What is ARCNET?

What is ARCNET and what would cause excessive reconfigs? A bad switch? Faulty EB2? Program bug? There is a new reconfig about once/sec.


I will leave it to you to Google exact specifics (if and only if you are really interested) of ARCNET, but enough to say its the bus protocol of how our smart modules talk on the back plane to the PAC controller.

There are some helpful hints about what you are seeing the in PAC Manager guide and there are more than a few posts in these forums about it as well.

Bottom line, its an issue with a few possibilities.
Most common is bad power. You should be getting 5.1volts at the terminal of the rack.
Also it could be noise on the power. Even if it measures 5.1 volts, the power could be spiking or have some noise on it from a nearby VFD or some such.

Next is a possible bad smart module. That means a high density digital or analog. The standard 4 channel digital modules do not use the ARCNET to communicate to the brain/controller.

Lastly is a bad brain/controller and in very rare cases a bad rack.

Short story long, you should not be getting reconfigs very often at all… Once per second is really bad. Something is up and needs to be addressed.

I did a search and only a few posts popped up that had little to do with my question (or maybe only offered a partial answer as the main topic was something else)
With that said, Thank you for the quick informative response.

Check. Measuring 5.15v

Maybe check, I need to get my better (faster) meter to see any spikes/crashes, but casually it seems steady. No VFDs anywhere near or VFD controlled motors/wires. There is a single 480v motor starter in the same cabinet and the 480v has been separated as far as physically possible. Still, there might be enough induction to cause problems, but the arcnet reconfig is occurring with the motor turned off.

There are no smart modules. Just standard digital I/O. This leaves me with a brain going bad. I guess I need to get a new one to swap out and see if that fixes it.

Thanks for the pointers.
FYI-I noticed the issue because the piece of equipment is starting to become somewhat erratic and I/O responses seem to be slow.

You might have other issues, but I see this count incrementing on all our EB2’s that only have 4 channel digital IO. As per the PAC Manager manual.

Yeah, but then there is the line below it. ??? :man_shrugging: