ST STM32L4x6 User Manual

Serial audio interface (SAI) RM0351
1332/1693 DocID024597 Rev 3
39.3.9 AC’97 link controller
The SAI is able to work as an AC’97 link controller. In this protocol:
• The slot number and the slot size are fixed.
• The frame synchronization signal is perfectly defined and has a fixed shape.
To select this protocol, set PRTCFG[1:0] bits in the SAI_xCR1 register to 10. When AC’97
mode is selected, only data sizes of 16 or 20 bits can be used, otherwise the SAI behavior is
not guaranteed.
• NBSLOT[3:0] and SLOTSZ[1:0] bits are consequently ignored.
• The number of slots is fixed to 13 slots. The first one is 16-bit wide and all the others
are 20-bit wide (data slots).
• FBOFF[4:0] bits in the SAI_xSLOTR register are ignored.
• The SAI_xFRCR register is ignored.
• The MCLK is not used.
The FS signal from the block defined as asynchronous is configured automatically as an
output, since the AC’97 controller link drives the FS signal whatever the master or slave
configuration.
Figure 443 shows an AC’97 audio frame structure.
Figure 443. AC’97 audio frame
Note: In AC’97 protocol, bit 2 of the tag is reserved (always 0), so bit 2 of the TAG is forced to 0
level whatever the value written in the SAI FIFO.
For more details about tag representation, refer to the AC’97 protocol standard.
One SAI can be used to target an AC’97 point-to-point communication.
Using two SAIs (for devices featuring two embedded SAIs) allows controlling three external
AC’97 decoders as illustrated in Figure 444.
In SAI1, the audio block A must be declared as asynchronous master transmitter whereas
the audio block B is defined to be slave receiver and internally synchronous to the audio
block A.
The SAI2 is configured for audio block A and B both synchronous with the external SAI1 in
slave receiver mode.
069
)6
        
6',
6'2
7DJ
&0'
$''5
&0'
'$7$
/,1(
'$&
3&0
/)5217
3&0
5)5217
3&0
&(17(5
3&0
/6855
3&0
56855
3&0
/)(
/,1(
'$&
+6(7
'$&
,2
&75/
7DJ
67$786
$''5
67$786
'$7$
/,1(
$'&
3&0
/()7
3&0
5,*+7
3&0
0,&
565
9'
565
/9'
/,1(
$'&
+6(7
,2
67$786
565
9'

ST STM32L4x6 Specifications

General

Brand	ST
Model	STM32L4x6
Category	Microcontrollers
Language	English