ADV7175/ADV7176

REV. A

–24–

APPENDIX 2

CLOSED CAPTIONING

The ADV7175/ADV7176 supports closed captioning conforming to the standard television synchronizing waveform for color trans-

mission. Closed captioning is transmitted during the blanked active line time of line 21 of the odd fields.

Closed captioning consists of a 7-cycle sinusoidal burst that is frequency and phase locked to the caption data. After the clock run in

signal, the blanking level is held for two data bits and is followed by a Logic Level “1” start bit. Sixteen bits of data follow the start

bit. These consist of two 8-bit bytes. The data for these bytes is stored in closed captioning data registers 0 and 1.

The ADV7175/ADV7176 also supports the extended closed captioning operation which is active during even fields and is encoded

on scan line 284. The data for this operation is stored in closed captioning extended data registers 0 and 1.

All clock run-in signals and timing to support closed captioning on lines 21 and 282 are generated automatically by the ADV7175/

ADV7176. All pixels inputs are ignored during lines 21 and 282.

FCC Code of Federal Regulations (CFR) 47 section 15.119 and EIA208 describe the closed captioning information for lines

21 and 284.

13.407µs

S

T

A

R

T

P

A

R

I

T

Y

P

A

R

I

T

Y

D6–D0

D6–D0

10.003µs

17.379µs

33.764µs

50 IRE

40 IRE

AMPLITUDE = 40 IRE

REFERENCE COLOR BURST

(9 CYCLES)

Figure 43. Closed Captioning Waveform (NTSC)