LSI Logic Confidential
12-10
Audio Interface
Copyright © 2001, 2002 by LSI Logic Corporation. All rights reserved.
output subframe. I9S32 also determines the source of the
U and C bits as shown below.
I958
13
Set by microcode to indicate that IEC958 output data
should be transferred in addition to audio output stream
1 data when GoO is set. The IEC958 DMA transfer uses
the most recently stored value in the IEC958 Output DMA
address register. The length of the I958 transfer is the
output length divided by the output sample memory size
in bytes divided by the number of active channels
specified by chCnt times two times the IEC958 sample
size divided by the R958 sample rate divisor. When I958
is not set in an output transfer, zero data is transferred on
the I958 output pin, with the usual IEC958 framing.
IEC958 timing is generated from the master audio clock,
and is adjusted so that one/one half or one fourth of an
IEC958 sample is transmitted in each audio output
sample time as determined by the OTIM bits and R958
field. The length of audio output 1 transfers with I958 set
must correspond to an even number of IEC958 samples.
IEC958 length = audio output length x 2
I9S32
/2
OS32
x
2/audio_channels_per_2_samples x 1/2
R958
.
I9S32
cValue
Bits in
Memory
How Bits Fit
into 24-bit
Output
U Bit
C Bit
0
16
Fits into upper
16 bits of output,
the lower 8 bits
being zero filled
0
Status
1
32
Only upper 24
bits of data are
used
mem data
LSB bit 6
mem data
LSB bit 5
I958
Value Description
0
Disabled: IEC958 will not respond to GoO; Stream
audio output doesn’t sync with IEC958 block 0.
1
Enabled: IEC958 responds to stream 1 GoO; Stream
audio output syncs with IEC958 block 0.
Содержание DMN-8600
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