RM0316 Datasheet, PDF (1012/1141 Pages) STMicroelectronics – This reference manual targets application developers

Serial peripheral interface / inter-IC sound (SPI/I2S)
RM0316
Bit 3 CKPOL: Steady state clock polarity
0: I²S clock steady state is low level
1: I²S clock steady state is high level
Note: For correct operation, this bit should be configured when the I²S is disabled.
It is not used in SPI mode.
Bits 2:1 DATLEN: Data length to be transferred
00: 16-bit data length
01: 24-bit data length
10: 32-bit data length
11: Not allowed
Note: For correct operation, these bits should be configured when the I²S is disabled.
They are not used in SPI mode.
Bit 0 CHLEN: Channel length (number of bits per audio channel)
0: 16-bit wide
1: 32-bit wide
The bit write operation has a meaning only if DATLEN = 00 otherwise the channel length is fixed to
32-bit by hardware whatever the value filled in.
Note: For correct operation, this bit should be configured when the I²S is disabled.
It is not used in SPI mode.
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DocID022558 Rev 5