ADV7181B
Rev. B | Page 52 of 100
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CS[8:2]. The checksum is provided to determine the
integrity of the ancillary data packet. It is calculated by
summing up D[8:2] of DID, SDID, the data count byte, and
all UDWs, and ignoring any overflow during the
summation. Since all data bytes that are used to calculate
the checksum have their two LSBs set to 0, the CS[1:0] bits
are also always 0.
!CS[8] describes the logic inversion of CS[8]. The value
!CS[8] is included in the checksum entry of the data
packet to ensure the reserved values of 0x00 and 0xFF do
not occur.
Table 65 to Table 68 outline the possible data packages.
Gemstar 2× Format, Half-Byte Output Mode
Half-byte output mode is selected by setting CDECAD = 0;
full-byte output mode is selected by setting CDECAD = 1.
See the GDECAD Gemstar Decode Ancillary Data Format,
Address 0x4C[0] section.
Gemstar 1× Format
Half-byte output mode is selected by setting CDECAD = 0;
full-byte output mode is selected by setting CDECAD = 1.
See the GDECAD Gemstar Decode Ancillary Data Format,
Address 0x4C[0] section.
Table 65. Gemstar 2× Data, Half-Byte Mode
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
1
Line[3:0]
0 0 SDID
5 !EP EP
0 0 0 0
1 0
0 0 Data
count
6 !EP EP
0 0
Gemstar
Word1[7:4]
0 0 User
data-words
7 !EP EP
0 0
Gemstar
Word1[3:0]
0 0 User
data-words
8 !EP EP
0 0
Gemstar
Word2[7:4]
0 0 User
data-words
9 !EP EP
0 0
Gemstar
Word2[3:0]
0 0 User
data-words
10
!EP EP
0 0
Gemstar
Word3[7:4]
0 0 User
data-words
11
!EP EP
0 0
Gemstar
Word3[3:0]
0 0 User
data-words
12
!EP EP
0 0
Gemstar
Word4[7:4]
0 0 User
data-words
13
!EP EP
0 0
Gemstar
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] CS[1] CS[0] Checksum
Table 66. Gemstar 2× Data, Full-Byte Mode
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
1
Line[3:0]
0 0 SDID
5 !EP
EP
0 0 0 0
0 1
0 0 Data
count
6
Gemstar
Word1[7:0]
0 0 User
data-words
7
Gemstar
Word2[7:0]
0 0 User
data-words
8
Gemstar
Word3[7:0]
0 0 User
data-words
9
Gemstar
Word4[7:0]
0 0 User
data-words
10
!CS[8] CS[8] CS[7] CS[6] CS[5] CS[4] CS[3] CS[2] CS[1] CS[0] Checksum
