Clock Generator; Figure 281. Pcm Standard Waveforms (16-Bit Extended To 32-Bit Packet Frame); Figure 282. Audio Sampling Frequency Definition - ST STM32F207 Series Reference Manual

Serial peripheral interface (SPI)

Figure 281. PCM standard waveforms (16-bit extended to 32-bit packet frame)

Note: For both modes (master and slave) and for both synchronizations (short and long), the
number of bits between two consecutive pieces of data (and so two synchronization signals)
needs to be specified (DATLEN and CHLEN bits in the SPI_I2SCFGR register) even in
slave mode.
25.4.3

Clock generator

2
The I S bitrate determines the dataflow on the I
frequency.
2
I S bitrate = number of bits per channel × number of channels × sampling audio frequency
For a 16-bit audio, left and right channel, the I
2
I S bitrate = 16 × 2 × F
It will be: I
When the master mode is configured, a specific action needs to be taken to properly
program the linear divider in order to communicate with the desired audio frequency.
716/1381
CK
WS
short frame
Up to 13-bits
WS
long frame
SD
MSB
S
2
S bitrate = 32 x 2 x F

Figure 282. Audio sampling frequency definition

16-or 32-bit left
sampling point
F : audio sampling frequency
S
16 bits
LSB
2
S data line and the I
2
S bitrate is calculated as follows:
if the packet length is 32-bit wide.
S
16-or 32-bit
right channel
channel
32- or 64-bits
F
S
RM0033 Rev 9
2
S clock signal
sampling point
RM0033
MS30107V1
MS30108V1