Cirrus Logic CS4955 - Manual (Page 19)

CS4954 CS4955
DS278F6 19
Field two begins with VSYNC transitioning low at
line 266. VSYNC stays low for 3 line cycles and
transitions high during the end of line 268. Video
input on the V [7:0] pins is expected between line
284 and line 522. Field two is 263 lines; field one
is 262 lines.
5.2.9 PAL Progressive Scan
VSYNC will transition low at the beginning of the
odd field and will remain low for 2.5 lines or 2160
pixel cycles (864 × 2.5). PAL non-interlaced tim-
ing is illustrated in Figure
10 . In this mode, the
CS4954/5 expects digital video input on the V [7:0]
pins for 288 lines, beginning on active video line 23
and continuing through line 309.
The second field begins with VSYNC transitioning
low after 312 lines from the beginning of the first
field. VSYNC stays low for 2.5 line-times and tran-
sitions high during the middle of line 315. Video
input on the V [7:0] pins is expected between line
335 through line 622. Field two is 313 lines; field
one is 312 lines.
5.3 ITU-R.BT656
The CS4954/5 supports an ITU-R.BT656 slave
mode feature that is selectable through the ITU-
R.BT656 bit of the CONTROL_0 Register. The
ITU-R.BT656 slave feature is unique because the
horizontal and vertical timing and digital video are
combined into a single 8-bit 27 MHz input. With
ITU-R.BT656 there are no horizontal and vertical
input or output strobes, only 8-bit 27 MHz active
CbYCrY data, with start- and end-of-video codes
implemented using reserved 00 and FF code se-
quences within the video feed. As with all modes,
V [7:0] are sampled with the rising edge of CLK.
The CS4954/5 expects the digital ITU-R.BT656
stream to be error-free. The FIELD
(1)
output tog-
gles as with non ITU-R.BT656 input. ITU-
R.BT656 input timing is illustrated in Figure
11 .
523 524 525 1 2 3 4 5 6 7 8 9
VSYNC Drops
10 22
Analog
Field 1
261 262 263
Analog
Field 2
285 284 272 271 270 269 268 267 266 265 264
523 524 525 1 2 3 4 5 6 7 8 9
VSYNC Drops
10 22
Analog
Field 3
261 262 263
Analog
Field 4
285 284 272 271 270 269 268 267 266 265 264
Burst begins with positive half-cycle Burst begins with negative half-cycle
Figure 7. NTSC Video Interlaced Timing