Texas Instruments TMS320C64x DSP - Manual (Page 82)

BT.656 and Y/C Mode Field and Frame Operation
Video Capture Port 3-20 SPRU629
Table 3–7. Vertical Synchronization Programming
VCxCTL Bit
VMode EXC VRST Vertical Counter Reset Point
0 0 0 First EAV with V=1 after EAV with V=0 – beginning of vertical blanking period.
VCOUNT increments on each EAV.
1 0 1 First EAV with V=0 after EAV with V=1 – first active line. VCOUNT
increments on each EAV.
2 1 0 On HCOUNT reset after VCTL2 input active edge – beginning of vertical
blanking or vertical sync period. (VCTL2 must be configured as vertical
control signal). VCOUNT increments when HCOUNT is reset.
3 1 1 On HCOUNT reset after VCTL2 input inactive edge – end of vertical sync or
first active scan line. (VCTL2 must be configured as vertical control signal).
VCOUNT increments when HCOUNT is reset.
VMode 0 is used for BT.656 or Y/C capture (with embedded control) and corre-
sponds to most digital video standards that number lines beginning with the
start of vertical blanking. VMode 1 can also be used for BT.656 or Y/C capture
but counts from the first active video line. This makes field detection more
straightforward in some instances (see section 3.4.4) and allows the
VCYSTARTn bit to be set to 1, but also has the effect of associating vertical
blanking periods with the end of the previous field rather than the beginning
of the current field. (This could be an issue when capturing VBI data.)
VCOUNT operation for VMode 0 and VMode 1 is shown in Figure 3–8.
VMode 2 and VMode 3 are used for BT.656 or Y/C capture without embedded
EAV/SAV codes and allow alignment with either the active or inactive edge of
the vertical control signal on VCTL2. This can be a VBLNK or VSYNC signal
from the video decoder.