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3.4.3 Horizontal Synchronization
VDIN[9−2]
80.0
80.0
10.0
FF
.C
00.0
00.0
Cb 0
Y 2
Cb 359
Cr 359
Y 719
Y 0
Cr 0
Y 1
Cb 1
One Line
XY
.0
10.0
80.0
10.0
FF
.C
00.0
00.0
XY
.0
80.0
80.0
10.0
FF
.C
00.0
00.0
XY
.0
10.0
855 856 857
0
1
2
718 719 720 721 722 723
720 721 722 723
HCOUNT
SAV
EAV
Blanking Data
EAV
Active Video
Blanking
VCLKIN
Next Line
4
4
268
1440
EXC=0
HRST=0
One Line
133 134 135 136 273 274
854 855 856 857
0
1
856 857
0
1
HCOUNT
Next Line
EXC=0
HRST=1
n
n+1
n−1
VCOUNT
Y 718
BT.656 and Y/C Mode Field and Frame Operation
Horizontal synchronization determines when the horizontal pixel/sample counter is reset. The EXC and
HRST bits in VCxCTL allow you to program the event that triggers the start of a line. The encoding of
these bits is shown in
Table 3-8. Horizontal Synchronization Programming
VCxCTL Bit
HMode
EXC
HRST
Horizontal Counter Reset Point
0
0
0
EAV code (H=1) - beginning of horizontal blanking.
1
0
1
SAV code (H=0) - Start of active video.
2
1
0
VCTL1 input active edge - beginning of horizontal blanking or horizontal sync
period. (VCTL1 must be configured as a horizontal control signal.)
3
1
1
VCTL1 input inactive edge - first active pixel on line or end of horizontal sync.
(VCTL1 must be configured as a horizontal control signal.)
HMode 0 is used for BT.656 or Y/C capture (with embedded control) and corresponds to the idea that
each line begins with the horizontal blanking period. It does not align with most standards that start
counting with the first active pixel; therefore, is only useful if capturing of HANC data before the SAV code
is desired. HMode 1 is the default mode and corresponds to most digital video standards by making the
first active pixel pixel0. It has the effect of associating horizontal blanking periods with the end of the
previous line rather than the beginning of the line, but this is only an issue if you try to capture HANC data.
In either mode, HCOUNT increments on every VCLKIN edge for Y/C operation and on every other
VCLKIN edge for BT.656 operation but only when CAPEN is active. HCOUNT operation for HMode 1 and
HMode 2 is shown in
HMode 2 and HMode 3 are used for BT.656 or Y/C capture without embedded EAV/SAV code and allow
alignment with either the beginning of the horizontal blanking period or the first active pixel, or the
beginning or end of horizontal sync depending on the VCTL1 input. When VCTL1 is configured as a
horizontal control input, no external CAPEN signal is available so the CAPEN signal is considered to
always be active. HCOUNT operation for HMode 3 and HMode 4 is shown in
for VCTL
operating as either HSYNC or AVID.
Figure 3-5. HCOUNT Operation Example (EXC = 0)
SPRUEM1 – May 2007
Video Capture Port
55