Intel
®
81341 and 81342—UARTs
Intel
®
81341 and 81342 I/O Processors
Developer’s Manual
December 2007
880
Order Number: 315037-002US
The UART hardware is responsible for executing serial protocol communication and for
providing the programming interface. The UART features include:
• Registers are compatible with the 16550 and 16750
• Adds or deletes standard asynchronous communications bits (start, stop, and
parity) to or from the serial data
• Independently controlled transmit, receive, line status and data set interrupts
• Baud-rate generator allows division of clock by 1 to (2
16 –
1) and generates an
internal 16X clock; baud-rate can be manually or automatically programmed via
auto-baud-rate detection circuitry
• Modem control functions (CTS#, RTS#)
• Autoflow capability controls data I/O without generating Interrupts:
— RTS# (output) controlled by UART Receiver FIFO
— CTS# (input) from modem controls UART transmitter
• Fully programmable serial-interface characteristics:
— 5, 6, 7 or 8-bit characters
— Even, odd, or no parity detection
— 1, 1-1/2, or 2 stop bit generation
— Baud rate generation (up to 115kbps)
• False start bit detection
• 64-byte Transmit FIFO
• 64-byte Receive FIFO with programmable threshold
• Complete status reporting capability
• Break generation and detection
• Internal diagnostic capabilities include:
— Loopback controls for communications link fault isolation
— Break, parity, overrun, and framing error simulation
• Fully prioritized interrupt system controls
15.1.1
Compatibility with 16550 and 16750
The UARTs can be programmed to be functionally compatible with industry standard
16550 and 16750. Each UART supports most of the 16550 and 16750 functions and has
additional features, as listed below.
• DMA requests for transmit and receive data services
• NRZ encoding/decoding function
• 64 byte Transmit/Receive FIFO buffers
• Programmable Receive FIFO threshold
• Auto baud-rate detection
• Auto flow