Transmitter (Usart) - ST STM32L4x6 Reference Manual

Universal synchronous asynchronous receiver transmitter (USART)
36 Universal synchronous asynchronous receiver

transmitter (USART)

36.1 Introduction
The universal synchronous asynchronous receiver transmitter (USART) offers a flexible
means of full-duplex data exchange with external equipment requiring an industry standard
NRZ asynchronous serial data format. The USART offers a very wide range of baud rates
using a programmable baud rate generator.
It supports synchronous one-way communication and half-duplex single wire
communication, as well as multiprocessor communications. It also supports the LIN (Local
Interconnect Network), smartcard protocol and IrDA (Infrared Data Association) SIR
ENDEC specifications and modem operations (CTS/RTS).
High speed data communication is possible by using the DMA (direct memory access) for
multibuffer configuration.
36.2 USART main features
•
Full-duplex asynchronous communications
•
NRZ standard format (mark/space)
•
Configurable oversampling method by 16 or 8 to give flexibility between speed and
clock tolerance
•
A common programmable transmit and receive baud rate of up to 10 Mbit/s when the
clock frequency is 80 MHz and oversampling is by 8
•
Dual clock domain allowing:
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–
• Auto baud rate detection
•
Programmable data word length (7, 8 or 9 bits)
• Programmable data order with MSB-first or LSB-first shifting
•
Configurable stop bits (1 or 2 stop bits)
• Synchronous mode and clock output for synchronous communications
•
Single-wire half-duplex communications
• Continuous communications using DMA
•
Received/transmitted bytes are buffered in reserved SRAM using centralized DMA
• Separate enable bits for transmitter and receiver
•
Separate signal polarity control for transmission and reception
• Swappable Tx/Rx pin configuration
•
Hardware flow control for modem and RS-485 transceiver
1178/1693
USART functionality and wakeup from Stop mode
Convenient baud rate programming independent from the PCLK reprogramming
DocID024597 Rev 3
RM0351