Figure 341. Slot Size Configuration With Fboff = 0 In Sai_Xslotr - ST STM32F413 Reference Manual

Serial audio interface (SAI)
Each slot can be defined as a valid slot, or not, by setting bit SLOTEN[15:0] in the
SAI_xSLOTR register. In an audio frame, during the transfer of a non-valid slot, 0 value will
be forced on the data line or the SD data line will be released to HI-z (refer to
Section 30.12.4) if the audio block is transmitter, or the received value from the end of this
slot will be ignored. Consequently, there will be no FIFO access and so no request to read
or write the FIFO linked to this inactive slot status.
The slot size is also configurable as shown in the
selected by setting bit SLOTSZ[1:0] in the SAI_xSLOTR register. The size is applied
identically for each slot in an audio frame.
It is possible to choose the position of the first data bit to transfer within the slots, this offset
is configured by bit FBOFF[5:0] in the SAI_xSLOTR register. 0 values will be injected in
transmitter mode from the beginning of the slot until this offset position is reached. In
reception, the bit in the offset phase is ignored. This feature targets the LSB justified
protocol (if the offset is equal to the slot size minus the data size).
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Figure 341. Slot size configuration with FBOFF = 0 in SAI_xSLOTR

DocID029473 Rev 3
Figure 341.
Figure 342. First bit offset
RM0430
The size of the slots is