DocID024597 Rev 3 1339/1693
RM0351 Serial audio interface (SAI)
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It is important to note that the two transmitters cannot attempt to drive the same SD output
pin simultaneously, which could result in a short circuit. To ensure a gap between
transmissions, if the data is lower than 32-bit, the data can be extended to 32-bit by setting
bit SLOTSZ[1:0] = 10 in the SAI_xSLOTR register. The SD output pin will then be tri-stated
at the end of the LSB of the active slot (during the padding to 0 phase to extend the data to
32-bit) if the following slot is declared inactive.
In addition, if the number of slots multiplied by the slot size is lower than the frame length,
the SD output line will be tri-stated when the padding to 0 is done to complete the audio
frame.
Figure 448 illustrates these behaviors.