GS9023 데이터 시트보기 (PDF) - Gennum -> Semtech
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GS9023 Datasheet PDF : 33 Pages
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Audio Data Packets
The GS9023 can multiplex up to four audio channels. The
channels are selectable via the “CHACT(4-1)” bits of Host
Interface Register #1h. The audio group (Audio packet data
ID) for each device is configured in “AD20ID[3:0]” of Host
Interface Register #3h. On power up, the four audio
channels and audio group 1 are selected by default.
NOTE: Do not rely on default value. Reprogram on power
up or reset.
The “CASCADE” bit in Host Interface Register #4h controls
the manner in which multiplexing is performed. When
“CASCADE” is LOW, the GS9023 deletes all existing
ancillary packets. New packets are multiplexed at the first
location after the end of active video (EAV) in the horizontal
ancillary space (HANC). See Figure 2.
When “CASCADE” is HIGH, the GS9023 multiplexes
packets at the first free location in the horizontal ancillary
(HANC) space after the end of active video (EAV) if there is
sufficient space remaining to insert the packet. The GS9023
does not check if existing audio group samples are present
in the video signal. Use caution in applications where the
video signal contains existing audio packets to avoid
adding identical group samples. See Figure 3.
The GS9023 assumes that the ancillary space from the first
free location is empty to the start of active video (SAV).
Existing ancillary data packets (inserted by previous
devices) in the video signal must be contiguous from the
beginning of the HANC space or the insertion of a new
audio data packet may overwrite existing data. See
Figure 4.
Video Signal before GS9023
Empty
Empty
Video Signal after GS9023 Insertion of Audio Group 1 ("CASCADE" = LOW)
Fig. 2
Video Signal before GS9023
Empty
Empty
Video Signal after GS9023 Insertion of Audio Group 3 ("CASCADE" = HIGH)
Fig. 3
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