ST STM32F301 6 Series Reference Manual page 714

Universal synchronous/asynchronous receiver transmitter (USART/UART)
26.4 USART implementation
Hardware flow control for modem
Continuous communication using DMA
Multiprocessor communication
Synchronous mode
Smartcard mode
Single-wire half-duplex communication
IrDA SIR ENDEC block
LIN mode
Dual clock domain and wake-up from Stop mode
Receiver timeout interrupt
Modbus communication
Auto baud rate detection
Driver Enable
USART data length
1. X = supported.
2. With CK always available when CLKEN = 1, regardless of the UE bit value.
3. In 7-bit data length mode, smartcard mode, LIN master mode and Auto baud rate (0x7F and 0x55 frame
detection) are not supported.
26.5 USART functional description
Any USART bidirectional communication requires a minimum of two pins: Receive data In
(RX) and Transmit data Out (TX):
•
RX: Receive data Input.
This is the serial data input. Oversampling techniques are used for data recovery by
discriminating between valid incoming data and noise.
•
TX: Transmit data Output.
When the transmitter is disabled, the output pin returns to its I/O port configuration.
When the transmitter is enabled and nothing is to be transmitted, the TX pin is at high
level. In single-wire and smartcard modes, this I/O is used to transmit and receive the
data.
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Table 99. STM32F3xx USART features
USART modes/features
RM0366 Rev 5
(1)
RM0366
USART2/
USART1
USART3
X X
X X
X X
X X
(2)
X -
X X
X -
X -
X -
X -
X -
X (4 modes) -
X X
(3)
7 , 8 and 9 bits