LSI Logic Confidential
12-14
Audio Interface
Copyright © 2001, 2002 by LSI Logic Corporation. All rights reserved.
AudInt
4
I
f set, an audio output stream DMA transfer completion
interrupt will be generated when an audio output DMA
transfer has been completed. Completion interrupts are
queued by the hardware, resulting in a separate interrupt
for each transfer, even if a second transfer completes
before the first interrupt is taken. When the interrupt is
taken, the count of outstanding interrupts is decremented
by one.
OQF
2
A read-only bit which is set when there are two
outstanding DMA transfers in the audio output stream
command queue. A transfer is loaded into the queue
each time the GoO bit is set by software. A command is
removed from the queue each time the transfer
completes. This bit can be used by software to poll for
when to load the next command. Polling is typically used
for short transfers (<10 microseconds) and interrupts are
used for longer transfers.
0
1
This bit must be programmed to 0.
GoO
0
Set by microcode to queue up an audio output stream
DMA transfer using the most recently stored values in the
Audio Output DMA address and length registers. The
goO bit remains set while there is at least one audio
output DMA transfer outstanding. When all audio output
outstanding transfers are done, the DMA will clear the bit,
to allow software polling of completion. If the stream
output DMA queue is empty when a transfer is queued
up, then the first frame of output on the audio pins will be
synchronized to the start of an IEC958 block boundary to
allow consistent IEC958 user status and audio data.
Programming note: When changing IEC958 user status,
ChCnt Value
Total Channels
Description
0
1
1 channel
1
2
1 Left + 1 Right
2
4
2 Left + 2 Right
3
8
4 Left + 4 Right