Modbus Communications Between GE Fanuc 90-30 and AB Controllogix 5555


Thread Starter



i want to set up the communication network between a GE Fanuc 90-30 and a Allen Bradley Controllogix 5555 using Modbus RTU. I know i can buy modbus modules to do this, but i'm trying to save the company some money and trying to do it without buying the modbus modules. I have already configured the Controllogix as a master (using the cig-ap129_en-p.pdf) and the fanuc is configured for modbus as well. The part that i'm struggling with currently, is the programming... How do i get the data from the registers in the Fanuc and store them in the Controllogix? Is there any sample code that would be of use? Has anyone done this before?

Wassim Daoud

You can do that with programming and hard wires connected both inputs and outputs of control systems to transfer such data. However, i must warn you, this will introduce a complexity in the control systems, and raise the cost of maintenance. OPC Data Manager is specifically designed to share real-time, historical, and Alarm and Events data between two or more control systems in a secure and reliable manner. In summary, OPC Data Manager, will share your Alarms and Real-time data between your GE Fanuc and Controllogix and vice versus. Download it from here:

You might need an OPC Server for GE Fanuc, if you don't already have one:

and also an OPC Server for Allen Bradley:

Hope this was helpful

Wassim Daoud
Global Solutions Architect
If you use Control Logix as a Modbus Master you will need a serial communication module in the GE Fanuc (this is the CMM311 communications module). This module can be configured as a Modbus RTU Slave. At the slave PLC side the only thing you have to configure is to copy the memory register to the Modbus map in order to be "visible" from the Master PLC side. At the master PLC side, simply follow the instructions that AB give to configure the Modbus RTU Master module.