ST STM32L4+ Series Reference Manual page 1925

RM0432
Figure 564. Tristate strategy on SD output line on an inactive slot
sck
slot Slot 0 ON
SD (output)
slot
Slot 0 ON
SD (output) Data 0
slot
Slot 0 ON
SD (output)
sck
slot Slot 0 ON
SD (output)
slot Slot 0 ON
Data 0
SD (output)
slot Slot 0 ON
SD (output)
When the selected audio protocol uses the FS signal as a start of frame and a channel side
identification (bit FSDEF = 1 in the SAI_xFRCR register), the tristate mode is managed
according to
half frame length is higher than number of slots/2, and NBSLOT=6).
Bit TRIS = 1 in the SAI_xCR1 and frame length = number of slots
Slot 1 OFF
Data 0
Slot 1 OFF
Slot 1 OFF
Bit TRIS = 1 in the SAI_xCR1 and frame length > number of slots
Slot 1 OFF
Data 0
Slot 1 OFF
Slot 1 OFF
Figure 565 (where bit TRIS in the SAI_xCR1 register = 1, and FSDEF=1, and
Audio frame
Slot size = data size
Slot 2 OFF Slot 3 ON
Data 1
Slot size > data size
Slot 2 OFF Slot 3 ON
Data 1
Slot 2 OFF Slot 3 ON
Data 0
Audio frame
Slot size = data size
Slot 2 OFF .. ON
..
Slot size > data size
Slot 2 OFF .. ON
..
Slot 2 OFF .. ON
..
RM0432 Rev 6
Serial audio interface (SAI)
.. ON .. ON
.. ..
.. ON .. ON
.. ..
.. ON .. ON
.. ..
Slot n ON
Data m
Slot n ON
Data m
.. ON
Data m
Slot n ON
Data m
Slot n ON
Data m
Slot n ON
Data m
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