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CS4955-CQ

NTSC/PAL Digital Video Encoder

Cirrus Logic 

CS4954 CS4955

Composite

Video

ITU R.BT656 V[7:0]

DATA

Y Cr Y FF 00 00 XY 80 10 80 10

EAV Code

80 10 80 10 80 10

Ancilliary Data

80 10 80 10 FF 00 00 XY Cb Y Cr Cb Y Cr

SAV Code

Active Video

4 Clocks

268 Clocks (NTSC)

280 Clocks (PAL)

Horizontal Blanking

4 Clocks

1440 Clocks

Active Video

Figure 11. CCIR656 Input Mode Timing

5.4. Digital Video Input Modes

The CS4954/5 provides two different digital video

input modes that are selectable through the

IN_MODE bit in the CONTROL_0 Register.

In Mode 0 and upon RESET, the CS4954/5 de-

faults to output a solid color (one of a possible of

256 colors). The background color is selected by

writing the BKG_COLOR Register (0x08). The

colorspace of the register is RGB 3:3:2 and is unaf-

fected by gamma correction. The default color fol-

lowing RESET is blue.

In Mode 1 the CS4954/5 supports a single 8-bit

27 MHz CbYCrY source as input on the V [7:0]

pins. Input video timing can be ITU-R.BT601 mas-

ter or slave and ITU-R.BT656.

5.5. Multi-standard Output Format

Modes

The CS4954/5 supports a wide range of output for-

mats compatible with worldwide broadcast stan-

dards. These formats include NTSC-M, NTSC-J,

PAL-B/D/G/H/I, PAL-M, PAL-N, and PAL Com-

bination N (PAL-Nc) which is the broadcast stan-

dard used in Argentina. After RESET, the CS4954/5

defaults to NTSC-M operation with ITU R.BT 601

analog timing. NTSC-J can also be supported in the

Japanese format by turning off the 7.5 IRE pedestal

through the PED bit in the CONTROL_1 Register

(0x01).

Output formats are configured by writing control

registers with the values shown in Table 3.

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.

System

Fsubcarrier Value (hex)

NTSC-M, NTSC-J 3.5795455 MHz 43E0F83E

PAL-B, D, G, H, I, N 4.43361875 MHz 54131596

PAL-N (Argentina) 3.582056 MHz 43ED288D

PAL-M

3.579611 MHz 43CDDFC7

Table 3.

5.7. Subcarrier Compensation

Since the subcarrier is synthesized from CLK the

subcarrier frequency error will track the clock fre-

quency error. If the input clock has a tolerance of

200 ppm then the resulting subcarrier will also

have a tolerance of 200 ppm. Per the NTSC speci-

fication, the final subcarrier tolerance is ±10 Hz

DS278PP4

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