User's Manual

3.3.3 UART Ports

Two RS-232/422/485 ports and two RS-232 ports on the rear panel for communicating with

external devices. COM1~COM4 are located on the rear panel via 9-pin D-Sub male

connectors. COM 1/2 can be configured for full RS-232, RS-422 or RS-485 with auto flow

control communication. Mode selection is by BIOS, the default definition is RS-232.

Each of the serial ports individually contains a programmable baud rate generator which is

capable of dividing the input clock by a number ranging from 1 to 65535. The data rate of

each serial port can be programmed from 115.2K baud (COM1 baud rate up to 912.6Kbit/s)

and down to 50 baud. The character options are programmable for 1 start bit; 1, 1.5 or 2

stop bits; even, odd, stick or no parity; and privileged interrupts. Each port supports 128

bytes RX FIFO depths and 16 bytes TX FIFO depths.

All transmitter outputs and receiver inputs feature robust electrostatic discharge (ESD)

protection to ±15kV Human Body Model (HBM) and ±8kV IEC- 61000-4-2 Contact. Each

receiver output has full fail-safe protection to avoid system lockup, oscillation, or

indeterminate states by defaulting to logic-high output level when the inputs are open,

shorted, or terminated but undriven.

The following table describes the pin definition of UART ports.

COM1, COM2:

UART mode RS-232

RS-422

(5-wire)

RS-422

(9-wire)

RS-485

(3-wire)

D-Sub 9 Male

COM1,COM2

Pin 1 DCD# TxD- TxD- Data-

Pin 2 RxD TxD+ TxD+ Data+

Pin 3 TxD RxD+ RxD+ -

Pin 4 DTR# RxD- RxD- -

Pin 5 GND GND GND GND

Pin 6 DSR - RTS- -

Pin 7 RTS# - RTS+ -

Pin 8 CTS# - CTS+ -

Pin 9 RI# - CTS- -

COM3, COM4:

UART mode RS-232 Description

D-Sub 9 Male

COM3,COM4

Pin 1 DCD# Data Carrier Detect

Pin 2 RxD Receive Data

Pin 3 TxD Transmit Data

Pin 4 DTR# Data Terminal Ready