We have two separate chassis with A-B 1756-L73 Rev. 20.0.1 processors and four EN2T/C ethernet modules. Occasionally, at the worst time, the processor will freeze and when trying to connect, the Run and Program options are grayed out. The only solution we've found is to power off the PLC, unplug all the comm cables, re-apply power and plug cables in one at a time. Unfortunately, this happens during a production run and we don't have a lot of time for troubleshooting and so far have not figured out how to duplicate this anomaly. Hoping someone has seen this and can offer suggestions. Thanks

 

Incorporate a fault capture routine with a GSV instruction in the controller program code...that would help you to diagnose the problem...you can even reset the fault when it happens by incorporating a rest rung for the particular fault. Now, implementing this would require a download and best would be to do it during a planned shutdown.
Additionally for the time being you can go online and check in the controller properties of what major/minor faults are logged.
With that knowledge you can look into the controller manual and look for solutions. Also on the RA website you can create an account and look for answers related to your problem or take a customer support.
Hope this helps.
Thanks

 

Why are there 2 EN2T cards in each rack and what else is hooked up to the Ethernet? This behaviour can be an I/O fault (look for a tiny yellow triangle in Studio5k I/O tree) or a network loop, don't make loops by running ethernet from a switch, round all the other devices then back to that switch, it causes Mac address flapping and shuts the switch down for a while until it applies STP flood control if configured. This can look like a freeze. If Rapid PVST+ is not configured then the switch can crash from packet flooding. You are probably loosing comms to the PLC. Is something else going online in the network, like an operator turned on a laptop for example?

 

We have two separate chassis with A-B 1756-L73 Rev. 20.0.1 processors and four EN2T/C ethernet modules. Occasionally, at the worst time, the processor will freeze and when trying to connect, the Run and Program options are grayed out. The only solution we've found is to power off the PLC, unplug all the comm cables, re-apply power and plug cables in one at a time. Unfortunately, this happens during a production run and we don't have a lot of time for troubleshooting and so far have not figured out how to duplicate this anomaly. Hoping someone has seen this and can offer suggestions. Thanks

Some additional information is required:

When you say the processor "freezes" what exactly do you mean?​

Do the processors fault? (Look at the "OK" LED on the processor, is it Solid Green or Flashing Red?)​

What is the state of the "OK" LED on the EN2T modules? (Solid Green, Flashing Red, Solid Red?)​

Do the processors stay in "RUN" mode? (What is the state of the "RUN" LED Solid Green or OFF?)
Are there any messages scrolling across the 4 character displays on the processor or the EN2T modules?​

Can you connect to the processor through the USB port on the front of the processor?​

Can you connect to the EN2T modules through the USB port on the front of the EN2T module?​

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I look forward to hearing back from you.

 

Had an opportunity to look at it this weekend. Apparently, there is a defect in firmware rev 20.011 &.012 that does not allow processor to transition to run mode when used with some PowerFlex drives. We did find a product notice on the Knowledgebase that addresses this. PN739