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4.7VideoDisplayFieldandFrameOperation
4.7.1DisplayDeterminationandNotification
VideoDisplayFieldandFrameOperation
Asavideosource,thevideoportalwaysoutputsentireframesofdataandtransmitscontinuousvideo
controlsignals.DependingontheEDMAstructure,however,thevideoportmayneedtointerrupttheDSP
onafieldorframebasistoallowittoupdatevideoportregistersorEDMAparameters.Toachievethis,
thevideoportprovidesprogrammablecontroloverthedisplayprocess.
Inordertoaccommodatevariousdisplayscenarios,EDMAstructures,andprocessingflows,thevideo
portemploysaflexibledisplayandDSPnotificationsystem.ThisisprogrammedusingtheCON,FRAME,
DF1,andDF2bitsinVDCTL.
TheCONbitcontrolsthedisplayofmultiplefieldsorframes.WhenCON=1,continuousdisplayis
enabled,thevideoportdisplaysoutgoingfields(assumingtheVDENbitisset)withouttheneedforDSP
interaction.ItreliesonasingledisplaybufferinmemoryoronaEDMAstructurewithcircularbuffering
capabilitytoservicethedisplayFIFOs.WhenCON=0,continuousdisplayisdisabled,thevideoportsets
afieldorframedisplaycompletebit(F1D,F2D,orFRMD)inVDSTATuponthedisplayofeachfieldas
determinedbythestateoftheotherdisplaycontrolbits(FRAME,CD1,andCD2).Oncethedisplay
completebitisset,theprocessormustupdatetheappropriateEDMAparameterswithintheallottedtime
frameorasubsequentfieldorframemayoutputinvaliddata.Inthiscase,thevideoportcontinuesto
generateEDMArequestsbutitissuesaDCNA(displaycompletenotacknowledged)interrupttoindicate
thattheEDMAparametersmaynothavebeenupdatedandbaddataisbeingsenttothevideoport.
Whenafieldorframehasnotbeenenabledfordisplay,noEDMAeventsaresentforthatfieldorframe.
Thevideoportstillgeneratesalltimingsforthefieldbutoutputsthedefaultdatavaluesratherthandata
fromthedisplayFIFOduringthedisplayimagewindow.
TheCON,FRAME,DF1,andDF2bitsencodethedisplayoperationsaslistedinTable4-4.
Table4-4.DisplayOperation
VDCTLBit
CONFRAMEDF2DF1Operation
0000Reserved
0001Noncontinuousfield1display.Displayonlyfield1.F1Dissetafterfield1
displayandcausesDCMPxtobeset.TheF1DbitmustbeclearedbytheDSP
oraDCNAinterruptoccurs.(TheDSPhastheentirefield2timetoclearF1D
beforenextfield1begins.)Canalsobeusedforsingleprogressiveframe
display(internaltimingcodesonly).(TheDSPhasverticalblankingtimeto
clearF1Dbeforenextframebegins.)
0010Noncontinuousfield2display.Displayonlyfield2.F2Dissetafterfield2
displayandcausesDCMPxtobeset.TheF2DbitmustbeclearedbytheDSP
oraDCNAinterruptoccurs.(TheDSPhastheentirefield1timetoclearF2D
beforenextfield2begins.)
0011Noncontinuousfield1andfield2display.Displaybothfields.F1Dissetafter
field1displayandcausesDCMPxtobeset.TheF1Dbitmustbeclearedby
theDSPbeforethenextfield1displayoraDCNAinterruptoccurs.(TheDSP
hastheentirefield2timetoclearF1Dbeforenextfield1begins.)F2Disset
afterfield2displayandalsocausesDCMPxtobeset.TheF2Dbitmustbe
clearedbytheDSPbeforethenextfield2displayoraDCNAinterruptoccurs.
(TheDSPhastheentirefield1timetoclearF2Dbeforenextfield2begins.)
0100Noncontinuousframedisplay.Displaybothfields.FRMDissetafterfield2
displayandcausesDCMPxtobeset.ADCNAinterruptoccursupon
completionofthenextframeunlesstheFRMDbitiscleared.(TheDSPhas
theentirenextframetimetoclearFRMD.)
0101Noncontinuousprogressiveframedisplay.Displayfield1.FRMDissetafter
field1displayandcausesDCMPxtobeset.ADCNAinterruptoccursupon
completionofthenextframeunlesstheFRMDbitiscleared.(TheDSPhas
theentirenextframetimetoclearFRMD.)Ifexternalcontrolsignalsareused,
theymustfollowprogressiveformat.
0110Reserved
108VideoDisplayPortSPRUEM1–May2007
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