中英文翻译The Designing of Serial Communication Based on RS232.docx
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中英文翻译The Designing of Serial Communication Based on RS232.docx
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中英文翻译TheDesigningofSerialCommunicationBasedonRS232
TheDesigningofSerialCommunicationBasedonRS232
Abstract—ThisPaperdiscussedtheprincipleofserialcommunicationmainly,proposedthedesignmethodbasedonRS232,designedthehardcircuitofserialcommunication,andrealizedtheprogrammingtoPCMicrocomputerandsinglechipmicrocomputerbyusingassemblylanguageandC++Builderseparately.
Keywords-serialcommunication;singlechipmicrocomputer;programdesign
I.INTRODUCTION
Duringworkinginthecontrolsystem,thePCmicrocomputersendsinstructionsforstep-by-stepmotortocollecttheimageinformation.ThereforethecommunicationbetweenthePCmicrocomputerandthedrivingsystemisneededforthecommunicationsystem.Ingeneral,acompletecommunicationsystemconsistsoftransmitter,receiver,convertingthedatainterfaceandtransmittingdatachannel.Thecontrolofthestep-by-stepmotorisrealizedthroughthepulsedistributionbysinglechipmicrocomputer.Onthemotorcontrolsystem,thePCmicrocomputeriscalledasuppercomputer,andthesinglechipmicrocomputerfordrivingstep-by-stepmotoriscalledaslowercomputer.Thecommunicationbetweentheuppercomputerandthelowercomputerhastwomethods,thatistosaytheparallelcommunicationandserial
communication.Parallelinterfacecantransmitmuchdataatthesametimeandhasthefastspeed,butwhenthetransmissiondistanceisfarandthenumberofdataismuch,itneedsmorethenumberoftransmissionlines.Inaddition,thevoltagelevelmaybechangedbythetransmissionlinefactorandelectromagneticinterference.Serialcommunicationisaonewaythatthedataistransmittedbyabitinorder,inwhichtwotransitionlinesisneededtorealizebidirectionalcommunication.Itistakenintoconsiderationthatthedataismuchandthetransmutationnumberislittle,theserialcommunicationisutilizedinthecontrolsystemsoastosimplifythehardwareandsavethecost.
II.THEBRIEFDESCRIPTIONOFSERIALPORTCOMMUNITION
Serialcommunicationisthecommunicationbetweensenderandreceiverdatatransferisinthesingledataline,tomoveeachtimeabit.Theadvantageisthatonlyapairoftransmissionlinestosendinformation,soitslowcost,suitableforlong-distancecommunications;itsdisadvantageisthattransmissionspeedislow.
Serialcommunicationwithasynchronouscommunicationandsynchronouscommunicationaretwobasicmeansofcommunication.Synchronouscommunicationforthecaseofhightransmissionspeed,thehardwarecomplexity.Theasynchronouscommunicationusedintransmissionspeedbetween50and19200baud.Transmissionisrelativelycommon.Inasynchronouscommunication,dataistransmittedframebyframe,eachframeofserialdataformatbyastartbit,5to8databits,aparitybit(optional)andaStopbitoffourparts.Beforetheserialcommunication,thesenderandreceivertoagreethespecificdataformatandbaudrate(communicationprotocol).PC-programmableserialasynchronouscommunicationcontroller8250toimplementasynchronousserialcommunication.By8250theinitialprogramming,youcancontrolserialdatatransmissionformatandspeed.InthePC,ingeneraltherearetwostandardRS-232CserialinterfaceCOM1andCOM21MCS-51seriesmicrocontrollerchipincludesafull-duplexserialinterface,canalsoberealizedbyprogrammingtheserialcommunications.
CMOSsmartsensorIChasreceivedwideapplicationforlowcost,miniaturization,intelligenceandstandardization.InsmartsensorICdesigns,thecommunicationinterfacecircuitsalsoplayanimportantroleotherthansensorsandsignalprocessingcircuits.Therearemoreserialcommunicationstandardinterfaces,suchasRS-232,RS-485,USBInterface,IEEE-1394,whichhasitselfgoodfeaturesandalsohasfocusedonareasofapplication.RS-485hasaanti-noisecapacitytransmittingdata,soitiscommonlyusedinindustrialproduction.USBinterfaceandIEEE-1394havefastspeed,butsomecomputersandoperatingsystemsdonotsupportsuchinterfaces.RS-232ismostwidelyusedasaserialinterfaceinaPCcomputerandcommunicationsindustries.RS232CstandardisaprotocolofasynchronousserialcommunicationandhasbeenwidelyusedinPCandcommunicationindustries.ManyshortdistancecommunicationalperipheralsofPCsuchasprinters,disksandterminalsallcommunicatewithPCviaRS232serialinterface.
RS-232Cstandard
RS-232CistheAmericanElectronicsIndustryAssociation(EIA)formallyannounced,intheasynchronousserialcommunication,themostwidelyusedstandardbus.ThestandardforDCEandDTEserialbinarycommunicationbetweenthemaximumdatatransferrateofupto19.2kbps,thelongesttransmissioncablesupto15meters1RS-232Cstandarddefinesthe25-lead,two-waycommunicationingeneral,justSerialinputRXD,serialoutputTXDandgroundGND1RS-232Cstandardlevelsusingnegativelogic,theprovisionsof+3V~+15Vatanylevelbetweenalogic"0"level,-3V~-15VofAnylevelbetweenalogic"1"level,withTTLandCMOSlevelsaredifferent.IntheinterfacecircuitandcomputerinterfacechipinthemostlylevelTTLorCMOS,sothecommunication,theneedforlevelconversion,sowiththeRS-232Cstandardlevelmatching1MAX232chiplevelconversioncanbedoneinthiswork.
RS-232isdefinedasthesingle-endedstandards,whichhasmuchcharacteristic,suchasmorecommunicationdistanceinalow-speedserialcommunications,moderatepriceandgoodpracticalityofthesystem,soitismostappropriatetobeacommunicationport.RS-232isanessentialmoderncomputerinterface,itincludesportsCOM1andCOM2,theportCOM1has9-pinconnector.Thenewgenerationcomputerhasa9-pinconnector(DB9)soastoconnectwiththeRS-232communicationport.Inordertoachievereliableandrealtimetransmission,thesystemadoptathree-wireconnectionmethod,thatistosaythattheGNDpin,RXDpinandTXDpinofRS-232portisconnectedwiththeexternalport,itisshowninFigure1.
Figure1.TheRS-232port
III.THEHARDWAREDESIGNOFSERIALPORTCOMMUNICATION
Thein-outlevelofsinglechipcomputerisTTLlevel,whiletheRS-232serialinterfaceofaPCcomputerisstandardserialinterface,soboththeelectricalspecificationsareinconsistent.inordertocommunicatewiththeupperandlowercomputer,itisneededthattheoutlevelofsinglechipcomputerischangedtotheTTLlevel.ThecommonlevelconverterchipbetweenTTLandRS-232levelisMCI1488andMCI1489.TheMCI1488convertsTTLleveltoRS-232level,itneedsthesupplyvoltageof±12V,andthattheMCI1489convertstheRS-232standardlevelTTLlevel,itneedspowersupplyvoltageof+5V.Duetothreepowersupplyvoltage,thecircuitwillbecomplicated,sothiscircuitadoptsthestandardRS-232chipMAX232.
MAX232istheproductoftheMAXIMcompany,itistheroadreceiveranddriverICchip.
AboutMAX232chip
MAXIMMAX232chipisproducedbylow-power,single-supplydualRS232transmit/receiver1forallEIA-232EandV.28/V.24communicationinterfaces1MAX232achipsupplyvoltageconverter,can+5VinputpowerconvertedintoRS-232C±10Voutputvoltagelevelrequired,sousingthischipserialcommunicationsinterfacesystemaslongasasingle+5Vpowersupplycan.
MAX232requiresfourexternalelectrolyticcapacitorsC1,C2,C3,C4,istheinternalcapacitanceofapowerconversionrequirementsare1μF/25V1shouldchooseitsvalueandshouldbeascloseaspossibletantalumchipcapacitor1C5is0.1μFdecouplingcapacitor.
MAX232pinT1IN,T2IN,R1OUT,R2OUTtopickTTL/CMOSlevelpin1pinT1OUT,T2OUT,R1IN,R2INtoaccessRS-232Clevel1sothepinTTL/CMOSlevelT1IN,T2INMCS-51pinshouldbeconnectedtotheserialtransmitpinTXD;R1OUT,R2OUTshouldtakeMCS-51intheserialreceivepinsRXD1correspondingRS-232ClevelT1OUT,T2OUTshouldbeconnectedtoPC-receiverRD;R1IN,R2INshouldbeconnectedPC-senderTD.
MAX232chiphasavoltageconverterwhichcantransformthevoltageof+5Vtotherequiredvoltage.Therefore,itadaptstotheserialcommunicationinterface,moreoverithasmuchcharacteristic,suchasmoderateprice,thehardwaresimple,soitisusedtobeavoltageconverter.ThehardwarecircuitofserialcommunicationmoduleisshowninFigure2.
Figure2.Thehardwarecircuitofserialcommunicationmodule
IV.THESOFTWAREDESIGNOFSERIALPORTCOMMUNICATION
ThecommunicationprogramofthesinglechipmicrocomputercommunicateswithPCcomputerbyinterruptandPCcomputeriscalledasmaincontroller.WhenthesinglechipcomputerreceivesthedatasignalssentbyPCcomputer,thenitcallsinterruptserviceprogram.TheflowchartoftheinterruptservicemainsubprogramisshowninFigure3.InordertofullyexploittheefficiencyofsinglechipcomputertominimizeCPU‘timeoccupiedbycommunication,thecontrolprogramwillbewewillpromptlyrespondtoandcontrolobjects.Thecommunicationprogramwillbeoptimized.Thesubprogramofserialportinterruptforreceivingdata,thesubprogramforsendingstep-by-stepimpulse,thesubprogramforjudginginstructionandthesubprogramfoesendingdata.
A.Thesubprogramofserialportinterruptsforreceivingdata
ThesubprogramofserialportinterruptsforreceivingdataismainlyresponsibleforreceivingdatasentbyPCmicrocomputerandstoringthedataintoallocatedmemory(itdoesnotdealwithdatasoastoreducethetimetakenupbyinterruptions).Thedatareceivedbythesinglechipmicrocomputerincludeslittleinformation,suchasspeed,stepsandon/offinstructions,andthebufferislargeenoughtosendthecomputer,sothesoftwareshakehandsprotocolisomitsoastoraisestheCPUut
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