
Universal synchronous asynchronous receiver transmitter (USART)
RM0351
1304/1830
DocID024597 Rev 5
40.4 USART
implementation
The STM32L4x5/STM32L4x6 devices embed 3 USARTs, 2 UARTs and 1 LPUART. The
describes the features supported by each peripheral.
Note:
In the STM32L496xx/4A6xx devices only, bit TCBGT in USART_ISR, bit TCBGTIE in
USART_CR3 and bit TCBGTCF in USART_ICR are available, allowing detecting the
character end of transmission without waiting until the end of the guard time completion.
40.5
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.
Table 232. STM32L4x5/STM32L4x6 USART/UART/LPUART features
USART modes/features
(1)
USART1 USART2 USART3 UART4
UART5
LPUART1
Hardware flow control for modem
X
X
X
X
X
X
Continuous communication using DMA
X
X
X
X
X
X
Multiprocessor communication
X
X
X
X
X
X
Synchronous mode
X
X
X
-
-
-
Smartcard mode
X
X
X
-
-
-
Single-wire Half-duplex communication
X
X
X
X
X
X
IrDA SIR ENDEC block
X
X
X
X
X
-
LIN mode
X
X
X
X
X
-
Dual clock domain and wakeup from Stop mode
X
X
X
X
X
X
Receiver timeout interrupt
X
X
X
X
X
-
Modbus communication
X
X
X
X
X
-
Auto baud rate detection
X (4 modes)
-
Driver Enable
X
X
X
X
X
X
LPUART/USART data length
7, 8 and 9 bits
1. X = supported.