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1、EDIDWhitepaperMay14,2008,Alameda,CA-SurprisinglyfewpeopleareawareofEDIDanditsimportantroleinthedistributionofDVIvideosignals.Whenthestandardforconnectingbetweenavideocard(alsoreferredtoasagraphicsacceleratorcard,graphicsadapter,graphicssource,graphicscardordisplayadap
2、ter)andamonitorwasanalog,videocardscontrolledtheprocess.Theusersetthegraphicsadaptertoaparticularscanrateandresolutionforthereceivingmonitor(display).Hopefully,theymatched...EarlyMonitorswereCRT(CathodeRayTubes)andusuallypossessedtheabilitytoadjusttoavarietyofscanrate
3、s(multi-sync)buthadnowayofcommunicatingthisinformationtothegraphicsadapter.DVI(DigitalVisualInterface)changedallthat.Notonlyisthistransmissionprotocoldigital,butthereisalsoadedicateddatacommunicationschannelforthedisplaydevicetoinformthegraphicsadapterwhatitscapabilit
4、iesare.Moderndigitaldisplaydevicesnowprovidethegraphicsadapteralistofwhatscanratesandresolutionstheycandisplay.WhenaDVIconnectionismadebetweenagraphicsadapterandamonitordevice,thereismoregoingonthanmeetstheeye.Thereare3serialdifferentialpairsthatcarryT.M.D.S.(Transiti
5、onMinimizedDifferentialSignaling)dataforRed,GreenandBluesignals,plusa4thpairforasynchronizingclocksignal.Thereisalsoadatatransfertakingplaceovertheconnection:ExtendedDisplayIdentificationDataorEDIDforshort,istransportedoveradedicatedDisplayDataChannel(currentversionde
6、signatedDDC2)alsoinaserialdifferentialformat.TheEDIDisacomprehensivecollectionofperformanceinformationaboutthemonitordevice.EDIDisdefinedinastandardpublishedbyVESA(VideoElectronicsStandardsAssociation).TheEDIDincludesthemanufacturer'sname,producttype,phosphororfiltert
7、ype,timingssupportedbythemonitor,monitorsize,luminancedataand(fordigitalmonitorsonly)pixelmappingdata.ThedataformatthatcarriesthesesignalsisreferredtoastheI2Cbuss.Whereasthepictureinformationtravelsfromthegraphicscardtothemonitor,theEDIDtravelstothegraphicsadapterfrom
8、themonitor.WhenaDVIconnectionisfirstmade,thegraphicsadapterqueriesthemonitorforinformation.Inresponsethemonitorsendsadatastr
