GENNUM CORPORATION

522 - 45 - 05

11

Fig. 4

In cases where an audio data packet does not fit inside the

remaining HANC space, the audio packet is discarded. In

this case, the “ADERR” bit of Host Interface Register #7h is

HIGH indicating an audio packet multiplexing error. The

error bit is cleared once accessed by the Host Interface.

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.

Cascade operation is not recommended with a composite

video signal, as there is insufficient HANC space for more

than four channels of audio. Audio packet insertion is not

guaranteed in this case.

The audio data packet structure as described in SMPTE

272M is shown in Figure 5.

The 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. Audio data packets corresponding to an

audio group are selected by programming “A20ID[3:0]” of

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

follows:

Group 1: Fh (2FFh)

Group 2: Dh (1FDh)

Group 3: Bh (1FBh)

Group 4: 9h (2F9h)

NOTE: The six most significant bits of the DID are internally

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.

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.

The serial audio data samples, are mapped into three

contiguous ancillary data words (X, X+1, X+2) as shown in

Table 3.

Fig. 5: Audio Data Packet Structure with 4 Audio Channels, 1 Audio Group

Empty

Video signal before GS9023

Empty

Video signal after GS9023 Insertion of Audio Group 1 ("CASCADE" = HIGH)

Empty

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

in component systems (ANSI/SMPTE 125M).

X

X+1 X+2

X

X+1 X+2

X

X+1 X+2

X

X+1 X+2

X

X+1 X+2

X

X+1 X+2