User`s manual

Second Serial Port, CN8

The second serial port is implemented on connector CN8. It is normally configured as a PC compat-

ible full-duplex RS232 port, but you may use the Setup program to re-configure is as half- or full-

duplex RS422 or RS485. The I/O address and corresponding interrupt must also be selected using

Setup. The available I/O addresses and the corresponding interrupts are shown in the following table

Second Serial Port UART

The second serial port is implemented with a 16550-compatible UART (Universal Asynchronous

Receiver/Transmitter). This UART is capable of baud rates up to 115.2 kbaud, and includes 16-byte

FIFOs on both receive and transmit. Please refer to any standard PC-AT hardware reference for the

RS232 Serial Port (Default)

The full-duplex RS232 mode is the default setting on the cpuModule. With this mode enabled, con-

nector CN8 must be connected to RS232 compatible devices.

The following table gives the connector pinout and shows how to connect to an external serial con-

nector, either XT(DB25) or AT(DB 9) compatible.

Facing the connector pins, the pinout is:

Second Serial Port Settings

I/O Address

Default IRQ Optional IRQs

02F8H IRQ4 IRQ3, IRQ5

02E8H IRQ3 IRQ4, IRQ5

Connector CN8: Pin Assignment in RS232 Mode

Pin Signal Function in/out DB25 DB9

1 DCD Data Carrier Detect in 8 1

2 DSR Data Set Ready in 6 6

3 RXD Receive Data in 3 2

4 RTS Request To Send out 4 7

5TXDTransmitdataout23

6 CTS Clear To Send in 5 8

7 DTR Data Terminal Ready out 20 4

8 RI Ring Indicate in 22 9

9,10 GND Signal Ground -- 7 5

9 7 5 3 1

GND DTR TXD RXD DCD

GND RI CTS RTS DSR

10 8 6 4 2