CS4954 datasheet(25/56 Pages) CIRRUS

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CS4954 CS4955

DS278PP4

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, the request pulses

become a window where the bit provided on the

TTXDAT pin are valid (see Figure 13).

Alternately to the pulsation mode (where the num-

ber of request pulses are determined by the teletext

standard chosen), the length of the window must be

programmed by the user independently of the tele-

text standard used. The length of the window is

programmed through register 0×29 TTXHS (start

of window) and register 0×2A (TTXHD) and 0×31

(end of window). 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)

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, the color bar generator will override the vid-

eo 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. .

5.13. VBI encoding

VBI (Vertical Blanking Interval) encoding is per-

formed according to SMPTE RP 188 recommenda-

tions. In NTSC mode lines 10 - 20 and lines 272 -

283 are used for the transmission of ancillary data.

In PAL mode lines 6 - 22 and lines 318 -335 are

used. The VBI encoding mode can be set through

the CONTROL_3 register.

All digital input data is passed through the chip

when this mode is enabled. It is therefore the re-

sponsibility of the user to ensure appropriate ampli-

TV standard

Teletext

standard

TTXHS

(register

value)

tTTX

NTSC-M

NABTS

161

10.5

µs

NTSC-M

WST-NTSC

142

9.8

µs

PAL-B

Europe TTX

204

12.0

µs

PAL-B

WST-PAL

163

10.5

µs

PAL-M

NABTS

161

10.5

µs

PAL-M

WST-NTSC

142

9.8

µs

PAL-N (non Arg.)

Europe TTX

204

12.0

µs

PAL-N (non Arg.)

WST-PAL

163

10.5

µs

PAL-N (Arg.)

Europe TTX

204

12.0

µs

PAL-N (Arg.)

WST-PAL

163

10.5

µs

Table 5. Teletext timing parameters

Color

White

+ 167

Yellow

- 84

+ 14

+ 156

Cyan

+ 28

- 84

+ 138

Green

- 56

- 70

+ 127

Magenta

+ 56

+ 70

+ 110

Red

- 28

+ 84

+ 99

Blue

+ 84

- 14

+ 81

Black

+ 70

Table 6. Internal Color Bar Values (8-bit values, Cb/Cr

are in twos complement format)

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