Analog Devices ADV7181BCP Manual page 55

Table 72. PAL CCAP Data, Full-Byte Mode
Byte D[9]
0 0
1 1
2 1
3 0
4 !EP
5 !EP
6
7
8 1
9 1
10 !CS[8]
GDECEL[15:0] Gemstar Decoding Even Lines,
Address 0x48[7:0]; Address 0x49[7:0]
The 16 bits of the GDECEL[15:0] are interpreted as a collection
of 16 individual line decode enable signals. Each bit refers to a
line of video in an even field. Setting the bit enables the decoder
block trying to find Gemstar or closed caption-compatible data
on that particular line. Setting the bit to 0 prevents the decoder
from trying to retrieve data. See Table 73 and Table 74.
To retrieve closed caption data services on NTSC (Line 284),
GDECEL[11] must be set.
To retrieve closed caption data services on PAL (Line 335),
GDECEL[14] must be set.
The default value of GDECEL[15:0] is 0x0000. This setting
instructs the decoder not to attempt to decode Gemstar or
CCAP data from any line in the even field.
GDECOL[15:0] Gemstar Decoding Odd Lines, Address
0x4A[7:0]; Address 0x4B[7:0]
The 16 bits of the GDECOL[15:0] form a collection of 16
individual line decode enable signals. See Table 73 and Table 74.
To retrieve closed caption data services on NTSC (Line 21),
GDECOL[11] must be set.
To retrieve closed caption data services on PAL (Line 22),
GDECOL[14] must be set.
The default value of GDEC0L[15:0] is 0x0000. This setting
instructs the decoder not to attempt to decode Gemstar or
CCAP data from any line in the odd field.
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D[8] D[7] D[6] D[5]
0 0 0 0
1 1 1 1
1 1 1 1
1 0 1 0
EP EF 0 1
EP 0 0 0
CCAP Word1[7:0]
CCAP Word2[7:0]
0 0 0 0
0 0 0 0
CS[8] CS[7] CS[6] CS[5]
D[4] D[3] D[2] D[1]
0 0 0 0
1 1 1 1
1 1 1 1
0 0 0 0
0 1 0 0
0 0 1 0
0
0
0 0 0 0
0 0 0 0
CS[4] CS[3] CS[2] CS[1]
GDECAD Gemstar Decode Ancillary Data Format,
Address 0x4C[0]
The decoded data from Gemstar-compatible transmissions
or closed caption transmissions is inserted into the horizontal
blanking period of the respective line of video. A potential
problem can arise if the retrieved data bytes have the value 0x00
or 0xFF. In an ITU-R BT.656-compatible data stream, those
values are reserved and used only to form a fixed preamble.
The GDECAD bit allows the data to be inserted into the
horizontal blanking period in two ways
•
Insert all data straight into the data stream, even the reserved
values of 0x00 and 0xFF, if they occur. This can violate the
output data format specification ITU-R BT.1364.
•
Split all data into nibbles and insert the half-bytes over
double the number of cycles in a 4-bit format.
When GDECAD is 0, the data is split into half-bytes and
inserted (default).
When GDECAD is 1, the data is output straight in 8-bit format.
Rev. B | Page 55 of 100
ADV7181B
D[0] Description
0 Fixed preamble
1 Fixed preamble
1 Fixed preamble
0 DID
0 SDID
0 Data count
0 User data-words
0 User data-words
0 UDW padding 0x200
0 UDW padding 0x200
CS[0] Checksum