CME34M Hardware Manual - RTD Embedded Technologies, Inc.

Facing the serial port’s connector pins, the pinout is:
9 7 5 3 1
GND DTR TXD RXD DCD
GND RI CTS RTS DSR
10 8 6 4 2
RS-422 or RS-485 Serial Port
You may use Setup to configure the serial ports as RS-422 or RS-485. In this case, you must connect the serial
port to an RS-422 or RS-485 compatible device.
When using RS-422 or RS-485 mode, you can use the serial ports in either half-duplex (two-wire) or full-duplex
(four-wire) configurations. For half-duplex (2-wire) operation, you must connect RXD+ to TXD+, and connect
RXD– to TXD–.
Note The cpuModule has a 120 Ω termination resistor. Termination is usually necessary on all RS-422
receivers and at the ends of the RS-485 bus. Termination resistors can be enabled in the BIOS setup utility.
When using full-duplex (typically in RS-422 mode), connect the ports as shown in Table 15.
Table 15
Full-Duplex Connections
Port 1 Port 2
RXD+
TXD+
RXD–
TXD–
TXD+
RXD+
TXD–
RXD–
When using half-duplex in RS-485 mode, connect the ports as shown in Table 16.
Table 16
Half-Duplex RS-485 Mode
From
Port 1 TXD+
Port 1 TXD–
Port 1 TXD+
Port 1 RXD–
To
Port 1 RXD+
Port 1 RXD–
Port 2 RXD+
Port 2 TXD–
BDM-610000076 Rev A Chapter 3: Connecting the cpuModule 33