Allen Bradley ControlLogix PLC communication with Delta V DCS

[Aqib]

Hi Everyone,
I am currently trying to communicate ControlLogix PLCs via EtherNet/IP with Delta V DCS. There is a VIM2 card configured for EtherNet/IP devices.
As per Mynah's knowledge base, VIM2 supports Class 1 (I/O) connection with ControlLogix PLCs as well. The VIM communicates with ControlLogix devices using the generic 1756-ENBT format. Each ENBT corresponds to a VIM dataset. This functionality is available in simplex VIM architecture only.
I was able to get success along the way.
I have configured 3 PLCs with DCS. They were never connected to the DCS at the same time together as the plant was shut down for maintenance. Now on startup, once all 3 PLCs came online I started getting communication errors with DCS.
During troubleshooting, I observed that when either one of the 3 configured ControlLogix PLCs is connected with the DCS, it works seamlessly. and just when any other PLC is connected alongside, both of them lose communication. Further troubleshooting is being carried out. The communication gets back up only when I have removed all but one and unplug/replug the cable.
PS: I double-checked the network for duplicate IP addresses but didn't find one.
Am I missing something? I do not have much experience with the Delta V DCS.
Thanks,

 

[Ken Roach]

Are you working for Emerson, or the end user ? Emerson requires expensive and thorough support contracts for their systems; do you have one ?

In my experience, a Mynah VIM that is set for the default update rates can quickly overwhelm the communications capacity of a 1756-ENBT with Class 3 tag reads and writes. The last time I worked with them, the "inter-scan delay" feature simply did not function; the Mynah sent another request immediately after receiving a reply, and could not be "throttled back". That was 15 years ago, so the product may have been improved. At the time they were... unreceptive to cooperation.

How exactly are the Class 1 connections configured ? Do the Mynah VIM2's appear in the ControlLogix I/O tree as Generic Modules, or as though they are I/O modules in a chassis with a 1756-ENBT as an adapter ? Are you literally using 1756-ENBTs, or are you using modern 1756-EN2T, -EN3T, etc ?

IF you have three PLCs trying to create an "owner"/"originator" connection with the DCS as an "adapter"/"target", does the VIM2 differentiate them based on the source IP of the connection, or in some other way like the CIP Slot Number ?

Watch the I/O connection status in Studio 5000 and see if you can capture any error codes with GSV instructions. If you have the ability to connect to a managed switch, set up a mirror port, and capture the data with Wireshark that might help too.