Can You Measure Load on Unscheduled Bandwidth in ControlLogix?

I'm going to through this feeler out here because there is a lot of knowledge here.

I have a project that I'm working on that uses a L73 processor (using controllogix redundancy) and am looking for a way to measure how much data total is going through the unscheduled portion of the controller.

The main chassis has the processor, two EN2TR modules, and two EN2T modules, and the RM module. There are two rings, one of which goes to a chassis with hardwired I/O, while the other goes to two chassis' (think A and B) where each has a communication module. Each of these communication modules solicit all traffic to and from the controller and use their own CIP library/backplane access functions to read/write data to the processor. One EN2T serves data up to an HMI system, and the last EN2T provides data to a third party interface which polls data from our system via Ethernet/IP.

The overhead time slice is set to 30%, I have 1 continuous task and no periodic tasks. I know this is unconventional but it needs to run this way.

We are experiencing issues where the HMI is losing communication to the PLCs or the special communication modules are not able to read/write to the PLCs quickly, and this seemed to start when the third party system connected to our system. It seems to me that I have an awful lot of connections here fighting for unscheduled bandwidth, but I'm not in a position to be able to increase my overhead timeslice, because total scan time matter in this application.

Slowing down the special module seems to have a positive effect on the # of communication issues we see. I've looked in Rockwell's Task Monitor utility and didn't get a feel for how to identify this information or when it occurs. The DLRs are running in their default configuration and do not have any special schedule setup. Any ideas on how I can figure out what is going on?

Is the third party device a DeltaV/Mynah Ethernet VIM ?

The Task Monitor Utility is going to be your best tool; that's the best way to monitor the number of connections to the CPU, the usage of the buffers, and the CPU loading on all the elements of the system.

What exactly you're looking for is unlikely to be determined by speculation; your system sounds like it has several unusual elements.

My approach is always to use the Task Monitor to get measurable performance conditions, then change something, then return to the Task Monitor to see what measurable effect the change had.

The third party system is Yokogawa Universal Gateway Server. The main issue I'm having with the task manager is that I while I can see symptoms of higher loading with communication problems with the HMI or the other module, I cannot seem to see them with the Task Monitor on the PLC. I still have a few things to try so hopefully I can come up with something.

If the problem is communication bandwidth vs processor time you could install another Ethernet com card for the third party application.

Quick recap of the architecture: The first Ethernet card (ring) has the special communications modules that read/write data to the PLC (how much they read/write is variable), the second Ethernet card (ring) is for a couple of 16 point digital input cards, the third Ethernet card is dedicated for HMI communications and the fourth Ethernet card is dedicated for the third party link.

I'm not sure how an additional card for the third party link would help. Am I missing something?

Sorry, I missed read how you were doing some of the comms. Just trying to suggest a way to relieve some of the comm traffic. Is all the traffic to your HMI & third party system going through the same Ethernet line and switch. If so are you using a managed switch to control your traffic. Not sure if this is helpful but Rockwell has an Ethernet configuration tool that may show where some of the problems lie(Ethernet IP Capacity Tool).

HMI traffic is going through Hirschmann switches and that is the only thing on that network. Third party system is on a separate network, their switches and firewalls.

I did not know about the capacity tool. I am downloading now and will give that a look. This is our first time using EN2TRs instead of ControlNet so we will have some adjustments to make I'm sure. It doesn't help that we have so many unscheduled communications to accommodate.

I did some more testing today and there is nothing in the Task Monitor that significantly changes when I'm performing the read/writes to the PLC uses the special comms module. I can, however, see a noticeable affect in the online monitor for how quickly that module is able to read/write to the PLC based upon the load of data coming into the module and being sent to the PLC. On the surface, it seems I'm overloading the Ethernet/IP capabilities of the processor, which is only made worse when the third party system tries to read/write via Ethernet/IP. I will keep digging and let you know if I ever turn anything up.