25.2 Overview

The Universal Synchronous and Asynchronous serial Receiver and Transmitter (USART) is a fast and flexible serial communication peripheral. The USART supports several different modes of operation, accommodating multiple types of applications and communication devices. For example, the One-Wire Half-Duplex mode is useful in low pin-count applications. Communication is frame-based, and the frame format can be customized to support a wide range of standards.

The USART is buffered in both directions, enabling continued data transmission without any delay between frames. Separate interrupts for receive and transmit completion allow fully interrupt-driven communication.

The transmitter consists of a two-level write buffer, a shift register, and control logic for different frame formats. The receiver consists of a two-level receive buffer and a shift register. The status information of the received data is available for error checking, and a separate error interrupt is available. Data and clock recovery units ensure robust synchronization and noise filtering during asynchronous data reception.

Interfaces such as RS-485 and LIN is supported in hardware. The USART also includes specialized hardware to accelerate encoding and decoding of various communication protocols, and includes sophisticated error handling mechanisms such as Collision Detection with automatic disabling of the transmitter.