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Universal synchronous asynchronous receiver transmitter (USART) RM0090

958/1731 DocID018909 Rev 11

30 Universal synchronous asynchronous receiver

transmitter (USART)

This section applies to the whole STM32F4xx family, unless otherwise specified.

30.1 USART 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 fractional baud rate generator.

It supports synchronous one-way communication and half-duplex single wire

communication. It also supports the LIN (local interconnection network), Smartcard Protocol

and IrDA (infrared data association) SIR ENDEC specifications, and modem operations

(CTS/RTS). It allows multiprocessor communication.

High speed data communication is possible by using the DMA for multibuffer configuration.

30.2 USART main features

• Full duplex, asynchronous communications

• NRZ standard format (Mark/Space)

• Configurable oversampling method by 16 or by 8 to give flexibility between speed and

clock tolerance

• Fractional baud rate generator systems

– Common programmable transmit and receive baud rate (refer to the datasheets

for the value of the baud rate at the maximum APB frequency.

• Programmable data word length (8 or 9 bits)

• Configurable stop bits - support for 1 or 2 stop bits

• LIN Master Synchronous Break send capability and LIN slave break detection

capability

– 13-bit break generation and 10/11 bit break detection when USART is hardware

configured for LIN

• Transmitter clock output for synchronous transmission

• IrDA SIR encoder decoder

– Support for 3/16 bit duration for normal mode

• Smartcard emulation capability

– The Smartcard interface supports the asynchronous protocol Smartcards as

defined in the ISO 7816-3 standards

– 0.5, 1.5 stop bits for Smartcard operation

• Single-wire half-duplex communication

• Configurable multibuffer communication using DMA (direct memory access)

– Buffering of received/transmitted bytes in reserved SRAM using centralized DMA

• Separate enable bits for transmitter and receiver

STMicroelectronics STM32F407 User Manual

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