ADV7181B
Rev. B | Page 51 of 100
00
FF
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)
04984-034
Figure 34. Gemstar and CCAP Embedded Data Packet (Generic)
Table 63. 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 0 0 0 0 0 0 0 0 0 0 Fixed
preamble
1 1 1 1 1 1 1 1 1 1 1 Fixed
preamble
2 1 1 1 1 1 1 1 1 1 1 Fixed
preamble
3 0 1 0 1 0 0 0 0 0 0 DID
4 !EP EP EF 2X
Line[3:0]
0 0 SDID
5 !EP EP
0 0 0 0 DC[1]
DC[0]
0 0 Data
count
(DC)
6 !EP EP 0 0
Word1[7:4]
0 0 User
data-words
7 !EP EP 0 0
Word1[3:0]
0 0 User
data-words
8 !EP EP 0 0
Word2[7:4]
0 0 User
data-words
9 !EP EP 0 0
Word2[3:0]
0 0 User
data-words
10 !EP EP 0 0
Word3[7:4]
0 0 User
data-words
11 !EP EP 0 0
Word3[3:0]
0 0 User
data-words
12 !EP EP 0 0
Word4[7:4]
0 0 User
data-words
13 !EP EP 0 0
Word4[3:0]
0 0 User
data-words
14
!CS[8] CS[8] CS[7] CS[6] CS[5] CS[4] CS[3] CS[2] 0
0
Checksum
Table 64. Data Byte Allocation
2×
Raw Information Bytes
Retrieved from the Video Line
GDECAD
User Data-Words
(Including Padding)
Padding Bytes
DC[1:0]
1 4
0
8
0
10
1 4
1
4
0
01
0 2
0
4
0
01
0 2
1
4
2
01
Gemstar Bit Names
•
DID. The data identification value is 0x140 (10-bit value).
Care has been taken so the two LSBs do not carry vital
information in 8-bit systems.
•
EP and !EP. The EP bit is set to ensure even parity on the
data-word D[8:0]. Even parity means there is always an
even number of 1s within the D[8:0] bit arrangement. This
includes the EP bit. !EP describes the logic inverse of EP
and is output on D[9]. The !EP is output to ensure the
reserved codes of 00 and FF cannot happen.
•
EF. Even field identifier. EF = 1 indicates the data was
recovered from a video line on an even field.
•
2×. This bit indicates whether the data sliced was in
Gemstar 1× or 2× format. A high indicates 2× format.
•
line[3:0]. This entry provides a code that is unique for each
of the possible 16 source lines of video from which
Gemstar data can be retrieved. See Table 73 and Table 74.
•
DC[1:0]. Data count value. The number of user data-words
(UDW) in the packet divided by 4. The number of UDWs
in any packet must be an integral number of 4. Padding is
required at the end, if necessary (requirement as set in
ITU-R BT.1364). See Table 64.
•
The 2× bit determines whether the raw information
retrieved from the video line was 2 or 4 bytes. The state of
the GDECAD bit affects whether the bytes are transmitted
straight (that is, two bytes transmitted as two bytes) or
whether they are split into nibbles (that is, two bytes
transmitted as four half bytes). Padding bytes are then
added where necessary.
