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ADV7183B
Rev. B | Page 51 of 100
The recovered data is not available through I2C, but is inserted
into the horizontal blanking period of an ITU-R BT656-com-
patible data stream. The data format is intended to comply with
the recommendation by the International Telecommunications
Union, ITU-R BT.1364. For more information, see the ITU
website at
66H
www.itu.ch. See
226H
Figure 35.
The format of the data packet depends on the following criteria:
Transmission is 1× or 2×.
Data is output in 8-bit or 4-bit format (see the description
of the
227H
GDECAD Gemstar Decode Ancillary Data Format,
Address 0x4C[0] bit).
Data is closed caption (CCAP) or Gemstar-compatible.
Data packets are output if the corresponding enable bit is set
(see the GDECEL and GDECOL descriptions) and if the
decoder detects the presence of data. This means that for video
lines where no data has been decoded, no data packet is output
even if the corresponding line enable bit is set.
Each data packet starts immediately after the EAV code of the
preceding line. See
228H
Figure 35 and
229H
Table 64, which show the
overall structure of the data packet.
Entries within the packet are as follows:
Fixed preamble sequence of 0x00, 0xFF, 0xFF.
Data identification word (DID). The value for the DID
marking a Gemstar or CCAP data packet is 0x140
(10-bit value).
Secondary data identification word (SDID) contains
information about the video line from which data was
retrieved, whether the Gemstar transmission was of 1× or
2× format, and whether it was retrieved from an even or
odd field.
Data count byte, giving the number of user data-words that
follow.
User data section.
Optional padding to ensure the length of the user data-
word section of a packet is a multiple of four bytes
(requirement as set in ITU-R BT.1364).
Checksum byte.
230H
Table 64 lists the values within a generic data packet that is
output by the ADV7183B in 8-bit format.
00
FF
DID
SDID
DATA
COUNT
USER DATA
OPTIONAL PADDING
BYTES
CHECK
SUM
SECONDARY DATA IDENTIFICATION
PREAMBLE FOR ANCILLARY DATA
DATA IDENTIFICATION
USER DATA (4 OR 8 WORDS)
04997
-035
Figure 35. Gemstar and CCAP Embedded Data Packet (Generic)
Table 64. Generic Data Output Packet
Byte
D[9]
D[8]
D[7]
D[6]
D[5]
D[4]
D[3]
D[2]
D[1]
D[0]
Description
0
Fixed preamble
1
Fixed preamble
2
1
Fixed preamble
3
0
1
0
1
0
DID
4
!EP
EP
EF
2X
Line[3:0]
0
SDID
5
!EP
EP
0
DC[1]
DC[0]
0
Data count (DC)
6
!EP
EP
0
Word1[7:4]
0
User data-words
7
!EP
EP
0
Word1[3:0]
0
User data-words
8
!EP
EP
0
Word2[7:4]
0
User data-words
9
!EP
EP
0
Word2[3:0]
0
User data-words
10
!EP
EP
0
Word3[7:4]
0
User data-words
11
!EP
EP
0
Word3[3:0]
0
User data-words
12
!EP
EP
0
Word4[7:4]
0
User data-words
13
!EP
EP
0
Word4[3:0]
0
User data-words
14
!CS[8]
CS[8]
CS[7]
CS[6]
CS[5]
CS[4]
CS[3]
CS[2]
0
Checksum