577
6437E–ATARM–23-Apr-13
SAM9M11
33. Universal Synchronous Asynchronous Receiver Transmitter (USART)
33.1
Description
The Universal Synchronous Asynchronous Receiver Transmitter (USART) provides one full
duplex universal synchronous asynchronous serial link. Data frame format is widely programma-
ble (data length, parity, number of stop bits) to support a maximum of standards. The receiver
implements parity error, framing error and overrun error detection. The receiver time-out enables
handling variable-length frames and the transmitter timeguard facilitates communications with
slow remote devices. Multidrop communications are also supported through address bit han-
dling in reception and transmission.
The USART features three test modes: remote loopback, local loopback and automatic echo.
The USART supports specific operating modes providing interfaces on RS485, LIN and SPI
buses, with ISO7816 T = 0 or T = 1 smart card slots and infrared transceivers. The hardware
handshaking feature enables an out-of-band flow control by automatic management of the pins
RTS and CTS.
The USART supports the connection to the Peripheral DMA Controller, which enables data
transfers to the transmitter and from the receiver. The PDC provides chained buffer manage-
ment without any intervention of the processor.
33.2
Embedded Characteristics
Programmable Baud Rate Generator
5- to 9-bit full-duplex synchronous or asynchronous serial communications
– 1, 1.5 or 2 stop bits in Asynchronous Mode or 1 or 2 stop bits in Synchronous Mode
– Parity generation and error detection
– Framing error detection, overrun error detection
– MSB- or LSB-first
– Optional break generation and detection
– By 8 or by-16 over-sampling receiver frequency
– Hardware handshaking RTS-CTS
– Receiver time-out and transmitter timeguard
– Optional Multi-drop Mode with address generation and detection
– Optional Manchester Encoding
RS485 with driver control signal
ISO7816, T = 0 or T = 1 Protocols for interfacing with smart cards
– NACK handling, error counter with repetition and iteration limit
IrDA modulation and demodulation
– Communication at up to 115.2 Kbps
Test Modes
– Remote Loopback, Local Loopback, Automatic Echo