ST STM32F446 Series Reference Manual page 961

RM0390
Bits 11:10 SYNCEN[1:0]: Synchronization enable
These bits are set and cleared by software. They must be configured when the audio sub-block is
disabled.
00: audio sub-block in asynchronous mode.
01: audio sub-block is synchronous with the other internal audio sub-block. In this case, the audio
sub-block must be configured in slave mode
10: audio sub-block is synchronous with an external SAI embedded peripheral. In this case the
audio sub-block should be configured in Slave mode.
11: Reserved
Note: The audio sub-block should be configured as asynchronous when SPDIF mode is enabled.
Bit 9 CKSTR: Clock strobing edge
This bit is set and cleared by software. It must be configured when the audio block is disabled. This
bit has no meaning in SPDIF audio protocol.
0: Signals generated by the SAI change on SCK rising edge, while signals received by the SAI are
sampled on the SCK falling edge.
1: Signals generated by the SAI change on SCK falling edge, while signals received by the SAI are
sampled on the SCK rising edge.
Bit 8 LSBFIRST: Least significant bit first
This bit is set and cleared by software. It must be configured when the audio block is disabled. This
bit has no meaning in AC'97 audio protocol since AC'97 data are always transferred with the MSB
first. This bit has no meaning in SPDIF audio protocol since in SPDIF data are always transferred
with LSB first.
0: Data are transferred with MSB first
1: Data are transferred with LSB first
Bits 7:5 DS[2:0]: Data size
These bits are set and cleared by software. These bits are ignored when the SPDIF protocols are
selected (bit PRTCFG[1:0]), because the frame and the data size are fixed in such case. When the
companding mode is selected through COMP[1:0] bits, DS[1:0] are ignored since the data size is
fixed to 8 bits by the algorithm.
These bits must be configured when the audio block is disabled.
000: Reserved
001: Reserved
010: 8 bits
011: 10 bits
100: 16 bits
101: 20 bits
110: 24 bits
111: 32 bits
RM0390 Rev 4
Serial audio interface (SAI)
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