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GS9023A Datasheet PDF : 37 Pages
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* The ancillary data flag, ADF, is one word in composite systems (ANSI/SMPTE 259M)
and three words in component systems (ANSI/SMPTE 125M).
Figure 9 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
GS9023A does not multiplex the audio data packet and the
associated extended audio data packet if there is
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 GS9023A devices, it is possible to
multiplex up to 16 audio channels (according to SMPTE
272) in a component video signal as shown in Figure 5.
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 9.
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 GS9023A.
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 GS9023A.
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
GS9023A.
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 GS9023A.
DATA WORDS: The extended audio data samples are
mapped into ancillary data words as shown in Table 5.
TABLE 5 EXTENDED AUDIO PACKET DATA SAMPLE
STRUCTURE
BIT
ANC DATA WORD
b9
not b8
b8
a
b7
y3 (MSB)
b6
y2
b5
y1
b4
y0 (LSB)
b3
x3 (MSB)
b2
x2
b1
x1
b0
x0 (LSB)
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
GS9023A.
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 GS9023A.
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