Texas Instruments TMS320C64x DSP Benutzerhandbuch

3-6

0111

100

–

–

011

100

100

100

–

1000

000

–

–

–

–

101

110

–

1001

–

001

010

–

–

–

–

111

1010

–

101

010

–

101

101

–

101

1011

010

–

010

010

–

101

010

–

1100

–

001

110

–

110

–

110

110

1101

001

001

–

001

–

001

110

–

1110

–

–

–

011

–

101

110

–

1111

–

001

010

–

100

–

–

–

The BT.656 format is an interlaced format consisting of two fields. The video
port allows capture of one or both fields. The captured image is a subset of
each field and can be larger or smaller than the active video region. The cap-
tured image position is defined by the VCxSTRT1 and VCxSTOP1 registers
for field 1, and the VCxSTRT2 and VCxSTOP2 registers for field 2. The
VCXSTART and VCXSTOP bits set the horizontal window position for the field
relative to the HCOUNT pixel counter. The VCYSTART and VCYSTOP bits set
the vertical position relative to the VCOUNT line counter. This is shown in
Figure 3–1.

HCOUNT increments on every chroma sample period (every other VCLKIN
rising edge) for which capture is enabled. Once VCOUNT = VCYSTART, line capture
begins when HCOUNT = VCXSTART. It continues until HCOUNT = VCXSTOP. A
field’s capture is complete when HCOUNT 

= 

VCXSTOP and

VCOUNT = VCYSTOP.