ModBus to ControlNet converter


Thread Starter

David Gómez

Hello, i Have a Modbus Network and my general system is in ControlNet Network, I want to integrate both networks in a ControlNet Network.
Anyone know about a ModBus/ControlNet converter?

Thank you for your Help.

Mubarik Mustafa

I've never heard of a Modbus/ControlNet converter. However, you can integrate Modbus data into ControlNet in different ways (depending on your overall system architecture).

1. If your main system on ControlNet is Allen Bradley and you want to exchange data with a few Modbus devices, then the best option is to put a Modbus communication module in your Allen Bradley system. Then your Allen Bradley system can read/write data from/to Modbus devices. Prosoft Technology Inc. ( is one company which makes Modbus communication modules for AB PLC, SLC and ControlLogix system.

2. If your Modbus system is large (e.g. has many Modicon PLCs) and the ControlNet system is also large (e.g. many AB systems) and you want to exchange data between the two, the best option would be to put a communication gateway between the two systems. Again, I don't know of any product that is sold as "Modbus/ControlNet gateway". However, you can make your own gateway, using, for example, an AB ControlLogix PLC with a ControlNet interface module and a Modbus communication module. You will have to program this PLC to exchange data from Modbus devices and store it in its memory. The AB systems can then exchange data from this gateway over ControlNet.

Hope it helps.
Mubarik Mustafa
INTECH Process Automation Inc.


You probably won't find an easy Modbus to ControlNet converter. I will omit the sermon, but they're just in different leagues.

I can recommend five other Modbus connectivity methods for Rockwell Automation networks:

1. Prosoft's 3100/3150 - MCM modules. These fit into a PLC or SLC (or Logix) chassis and allow data table access to Modbus RTU and Modbus ASCII slave devices. ( If you have a PLC, SLC, or Logix on your ControlNet, it can act as a data concentrator for your Modbus data using these modules. I just consulted on a telemetry retrofit with six disparate control systems and these 3150-MCM mastering Modbus RTU are our lingua franca.

2. Prosoft's ProLinx units. These will run Rockwell's EtherNet/IP protocol and act as a data exchange to Modbus RTU and Modbus ASCII slave
devices. These are standalone, DIN-rail mounted, and may be considered a limited-protocol equivalent to the SST X-Link.

3. Lantronix Cobox-DIN Ethernet/Modbus converters ( These are as close as you'll come to a true "bridge" product for Modbus, which passes through messages to a remote network rather than just acting as a shared-memory data concentrator. Modbus OPC servers (there have been lots of threads about these) can use their ComPort Redirector method to
access serial Modbus products that are located on a TCP/ IP Ethernet network, or Modbus/TCP drivers can access RTU slaves on the "Industrial Automation Protocol" version as though they were Modbus/TCP devices.

4. The SST X-Link product ( can act as a data exchange for nearly any protocol (including Controlnet and Modbus) but it's a fairly pricey and complex way to go and I don't favor it except for high-value network problems, where it excels.

5. DIP Inc's DeviceNet to Modbus CDN-066-3 ( is a clever and inexpensive way to treat Modbus RTU slaves like DeviceNet slaves.
These are terrific for getting data from, for example, Modbus-equipped wattmeters into a DeviceNet motor control center, which of course are compatible with the 1788-CN2DN ControlNet/DeviceNet bridge.

Good luck,

Ken Roach
Rockwell Automation / Seattle
[email protected]

Chris Kellock

Prolinx is supposed to be releasing some ControlNet gateways, for Modbus, Modbus Plus, and Modbus TCP. However I think they were delayed until next year. Might be too late for your application.

Andrew Piereder

SST has a ControlNet to Modbus, Modbus TCP or Modbus Plus gateway now. I think they've had it for a number of years. I believe Georgia Pacific applied a number of them some years ago.

Andy Piereder
Pinnacle IDC

Richard Theron - FieldServer has a ControlNet to Modbus TCP converter which can be expanded up to 40 000 points, it also has a number of serial ports on the same device which can be loaded with different protocols.

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