双语教学双语教学8.doc

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1、Ch8   Serial Port Communicate TechnologylKeywords:串行口（SerialPort）并行口（ParallelPort）通信（Communication）字符帧（Characterframe）波特率（BaudRate）异步通信（AsynchronousCommunication）同步通信（SynchronousCommunication）通用异步收发器（UART，UniversalAsynchronousReceiverTransmitter）通用同步收发器（US

2、RT，UniversalSynchronousReceiver/Transmitter）全双工（FD/FDX，FullDuplex）半双工（Semiduplex）单工（SPX，Simplex）lIntroduction:    Each8031microcomputercontainsahighspeedfullduplex(meansyoucansimultaneouslyusethesameportforbothtransmittingandreceivingpurposes)serialportwhi

3、chissoftwareconfigurablein4basicmodes:8bitUART;9bitUART;InterprocessorCommunicationslinkorasshiftregisterI/Oexpander.          Forthestandardserialcommunicationfacility,8031canbeprogrammedforUARToperationsandcanbeconnectedwithregularpersonalcomputers,telet

4、ypewriters,modematdataratesbetween122baudsand31kilobauds.Gettingthisfacilityismadeverysimpleusingsimpleroutineswithoptiontoselectevenoroddparity.YoucanalsoestablishakindofInterprocessorcommunicationfacilityamongmanymicrocomputersinadistributedenvironmentwi

5、thautomaticrecognitionofaddress/data.                                Apartfromallabove,youcanalsogetsuperfastI/OlinesusinglowcostsimpleTTLorCMOSshiftregisters.     Communicationwithexternaldevicesoverdistancesofmorethanafewfeetisoftendoneinaserialmanner–on

6、ebitatatimeoveroneortwolines(onelineforreceivinginformationandoneforsending).The8051familyofmicrocontrollerstypicallyincludeaUniversalAsynchronousReceiverTransmitter(UART)forthispurpose.ThisisthesametypeofdeviceusedtoimplementtheCOMportsofaPC.Althoughitisp

7、ossibletousesimplesoftwarepollingroutinestoserviceaUART,itwastesCPUtimeandpreventstheCPUfromperformingothertasks,sointerruptsaremorecommonlyused.Inthislab,youwilldesignaprogramtosendandreceiveserialdatausinginterrupts.AUARTdevicedrivercanbedifficulttodebug

8、usingstandardsoftware-simulationtools.Insuchcases,itiscommontodevelopmodelsthatsimulateexternalhardwareandallowyoutoseehowyourhardware-softwaredesignwillinteractwiththishardware.Amodelofanexternalserialdevice