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Author Topic: DM1E stops working and communicating but no clue why  (Read 48972 times)

Controls Guy

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DM1E stops working and communicating but no clue why
« on: May 28, 2021, 02:09:51 PM »
I've been having a recurring problem with a BX-DM1E-M over the last few days.    System is in Run, no faults indicated, but program not performing normally.

I have a PC in the subnet with the PLC that I can remote desktop into and it also acts as a VPN router for remote programming and monitoring via DMD.   Remote access to the PC is working fine, I remote in, and can't ping the problem PLC.   There are two HMIs, two PLCs, and the PC in the subnet.   From the PC, I can ping both HMIs and the other PLC.    The other PLCs job is primarily to mediate comms between the site and the main PLC.   I log into that one, and MWXs and MRXs to the main PLC are continuously failing, so he can't see him either.

Cycling power causes the comms to work and the program behavior to act normal again.

Event log shows nothing in the last three months except the occasional power cycle or legit program changes.   ???

PLC photo while in this mode attached, and Sysinfo dialog attached, including S/N, all version info, etc.

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BobO

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Re: DM1E stops working and communicating but no clue why
« Reply #1 on: May 28, 2021, 02:46:00 PM »
This could easily be the same issue we've been discussing in the Modbus thread. Update to 2.8.6 and see if it gets better.
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Controls Guy

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Re: DM1E stops working and communicating but no clue why
« Reply #2 on: May 28, 2021, 02:51:33 PM »
OK, will try that!   Thanks!
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Controls Guy

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Re: DM1E stops working and communicating but no clue why
« Reply #3 on: May 28, 2021, 02:52:34 PM »
Quote from: BobO on May 28, 2021, 02:46:00 PM
This could easily be the same issue we've been discussing in the Modbus thread. Update to 2.8.6 and see if it gets better.

Would it cause the program to pause as well?   As best as we can see without being able to talk to it, ladder execution looks like it might be hung.   All outputs off, etc.   Well, not sure how the I/O subsystem works, and if it doesn't hear from the CPU, does it shut everything off?   No scan timeouts on the event log though.  Weird.

Does updating the OS clear the event log, or does it get recorded as an event?
« Last Edit: May 28, 2021, 02:56:35 PM by Controls Guy »
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BobO

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Re: DM1E stops working and communicating but no clue why
« Reply #4 on: May 28, 2021, 02:57:34 PM »
Quote from: Controls Guy on May 28, 2021, 02:52:34 PM
Does updating the OS clear the event log, or does it get recorded as an event?

Recorded.
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Controls Guy

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Re: DM1E stops working and communicating but no clue why
« Reply #5 on: May 28, 2021, 03:15:03 PM »
Any idea about the other stuff?
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Re: DM1E stops working and communicating but no clue why
« Reply #6 on: May 28, 2021, 03:21:53 PM »
OK, that fixed it for the moment, but since a power cycle does too, have to wait and see if it was just the Run Mode transition that did the trick.   Problem seems to come up fairly frequently, so should know before too long.   Will advise.
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BobO

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Re: DM1E stops working and communicating but no clue why
« Reply #7 on: May 28, 2021, 03:29:46 PM »
Quote from: Controls Guy on May 28, 2021, 03:15:03 PM
Any idea about the other stuff?

The comms issues really shouldn't affect ladder execution. These broadcast storms have definitely caused big spikes in scantime, so if that is really bad and persistent, I guess other things could go wrong. Gut tells me this may not be your issue, but, we don't see too many cases where a hardware failure just kinda breaks stuff. It's usually terminal or fine.
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Re: DM1E stops working and communicating but no clue why
« Reply #8 on: May 28, 2021, 03:43:16 PM »
I know, weird.
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ATU

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Re: DM1E stops working and communicating but no clue why
« Reply #9 on: May 28, 2021, 07:48:03 PM »
Towards the end of last year I was having similar strangeness. it was so random that it was hard to pin down. Its been too long to remember too many details.
It just seemed to stop working and I had to reboot to get it work again.  May not be the same issue, but  I separated each modbus coms on its own device driver. It seemed to help.
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Controls Guy

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Re: DM1E stops working and communicating but no clue why
« Reply #10 on: May 28, 2021, 09:49:27 PM »
In my case, the PLC in question is server only, with the other plc and both HMIs talking to it via Modbus.  Been working ok on 2.8.4 for just under a year.   No ECOM in this one, one in the other plc an LT I think.

Flashing to 2.8.6 didn't help.   Happened two more times this afternoon.  Have to see if wiggling the mode switch clears it too.
« Last Edit: May 28, 2021, 11:45:40 PM by Controls Guy »
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BobO

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Re: DM1E stops working and communicating but no clue why
« Reply #11 on: May 29, 2021, 12:16:45 AM »
Quote from: Controls Guy on May 28, 2021, 09:49:27 PM
In my case, the PLC in question is server only, with the other plc and both HMIs talking to it via Modbus.  Been working ok on 2.8.4 for just under a year.   No ECOM in this one, one in the other plc an LT I think.

Flashing to 2.8.6 didn't help.   Happened two more times this afternoon.  Have to see if wiggling the mode switch clears it too.

There is a counter in DST that tracks failed backplane accesses. I don?t remember what it is, in the 400s maybe. I?m curious. A backplane issue (which I?ve never seen or heard of) might be able to cause what you are describing.
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Re: DM1E stops working and communicating but no clue why
« Reply #12 on: May 29, 2021, 02:22:30 PM »
I'll take a look at that and let you know.
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BobO

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Re: DM1E stops working and communicating but no clue why
« Reply #13 on: May 29, 2021, 02:47:20 PM »
Quote from: Controls Guy on May 29, 2021, 02:22:30 PM
I'll take a look at that and let you know.

It's undocumented. DST454.
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BobO

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Re: DM1E stops working and communicating but no clue why
« Reply #14 on: May 29, 2021, 02:49:48 PM »
And to prove we are doing useful things other than create annoying comm bugs, and whatever this might be, here's a screen shot from current work. Pay attention to the parameters.  ;)


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