Description
STM32F21xxx
Table 4. USART feature comparison
USART
name
Standard Modem
features (RTS/CTS)
LIN
SPI
master
irDA
Max. baud rate Max. baud rate
Smartcard in Mbit/s
in Mbit/s
(ISO 7816) (oversampling (oversampling
by 16)
by 8)
APB
mapping
USART1 X
X
XX
X
X
1.87
7.5
APB2 (max.
60 MHz)
USART2 X
X
XX
X
X
1.87
3.75
APB1 (max.
30 MHz)
USART3 X
X
XX
X
X
1.87
3.75
APB1 (max.
30 MHz)
UART4 X
-
X
-
X
-
1.87
3.75
APB1 (max.
30 MHz)
UART5 X
-
X
-
X
-
3.75
3.75
APB1 (max.
30 MHz)
USART6 X
X
XX
X
X
3.75
7.5
APB2 (max.
60 MHz)
2.2.23
2.2.24
Serial peripheral interface (SPI)
The STM32F21x devices feature up to three SPIs in slave and master modes in full-duplex
and simplex communication modes. SPI1 can communicate at up to 30 Mbits/s, while SPI2
and SPI3 can communicate at up to 15 Mbit/s. The 3-bit prescaler gives 8 master mode
frequencies and the frame is configurable to 8 bits or 16 bits. The hardware CRC
generation/verification supports basic SD Card/MMC modes. All SPIs can be served by the
DMA controller.
The SPI interface can be configured to operate in TI mode for communications in master
mode and slave mode.
Inter-integrated sound (I2S)
Two standard I2S interfaces (multiplexed with SPI2 and SPI3) are available. They can
operate in master or slave mode, in half-duplex communication modes, and can be
configured to operate with a 16-/32-bit resolution as input or output channels. Audio
sampling frequencies from 8 kHz up to 192 kHz are supported. When either or both of the
I2S interfaces is/are configured in master mode, the master clock can be output to the
external DAC/CODEC at 256 times the sampling frequency.
All I2Sx interfaces can be served by the DMA controller.
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Doc ID 17050 Rev 8