StructureandfunctionoftheMCS-51seriesStructureandfunctionoftheMCS-51seriesone-chipcomputerMCS-51isanameofapieceofone-chipcomputerserieswhichIntelCompanyproduces.Thiscompanyintroduced8top-gradeone-chipcomputersofMCS-51seriesin1980afterintroducing8one-chipcomputersofMCS-48seriesin1976.Itbelongtoalotofkindsthislineofone-chipcomputerthechipshave,suchas8051,8031,8751,80C51BH,80C31BH,etc.,theirbasiccomposition,basicperformanceandinstructionsystemareallthesame.8051dailyrepresentatives-51serialone-chipcomputer.Anone-chipcomputersystemismadeupofseveralfollowingparts:(1)Onemicroprocessorof8(CPU).(2)AtslicedatamemoryRAM(128B/256B),itusedtodepositingnotcanreading/datathatwrite,suchasresultnotmiddleofoperation,finalresultanddatawantedtoshow,etc.(3)ProcedurememoryROM/EPROM(4KB/8KB),isusedtopreservetheprocedure,someinitialdataandforminslice.ButdoesnottakeROM/EPROMwithinsomeone-chipcomputers,suchas8031,8032,80C,etc.(4)Four8runsidebysideI/OinterfaceP0fourP3,eachmouthcanuseasintroduction,mayuseasexportingtoo.(5)Twotimer/counter,eachtimer/countermaysetupandcountintheway,usedtocounttotheexternalincident,cansetupintoatimingwaytoo,andcanaccordingtocountorresultoftimingrealizethecontrolofthecomputer.(6)Fivecutoffcuttingoffthecontrolsystemofthesource.(7)OneallduplexserialI/OmouthofUART(universalasynchronousreceiver/transmitter(UART),isitrealizeone-chipcomputerorone-chipcomputerandserialcommunicationofcomputertousefor.(8)Stretchoscillatorandclockproducecircuit,quartzcrystalfinelytuneelectriccapacityneedouter.Allowoscillationfrequencyas12nowatmost.Everytheabove-mentionedpartwasjoinedthroughtheinsidedatabus.Amongthem,CPUisacoreoftheone-chipcomputer,itisthecontrolofthecomputerandcommandcentre,madeupofsuchpartsasarithmeticunitandcontroller,etc.Thearithmeticunitcancarryon8personsofarithmeticoperationandunitALUoflogicoperationwhileincludingone,the1storingdevicetemporarilyof8,storingdevice2temporarily,8saccumulationdeviceACC,registerBandprocedurestateregisterPSW,etc.PersonwhoaccumulateACCcountby2inputendsenteredofcheckingetc.temporarilyasoneoperationoften,comefrompersonwhostore1operationisitisitmakeoperationtogoontocounttemporarily,operationresultandloopbackACCwithanotherone.Inaddition,ACCisoftenregardedasthetransferstationofdatatransmissionon8051inside.Thesameasgeneralmicroprocessor,itisthebusiestregister.HelprememberingthatagreeingwithAexpressesintheorder.Thecontrollerincludestheprocedurecounter,theorderisdeposited,theorderdecipher,theoscillatorandtimingcircuit,etc.Theprocedurecounterismadeupofcounterof8fortwo,amountsto16.Itisabyteaddresscounteroftheprocedureinfact,thecontentisthenextIAthatwillcarriedoutinPC.Thecontentwhichchangesitcanchangethedirectionthattheprocedurecarriesout.Shakethecircuitin8051one-chipcomputers,onlyneedouterquartzcrystalandfrequencytofinelytunetheelectriccapacity,itsfrequencyrangeisits12MHZof1.2MHZ.Thispulsesignal,as8051basicbeatsofworking,namelytheminimumunitoftime.8051isthesameasothercomputers,theworkinharmonyunderthecontrolofthebasicbeat,justlikeanorchestraaccordingtothebeatplaythatiscommanded.ThereareROM(procedurememory,canonlyread)andRAMin8051slices(datamemory,canisitcanwrite)twotoread,theyhaveeachindependentmemoryaddressspace,disposewaytobethesamewithgeneralmemoryofcomputer.Procedure8051memoryand8751sliceprocedurememorycapacity4KB,addressbeginfrom0000H,usedforpreservingtheprocedureandformconstant.Data8051-87518031ofmemorydatamemory128B,addressfalse00FH,useformiddleresulttodepositoperation,thedataarestoredtemporarilyandthedataarebufferedetc.InRAMofthis128B,thereisunitof32bytesthatcanbeappointedasthejobregister,thisandgeneralmicroprocessorisdifferent,8051sliceRAMandjobregisterrankoneformationthesametoarrangethelocation.ItisnotverythesamethatthememoryofMCS-51seriesone-chipcomputerandgeneralcomputerdisposesthewayinaddition.Generalcomputerforfirstaddressspace,ROMandRAMcanarrangeindifferentspacewithintherangeofthisaddressatwill,namelytheaddressesofROMandRAM,withdistributingdifferentaddressspaceinaformation.Whilevisitingthememory,correspondingandonlyanaddressMemoryunit,canROM,itcanbeRAMtoo,andbyvisitingtheordersimilarly.ThiskindofmemorystructureiscalledthestructureofPrinceton.8051memoriesaredividedintoprocedurememoryspaceanddatamemoryspaceonthephysicsstructure,therearefourmemoryspacesinall:Theprocedurestoresinoneanddatamemoryspaceoutsidedatamemoryandoneinprocedurememoryspaceandoneoutsideone,thestructureformsofthiskindofproceduredeviceanddatamemoryseparatedformdatamemory,calledHarvardstructure.Butusetheanglefromusers,8051memoryaddressspaceisdividedintothreekinds:(1)Intheslice,arrangeblocksofFFFFH,0000Hoflocation,inunisonoutsidetheslice(use16addresses).(2)Thedatamemoryaddressspaceoutsideoneof64KB,theaddressisarrangedfrom0000H64KBFFFFH(with16addresses)tootothelocation.(3)Datamemoryaddressspaceof256B(use8addresses).Threeabove-mentionedmemoryspaceaddressesoverlap,fordistinguishinganddesigningtheordersymbolofdifferentdatatransmissionintheinstructionsystemof8051:CPUvisitslice,ROMorderspendMOVC,visitblockRAMorderusesMOVXoutsidetheslice,RAMorderusesMOVtovisitinslice.8051one-chipcomputerhavefour8walkabreastI/Oport,callP0,P1,P2andP3.Eachportis8accuratetwo-waymouths,accountsfor32pinsaltogether.EveryoneI/Olinecanbeusedasintroductionandexportedindependently.Eachportincludesalatch(namelyspecialfunctionregister),oneexportsthedriverandaintroductionbuffer.Makedatacanlatchwhenoutputting,datacanbufferwhenmakingintroduction,butfourfunctionofpasswaytheseself-same.Expandamongthesystemofmemoryoutsidehavingslice,fourportthesemayserveasaccuratetwo-waymouthofI/Oincommonuse.Expandamongthesystemofmemoryoutsidehavingslice,P2mouthseehigh8addressoff；P0mouthisatwo-waybus,sendtheintroductionof8lowaddressesanddata/exportintimesharingThecircuitof8051one-chipcomputersandfourI/Oportsisveryingeniousindesign.FamiliarwithI/Oportlogicalcircuit,notonlyhelptouseportscorrectlyandrationally,andwillinspiretodesigningtheperipherallogicalcircuitofone-chipcomputertosomeextent.Loadabilityandinterfaceofporthavecertainrequirement,becauseoutputgrade,P0ofmouthandP1endoutput,P3ofmouthgradedifferentatstructure,so,theloadabilityandinterfaceofitsdoordemandtohavenothingincommonwitheachother.P0mouthisdifferentfromothermouths,itsoutputgradedrawstheresistancesupreme.Whenusingitasthemouthincommonusetouse,outputgradeisitleakcircuittoturnon,isitisiturgeNMOSdrawtheresistanceontakingtobeouterwithitwhileinputtingtogoouttofail.Whenbeingusedasintroduction,shouldwrite1toalatchfirst.EveryonewithP0mouthcandrive8ModelLSTTLloadtoexport.P1mouthisanaccuratetwo-waymouthtoo,usedasI/Oincommonuse.DifferentfromP0mouthoutputofcircuitits,drawloadresistancelinkwithpoweroninsidehave.Infact,theresistanceisthattwoeffectsareinchargeofFETandtogether:OneFETisinchargeofload,itsresistanceisregular.Anotheronecanisitleadtoworkwithcloseattwostate,makeitsPresidentresistancevaluechangeapproximate0orgroupvalueheavytwosituationvery.Whenitis0thattheresistanceisapproximate,candrawthepintothehighlevelfast；Whenresistancevalueisverylarge,P1mouth,inordertohindertheintroductionstatehigh.OutputasP1mouthhighelectricityatordinarytimes,canisitdrawelectriccurrentloadtoofferoutwards,drawtheresistanceonneedntanswerandthen.Herewhentheportisusedasintroduction,mustwriteinto1tothecorrespondinglatchfirsttoo,makeFETend.ThestructureofP2somemouthissimilartoP0mouth,thereareMUXswitches.Isitsimilartomouthpartlytourge,butmouthlargeaconversioncontrolssomethanP1.P3mouthonemulti-functionalport,mouthgettingmanythanP1ithaveand3doorand4buffer.Twopartthese,makeherbesidesaccuratetwo-wayfunctionwithP1mouthjust,canalsousethesecondfunctionofeverypin,anddoor3functiononeswitchinfact,itdeterminestobetooutputdataoflatchtooutputsecondsignaloffunction.ActasW=At1oclock,outputQendsignal；ActasQ=At1oclock,canoutputWlinesignal.Atthetimeofprogramming,itisthatthefirstfunctionisstillthesecondfunctionbutneednthavesoftwarethatsetupP3mouthinadvance.IthardwarenotinsideistheautomatictohavetwofunctionoutputtedwhenCPUcarriesonSFRandseeksthelocation(thelocationorthebyte)tovisittoP3mouth/atnotlastinglining,thereareinsidehardwarelatchQs=1.TheoperationprincipleofP3mouthissimilartoP1mouth.Outputgrade,P3ofmouth,P1ofP1,connectwithinsidehaveloadresistanceofdrawing,everyoneoftheycandrive4ModelLSTTLloadtooutput.Aswhileinputtingthemouth,anyTTLorNMOScircuitcandriveP1of8051one-chipcomputersasP3mouthinanormalway.Becausedrawresistanceonoutputgradeofthemhave,canopenawaycollectortooordrain-sourceresistanceisiturge