ADV7181 AD [Analog Devices], ADV7181 Datasheet - Page 51

• Manufacturer Part Number: ADV7181
• Description: Multiformat SDTV Video Decoder
• Manufacturer: AD [Analog Devices]

Table 63. Data Byte Allocation
2×
1
1
0
0
Gemstar Bit Names
•
•
•
•
•
•
•
DID. The data identification value is 0x140 (10-bit value).
Care has been taken that in 8-bit systems, the 2 LSBs do
not carry vital information.
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 that the
reserved codes of 00 and FF cannot happen.
EF. Even field identifier. EF = 1 indicates that the data was
recovered from a video line on an even field.
2X. 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 may have been retrieved. Refer to Table 72
and Table 73.
DC[1:0]. Data count value. The number of User Data
Words in the packet divided by 4. The number of user data
words (UDW) 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). Refer to Table 63.
The 2X 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 (i.e., two bytes transmitted as two bytes) or
whether they are split into nibbles (i.e., two bytes
transmitted as four half bytes). Padding bytes are then
added where necessary.
Raw Information Bytes
Retrieved from the Video Line
4
4
2
2
GDECAD
0
1
0
1
Rev. 0 | Page 51 of 96
User Data-Words
(Including Padding)
8
4
4
4
•
Table 64 to Table 67 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.
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 2 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 that the reserved values of 0x00 and 0xFF do not
occur.
Padding Bytes
0
0
0
2
ADV7181B
DC[1:0]
10
01
01
01