bt865a Conexant Systems, Inc., bt865a Datasheet - Page 34

• Manufacturer Part Number: bt865a
• Description: Ycrcb To Ntsc/pal Digital Video Encoder
• Manufacturer: Conexant Systems, Inc.

Circuit Description
Figure 1-18. DAC Sinx/x Response (Passband)
1.8
1-24
Closed Captioning
–0.1
–0.2
–0.3
–0.4
–0.5
–0.6
–0.7
–0.8
–0.9
The Bt864A/Bt865A encodes NTSC/PAL–M closed captioning on scan line 21 and
NTSC/PAL–M extended data services on scan line 284. Four 8-bit registers (CCF1B1,
CCF1B2, CCF2B1, and CCF2B2) provide the data while bits ECCF1and ECCF2
enable display of the data. A logical zero corresponds to the blanking level of 0 IRE,
while a logical one corresponds to 50 IRE above the blanking level.
Closed captioning for PAL–B, D, G, H, I, N, Nc is similar to that for NTSC. Closed
caption encoding is performed for 625-line systems according to the system proposed
by the National Captioning Institute; clock and data timing is identical to that of
NTSC system, except that encoding is provided on lines 22 and 335.
The Bt864A/Bt865A generates the clock run-in and appropriate timing automatically.
Pixel inputs are ignored during CC encoding. See FCC Code of Federal Regulations
(CFR) 47 Section 15.119 (10/91 edition or later) for programming information.
EIA608 describes ancillary data applications for FIELD 2 Line 21 (line 284).
When CCF1B2 is written, CCSTAT1 is set; when CCF2B2 is written CCSTAT2 is set
(CCSTAT1 and CCSTAT2 are defined in
for FIELD 1 are encoded, CCSTAT1 is cleared; after the closed-caption bytes for
FIELD 2 are encoded, CCSTAT2 is cleared. If the ECCGATE bit is set, no further
encoding will be performed until the appropriate registers are again written; a NULL
with odd parity will be transmitted on the appropriate closed caption line in that case.
User must set the odd parity bit. If the ECCGATE bit is not set, the user must rewrite
the closed-caption registers prior to reaching the closed-caption line, otherwise the
last bytes will be re-encoded.
–1
0
0
1
2
Frequency (MHz)
Conexant
CLK = 27 MHz
3
4
Table
2-1). After the closed-caption bytes
5
6
100138_019
Bt864A/Bt865A Data Sheet
100138C
02/17/03