Figure 358. Slot Size Configuration With Fboff = 0 In Sai_Xslotr; Figure 359. First Bit Offset - ST STM32F446 Series Reference Manual

Serial audio interface (SAI)
It is possible to choose the position of the first data bit to transfer within the slots. This offset
is configured by FBOFF[4:0] bits 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).
It is mandatory to respect the following conditions to avoid bad SAI behavior:
FBOFF ≤(SLOTSZ - DS),
DS ≤SLOTSZ,
NBSLOT x SLOTSZ ≤FRL (frame length),
The number of slots must be even when bit FSDEF in the SAI_xFRCR register is set.
In AC'97 and SPDIF protocol (bit PRTCFG[1:0] = 10 or PRTCFG[1:0] = 01), the slot size is
automatically set as defined in
940/1328

Figure 358. Slot size configuration with FBOFF = 0 in SAI_xSLOTR

Section 28.3.10: AC'97 link

Figure 359. First bit offset

RM0390 Rev 4
controller.
RM0390