GS2971A Datasheet, PDF (92/152 Pages) Gennum Corporation – Integrated audio clock generator

Table 4-23:Audio Sample Word Lengths
ASWL[1:0]
Audio Sample Word Length
(SD)
Audio Sample Word Length
(HD)
00
24-bit
24-bit
01
20-bit
20-bit
10
16-bit
16-bit
11
Auto 24/20-bit (Default)
Reserved (Default)*
*NOTE: By default, for HD at power-up, the word length is invalid. The desired word
length should be programmed through the host interface.
4.19.3.6 Audio Channel Status
The GS2971A detects the AES/EBU Audio Channel Status (ACS) block information for
each of the selected channel pairs.
ACS data detection is indicated by corresponding ACS_DET flag bits in the host
interface. The flag is cleared by writing to the same location.
Audio Channel Status Read
AES/EBU ACS data is available separately for each of the channels in a stereo pair. The
GS2971A defaults to reading the first channel of each pair. There are 184 bits in each
ACS packet, which are written to twelve 16-bit right-justified registers in the host
interface.
The ACS_USE_SECOND bit (default LOW) selects the second channel in each audio pair
when set HIGH.
Once all of the ACS data for a channel has been acquired, the corresponding ACS_DET
bit is set, and acquisition stops. The ACS data is overwritten with new data when the
ACS_DET bit is cleared in the system.
Audio Channel Status Regeneration
When the ACS_REGEN bit in the host interface is set HIGH, the audio de-embedder
embeds the 24 bytes of the Audio Channel Status information programmed in the
ACSR[183:0] registers into the 'C' bit of the AES/EBU outputs. The same Audio Channel
Status information is used for all output channels.
In order to apply ACSR data;
• Set the ACS_REGEN bit to logic HIGH
• Write the desired ACSR data to the ACSR registers
• Set the ACS_APPLY bit to HIGH
At the next status boundary, the device outputs the contents of the ACSR registers as
ACS data. This event may occur at a different time for each of the output channels. While
waiting for the status boundary, the device sets the appropriate ACS_APPLY_WAIT[A:D]
flag.
GS2971A 3Gb/s, HD, SD SDI Receiver
Data Sheet
54311 - 2
September 2012
92 of 152