基于AT89C51单片机的LED显示控制系统.docx

基于AT89C51单片机的LED显示控制系统.docx

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基于AT89C51单片机的LED显示控制系统

本文摘译自：

ApplicationofElectronicTechnique

外文文献原文：

DesignofLEDDisplayControlSystemBasedonAT89C52SingleChipMicrocomputer

Abstract—ThispaperintroducesdisplaydesignprocessabouthardwareandsoftwarebasedonAT89C52singlechipmicrocomputer.Weuseasimpleexternalcircuittocontrolthedisplayscreen,whichsizeis32×192.Thedisplayscreenalsocandisplaythesizeofthesix32×32dotmatrixChinesecharactersbyadynamicscanmode,andcanbedividedintotwosmalldisplayscreen,whichcandisplaytwenty-fourChinesecharacterswhosesizeis16×16.Wecanmodifythecodetochangethecontentofthedisplay,subtitlescanachievescrollingfunctionandthescrollspeedcanbeadjustedaccordingtorequirements,subtitlescanalsoachievepausefunction.TheChinesecharactercodestoredinexternaldatamemory,thecapacityofdatamemoryisexpandedaccordingtotherequirementsofChinesecharacterswewanttoshow.Thisdisplayscreenhasadvantagesofsmallvolume,fewhardwareandsimplecircuitstructure.

IndexTerms—LED,ChineseCharacterDisplay,AT89C52

I.INTRODUCTION

LEDdisplayhasbecomeanimportantsymbolofthecitylighting,modernizationandinformationsocietywithcontinuousimprovementandbeautificationofpeople'slivingenvironment[6].LEDlightscanbeseeninthelargeshoppingmalls,railwaystation,docks,undergroundstation,avarietyofmanagementwindowandsoon.LEDbusinesshasbecomeafast-growingnewindustry,ahugemarketspaceandbrightprospects[9].Thetext,pictures,animationandvideoaredisplayedbyLED’slight,andcontentcanbechanged.Somecomponentsarethedisplaydevicesofthemodularstructure,andwhichusuallyconsistsofadisplaymodule,controlsystemandpowersystem.ThedisplaymoduleisconstitutedbythelatticestructurewhichconsistsofLED,andisresponsibleforlight-emittingdisplay;thescreencandisplaytext,pictures,videoandsoonbycontrolsystemwhichcancontrollightordarkofLEDinthecorrespondingregion;Powersystemisresponsiblefortransforminginputvoltageandcurrentintovoltageandcurrentwhichthescreenneeds.LEDdotmatrixdisplayextracteddisplaycharacterfontthroughPC,andsenttothemicrocontroller,thendisplayedinthedotmatrixscreen,whichmainlyusedfordisplayofindoorandoutdoorcharacters.LEDdotmatrixdisplaycanbedividedintographicdisplay,imagedisplayandvideodisplaybydisplayedcontent.Comparedwiththeimagedisplay,thecharacteristicsofgraphicdisplayisnodifferenceingraycolorwhetheritismonochromeorcolordisplay.Therefore,graphicdisplayalsofailstoreflecttherichnessofcolor,andvideodisplaycannotonlyshowexercise,clearandfull-colorimages,butalsoshowtelevisionandcomputersignals.Althoughtherearesomedifferencesbetweenthethree,butthemostbasicprinciplesaresimilar[6].SCMhasexcellentcostperformance,smallsize,highreliability,strongcontrol,andwidelyusedinsmartinstruments,mechanicalandelectricalintegration,realtimeprocesscontrol,robotics,domesticappliances,fuzzycontrol,communicationssystemsandsoon.ThisarticledescribedthedesignbytheLEDdisplayrelevantprinciple,andthedesignofhardwareandsoftwarestructurearedescribedindetail,finally,wesimulatefortheoveralldesignandanalyzetheresults.

II.SystemOverallStructureDesign

SingleChipMicrocomputer（SCM）modelswereselectedaccordingtothetarget,function,reliability,cost,accuracyandspeedofthecontrolsystem.Accordingtotheactualsituationofthesubject,thechoiceofSCMmodelsmainlyconsideredfromthefollowingtwoaspects:

First,SCMhasstronganti-interferenceability;Second,SCMhasahighercost-effective.DuetoMCS-51iswidelyusedinChina,hasmoreinformationandcancompatiblewiththemoreperipheralchipstoo,inparticular,ATMELCorporation,introducedanewgenerationmicrocontrollerin2003,thatis89Sseries,anditstypicalproductswithhighperformanceandlowcostmicrocontrollerisAT89C52.AT89C52isalowvoltage,high-performanceCMOS8-bitmicrocontroller,thechipincludes8KBread-onlyprogrammemory（PEROM）whicherasecanberepeated,256byterandomaccessdatamemory（RAM）,devicesadopthigh-densitynonvolatilememorytechnologytoproduce,compatiblewiththestandardMCS-51instructionsetandthe8052products,whilethechipbuilt-ingeneral-purpose8-bitcentralprocessing（CPU）,Flashstorageunit,canbeappliedtothemorecomplexcontrolapplications[10].ThesystemwasrealizedbythecircuitrywhichismadeupofAT89C52chip,Clockcircuit,resetcircuit,columnscandrivercircuit,linedrivecircuitandthesix32×32LEDdotmatrix,theoverallstructureofLEDcharactersdisplayisshowninFig.1.Adisplayunitiscomposedofdotmatrixandtwo74HC154.Linedatasignalisdividedintotwoparts,whichisgivenbythetwo8255Arespectively,butthe8255AdataarefromtheP0portthemastercontrollerAT89C52.Thecolumnscanningsignalofeachcharacterwasgivenbythetwo74HC154,the74HC15412piecesandwasdividedintosixgroups.Theinputsignalof74HC154wasgivenbytheP1.0~P1.3ofAT89C52.Externaldatamemory6264connectedwiththeAT89C52theP0port.

Figure1TheoverallstructureofLEDcharactersdisplay

III.SYSTEMHARDWARECIRCUITDESIGN

A.CircuitDesignofMCUControlSystem

ThesizeofChinesecharactersis32×32,butmicrocontrollerhas32I/Oport,andcan’tmeetdesignrequirements,sotheI/Oportmustexpand,thedataportexpansionwasimplementedbytwo8255A.ThedataportexpansionisshowninFig.2,74HC373istheaddresslatch,andlatchloweightaddress,theloweightaddresssignalsof6264providedbyit,butthehigheightaddresssignalsof6264providedbyP2.0~P2.4,Internalportof8255AwaschosenbyA0andA1.74HC139is2-4decoder,whoseinputsignalsareprovidedbyP2.6andP2.7ofSCM,andprovidedstrobefortheexternalI/Odevices,becausethesystemhasmorethanoneexternaldevice,makesurethattheycannotbegated,sothattheiraddressesistheonlyanddonotrepeat.TheclockcircuitofAT89C52composedof18,19feetfromtheclockside（XTALIandXTAL2）,and12MHzcrystalX,capacitorC1andC2,anduseson-chiposcillatormode.Resetcircuitusesasimplepower-onresetcircuit,andmainlyconstituteofresistorR1,capacitorC3,connectedtotheAT89C52'sresetinputpin.

Figure.2.SCMcontrolsystemcircuit

BTheCircuitDesignofDisplayMemoryUnit

ThesizeofChinesecharactersis32×32inthedesign,eachcharactercomposedoffourpartswhichare（a）,（b）,（c）,and（d）,andeachpartcomposedoffourLEDmatrixwhichthesizeis8×8,circuitdecompositionmapofdisplayunitisshowninFig.3.

（A）（B）

（C）（D）

Figure.3.Circuitdecompositionmapofdisplayunit

Thelinesignalsof（a）~（b）aregivenbytwo8255A,1PA0~1PA7and1PB0~1PB7arePAandPBportof8255A-1,2PA0~2PA7and2PB0~2PB7arePAandPBportof8255A-2,therightfiguresrepresentcolumnscansignalswhichisgivenby74HC154.16columnstrobesareprovidedby74HC154,（a）~（d）requireseightsignal,respectively,so（a）and（b）sharea74HC154,（c）and（d）shareda74HC154.Displayacharacterneedtwo74HC154whichprovidecolumnscansignals.Whenthecircuitworks,the（a）~（d）isgatedbyscanningsignalinproperorder,onlyonewasgatedatatime,andothercolumnsareextinguished,thedisplayeddataisgivenbytwopiecesof8255Asimultaneously,thehumaneyewillseeastablecharacterbecauseofthehumaneye'spersistenceofvision.Inaddition,becausetheChinesecharacterforeachdisplayneeds128bytesstoragespace,butAT89C52microcontrollerchipisonly256bytesdatamemory,itisfarlessthanthedesignrequirements,sowetheexpandedstoragespaceby8K×8externaldatamemory6264.（a）（b）JOURNALOFCOMPUTERS,VOL.6,NO.4,APRIL2011719©2011ACADEMYPUBLISHER

CTheDesignofRanksDataUnitCircuit

Inte18255Aisauniversalprogrammableparallelinput/outputinterfacechip.Itsfunctioncanbesetthroughthesoftwareprogram,andhasastrongversatility.ItcanbedirectlythroughtheCPUdatabusconnectedtoexternaldevices,easytouseandflexible.Inte18255Ainterfacechiphasthree8-bitparallelinputandoutputports,programmingmethodscanbeusedtosetthreeportsasinputportsoroutputports.Chipsworkhavethebasicinputandoutput,strobeinput/outputandbidirectionalinput/output.WhenthedataweretransmittedbydatabusofCPU,itscanchoosetounconditionallytransfer,querytransmissionorinterrupttransmission.DuringInte18255Achipthree-port,theportCcanbeusedasnotonlythedataport,butalsothecontrolport.WhentheportCistakenasadataport,itcanbeusedasnotonly8-bitdataport,butalsoseparatelyastwo4-bitdataport,andeachbitoftheportCcanbeoperated,cansetaparticularbittoinputoroutput,soprovideconvenientconditionsforbitscontrol.Figure.4.

Figure.4.Linedataunitcircuit

LinedataunitcircuitIndesignofthedisplayunitcircuit,thelinesdataaregivenbytwo8255A,asisshowninFigure4.ThisdesignusesdynamicdisplaymeanstodisplayChinesecharacters,whichcanbecontrolledthebythemeansoflineorcolumnscanning,Thesystemusesthemethodofcolumnscanningtocontrolscreen,SpecificcolumnscanningcircuitisshowninFigure5.Columnscanningcircuitcomposedof12piecesof74HC154.Twopiecesof74HC154provided32strobestodisplayacharacter.Theinputsignalof74HC154isP1.0~P1.3whichisprovidedbyAT89C52tocontrolscreen,but12piecesof74HC154wereusedinthedesign,theyworkaccordingtotheorder,theinputofanotherpieceof74HC154