I believe that's actually my fault. When I made the change from reading scattered tags to contiguous, I didn't let the values settle, so the mean response time was still influenced by the previous values.
Look now to the values when tags are contiguous and the response isn't influenced by previous values:
Mean Response Time of 15ms is already a good value (?)
Yes, that's much better.
Glad to see its improved! Another thing I thought i'd comment on is the 3ms PLC task time. That is really really quick, and a problem with that is that typically the Omron PLCs need some 'overhead time slice' to service the communications to external read / write requests.
If anyone else is struggling with Omron I'd recommend also playing around with the two settings in the Controller Setup that relate to % time allocated to system overheads.
I don't get it. It's the PLC that manages the time that it needs to execute all of its tasks. It's not a defined period.
So, based on this premiss, shouldn't it be able to have more than enough time to service the communications?
Or am I seeing this the wrong way?
Old-school PLCs just ran as fast as they could. What today would be called a continuous task. (Rockwell still offers this.) Today, most PLCs expect the programmer to declare the pace needed by the application. Time not needed to achieve that pace is available for housekeeping. If the pace cannot be achieved, typically the PLC will fault.
Sorry I've only briefly done some small tweaks to a CJ, so maybe its a non-issue, but on the NJ's / NX's the PLC does manage the time but if it doesn't have enough time to do its other "System services" then things go bad trying to read from the SCADA application.
If you define a 3ms periodic task for the entire PLC, but its taking say 2.6ms to execute purely the ladder logic alone, then there is not much time left for everything else. As a simplistic example.
This was an issue for us in the NJ PLCs, we ended up simply having to buy gruntier NX PLCs which had dedicated processor cores to run the system services.
