AT32F425
Series Reference Manual
2022.03.30
Page 173
Ver 2.01
13.2.14 Precautions
CRC value is obtained by software reading DT register at the end of CRC reception
In the case of CPOL=1 and CPHA=1, the clock divided by 3 that is generated inside the SPI
must be less than 32 MHz. To achieve a greater communication frequency, it is necessary to use a
clock divided by 2, and adjust the corresponding HCLK and PCLK frequencies. The SPI frequencies
must not exceed the maximum value programmed in the corresponding datasheet.
13.3
I
2
S functional description
13.3.1 I
2
S introduction
The I
2
S can be configured by software as master repection/transmission, and slave
reception/transmission, supporting foure kinds of audio protocols including Philips standard, MSB-
aligned standard, LSB-aligned standard and PCM standard, respectively. The DMA transfer is also
supported.
A single I
2
S supports half-duplex. However, it can work with two additional instantiated I
2
S modules
(I
2
S2EXT and I
2
S3EXT) to achieve full-duplex mode. In other words, combining the I
2
S2 with the
I
2
S2EXT enables the I
2
S2 to support full-duplex mode. This is true for the I
2
S3 through the combination
of the I
2
S3 with the I
2
S3EXT. Refer to I
2
S full-duplex section for more information.
Figure 13-16 I
2
S block diagram
I2S_CLK controller
SPI_STS
BF
ROE
RR
MME
RR
CCE
RR
TUER
R
ACS
TDBE RDBF
Communication controller
WS
controller
I2SCLKPOL
I2SDIV[9:0]
I2SMCLKOE
I2SODD
Transmitter logic
SD
CK
WS
Receiver logic
Receive & transmit date
shift logic
Interrupt generator
ERRIE TEIE RNEIE
MCK
Audio
protocol
selector
PCMFSSEL
STDSEL
I2SDBN
I2SCBN
Operation selector
OPERSEL[1:0]
Main features when the SPI is used as I
2
S:
Programmable operation mode
─
Slave device transmission
─
Slave device reception
─
Master device transmission
─
Master device reception
Programmable clock polarity
Programmable clock frequency (8 KHz to 192 KHz)
Prorammable data bits (16 bit, 24 bit, 32 bit)