Datasheet

264
XMEGA B [DATASHEET]
8291B–AVR–01/2013
21. USART
21.1 Features
 Full-duplex operation
 Asynchronous or synchronous operation
 Synchronous clock rates up to 1/2 of the device clock frequency
 Asynchronous clock rates up to 1/8 of the device clock frequency
 Supports serial frames with 5, 6, 7, 8, or 9 data bits and 1 or 2 stop bits
 Fractional baud rate generator
 Can generate desired baud rate from any system clock frequency
 No need for external oscillator with certain frequencies
 Built-in error detection and correction schemes
 Odd or even parity generation and parity check
 Data overrun and framing error detection
 Noise filtering includes false start bit detection and digital low-pass filter
 Separate interrupts for
 Transmit complete
 Transmit data register empty
 Receive complete
 Multiprocessor communication mode
 Addressing scheme to address a specific devices on a multi-device bus
 Enable unaddressed devices to automatically ignore all frames
 Master SPI mode
 Double buffered operation
 Configurable data order
 Operation up to 1/2 of the peripheral clock frequency
 IRCOM module for IrDA compliant pulse modulation/demodulation
21.2 Overview
The universal synchronous and asynchronous serial receiver and transmitter (USART) is a fast and flexible serial
communication module. The USART supports full-duplex communication and asynchronous and synchronous operation.
The USART can be configured to operate in SPI master mode and used for SPI communication.
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 complete enable fully interrupt driven communication. Frame error and buffer overflow
are detected in hardware and indicated with separate status flags. Even or odd parity generation and parity check can
also be enabled.
A block diagram of the USART is shown in Figure 21-1 on page 265. The main functional blocks are the clock generator,
the transmitter, and the receiver, which are indicated in dashed boxes.