Unity Pro XL - I/O Scanner and MSTR Block same NOE

Hello Everyone,

I was wondering if any other users at plctalk.net could comment on experience configuring the I/O scanner within Unity Pro XL as well as MSTR block modbus polling on the same NOE card (slot position).

I am using a 658 Quantum controller. The CPU's ethernet port is reserved for inter-PLC communication. When the PLC was installed, all of the modbus polling to various plant equipment was configured in the I/O scanner. The I/O Scanner is configured to use Slot 4 which has an NOE Card installed. As you may know, modifications to the I/O Scanner require a write to the PLC which is extremely hard to orchestrate as they require a station outage.

I have configured 4 MSTR Blocks to manage communication between 2 new flowmeters recently installed at site. The meters are wired on a 485 string through a Schneider ETG ethernet gateway. When initiated they do not function and the MSTR block provides an error code that cannot be found in the help file.

Luckily, I had another NOE card configured in Slot 15 that is only used for the site HMI to talk to the controller on. I changed the routing address within the MSTR config and it works like a charm.

Does anyone know if NOE cards cannot handle I/O Scanning and MSTR blocks at the same time? Technical support cannot provide any case studies, wondering if anyone has had a similar experience.

Note: My I/O Scan list has 22 entries (Devices) and I am wondering if it could be a traffic problem?

Thanks for reading!

I doubt you will have any issues. I have run this as well, and as long as the module is not stressed too hard (i.e. thousands of packets per sec) you should be fine. Scan time has an effect here, that may not be obvious: the module moves data to/from the NOE at end of scan. So, the faster the scan time, the more work the module has to do (moving the IO image back and forth - writes from CPU to NOE, reads from NOE to CPU).

I don't know what the issue is with the Gateway devices, I would ask for a packet capture and that would be a huge help in determining root cause. Suspect you do not have one, and since it is working now, not sure it is worth finding root cause.

There are more issues with serial gateways and IOScanner due to the aggressive nature of this tool, but you are using MSTR blocks, so this is not in play.

So what is the RepRate(s) on the NOE that had trouble? What is the scantime? Hopefully, the RepRates are reasonable and represent what your process needs, not what is capable of configuring. I have to dig it up, but I measured the maximum number of packets an NOE device could handle, so we would be able to compare.

robertjonesjr,

Thank you for your advice. After further investigation I think your point made about stressing the module is correct. I realized that the specific PLC in question had 500 ms as the RepRate on every I/O Scanner entry. Also, the Unity Pro and Citect HMI connection to the PLC were on the same NOE as well.

When possible, I plan to lower the scan rates and possibly change a few network connections around. Thanks again.