GS9023 datasheet(13/33 Pages) ETC

13 / 33 page

GENNUM CORPORATION

522 - 45 - 05

Fig. 7: Extended Audio Data Packet Structure

To select 24 bit audio operation, the user must set the

AUXEN pin or the “A4ON” bit of Host Interface Register #1h

HIGH. When the AUXEN pin or “A4ON” bit is HIGH, the

GS9023 does not multiplex the audio data packet and the

associated

extended

audio

data

packet

there

insufficient room for both in the HANC space. In this case,

the “ADERR” bit of Host Interface Register #7h is set HIGH,

indicating an audio packet multiplexing error. The error bit is

cleared when accessed by the Host Interface. The audio

group (Extended packet data ID) for each device is

configured in “AD4ID[3:0]” of Host Interface Register #3h.

On power up, audio group 1 is selected by default.

By cascading four GS9023 devices, it is possible to

multiplex up to 16 audio channels (according to SMPTE

272) in a component video signal as shown in Figure 18.

NOTE: In the 525/D1 video format, only 15 channels of 24

bit audio can be multiplexed in the cascade configuration.

The extended audio data packet structure as described in

SMPTE 272M is shown in Figure 7.

The extended audio data packets words are defined as

follows:

ADF: Ancillary Data Flag. The ancillary data flag marks the

beginning of an ancillary packet and is automatically

generated by the GS9023.

DID: Data ID. Extended audio data packets corresponding

to an audio group are selected by programming “A4ID[3:0]”

of Host Interface Register #3h for audio groups 1 to 4 as

follows:

Group 1: Eh (1FEh)

Group 2: Ch (2FCh)

Group 3: Ah (2FAh)

Group 4: 8h (1F8h)

NOTE: The six most significant bits of the DID are

automatically generated by the GS9023.

DBN: Data Block Number. The data block number is used

when data blocks within a common data ID are to be linked

or to distinguish consecutive data blocks within a common

data ID. The data block number continuously increments

from 1 to 255 and is generated automatically by the

GS9023.

DC: Data Count. The data count represents the number of

user data words to follow (maximum of 255 words). The

data count is automatically generated by the GS9023.

DATA WORDS: The extended audio data samples are

mapped into ancillary data words as shown in Table 5.

The extended audio packet data sample bits are defined as

follows:

x[3:0]: Auxiliary data from subframe 1.

y[3:0]: Auxiliary data from subframe 2.

a: Address pointer. LOW for channels 1 and 2, and HIGH for

channels 3 and 4. This bit is internally generated by the

GS9023.

CS: Checksum. The checksum consists of nine bits. The

checksum is used to determine the validity of the words

data ID through user data. It is the sum of the nine least

significant bits of the words data ID through user data. The

checksum is automatically generated by the GS9023.

Audio Control Packets

The audio control packet structure is detailed in SMPTE

272M. The audio group (Audio control packet data ID) for

each device is configured in “ACID[3:0]” of Host Interface

in Host Interface Registers #Ah, #Bh, #Ch and #Dh. The

audio control packet multiplexing positions for the various

* The ancillary data flag, ADF, is one word in composite systems (ANSI/SMPTE 259M)

and three words in component systems (ANSI/SMPTE 125M).

TABLE 5: Extended Audio Packet Data Sample Structure

BIT

ANC DATA WORD

not b8

y3 (MSB)

y0 (LSB)

x3 (MSB)

x0 (LSB)

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