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AT32F435/437
Series Reference Manual
2022.11.11
Page 233
Rev 2.03
Programmable audio protocol
─
I
2
S Philips standard
─
MSB-aligned standard (left-aligned)
─
LSB-aligned standard (right-aligned)
─
PCM standard (long or short frame)
I
2
S full-duplex
DMA transfer
Main peripheral clock with a fixed frequency of 256x Fs (audio sampling frequency)
13.3.2 I
2
S full-duplex
Two extra I
2
S modules (I
2
S2EXT and I
2
S3EXT) are used to support I
2
S full-duplex mode. Combine
the I
2
S2 with the I
2
S2EXT, and I
2
S3 with I
2
S3EXT
to support full-duplex mode.
Note: I
2
S2EXT and I
2
S3EXT only used for I
2
S full-duplex mode.
Figure 13-17 I
2
S full-duplex structure
SPI/I
2
S
I
2
SxEXT
I2Sx_SCK
I2Sx_WS
SPIx_MOSI/I2Sx_SD(in/out)
I2Sx_SDext(in/out)
I
2
Sx can be used as master, where x should be 2 or 3
In half-duplex mode, only I
2
Sx can output SCK and WS
In full-duplex mode, only I
2
Sx can output SCK and WS
I
2
SxEXT is only used for full-duplex mode, and I
2
SxEXT only for slave mode
Both the I
2
Sx and I
2
SxEXT can be configured as transmit or receive mode.
13.3.3 Operating mode selector
The SPI, used as I
2
S selector, offers multiple operating modes for selection, namely, slave device
transmission, slave device reception, master device transmission and master device reception. This is
done by software configuration.
Slave device transmission:
Set the I2SMSEL bit, and OPERSEL[1:0] =00, the I
2
S will work in slave device transmission mode.
Figure 13-18 I
2
S slave device transm ission
I2S master
CK
SD
WS
I2S slave
CK
SD
WS