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 921,600 bps.

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 without generating 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 921 Kbps

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 simulation

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

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Intel® PXA255 Processor Developer’s Manual

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Intel PXA255 manual Hardware Uart