CS4955-CQZ 查看數據表（PDF） - Cirrus Logic

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CS4955-CQZ

NTSC/PAL Digital Video Encoder

Cirrus Logic 

CS4954 CS4955

order to maintain the strict timing requirements of

the teletext standard.

Table 5 shows how to program the TTXHS register

for teletext instantiation into the analog signals for

the various supported TV formats. TTXHS is the

time between the leading edge of the HSYNC sig-

nal and the rising edge of the first TTXRQ signal

and consists of multiples of 27 MHz clock cycles

Note that with increasing values of TTXHS the

time tTTX increases as well. The time tFD accounts

for the internal pipeline delay due to processing,

synchronization and instantiation of the teletext

data. The time tPD is dependant on the TTXHD

register.

Note that the teletext databits are shaped according

to the ITU R.BT653-2 specifications.

If register 0×31 bit 3 is set, (TTX_WINDOW=1)

the teletext is in windows mode. In this mode, the

request pulses become a window where the bit pro-

vided on the TTXDAT pin is valid (see Figure 13).

In pulse mode (where the number of request pulses

are determined by the teletext standard chosen), the

length of the window must be programmed by the

user independent of the teletext standard used. The

length of the window is programmed through reg-

ister 0×29 TTXHS (start of window), register

0×2A (TTXHD) and register 0×31 (end of win-

dow). The end-of-window register is a 11 bit value.

In teletext window mode, the TTXHS value can be

selected using the values in Table 5. Although

these values may need to be adjusted to match your

system delay, use the following equation to com-

pute the TTXHD value:

TTXHS + 1402 = TTXHD (for Europe)

TTXHS + 1151 = TTXHD (for WST)

TTXHS + 1122 = TTXHD (for NABTS)

TV standard

NTSC-M

NTSC-M

PAL-B

PAL-B

PAL-M

PAL-M

PAL-N (non Arg.)

PAL-N (non Arg.)

PAL-N (Arg.)

PAL-N (Arg.)

Teletext

standard

NABTS

WST-NTSC

Europe TTX

WST-PAL

NABTS

WST-NTSC

Europe TTX

WST-PAL

Europe TTX

WST-PAL

TTXHS

(register

value)

161

142

204

163

161

142

204

163

204

163

tTTX

10.5 μs

9.8 μs

12.0 μs

10.5 μs

10.5 μs

9.8 μs

12.0 μs

10.5 μs

12.0 μs

10.5 μs

Table 5. Teletext timing parameters

5.12 Color Bar Generator

The CS4954/5 is equipped with a color bar genera-

tor that is enabled through the CBAR bit of the

CONTROL_1 Register. The color bar generator

works in Master or Slave Mode and has no effect

on the video input/output timing. If the CS4954/5 is

configured for Slave Mode color bars, proper video

timing must be present on the HSYNC and

VSYNC pins for the color bars to be displayed.

Given proper Slave Mode input timing or Master

Mode timing, the color bar generator will override

the video input pixel data.

The output of the color bar generator is instantiated

after the chroma interpolation filter and before the

luma delay line. The generated color bar numbers

are for 100% amplitude, 100% saturation NTSC

EIA color bars or 100% amplitude, 100% satura-

tion PAL EBU color bars. For PAL color bars, the

CS4954/5 generates NTSC color bar values, which

are very close to standard PAL values. The exact

luma and chroma values are listed in Table 6.

26

DS278F6

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