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Serial peripheral interface/ inter-IC sound (SPI/I2S) RM0402

838/1163 RM0402 Rev 6

Figure 285. I

S Philips protocol waveforms (16/32-bit full accuracy, CPOL = 0)

Data are latched on the falling edge of CK (for the transmitter) and are read on the rising

edge (for the receiver). The WS signal is also latched on the falling edge of CK.

Figure 286. I

S Philips standard waveforms (24-bit frame with CPOL = 0)

This mode needs two write or read operations to/from the SPIx_DR register.

• In transmission mode:

If 0x8EAA33 has to be sent (24-bit):

Figure 287. Transmitting 0x8EAA33

• In reception mode:

If data 0x8EAA33 is received:

MS19591V1

Can be 16-bit or 32-bit

MSB

MSBLSB

Channel left

Channel

right

transmission reception

MS19592V1

Transmission Reception

24-bit data

MSB

LSB

Channel left 32-bit

Channel right

8-bit remaining 0 forced

MS19593V1

0x8EAA 0x33XX

First write to Data register Second write to Data register

Only the 8 MSB are sent

to compare the 24 bits

8 LSBs have no meaning

and can be anything

ST STM32F412 User Manual

Questions and Answers: