Datasheet

523
11011B–ATARM–21-Feb-12
SAM3N
523
11011B–ATARM–21-Feb-12
SAM3N
30. Universal Synchronous Asynchronous Receiver Transmitter (USART)
30.1 Description
The Universal Synchronous Asynchronous Receiver Transceiver (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 and SPI buses,
with ISO7816 T = 0 or T = 1 smart card slots and infrared transceivers (ISO7816 only on
USART0). 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.
30.2 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
– Optional Hardware Handshaking RTS-CTS
– Receiver Time-out and Transmitter Timeguard
– Optional Multidrop Mode with Address Generation and Detection
• RS485 with Driver Control Signal
• ISO7816, T = 0 or T = 1 Protocols for Interfacing with Smart Cards (Only on USART0)
– NACK Handling, Error Counter with Repetition and Iteration Limit
• IrDA Modulation and Demodulation (Only on USART0)
– Communication at up to 115.2 Kbps
• SPI Mode
–Master or Slave
– Serial Clock Programmable Phase and Polarity
– SPI Serial Clock (SCK) Frequency up to Internal Clock Frequency MCK/6
• Test Modes
– Remote Loopback, Local Loopback, Automatic Echo
• Supports Connection of Two Peripheral DMA Controller Channels (PDC)
– Offers Buffer Transfer without Processor Intervention