Control Logix Control Net Communications

I have a PLC rack and remote I/O in another cabinet. Everything is communicating via Control Net. I just replace a Reliance GV3000 with a new Yaskawa A1000, 100hp drive. Yaskawa does not offer control net as an option card. All they offer is Modbus, Profibus and Ethernet. I have decided to use Ethernet due to the fact of down the road drive replacements. Here is my problem, I have an Ethernet card in the main rack that communicates with the plant network. The main PLC Rack is maxed out, but there are expansions slots open in the remote I/O rack. The remote I/O does all the communications to the drives and controller via control net. I wanted to install a 1756-ENET/B in the remote I/O to communicate with the new Yaskawa Drive and future drives and the controller. Will there be a conflict in communications to the main processors, or should I run Cat 5 from the Yaskawa to the main processor rack via the installed cisco switch?

Generally speaking, you might be able to do this. However you mention the 1756-ENET...which is very old. So I question how old your entire system is, and potentially if the firmware on your controller is capable.

If you can list the processor part number and firmware of the processor, ControlNet card, and Ethernet card it might provide more insight. For reference, 1756-EN2T is the current Ethernet card (yes EN2TR, EN3TR would be other options).

I'm sitting at home modifying other code for an Automation Direct PLC but I so physically I cannot look at the rack, but the information I have, assuming this code that was sent to me is correct, the controller is 1756- L1 jControlLogix 5550 Controller Revision 12.27 on a 10 slot Chassis.
Honestly I didn't even think about the ramifications of new verses old. There is some Modbus in the cabinet that is tied to some smaller Yaskawa A1000 10hp drives. I may have to just add another node to that chain.

Welcome to the Forum !

I can weigh in on this, because I have some detailed direct technical experience with the issue.

I/O connections over ControlNer or EtherNet/IP must be made via a "root bridge" network module located in the same chassis as the CPU.

An Ethernet module can be placed into a remote chassis and connected via a ControlNet link for messaging, or HMI, or upload/download. But not for I/O.

Studio 5000 won't warn you about the issue. And in fact, depending on the rest of the loading of the system it might function for a while.

But in the background the controller will be using a non-reserved buffer to keep the connection open, and eventually it will re-assign that buffer to another purpose and the connection will fail.

Again, I will be clear: The network architecture you describe may work, depending on network loading and other factors, but it will not be reliable and will eventually undergo a fault, failure, and restart at an unpredictable time.

Thanks Ken and Paully. Hearing all this, I will probably just add this drive to the Modbus to simplify the layout.

Thanks for that specific version update !

Now I'm trying to remember what version was the first to support EtherNet/IP I/O connections. v7, I think, with the 1756-ENET Series B firmware.

Another option might be to use a ControlNet to Modbus/RTU converter, specifically the http://www.anybus.com/products/gate...cator/detail/anybus-communicator---controlnet.

It won't give you the ability to get online with the drive's configuration software, but it will allow you to control it over the existing ControlNet network.