AT89C2051AT89C2051ismadeintheATMELCorporation,whichisthelow-voltage,high-performanceCMOS8-bitmicrocontroller,Tabletscontainingrepeated2kbytesofprogrammemoryerasableread-only(PEROM)andrandom128bytesdatamemory(RAM),deviceusingATMELshighdensity,non-volatilememorytechnology,CompatiblewiththestandardofMCS-51instructionset,built-chip8-bitgeneral-purposecentralprocessingunitandrepeatedlywritetheFlashmemory,whichcaneffectivelyreducethedevelopmentcosts.AT89C2051featuresapowerfulsingle-chipcanprovidecost-effectiveinmanyApplications.Mainfeatures:CompatibletheMCS51commandsystem；Containsthe2KBmemoryre-programmingFLASH(1000)；2.76Vvoltagerange；thewholeStaticwork:0Hz24KHz；Secrets2ProgramMemoryLock1288-bitinternalRAM15programmableI/OlinesTwo16-bittimer/counter6interruptsources,twoexternalinterruptsourcesProgrammableSerialChannelHighPrecisionVoltageComparator（P1.0，P1.1，P3.6）；HavetheoutputportoftheLEDdirectdriveLow-poweridleandpower-downmodeThepinPictureofAT89C2051PictureonethepinofAT89C2051123456ABCD654321DCBATitleNumberRevisionSizeBDate:21-May-2009SheetofFile:D:ProgramFilesDesignExplorer99SELibrarySchProtelDOSSchematicLibraries.ddbDrawnBy:20191817161514131211GNDP3.5P3.4P3.3P3.2XTAL1XTAL2P3.1P3.0RSTP3.7P1.0P1.1P1.2P1.3P1.4P1.5P1.6P1.7VCC12345678910AT89C2051sfunctionaldescription:VCC:PowerSupplyVoltageGND:landP1port:P1mouthisagroupof8-bitbi-directionalI/Ointerface,P1.2P1.7provideinternalpull-upresistor,P1.0andP1.1internalsupremepull-upresistor.P1mouthoutputbuffercanabsorbthecurrent20mAanddirect-driveLED.WhenProgrammingandcalibration,P1mouthastheeighthaddressreceive.P3mouth:P3portP3.0P3.5,P3.7istheinternalpull-upresistorwiththesevenbi-directionalI/Ointerface.DidnotbringouttheP3.6，ItasagenericI/Oport,butcannotvisit.Canbeusedasafixed-chipinputcomparatoroutputsignal.whenP3write1,theywerehighedtheinternalpull-upresistorcanberaisedasaninputport.P3portspecialfunctionasshownintable1:Table1P3mouthsspecialfeatures引腳功能特性P3.0RXD（串行輸入口)P3.1TXD（串行輸出口）P3.20INT(外中斷0)P3.31INT(外中斷1)P3.4T0(定時/計數(shù)器0外部輸入)P3.5T1（定時/計數(shù)器1外部輸入）RST：Resetoutput.Whentheoscillatordevicereset,RSTpintomaintainthehighleveloftwomachinecycletime.XTAL1:theRP-oscillatoramplifierandinternalclockgeneratorinput.XTAL2:RP-oscillatoroutputamplifier.TimerOverviewoftheTimer89C2051single-chip-chiphastwo16-bittimer/counter,Thatisthetimer0(T0)andTimer1(T1).Theyallhavefromtimetotimeandeventcountfunction,Canbeusedfortimingcontrol,delayofexternalevents,suchascountingandtestingoccasions.TimersT0andT1two16-bittimersinfactis16-bitcounterplus1.Amongthem,T0compositionedbythetwo8-bitspecialfunctionregistersTH0andTL0；T1posedbytheTH1andTL1.ThesefunctionswerecontroledbythespecialfunctionregistersTMODandTCONWhensettotheworkinthetiming,Throughthepincountoftheexternalpulsesignal.Whentheinputpulsesignalgeneratedbythefallingedgeof1-0,Thevalueoftimerplus1.AtofeverymachinecycleduringtheS5P2samplingpinT0andT1theinputlevel,ifamachinecyclebeforesamplevalueof1,Thenextmachinecyclesamplingvalueis0,Thecounterplus1.SincethenduringS3P1ofthemachinecycle,Newvaluewillintothecounter.soDetectionofa1-0transitionofthetwomachinecycles,SoThemaximumcountfrequencyofoscillationfrequencyof1/24.Inadditiontotheoptionofworkfromtimetotimeorcount,Eachtimer/counterhavefourkindsofworkmode,Thatis,eachoftimercircuitkindsoffourconstituteastructuralmodelTwolow-powermodeIdlemodeInidlemode,CPUtomaintainsleepandall-chipperipheralsremainactive,thiswaygeneratedinSoftware,Atthispoint,ChipRAMandallthecontentsofspecialfunctionregistersremainunchanged.Idlemodewasterminatedbyanyinterruptrequestpermissiontoorhardwarereset.P1.0andP1.1,inthenon-useofexternalpull-upresistoronthecaseshouldbesetto0,Orintheuseofpull-upresistorissetto1.Itshouldbenotedthat:whenusesofhardwareresetTerminationidlemode,AT89C2051isusuallystoppedfromtheprogramuntiltheinternalresetcontrolofthetwomachinecyclesbeforetherestoreprocedureService.InthiscasethehardwarewithintheprohibitionofthereadingandwritingofinternalRAM,However,toallowaccesstoports,ToeliminatetheHardwareresetintheidlemodeofportaccidentsmaywrite,Inprinciple,toentertheidlemodeofinstructionshouldnotbeunderthecommandofapinoranexternalmemoryportforavisit.Power-downmodeInpower-downmode,theoscillatortostopworking,enterthepower-downmode,Instructions,whowasthelastone,theimplementationoftheDirective,ChipRAMandallthecontentsofspecialfunctionregisterstheterminationofthepreviouspower-downmodebefrozen.Towithdrawfrompower-downmodeistheonlywaytoresetthehardware,ResetwillredefinealltheSpecialFunctionRegistersbutDoesnotchangethecontentsofRAMbeforethetheVccworkreturnedtonormallevelsShallbenullandvoidandmustberesettomaintainacertainperiodoftimeinordertorestartandoscillatorstabilityP1.0andP1.1inthenon-useofexternalpull-upresistoronthecaseshouldbesetto0,Orintheuseofpull-upresistorissetto1.OscillatorOscillatorconnectedclientXTAL1:RP-oscillatoramplifierandinternalclockgeneratorinputXTAL2:RP-oscillatoramplifieroutputCharacteristicsofOscillatorXTAL1,XTAL2waretheRP-chiposcillatoramplifierinputsandoutputs,Quartzcrystalcanbecomposedoftheclockoscillatororceramicoscillator,Formoreinformati