Clock Generator; Figure 280. Pcm Standard Waveforms (16-Bit); Figure 281. Pcm Standard Waveforms (16-Bit Extended To 32-Bit Packet Frame) - STMicroelectronics STM32F05 series Reference Manual

Serial peripheral interface / inter-IC sound (SPI/I2S)
PCM standard
For the PCM standard, there is no need to use channel-side information. The two PCM
modes (short and long frame) are available and configurable using the PCMSYNC bit in
SPIx_I2SCFGR register.

Figure 280. PCM standard waveforms (16-bit)

For long frame synchronization, the WS signal assertion time is fixed to 13 bits in master
mode.
For short frame synchronization, the WS synchronization signal is only one cycle long.

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 SPIx_I2SCFGR register) even in
slave mode.
26.6.3

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
660/742
CK
WS
short
frame
WS
long
frame
SD
MSB
CK
WS
short
frame
Up to 13-bits
WS
long
frame
SD
MSB
S
2
S bitrate = 32 x 2 x f
S
Doc ID 018940 Rev 1
13-bits
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.
LSB MSB
MS30106V1
MS30107V1
2
S clock signal
RM0091