The CTM-ONE can support 4 types of MODBUS:
MODBUS Master Gateway
MODBUS Slave Gateway
TCP Slave
Serial Slave
Self-Slave
The mode setting of the serial port must be set to MODBUS for the RS-232/RS-485 port setting for MODBUS configuration to work even if no physical RS-232 or RS-485 devices are physically connected to the CTM-ONE.
MODBUS Configuration is available on the CTM-ONE local web interface under serial <modbus tab.
The RS-232 and RS-485 tabs expand for specific MODBUS functionality. The CTM-ONE supports simultaneous RS-232 and RS-485 protocols so individual configurations can exist for either protocol.
For Ethernet-based MODBUS communication (TCP / RTU over UDP), either MODBUS RS-232 or RS-485 can be used.