The USART is a full-duplex synchronous/asynchronous receiver-transmitter proven in high-volume devices from National Semiconductor and available exclusively from IPextreme as synthesizable IP.
The USART supports a wide range of software programmable baud rates and data formats and operates in either Synchronous or Asynchronous (UART) mode. It implements automatic parity generation and several error detection schemes. The USART is capable of detecting a wakeup pattern to selectively enable the receiver and implements flow control logic for hardware handshaking.
The host interface of the USART complies with the AMBA 2.0 APB protocol. Control registers within the USART provide CPU control of baud rate, frame format, wakeup pattern detection, operating mode, and enabling/disabling interrupts. Status registers provide interrupt and error status. In addition, there are registers that hold the transmit/receive data.
In Asynchronous (UART) mode, the USART communicates with other devices using two signals: transmit (TDX) and receive (RDX). In Synchronous mode, the USART communicates with other devices using three signals: transmit (TDX), receive (RDX), and clock (CKX); data bits are transferred synchronously with the CKX signal. Flow control is available in both Asynchronous and Synchronous modes through RTS/CTS signaling.
To reduce chip-level pin count, the USART interface signals can be shared with other on-chip functions through a General Purpose I/O (GPIO) Controller.
- Full-duplex double-buffered receiver/transmitter
- Synchronous operation using the CKX clock pin
- CKX can be generated internally or externally
- Asynchronous (UART) operation
- Programmable baud rate between CLK/2 and CLK/32768 baud
- Programmable frame formats
- 7, 8, or 9 data bits
- 1 or 2 stop bits
- Odd, even, mark, space, or no parity
- Hardware support of parity-bit generation during transmission and parity-bit check during reception
- Software-controlled break transmission and detection
- Interrupt on transmit buffer empty, receive buffer full, receive error, and delta clear-to-send (flow control mode) conditions, each with a separate interrupt enable
- Internal diagnostic capability
- Automatic error detection
- Parity error
- Framing error
- Data overrun error
- 9-bit Attention mode
- DMA support for transmit and receive with separate enables
- Hardware flow control functions
- Clear-to-send (CTS)
- Request-to-send (RTS)
- Wakeup pattern detection according to ISO14230/KWP2000
- Debug support: Freeze/suspend USART activity