[Rockwell] PLC to PLC comms using Generic Ethernet Module

Powerchamp

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Dec 2015
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Is it possible to add another AB Rockwell PLC to the network tree as a Generic Ethernet Module and use it as IO?


Any idea where I would find information regarding assembly instance and size of I/O/C for AB Rockwell products?


If possible, what are the pros and cons when compared to produce/consume and MSG instructions?


Don't need to use it real world, just curious.


Many thanks in advance.
 
We do this with the Micro820/850 series Plc.

Just create a Modbus Table in the second plc with all the variables you need, then just treat it as you would any modbus I/O expander.

The first Plc can then read/write to the modbus variables thru ethernet (using Modbus tcp).
 
The model does matter, different models support different comms capabilities.


Why reinvent the wheel? Produce/consume was designed for this, and is well documented. Think of the guy coming after you who has to figure it out.
 
Yes you can. Provided EtherNet lines are set properly. The only down side is that is costly, since the PLC has a processor which are not cheap. It would be better for you to use an RTU with I/Os and EtherNet comm.
 
Is it possible to add another AB Rockwell PLC to the network tree as a Generic Ethernet Module and use it as IO?


Any idea where I would find information regarding assembly instance and size of I/O/C for AB Rockwell products?


If possible, what are the pros and cons when compared to produce/consume and MSG instructions?


Don't need to use it real world, just curious.


Many thanks in advance.

I've never seen this done before. I've only seen produce/consume tags and MSG instructions to communicate between two PLC's. (Allen-Bradley)
 
I would use Remote I/O instead of two PLCs and just have two different tasks in the solo PLC. This way, all tags are base tags and you don't have to create producer / consumer tags or MSG instructions.

But if the PLCs are already out in the field, it's probably easier to daisy chain them and do what the OP said.
 
Is it possible to add another AB Rockwell PLC to the network tree as a Generic Ethernet Module and use it as IO?

It is not. No Rockwell controller suports a "Generic I/O Adapter" object.

This kind of functionality was available with Remote I/O protocol on the old PLC-5 Enhanced controllers, by setting up a RIO channel in Adapter mode and using Block Transfer instructions. It was complex and hard to follow when you found it in the field.

This sort of controller interlocking is done today with Produced/Consumed Tags.

If you have a good reason to do it, you could establish a Listen-Only connection to 1756-series I/O modules in another chassis. I don't believe that's possible with the 5069 CompactLogix platform.
 
With all due respect, that's kinda like asking "I need to get from Seattle to Portland and I don't care how I get there. What's better, a Ford or Chevy?"
There are hundreds if not thousands of answers to your question depending on variables you are saying don't matter. Can it be done? Yes. What's the best way to do it? Yes.
 

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