17-2 Intel® PXA255 Processor Developer’s Manual
Hardware UART
— Non-Return-to-Zero (NRZ) encoding/decoding function
— 64 byte transmit/receive FIFO buffers
— Programmable receive FIFO trigger threshold
— Auto baud-rate detection
— Auto flow
•Maximum baud rate of 921,600bps.
•Ability to add or delete standard asynchronous communications bits (start, stop, and parity) in
the serial data
•Independently controlled transmit, receive, line status, and data set interrupts
•Programmable baud rate generator that allows the internal clock to be divided by 1 to 216–1 to
generate an internal 16X clock. This clock can be used to drive the internal transmitter and
receiver logic.
•Modem control functions – clear to send (nCTS) and request to send (nRTS)
•Autoflow capability controls data I/O withou t ge nerating interrupts:
— nRTS (output) controlled by UART receiver FIFO
— nCTS (input) from modem controls UART transmitter
•Fully programmable serial-interface:
— 5-, 6-, 7-, or 8-bit characters
— Even, odd, and no parity detection
— 1, 1.5, or 2 stop bit generation
— Baud rate generation up to 921Kbps
— False start bit detection.
•64-byte transmit FIFO
•64-byte receive FIFO
•Complete status reporting capability
•Ability to generate and detect line breaks
•Internal diagnostic capabilities that include:
— Loopback controls for communications link fault isolation
— Break, parity, and framing error sim ulation
•Fully prioritized interrupt system controls
•Separate DMA requests for transmit and receive data services
•Slow infrared asynchronous interface that conforms to the Infrared Data Association (IrDA)
standard