegativeinput(AIN1),respectively,oftheon-chipprecisionanalogcomparator.ThePort1outputbufferscansink20mAandcandriveLEDdisplaysdirectly.When1sarewrittentoPort1pins,theycanbeusedasinputs.WhenpinsP1.2toP1.7areusedasinputsandareexternallypulledlow,theywillsourcecurrent(IIL)becauseoftheinternalpullups.
Port1alsoreceivescodedataduringFlashprogrammingandprogramverification.
Port3
Port3pinsP3.0toP3.5,P3.7aresevenbidirectionalI/Opinswithinternalpullups.P3.6ishard-wiredasaninputtotheoutputoftheon-chipcomparatorandisnotaccessibleasageneralpurposeI/Opin.ThePort3outputbufferscansink20mA.When1sarewrittentoPort3pinstheyarepulledhighbytheinternalpullupsandcanbeusedasinputs.Asinputs,Port3pinsthatareexternallybeingpulledlowwillsourcecurrent(IIL)becauseofthepullups.
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)
Port3alsoservesthefunctionsofvariousspecialfeaturesoftheAT89C2051aslistedbelow:
1.5OscillatorCharacteristics
XTAL1andXTAL2aretheinputandoutput,respectively,ofaninvertingamplifierwhichcanbeconfiguredforuseasanon-chiposcillator,asshowninFigure1.Eitheraquartzcrystalorceramicresonatormaybeused.Todrivethedevicefromanexternalclocksource,XTAL2shouldbeleftunconnectedwhileXTAL1isdrivenasshowninFigure2.Therearenorequirementsonthedutycycleoftheexternalclocksignal,sincetheinputtotheinternalclockingcircuitryisthroughadivideby-twoflip-flop,butminimumandmaximumvoltagehighandlowtimespecificationsmustbeobserved.
1.6SpecialFunctionRegisters
Amapoftheon-chipmemoryareacalledtheSpecialFunctionRegister(SFR)spaceisshowninthetablebelow.
Notethatnotalloftheaddressesareoccupied,andunoccupiedaddressesmaynotbeimplementedonthechip.Readaccesses.totheseaddresseswillingeneralreturnrandomdata,andwriteaccesseswillhaveanindeterminateeffect.
Usersoftwareshouldnotwrite1stotheseunlistedlocations,sincetheymaybeusedinfutureproductstoinvokenewfeatures.Inthatcase,theresetorinactivevaluesofthenewbitswillalwaysbe0.
1.7RestrictionsonCertainInstructions
TheAT89C2051andisaneconomicalandcost-effectivememberofAtmel’sgrowingfamilyofmicrocontrollers.Itcontains2Kbytesofflashprogrammemory.ItisfullycompatiblewiththeMCS-51architecture,andcanbeprogrammedusingtheMCS-51instructionset.However,thereareafewconsiderationsonemustkeepinmindwhenutilizingcertaininstructionstoprogramthisdevice.
Alltheinstructionsrelatedtojumpingorbranchingshouldberestrictedsuchthatthedestinationaddressfallswithinthephysicalprogrammemoryspaceofthedevice,whichis2KfortheAT89C2051.Thisshouldbetheresponsibilityofthesoftwareprogrammer.Forexample,LJMP7E0HwouldbeavalidinstructionfortheAT89C2051(with2Kofmemory),whereasLJMP900Hwouldnot.
1.Branchinginstructions:
LCALL,LJMP,ACALL,AJMP,SJMP,JMP@A+DPTR
Theseunconditionalbranchinginstructionswillexecutecorrectlyaslongastheprogrammerkeepsinmindthatthedestinationbranchingaddressmustfallwithinthephysicalboundariesoftheprogrammemorysize(locations00Hto7FFHforthe89C2051).Violatingthephysicalspacelimitsmaycauseunknownprogrambehavior.
CJNE[...],DJNZ[...],JB,JNB,JC,JNC,JBC,JZ,JNZWiththeseconditionalbranchinginstructionsthesameruleaboveapplies.Again,violatingthememoryboundariesmaycauseerraticexecution.
Forapplicationsinvolvinginterruptsthenormalinterruptserviceroutineaddresslocationsofthe80C51familyarchitecturehavebeenpreserved.
2.MOVX-relatedinstructions,DataMemory:
TheAT89C2051contains128bytesofinternaldatamemory.Thus,intheAT89C2051thestackdepthislimitedto128bytes,theamountofavailableRAM.ExternalDATAmemoryaccessisnotsupportedinthisdevice,norisexternalPROGRAMmemoryexecution.Therefore,noMOVX[...]instructionsshouldbeincludedintheprogram.
Atypical80C51assemblerwillstillassembleinstructions,eveniftheyarewritteninviolationoftherestrictionsmentionedabove.Itistheresponsibilityofthecontrollerusertoknowthephysicalfeaturesandlimitationsofthedevicebeingusedandadjusttheinstructionsusedcorrespondingly.
1.8ProgramMemoryLockBits
Onthechiparetwolockbitswhichcanbeleftunprogrammed(U)orcanbeprogrammed(P)toobtaintheadditionalfeatureslistedinthetablebelow:
LockBitProtectionModes
(1)
ProgramLockBits
LB1
LB2
ProtectionType
1
U
U
Noprogramlockfeatures.
2
P
U
Furtherprogrammingofthe
Flashisdisabled.
3
P
P
Sameasmode2,alsoverify
isdisabled.
Note:
1.TheLockBitscanonlybeerasedwiththeChipEraseoperation
1.9IdleMode
Inidlemode,theCPUputsitselftosleepwhilealltheon-chipperipheralsremainactive.Themodeisinvokedbysoftware.Thecontentoftheon-chipRAMandallthespecialfunctionsregistersremainunchangedduringthismode.Theidlemodecanbeterminatedbyanyenabledinterruptorbyahardwarereset.
P1.0andP1.1shouldbesetto’0’ifnoexternalpullupsareused,orsetto’1’ifexternalpullupsareused.
Itshouldbenotedthatwhenidleisterminatedbyahardwarereset,thedevicenormallyresumesprogramexecution,fromwhereitleftoff,uptotwomachinecyclesbeforetheinternalresetalgorithmtakescontrol.On-chiphardwareinhibitsaccesstointernalRAMinthisevent,butaccesstotheportpinsisnotinhibited.ToeliminatethepossibilityofanunexpectedwritetoaportpinwhenIdleisterminatedbyreset,theinstructionfollowingtheonethatinvokesIdleshouldnotbeonethatwritestoaportpinortoexternalmemory.
1.10PowerDownMode
Inthepowerdownmodetheoscillatorisstopped,andtheinstructionthatinvokespowerdownisthelastinstructionexecuted.Theon-chipRAMandSpecialFunctionRegistersretaintheirvaluesuntilthepowerdownmodeisterminated.Theonlyexitfrompowerdownisahardwarereset.ResetredefinestheSFRsbutdoesnotchangetheon-chipRAM.TheresetshouldnotbeactivatedbeforeVCCisrestoredtoitsnormaloperatinglevelandmustbeheldactivelongenoughtoallowtheoscillatortorestartandstabilize.
P1.0andP1.1shouldbesetto’0’ifnoexternalpullupsareused,orsetto’1’ifexternalpullupsareused.
1.11ProgrammingTheFlash
TheAT89C2051isshippedwiththe2Kbytesofon-chipPEROMcodememoryarrayintheerasedstate(i.e.,contents=FFH)andreadytobeprogrammed.Thecodememoryarrayisprogrammedonebyteatatime.Oncethearrayisprogrammed,tore-programanynon-blankbyte,theentirememoryarrayneedstobeerasedelectrically.
InternalAddressCounter:
TheAT89C2051containsaninternalPEROMaddresscounterwhichisalwaysresetto000HontherisingedgeofRSTandisadvancedbyapplyingapositivegoingpulsetopinXTAL1.
ProgrammingAlgorithm:
ToprogramtheAT89C2051,thefollowingsequenceisrecommended.
1.Power-upsequence:
ApplypowerbetweenVCCandGNDpinsSetRSTandXTAL1toGND
Withallotherpinsfloating,waitforgreaterthan10milliseconds
2.SetpinRSTto’H’SetpinP3.2to’H’
3.Applytheappropriatecombinatio