Data Sheet

Atmel | SMART SAM D21 [DATASHEET]

Atmel-42181G–SAM-D21_Datasheet–09/2015

25. SERCOM USART – SERCOM Universal Synchronous and Asynchronous

Receiver and Transmitter

25.1 Overview

The universal synchronous and asynchronous receiver and transmitter (USART) is one of the available modes in the

Serial Communication Interface (SERCOM).

Refer to “SERCOM – Serial Communication Interface” on page 432 for details.

The USART uses the SERCOM transmitter and receiver configured as shown in Figure 25-1. Fields shown in capital

letters are synchronous to the CLK_SERCOMx_APB and accessible by the CPU, while fields with lowercase letters can

be configured to run on the internal generic clock or an external clock.

The transmitter consists of a single write buffer, a shift register and control logic for handling different frame formats. The

write buffer allows continuous data transmission without any delay between frames.

The receiver consists of a two-level receive buffer and a shift register. Status information for the received data is

available for error checking. Data and clock recovery units ensure robust synchronization and noise filtering during

asynchronous data reception.

25.2 Features

z Full-duplex operation

z Asynchronous (with clock reconstruction) or synchronous operation

z Internal or external clock source for asynchronous and synchronous operation

z Baud-rate generator

z Supports serial frames with 5, 6, 7, 8 or 9 data bits and 1 or 2 stop bits

z Odd or even parity generation and parity check

z Selectable LSB- or MSB-first data transfer

z Buffer overflow and frame error detection

z Noise filtering, including false start-bit detection and digital low-pass filter

z Collision detection

z Can operate in all sleep modes

z Operation at speeds up to half the system clock for internally generated clocks

z Operation at speeds up to the system clock for externally generated clocks

z RTS and CTS flow control

z IrDA modulation and demodulation up to 115.2 kbps

z LIN slave support

z Auto-baud and break character detection

z Start-of-frame detection

z Can be used with DMA