ADV7180WBSTZ datasheet(69/120 Pages) AD

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Data Sheet

ADV7180

Rev. G | Page 69 of 120

Gemstar Bit Names

The following are the Gemstar bit names:

•

DID—The data identification value is 0x140 (10-bit value).

Care has been taken so that in 8-bit systems, the two LSBs

do not carry vital information.

•

EP and EP—The EP bit is set to ensure even parity on the

D[8:0] data-word. 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 do not occur.

•

EF—Even field identifier. EF = 1 indicates that 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.

The 2× bit determines whether the raw information

retrieved from the video line was two bytes or four 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.

•

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 96

and Table 97.

•

DC[1:0]—Data count value. The number of UDWs in the

packet divided by 4. The number of UDWs in any packet

must be an integral number of 4. Padding may be required

at the end, as set in ITU-R BT.1364. See Table 87.

•

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.

Because 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

that the reserved values of 0x00 and 0xFF do not occur. Table 88

to Table 91 outline the possible data packages.

Gemstar_2× Format, Half-Byte Output Mode

Half-byte output mode is selected by setting GDECAD to 0;

full-byte output mode is selected by setting GDECAD to 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 to 0,

full-byte output mode is selected by setting CDECAD to 1. See

the GDECAD, Gemstar Decode Ancillary Data Format,

Address 0x4C[0] section.

Table 88. 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

Fixed preamble

DID

Line[3:0]

SDID

Data count

Gemstar Word1[7:4]

User data-words

Gemstar Word1[3:0]

User data-words

Gemstar Word2[7:4]

User data-words

Gemstar Word2[3:0]

User data-words

Gemstar Word3[7:4]

User data-words

Gemstar Word3[3:0]

User data-words

Gemstar Word4[7:4]

User data-words

Gemstar Word4[3:0]

User data-words

CS[8]

CS[7]

CS[6]

CS[5]

CS[4]

CS[3]

CS[2]

CS[1]

CS[0]

Checksum

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