ST STM32F405 User Manual

RM0090 Rev 18 933/1749
RM0090 Serial audio interface (SAI)
964
Figure 285. FS role is start of frame + channel side identification (FSDEF = TRIS = 1)
1. The frame length should be even.
If bit FSDEF in SAI_xFRCR is kept clear, so FS signal is equivalent to a start of frame, and
if the number of slots defined in bit NBSLOT[3:0] in SAI_xSLOTR multiplied by
the number of bits by slot configured in bit SLOTSZ[1:0] in SAI_xSLOTR is less than the
frame size (bit FRL[7:0] in the SAI_xFRCR register), then,
• if TRIS = 0 in the SAI_xCR2 register, the remaining bit after the last slot will be forced to
0 until the end of frame in case of transmission,
• if TRIS = 1, the line will be released to HI-Z during the transfer of these remaining bits.
In reception mode, these bits are discarded.
Figure 286. FS role is start of frame (FSDEF = 0)
29.8 Slot configuration
The slot is the basic element in the audio frame. The number of slots in the audio frame is
equal to the configured setting of bit NBSLOT[3:0] in the SAI_xSLOTR register +1.
The maximum number of slots per audio frame is fixed at 16.
For AC’97 protocol (when bit PRTCFG[1:0] = 10), the number of slots is automatically set to
target the protocol specification, and the value of NBSLOT[3:0] is ignored.
sck
slot
Audio frame
FS
Half of frame
Audio frame
FS
Half of frame
Number of slots not aligned with the audio frame
Number of slots aligned with the audio frame
MS30038V1
Slot 0
sck
slot
Slot 1 Slot 2
Slot 3 Slot 5
Slot 4
Slot 0 ON Slot 1 OFF
Slot 2 ON
Slot 3 ON Slot 4 OFF
Slot 5 ON
Audio frame
Data = 0 after slot n if TRIS = 0
SD output released (HI-Z) after slot n if TRIS = 1
MS30039V1
sck
slot
Slot 0 Slot 1
Slot 2 Slot n
...

ST STM32F405 Specifications

General

Brand	ST
Model	STM32F405
Category	Computer Hardware
Language	English