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 that can accommodate multiple types of applications and communication devices. For example, the One-Wire Half-Duplex mode is useful when low pin count applications are desired. The 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. Data and clock recovery units ensure robust synchronization and noise filtering during asynchronous data reception.