RM0440 Rev 4 1795/2126
RM0440 Serial audio interface (SAI)
1858
The audio subblock can be a transmitter or receiver, in master or slave mode. The master
mode means the SCK_x bit clock and the frame synchronization signal are generated from
the SAI, whereas in slave mode, they come from another external or internal master. There
is a particular case for which the FS signal direction is not directly linked to the master or
slave mode definition. In AC’97 protocol, it will be an SAI output even if the SAI (link
controller) is set-up to consume the SCK clock (and so to be in Slave mode).
Note: For ease of reading of this section, the notation SAI_x refers to SAI_A or SAI_B, where ‘x’
represents the SAI A or B subblock.
40.3.2 SAI pins and internal signals
40.3.3 Main SAI modes
Each audio subblock of the SAI can be configured to be master or slave via MODE bits in
the SAI_xCR1 register of the selected audio block.
Master mode
In master mode, the SAI delivers the timing signals to the external connected device:
• The bit clock and the frame synchronization are output on pin SCK_x and FS_x,
respectively.
• If needed, the SAI can also generate a master clock on MCLK_x pin.
Both SCK_x, FS_x and MCLK_x are configured as outputs.
Table 362. SAI internal input/output signals
Internal signal name Signal type Description
sai_a_gbl_it/
sai_b_gbl_it
Output Audio block A and B global interrupts.
sai_a_dma,
sai_b_dma
Input/output Audio block A and B DMA acknowledges and requests.
sai_a_ker_ck/
sai_b_ker_ck
Input Audio block A/B kernel clock.
sai_pclk Input APB clock.
Table 363. SAI input/output pins
Name Signal type Comments
SAI_SCK_A/B Input/output Audio block A/B bit clock.
SAI_MCLK_A/B Output Audio block A/B master clock.
SAI_SD_A/B Input/output Data line for block A/B.
SAI_FS_A/B Input/output Frame synchronization line for audio block A/B.
SAI_CK[4:1] Output PDM bitstream clock.
SAI_D[4:1] Input PDM bitstream data.
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