Cirrus Logic CS4955 - Manual (Page 22)

CS4954 CS4955
22 DS278F6
5.6 Subcarrier Generation
The CS4954/5 automatically synthesizes NTSC
and PAL color subcarrier clocks using the CLK fre-
quency and four control registers
(SC_SYNTH0/1/2/3). The NTSC subcarrier syn-
thesizer is reset every four fields (every eight fields
for PAL).
The SC_SYNTH0/1/2/3 registers used together
provide a 32-bit value that defaults to NTSC
(43E0F83Eh) following RESET. Table
4 shows
the 32-bit value required for each of the different
broadcast formats.
309 310 311
Analog
Field 1
Burst Phase = 135 degrees relative to U Burst Phase = 225 degrees relative to U
312 313 1 2 3 4 5 6 7 23 24
309
Analog
Field 2
308 311 312
VSYNC Drops
1 2 3 4 5 6 7 23 24 310
309 310 311
Analog
Field 3
312 313 1 2 3 4 5 6 7 23 24
309
Analog
Field 4
308 311 312 1 2 3 4 5 6 7 23 24 310
Figure 10. PAL Video Non-Interlaced Progressive Scan Timing
Y
Cr Y FF 00 00 XY 80 10 80 10 80 10 80 10 80 10
80 10 80 10 FF 00 00 XY Cb Y Cr Cb Y Cr
1440 Clocks
Active Video
SAV Code
Composite
Video
Ancilliary Data
268 Clocks (NTSC)
280 Clocks (PAL)
Horizontal Blanking
EAV Code
4 Clocks
Active Video
V[7:0]
ITU R.BT656
4 Clocks
Figure 11. CCIR656 Input Mode Timing
DATA