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3.3.4Y/CFIFOPacking
Cr 9
Cr 1
Cb 9
Cb 1
Y 9
Y 1
Y 25
Y 17
Cb 5
Y 10
Little-Endian Packing
Cr 14
Cr 6
Y 0
Cb 0
Cb 14
Cb 6
Y 14
Y 6
Y 30
Y 22Y 23
Cr 15
Cr 7
Cb 15
Cb 7
Y 15
Y 7
Cr FIFO
Cb FIFO
63
Y FIFO
63
5556
5556
Y 31
63
VDIN[19−12]
5556
VCLKINA
VDIN[9−2]
Cr 11
Cr 3
Cb 11
Cb 3
Y 11
Y 3
Y 27
Y 19
Cr 2
Y 5
Y 20Y 21
Cr 13
Cr 5
40
40
Cb 13
Cb 5
Y 13
Y 5
4748
48 47
Cb 12
Cr 12
Cr 4
Cb 4
39 3231
Y 12
Y 4
39 3231
Cb 1
Y 29
40
Y 2
Cr 0
48 47
Y 1
Cb 2
Y 28
39
Cr 1
32 31
Y 4Y 3
Y 18
Cr 10
Cr 2
Cb 10
Cb 2
Y 10
Y 2
2324
2324
1516
1516
Y 26
Cr 3
Y 7
Cb 3
2324
Y 6
1516
Cb 4
Y 9Y 8
Y 16
Cr 8
Cr 0
0
Cb 8
Cb 0
0
Y 8
Y 0
78
8 7
Y 24
0
Cr 5
8 7
Y 11
Cb 4
3.4BT.656andY/CModeFieldandFrameOperation
BT.656andY/CModeFieldandFrameOperation
FortheY/Cvideocapturemode,theFIFObufferisdividedintothreesections(threebuffers).Onesection
is2560bytesdeepandisdedicatedforstorageofYdatasamples.Theothertwosectionsarededicated
forstorageofCbandCrdatasamples,respectively.ThebuffersforCbandCrsamplesareeach1280
bytesdeep.TheincomingvideodatastreamisseparatedintoY,Cb,andCrdatastreams,scaled(if
selected)andtheY,Cb,andCrbuffersarefilled.Eachofthethreebuffershasamemory-mapped
locationassociatedwithit;YSRC,CBSRC,andCRSRC.TheYSRC,CBSRC,andCRSRClocationsare
readonlyandareusedbyEDMAstoaccessvideodatasamplesstoredintheFIFOs.Readsmustalways
be64bits.
Ifvideocaptureisenabled,pixelsinthecapturewindowarecapturedintheY,Cb,andCrbuffers.The
videocapturemoduleusestheYEVT,CbEVT,andCrEVTeventstonotifytheEDMAcontrollertocopy
datafromthecapturebufferstotheDSPmemory.Thenumberofpixelsrequiredtogeneratetheeventsis
setbytheVCTHRLDnbitsinVCxCTL(theVCTHRLDnvaluemustbeanevennumberforY/Cmode).
ThecapturemodulegeneratestheeventsafterVCTHRLDnewpixelshavebeenreceived.Onevery
YEVT,theEDMAshouldmovedatafromtheYbuffertoDSPmemoryusingtheYSRCregisterasthe
sourceaddress.OneveryCbEVT,theEDMAshouldmovedatafromtheCbbuffertoDSPmemoryusing
theCBSRCregisterasthesourceaddress.OneveryCrEVT,theEDMAshouldmovedatafromtheCr
buffertoDSPmemoryusingtheCRSRCregisterasthesourceaddress.Notethattransfersizefromthe
CbandCrbuffersishalfofthetransfersizefromtheYbuffersinceforeveryfourYsamples,thereare
twoCbandtwoCrsamples.
ThethreeEDMAeventsaregeneratedsimultaneouslywhenVCTHRLDisreached.Eacheventis
reenabledwhenthefirstreadoftherespectiveFIFObytherequestedEDMAbegins.
Captureddataisalwayspackedinto64bitsbeforebeingwrittenintothecaptureFIFO(s).Bydefault,data
ispackedintotheFIFOfromrighttoleft.
The8-bitY/CmodeusesthreeFIFOsforcolorseparation.Samplesarepackedintoeachwordasshown
inFigure3-3.
Figure3-3.8-BitY/CFIFOPacking
BecauseEDMAsareusedtotransferdatafromthecaptureFIFOstomemory,thereisalargeamountof
flexibilityinthewaythatcapturefieldsandframesaretransferredandstoredinmemory.Insomecases,
forexampleaEDMAstructurecanbecreatedtoprovideasetofping-pongorround-robinmemorybuffers
SPRUEM1–May2007VideoCapturePort51
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