Is there a way to find out if a program

[katratzi]

Do any PLCs give the programmer a way to tell if a program has been edited and/or reloaded? For example, if you supply a program to a customer, and after startup and debugging a plant "technician" one day edits the program, something goes awry, and the original copy is downloaded back to the processor to cover his error, is there a way to discover this? Hasn't happened yet, but it is something I've thought about.

 

[Ken Roach]

I understand your position; I did have such an incident happen to me, though eventually they found that the malfunction was mechanical and not program related. That didn't stop them from threatening to arrest me.

It's a tough question. I can't think of a controller that has a "elapsed run time" function that can't be written over, or anything that allows you to prevent downloads without also restricting access to other functions.

Most customers are going to want full access to the program, even if they promise not to edit it.

I thought about a free-running clock, or a checksum based on the realtime clock, but both of those would be subject to duplication and changing by somebody who knew what they were for.

Hmm.

ControlLogix allows you to hide certain routines from view using Routine Source protection (so do some other brands and models) but you'd still have to be sure that your checksum or tag couldn't be uploaded and therefore duplicated.

I had a boss once who prevented program changes in PLC-3 controllers by turning the keyswitch to RUN and breaking the key off inside.

 

[RussB]

Yes,
GE Fanuc sells a product called "Manager" it does what you are looking for. It works with most of the popular PLCs manufactured today and most any other document file i.e. CNC, CAD, Word, PDF documentation.
Check it out here:
http://www.gefanuc.com/Downloads/en/proficychangemgmt_technicalwhitepaper.pdf
FUN STUFF!

 

[Ken Roach]

Of course if the customer is interested in maintaining control and audit compliance over their system there are quite a few source-control and access-monitoring software systems out there. RSAssetSecurity will log the underwear changes of your technicians if you want it to.

But if they're not.... you gotta get more devious.

I have thought of a way to write some status data to ControlLogix that cannot be written over by a reload but it relies on some non-public functions. Contact me by PM or e-mail if you're interested in a Rockwell approach.

 

[katratzi]

Thanks for the link, Russ. I'll check that out.

Ken- I guess your old boss discovered the undocumented hardware program protection option!
I will e-mail you to get some more information. 90% of the PLCs we use are A-B, so the Rockwell approach works for me.

 

[JesperMP]

How about letting the HMI panel do the logging, if possible ?

If the HMI panel can read the CRC of the program code, directly or inderctly via the PLC program, then it could log it with on-change trigger.
It would require that there is a non-volatile storage for this log file, typically a flash-card.

Obviously this feature should not be known to the enduser. If he knew about it, and he had caused some trouble, then he would remove the evidence by simply removing the flash card.
I remember that there was a colision between a passenger ferry and a cargo ship over here. But no one was ever accused of any wrongdoing. There were systems to record everything, including the activities of the personnel on the bridge. But when the investigators came to get the tapes, they had vanished. So no one could be proven to have done anything wrong.