CS7654 Просмотр технического описания (PDF) - Cirrus Logic
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CS7654 Datasheet PDF : 62 Pages
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CS7654
Analog
Field 1
VSYNC Drops
523 524 525 1
2
3
4
5
6
7
8
9 10
22
Analog
Field 2
261 262 263 264 265 266 267 268 269 270 271 272
284
285
Analog
Field 3
VSYNC Drops
523 524 525 1
2
3
4
5
6
7
8
9 10
22
Analog
Field 4
261 262 263 264 265 266 267 268 269 270 271 272
284
285
Burst begins with positive half-cycle
Burst begins with negative half-cycle
Figure 5. NTSC Video Interlaced Timing
PAL Interlaced
The CS7654 supports analog 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 7 il-
lustrates PAL interlaced vertical timing. Each field
consists of 287 active lines of video plus 25.5 lines.
Progressive Scan
The CS7654 supports an analog progessive scan
mode in which the video output is non-interlaced.
This is accomplished by displaying only the odd
video field for NTSC or PAL. To preserve precise
MPEG-2 frame rates of 30 and 25 per second, the
CS7654 displays the same odd field repetitively but
alternately varies the field times. This mode is in
contrast to other digital video encoders, which
commonly support progressive scan by repetitively
displaying a 262 line field (524/525 lines for
NTSC). The common method is flawed: over time,
the output display rate will overrun a system-clock-
locked MPEG-2 decompressor and display a field
twice every 8.75 seconds. NTSC non-interlaced
timing is illustrated in Figure 7. PAL non-inter-
laced timing is illustrated in Figure 8.
Digital Video Input Modes
The CS7654 provides two different digital video
input modes that are selectable through the
IN_MODE bit in the CONTROL_0 Register at SA
0x00.
In Mode 0 and upon RESET, the CS7654 defaults
to output a solid color (one of a possible of 256 col-
ors). The background color is selected by writing
the BKG_COLOR Register (0x08) at SA 0x00.
The colorspace of the register is RGB 3:3:2 and is
unaffected by gamma correction. The default color
following RESET is blue.
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