Hardware reference guide

CPU Modules
170
35013379 11/2011
Modbus Port Modem Support
Modbus Port 1 has full modem interfacing ability. Modbus Port 2 RTS/CTS
connections function properly for normal non-modem communications but do not
support modems.
Modbus Ports Pinout Connections Figure
The following figure shows the Modbus port pinout connections for 9-pin and 25-pin
connections.
Modbus Ports Pinout Connections for Portable Computers
The following figure shows the Modbus port pinout connections for portable (laptop)
computers.
The following is the abbreviation key for the above figures.
TX: Transmitted Data DTR: Data Terminal Ready
RX: Received Data CTS: Clear to Send
RTS: Request to Send NC: No Connection
DSR: Data Set Ready CD: Carrier Detect