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DisplayTimingExamples
TheinterlacedBT.656verticaloutputtimingisshowninFigure4-26.TheBT.656activefield1is244-lines
highandactivefield2is243-lineshigh.Thisexampleshowsthe480-lineimagewindowcenteredinthe
screen.ThisresultsinanIMGVOFFnof3linesandalsoresultsinanon-datalineattheendoffield1due
toitsextraactiveline.
TheVBLNKandVSYNCsignalsareshownastheywouldbeoutputforactive-lowoperation.Notethat
onlyoneofthetwosignalsisactuallyavailableexternally.TheVBLNKandVSYNCedgesforfield1occur
attheendofanactivelinesotheirXSTART/XSTOPvaluesaresetto720(startofblanking).Forfield2,
VBLNKandVSYNCedgesoccurduringthemiddleoftheactivehorizontallinesotheirXSTART/XSTOP
valuesaresetto360.Notethat,fromananalogstandpoint,verticalblankingbeginsahalf-linebefore
digitalblankingsothatVBLNKYSTART2issetto263(withVBLNKXSTART2setto360)whileVBITSET2
isprogrammedto264.FortrueBT.656operation,neitherVBLNKnorVSYNCwouldbeused.
TheFLDoutputissetuptotransitionatthestartofeachanalogfield(startofverticalblanking).Since
EAV[F]transitionsonlines4and266,thisrequiresprogrammingFBITCLRto4,FBITSETto266,
FLD1YSTARTto1,andFLD2YSTARTto263.NotethatFLD2XSTRTis360sothatthefieldindicator
outputchangeshalfwaythroughtheline.
TheILCOUNToperationfollowsthedescriptioninSection4.1.2.ILCOUNTresetsto1atthefirst
displayedline(FLCOUNT=VBLNKSTOPx+IMGVOFFx)andstopscountingatthelastdisplayedpixel
(IPCOUNT=IMGVSIZEx).Theoperationduringnon-displaytimeisnotarequirement,itcouldcontinue
countinguntilthenextFLCOUNT=VBLNKSTOPx+IMGVOFFxpointoritcouldresetimmediatelyafter
IMGVSIZExorwhenFLCOUNTisreset.
Theactivehorizontaloutputcolumnshowstheoutputdataduringtheactiveportionofthehorizontalline.
ItisassumedthattheDVENbitinVDCTLissettoenablethedefaultoutput.
112VideoDisplayPortSPRUEM1–May2007
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