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3.4.1CaptureDeterminationandNotification
BT.656andY/CModeFieldandFrameOperation
towhichacontinuousstreamoffieldsarestoredwithoutDSPintervention.Inothercases,theDSPmay
needtomodifyEDMApointeraddressesaftereachfieldorframeiscaptured.Insomeapplications,only
onefieldmaybecapturedandtheotherignoredcompletely,oraframemayneedtobeignoredinorder
tohavetimetoprocessapreviousframe.Thevideoportaddressestheseissuesbyproviding
programmablecontroloverdifferentaspectsofthecaptureprocess.
Thevideoporttreatsthecaptureofeveryfieldasaseparateoperation.Inordertoaccommodatevarious
capturescenarios,EDMAstructures,andprocessingflows,thevideoportemploysaflexiblecaptureand
DSPnotificationmethod.ThisisprogrammedusingtheCON,FRAME,CF1,andCF2bitsinVCxCTL.
TheCONbitcontrolsthecaptureofmultiplefieldsorframes.WhenCON=1,continuouscaptureis
enabled,thevideoportcapturesincomingfields(assumingtheVCENbitisset)withouttheneedforDSP
interaction.ItreliesonaEDMAstructurewithcircularbufferingcapabilitytoservicethecaptureFIFOs.
WhenCON=0,continuouscaptureisdisabled,thevideoportsetsafieldorframecapturecompletebit
(F1C,F2C,orFRMC)inVCxSTATuponthecaptureofeachfieldasdeterminedbythestateoftheother
capturecontrolbits(FRAME,CF1,andCF2).Oncethecapturecompletebitisset,atmost,onemorefield
orframecanbereceivedbeforecaptureoperationishalted.Thispreventssubsequentdatafrom
overwritingpreviousfieldsuntiltheDSPhasachancetoupdateEDMApointersorprocessthosefields.
Whenacapturehaltoccurs,thevideoportstopscapturingdata(forthehaltedfield).Itthenchecksthe
appropriatecapturecompletebitatthestartofeachsubsequentfieldandresumescaptureifthebithas
beencleared.
TheCON,FRAME,CF1,andCF2bitsencodethecaptureoperationsaslistedinTable3-6.
Table3-6.BT.656andY/CModeCaptureOperation
VCxCTLBit
CONFRAMECF2CF1Operation
0000Reserved
0001Noncontinuousfield1capture.Captureonlyfield1.F1Cissetafterfield1
captureandcausesCCMPxtobeset.TheF1Cbitmustbeclearedbythe
DSPbeforecapturecancontinue.(TheDSPhastheentirefield2timeto
clearF1Cbeforenextfield1begins.)Canalsobeusedforsingleprogressive
framecapture.(TheDSPhasverticalblankingtimetoclearF1Cbeforenext
framebegins.)
0010Noncontinuousfield2capture.Captureonlyfield2.F2Cissetafterfield2
captureandcausesCCMPxtobeset.TheF2Cbitmustbeclearedbythe
DSPbeforecapturecancontinue.(TheDSPhastheentirefield1timeto
clearF2Cbeforenextfield2begins.)
0011Noncontinuousfield1andfield2capture.Capturebothfields.F1Cissetafter
field1captureandcausesCCMPxtobeset.TheF1Cbitmustbeclearedby
theDSPbeforeanotherfield1capturecanoccur.(TheDSPhastheentire
field2timetoclearF1Cbeforenextfield1begins.)F2Cissetafterfield2
captureandcausesCCMPxtobeset.TheF2Cbitmustbeclearedbythe
DSPbeforeanotherfield2capturecanoccur.(TheDSPhastheentirefield1
timetoclearF2Cbeforenextfield2begins.)
0100Noncontinuousframecapture.Capturebothfields.FRMCissetafterfield2
captureandcausesCCMPxtobeset.Capturehaltsuponcompletionofthe
nextframeunlesstheFRMCbitiscleared.(TheDSPhastheentirenext
frametimetoclearFRMC.)
0101Noncontinuousprogressiveframecapture.Capturefield1.FRMCissetafter
field1captureandcausesCCMPxtobeset.Capturehaltsuponcompletion
ofthenextframeunlesstheFRMCbitiscleared.(TheDSPhastheentire
nextframetimetoclearFRMC.)
0110Reserved
0111Singleframecapture.Capturebothfields.FRMCissetafterfield2capture
andcausesCCMPxtobeset.CapturehaltsuntiltheFRMCbitiscleared.
(TheDSPhasthefield2tofield1verticalblankingtimetoclearFRMC.)
1000Reserved
52VideoCapturePortSPRUEM1–May2007
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