3 vertical timing, 4 horizontal timing, 5 ntsc interlaced – Cirrus Logic CS4955 User Manual

Page 17: 6 pal interlaced

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CS4954 CS4955

DS278F6

17

PROG_VS Register (0x0D). VSYNC can be de-
layed by thirteen lines or advanced by eighteen lines.

5.2.3 Vertical Timing

The CS4954/5 can be configured to operate in any
of four different timing modes: PAL, which is 625
vertical lines, 25 frames per second interlaced;
NTSC, which is 525 vertical lines, 30 frames per
second interlaced; and either 625 or 525 line Pseu-
do-Progressive Scan (See

“Progressive Scan” on

page 18

)

.

These modes are selected in the

CONTROL_0 Register (0x00).

The CS4954/5 conforms to standard digital decom-
pression dimensions and does not process digital
input data for the active analog video half lines as
they are typically in the over/underscan region of
TV display. 240 active lines total per field are pro-
cessed for NTSC, and 288 active lines total per
field are processed for PAL. Frame vertical dimen-
sions are 480 lines for NTSC and 576 lines for
PAL. Table

2

specifies active line numbers for both

NTSC and PAL. Refer to Figure

6

for HSYNC,

VSYNC and FIELD signal timing.

5.2.4 Horizontal Timing

HSYNC is used to synchronize the horizontal-in-
put-to-output timing in order to provide proper hor-
izontal alignment. HSYNC defaults to an input pin
following RESET but switches to an output in Mas-
ter Mode (CONTROL_0 [4] = 1). Horizontal tim-
ing is referenced to HSYNC transitioning low. For
active video lines, digital video input is to be ap-
plied to the V [7:0] inputs for 244 (NTSC) or for
264 (PAL) CLK periods following the leading

(falling) edge of HSYNC if the PROG_HS Regis-
ters are set to default values.

5.2.5 NTSC Interlaced

The CS4954/5 supports NTSC-M, NTSC-J and
PAL-M modes where there are 525 total lines per
frame, two fixed 262.5-line fields per frame and 30
frames occurring per second. NTSC interlaced ver-
tical timing is illustrated in Figure

7

. Each field

consists of one line for closed caption, 240 active
lines of video, plus 21.5 lines of blanking.

VSYNC field one transitions low at the beginning
of line four and will remain low for three lines or
2574 pixel cycles (858 × 3). The CS4954/5 exclu-
sively reserves line 21 of field one for closed cap-
tion insertion. Digital video input is expected to be
delivered to the CS4954/5 V [7:0] pins for 240
lines beginning on active video lines 22 and con-
tinuing through line 261. VSYNC field two transi-
tions low in the middle of line 266 and stays low for
three line-times and transitions high in the middle
of line 269. The CS4954/5 exclusively reserves line
284 of field two for closed caption insertion. Video
input on the V [7:0] pins is expected between lines
285 through line 525.

5.2.6 PAL Interlaced

The CS4954/5 supports PAL modes B, D, G, H, I,
N, and Combination N, in which there are 625 total
lines per frame, two fixed 312.5 line fields per
frame, and 25 total frames per second. Figure

8

il-

lustrates PAL interlaced vertical timing. Each field
consists of 287 active lines of video plus 25.5 lines
of blanking.

VSYNC will transition low to begin field one and
will remain low for 2.5 lines or 2160 pixel cycles
(864 × 2.5). Digital video input is expected to be
delivered to the CS4954/5 V [7:0] pins for 287
lines beginning on active video line 24 and continu-
ing through line 310.

Field two begins with VSYNC transitioning low
after 312.5 lines from the beginning of field one.

Mode

Field

Active Lines

NTSC

1, 3;

2, 4

22-261;

285-524

PAL

1, 3, 5, 7;

2, 4, 6, 8

23-310;

336-623

NTSC Progressive-Scan

NA

22-261

PAL Progressive-Scan

NA

23-310

Table 2. Vertical Timing

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