毕业论文外文翻译--RS232串口通讯（外文原文+中文翻译）Word文件下载.docx

毕业论文外文翻译--RS232串口通讯（外文原文+中文翻译）Word文件下载.docx

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RXD.ThereareotherlinesonthisportasRTS,CTS,DSR,DTR,andRTS,RI.The‘1’and‘0’arethedatawhichdefinesavoltagelevelof3Vto25Vand-3Vto-25Vrespectively.

TheelectricalcharacteristicsoftheserialportaspertheEIA（ElectronicsIndustryAssociation）RS232CStandardspecifiesamaximumbaudrateof20,000bps,whichisslowcomparedtotoday’sstandardspeed.Forthisreason,wehavechosenthenewRS-232DStandard,whichwasrecentlyreleased.

TheRS-232Dhasexistedintwotypes.i.e.,D-TYPE25pinconnectorandD-TYPE9pinconnector,whicharemaleconnectorsonthebackofthePC.YouneedafemaleconnectoronyourcommunicationfromHosttoGuestcomputer.ThepinoutsofbothD-9&

D-25areshowbelow.

D-Type-9pinno.

D-Type-25pinno.

Pinouts

Function

3

2

RD

ReceiveData（Serialdatainput）

TD

TransmitData（Serialdataoutput）

7

4

RTS

Requesttosend（acknowledgetomodemthatUARTisreadytoexchangedata

8

5

CTS

Cleartosend（i.e.;

modemisreadytoexchangedata）

6

DSR

Datareadystate（UARTestablishesalink）

SG

Signalground

1

DCD

DataCarrierdetect（Thislineisactivewhenmodemdetectsacarrier

20

DTR

DataTerminalReady.

9

22

RI

RingIndicator（BecomesactivewhenmodemdetectsringingsignalfromPSTN

AboutDTE&

DCE:

Devices,whichuseserialcablesfortheircommunication,aresplitintotwocategories.TheseareDCE（DataCommunicationsEquipment）andDTE（DataTerminalEquipment.）DataCommunicationsEquipmentsaredevicessuchasyourmodem,TAadapter,plotteretcwhileDataTerminalEquipmentisyourComputerorTerminal.AtypicalDataTerminalDeviceisacomputerandatypicalDataCommunicationsDeviceisaModem.OftenpeoplewilltalkaboutDTEtoDCEorDCEtoDCEspeeds.DTEtoDCEisthespeedbetweenyourmodemandcomputer,sometimesreferredtoasyourterminalspeed.ThisshouldrunatfasterspeedsthantheDCEtoDCEspeed.DCEtoDCEisthelinkbetweenmodems,sometimescalledthelinespeed.

Mostpeopletodaywillhave28.8Kor33.6Kmodems.Therefore,weshouldexpecttheDCEtoDCEspeedtobeeither28.8Kor33.6K.ConsideringthehighspeedofthemodemweshouldexpecttheDTEtoDCEspeedtobeabout115,200BPS.（MaximumSpeedofthe16550aUART）.Thecommunicationsprogram,whichweuse,hassettingsforDCEtoDTEspeeds.However,thespeedis9.6KBPS,144KBPSetcandthemodemspeed.

Ifweweretransferringthattextfileat28.8K（DCE-DCE）,thenwhenthemodemcompressesityouareactuallytransferring115.2KBPSbetweencomputersandthushaveaDCE-DTEspeedof115.2KBPS.Thus,thisiswhytheDCE-DTEshouldbemuchhigherthanthemodem'

sconnectionspeed.Therefore,ifourDTEtoDCEspeedisseveraltimesfasterthanourDCEtoDCEspeedthePCcansenddatatoyourmodemat115,200BPS.

WhatisNULLMODEM?

NullmodemisusedtoconnecttwoDTE'

stogether.ThisisusedtotransferfilesbetweenthecomputersusingprotocolslikeZmodemprotocol,xmodemprotocol,etc

Figure:

AboveshowstheconnectionsoftheNullmodemusingRS-232Dconnecter

Above-mentionedfigureshowsthewiringofthenullmodem.Themainfeatureindicatedhereisthatthetomakethecomputertochatwiththemodemratherthananothercomputer.Theguest&

hostcomputerconnectedthroughtheTD,RD,andSGpins.AnydatathatistransmittedthroughTDlinefromtheHosttoGuestisreceivedonRDline.TheGuestcomputermusthavethesamesetupastheHost.Thesignal

ground（SG）lineofthebothmustbeshortedsothatgroundsarecommontoeachcomputer.

TheDataTerminalReady（DTR）isloopedbacktoDataSetReadyandCarrierDetectonbothcomputers.WhentheDataTerminalReadyisassertedactive,thentheDataSetReadyandCarrierDetectimmediatelybecomeactive.Atthispoint,thecomputerthinkstheVirtualModemtowhichitisconnectedisreadyandhasdetectedthecarrieroftheothermodem.

AlllefttoworryaboutnowistheRequesttoSendandClearToSend.Asboth

computerscommunicatetogetheratthesamespeed,flowcontrolisnotneededthusthesetwolinesarealsolinkedtogetheroneachcomputer.Whe