Datasheet

 2017 Microchip Technology Inc. DS60001516A-page 445
SAM9G20
31. Universal Synchronous Asynchronous Receiver Transmitter (USART)
31.1 Overview
The Universal Synchronous Asynchronous Receiver Transceiver (USART) provides one full duplex universal synchronous asynchronous
serial link. Data frame format is widely programmable (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 handling 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 buses, with ISO7816 T = 0 or T = 1 smart card slots, infrared
transceivers and connection to modem ports. The hardware handshaking feature enables an out-of-band flow control by automatic man-
agement 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 management without any intervention of the processor.
31.2 Block Diagram
Figure 31-1: USART Block Diagram
Peripheral DMA
Controller
Channel Channel
AIC
Receiver
USART
Interrupt
RXD
TXD
SCK
USART
PIO
Controller
CTS
RTS
DTR
DSR
DCD
RI
Transmitter
Modem
Signals
Control
Baud Rate
Generator
User Interface
PMC
MCK
SLCK
DIV
MCK/DIV
APB