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Universal synchronous asynchronous receiver transmitter (USART) RM0351

1302/1830 DocID024597 Rev 5

40 Universal synchronous asynchronous receiver

transmitter (USART)

40.1 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.

40.2 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:

– USART functionality and wakeup from Stop mode

– Convenient baud rate programming independent from the PCLK reprogramming

• 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

ST STM32L4 5 Series User Manual

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