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Old January 23rd, 2023, 12:22 PM   #1
Kefren
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PLC going into program mode by itself

Hello friends

I think this is the second post about this all over the internet, first one was in 2013 by some guy from Canada who experienced the same as me.

I have a CLX processor that turned into program mode by its own, nobody turned the keyswitch (the key was not inserted), the keyswitch was in REM mode and the PLC was running ok.

PLC is ControlLogix 1756-L75

I turned it into remote run by studio5000.

I found nothing in the major or minor faults, all I/O is working ok.

It was 2 weeks ago, until now nothing is changed, just turned it into remote run and continue working normally.

Please, do you know what else could cause a CLX goes into rem program mode by its own? where should i check? do i have to call an agent of the paranormal and occultism to find an answer?



I haven't been able to sleep since then

Last edited by Kefren; January 23rd, 2023 at 12:25 PM.
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Old January 23rd, 2023, 01:02 PM   #2
James Mcquade
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If there was no key and the processor went into remote program mode, no faults, i would say that one of 2 things may have occurred.
1. someone got on the plc with a laptop and turned the plc into remote program mode.
2. someone has a key to the plc (they are all the same) and turned it to program mode and then remote run mode.
others may have a better idea, but this is the only two things i can come up with.
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Old January 23rd, 2023, 02:11 PM   #3
Aardwizz
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Grasping at straws

There might be one other way:

PLC experiences an unrecoverable fault.
PLC has a fault routine to clear faults / fault codes.
But since the fault is unrecoverable, the PLC cannot go back into RUN mode, yet is no longer "faulted". Therefore it must be in PROGRAM mode.
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Old January 23rd, 2023, 04:02 PM   #4
Ken Roach
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There is nothing paranormal or inexplicable about it.

The most likely explanation is that someone using RSLogix 5000 switched the controller into Remote Program module. Maybe they were diagnosing something and did it accidentally then hushed it up: that happens all the time.

It's equally possible that the controller faulted and was restored to Remote Program after a power cycle, or a keyswitch cycle, because that's what it is configured to do.

If this were my system I would check the webpage of the Ethernet module and see the Uptime value for that module. That could tell you if there was a power cycle you don't know about.

When stuff happens on night shift, the probability of human error hidden by human embarrassment is very, very high.
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Old January 23rd, 2023, 09:15 PM   #5
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I work in a couple of factories that it is their rule all key switches are kept in RUN unless program updates are required. No REM allowed, I have to remember to turn the key back after being online with it..
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Old January 25th, 2023, 11:04 AM   #6
Kefren
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The only person with access to plc software is a college and me, at the time this happend we were both in the same room, the network is fully isolated to internet connection and we use a laptop for programing, the software is not installed in the operation stations

The keyswitch was in REM and the key was not inserted, also the cabinet was locked

The PLC that i am talking about is a set of two primary with synchronize

I also checked for the major and minor faults and found nothing

I hope this post help to resume tips to check to understand what happened
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Old January 25th, 2023, 01:18 PM   #7
Mickey
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Quote:
It's equally possible that the controller faulted and was restored to Remote Program after a power cycle, or a keyswitch cycle, because that's what it is configured to do.
Something Ken said.. Power surges can cause this. Also surge protection on all inductive loads.
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Old January 25th, 2023, 02:10 PM   #8
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So it's a ControlLogix Redundancy system ?

You need to double-check your assumptions about the security and isolation of your system. I believe that you believe that your system is isolated, well-administered, and physically secure.

But I've seen people who have to work on isolated, well-administered, and physically secure systems devise clever and well-hidden workarounds, and hiding them from the bosses is part of that process.

If it's a ControlLogix Redundancy system, then the 1756-RM2 module logs may also provide some information about the transition to PROG mode.
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Old January 25th, 2023, 02:49 PM   #9
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Quote:
Originally Posted by Mickey View Post
Something Ken said.. Power surges can cause this. Also surge protection on all inductive loads.

This makes it a good idea to keep ControlLogix keys in RUN at all times unless need to do online edits, but on a redundancy system editing the CPU and the RM2 would have to be done at the same time, wouldn't they?



I've ever attempted an online edit of a redundancy system as I'm thinking it's going to be similar to the GuardLogix in editing (not possible)



Can someone tell me if I'm right or guessing wrong about this?
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Old January 25th, 2023, 03:29 PM   #10
Ken Roach
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Actual ControlLogix Redundancy, with properly set up RM/RM2 modules and pairs of CPUs and network modules, looks like just one CPU to the user.

The paired controllers have to be in the same keyswitch mode, and it's normal to leave them in REM mode so that you can perform online edits.

ControlLogix Redundancy historically has more subtle bugs than ordinary ControlLogix because it's so much more complex. But in general, a failure or bug causes a fault or record. The system doesn't just "flip to REM PROG", even though ending up in REM PROG is a common result of major unrecoverable faults and power cycles.

Every instance I've personally investigated where an isolated, secured, well-administered system had an unexplained malfunction that was consistent with an unauthorized user or a fault and power cycle... actually had an unauthorized user or a fault and power cycle.

Last edited by Ken Roach; January 25th, 2023 at 03:38 PM.
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Old January 25th, 2023, 03:40 PM   #11
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Quote:
Originally Posted by Ken Roach View Post
Every instance I've personally investigated where an isolated, secured, well-administered system had an unexplained malfunction that was consistent with an unauthorized user... actually had an unauthorized user.

I worked in a shop that had Bubba working 3rd shift that had an HMI in his locker he would program to change a single bit or value to override the limits set in the HMI's.
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Old January 25th, 2023, 07:13 PM   #12
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Quote:
Originally Posted by I_Automation View Post
I worked in a shop that had Bubba working 3rd shift that had an HMI in his locker he would program to change a single bit or value to override the limits set in the HMI's.
This is classic 🌭
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Old January 25th, 2023, 07:36 PM   #13
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Originally Posted by lostcontrol View Post
This is classic ��

This is why I program the limits in the PLC and reject any value out of my limits, and the limits are not tags that can be changed but values that would need an online edit to change.

I also have a SetPoint tag that is used and an HMI_Entry tag. Changing the SetPoint directly the PLC will change it back to the HMI_Entry value the next scan, Changing the HMI_Entry to an out of range value is ignored and that tag is reset to the SetPoint. The only way around would be write to SetPoint AND HMI_Entry on the same scan - which an HMI that can do that I haven't seen yet (but not saying one doesn't exist)



As far as changing bits I try to have checks so they don't get changed unless conditions are right, but toggling a bit by an errant HMI is hard to overcome.


Here's a shot from my home automation SLC of how I change setpoints
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Last edited by I_Automation; January 25th, 2023 at 07:50 PM.
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Old January 26th, 2023, 03:50 AM   #14
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Quote:
Originally Posted by I_Automation View Post
Here's a shot from my home automation SLC of how I change setpoints
Silly question, but is this living permanently in your home controller? I just find it hilarious someone programming a PLC to do something on Christmas morning. Is it pre-heating the oven? :P
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Old January 26th, 2023, 05:44 AM   #15
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Originally Posted by cardosocea View Post
Silly question, but is this living permanently in your home controller? I just find it hilarious someone programming a PLC to do something on Christmas morning. Is it pre-heating the oven? :P
My home automation system (1 SLC5/05, 3 5/03's, 1 5/04, 1 ML1400, 2 Siemens S7-200's) controls about 140 circuits of Christmas lights and 40 circuits of Halloween lights along with 7 security lights, gate locks, fire and flood alarms, solar battery charging, 6 outdoor outlets controlled, 6 temperatures monitoring, electric blanket control, power changeover for air conditioner compressor when the controlled meter is turned off, slow cooker control, and more. Plus a fully functioning traffic light with left turn lights, Walk/Don't, Prepare To Stop When Flashing, School Speed When Flashing, antenna tower lights, block control and street lamps for a model train set I haven't built yet.
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