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ADV7189B
Rev. B | Page 52 of 104
The block is configured via I2C in the following ways:
GDECEL[15:0] allow data recovery on selected video lines
on even fields to be enabled and disabled.
GDECOL[15:0] enable the data recovery on selected lines
for odd fields.
GDECAD configures the way in which data is embedded
in the video data stream.
The recovered data is not available through I2C, but is being
inserted into the horizontal blanking period of an
ITU-R. BT656-compatible data stream. The data format
is intended to comply with the recommendation by the
International Telecommunications Union, ITU-R BT.1364.
See
221H
Figure 35. For more information, see the ITU website
at www.itu.ch.
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 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 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.
222H
Figure 35 and
223H
Table 64 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), which 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 that 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.
224H
Table 64 lists the values within a generic data packet that is
output by the ADV7189B in 10-bit format.
04983-0-035
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)
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