GS2971A Datasheet, PDF (86/152 Pages) Gennum Corporation – Integrated audio clock generator

4.19.2.4 Setting Packet DID
Table 4-19 below, shows the 2-bit host interface setting for the audio group DID's.
For 24-bit audio support in SD mode, extended audio packets for Group A must have the
same group DID set in IDA[1:0] of the host interface. Extended audio packets for Group
B must have the same group DID set in IDB[1:0] of the host interface.
The audio de-embedder automatically detects the presence of extended audio packets.
When detected, the audio output format is set to 24-bit audio sample word length.
The audio de-embedder defaults to audio Groups One and Two, where Group A is
extracted from packets with audio Group One DID, and Group B from packets with
audio Group Two DID.
Table 4-19:Audio Group DID Host Interface Settings
Audio
Group
1
2
3
4
SD Data
DID
2FFh
1FDh
1FBh
2F9h
SD Extended
DID
1FEh
2FCh
2FAh
1F8h
HD Data
DID
2E7h
1E6h
1E5h
2E4h
SD Control
DID
1EFh
2EEh
2EDh
1ECh
HD Control
DID
1E3h
2E2h
2E1h
1E0h
Host Interface Register Setting
(2-bit)
00b
01b
10b
11b
Table 4-20:Audio Data and Control Packet DID Setting Register
Name
IDA[1-0]
IDB[1-0]
Description
Default
Group A Audio data and control packet DID setting
00b
Group B Audio data and control packet DID setting
01b
NOTE: To keep sample delays between audio channels the same after changing the
value of IDA or IDB in the SD audio core, the audio FIFOs must be cleared. This is
accomplished by asserting CLEAR_AUDIO and de-asserting at least one frame later.
When the FIFOs are in the clear state, audio will be muted, but audio clocks will continue
to run.
4.19.2.5 Audio Packet Delete Block
To delete all ancillary data with a group DID shown in Table 4-19, the ALL_DEL bit in the
host interface must be set HIGH.
4.19.2.6 ECC Error Detection & Correction Block (HD Mode Only)
The audio de-embedder performs BCH(31,25) forward error detection and correction, as
described in SMPTE 299M. The error correction for all embedded audio data packets is
activated when the host interface ECC_OFF bit is set LOW (default LOW). The audio
de-embedder corrects any errors in both the audio output and the embedded packet.
GS2971A 3Gb/s, HD, SD SDI Receiver
Data Sheet
54311 - 2
September 2012
86 of 152