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Old April 23rd, 2021, 05:59 AM   #1
jds8086
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Question RSLogix 500 "Lock" an address so it can't be changed?

So I'm working with a machine that has a parameter on the HMI (EZ Automation EZ-T10C-F)that writes back to F11:17 on the PLC (SLC 5/04). The problem is the operator shouldn't be able to change this, a new operator did just that and goofed it up, took a while to figure out what happened. I do not have the software to alter the HMI program so that is out. Is there a way to make that address "locked" so if they try to change it from the HMI it won't actually write the change? Worst case I'll change the program so that it uses a different address all together but I'd rather not change the program if i don't have to. Any help is greatly appreciated.
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Old April 23rd, 2021, 06:39 AM   #2
plvlce
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Originally Posted by jds8086 View Post
So I'm working with a machine that has a parameter on the HMI (EZ Automation EZ-T10C-F)that writes back to F11:17 on the PLC (SLC 5/04). The problem is the operator shouldn't be able to change this, a new operator did just that and goofed it up, took a while to figure out what happened. I do not have the software to alter the HMI program so that is out. Is there a way to make that address "locked" so if they try to change it from the HMI it won't actually write the change? Worst case I'll change the program so that it uses a different address all together but I'd rather not change the program if i don't have to. Any help is greatly appreciated.
afaik there's not a 'lock' for single addresses as you describe. I don't think you're getting away without changing either the HMI or PLC program.

If you want to avoid changing existing logic, then you could add logic to overwrite any change with a change back to the original value (assuming the value is not expected to ever change).
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Old April 23rd, 2021, 06:42 AM   #3
JeffKiper
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You can't lock the address in a SLC that I know of. With that being said I would have a NEQ F11:17 ??? MOV ??? F11:17. This will move the value ??? into your F11:17. It is the dame as you just changing the address and move on with other problems in the plant.
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Old April 23rd, 2021, 08:25 AM   #4
g.mccormick
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You can't lock the address in a SLC that I know of. With that being said I would have a NEQ F11:17 ??? MOV ??? F11:17. This will move the value ??? into your F11:17. It is the dame as you just changing the address and move on with other problems in the plant.
I agree with Jeff. Change PLC program.
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Old April 23rd, 2021, 10:04 AM   #5
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I have had to do a lot of things for operators doing this


What I do now is add rungs at the begining: OTL things that have to be ON, OTU things that have to be OFF and MOV values that better not be changed.


And not just SLC's - Omron, Mitsubishia, Panasonic, Siemens, and more


I have even found settings that are not changeable by the machines HMI - but someone had a PV+ in his locker and would program it to change whatever he wanted on whatever PLC he wanted to.
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Old April 23rd, 2021, 10:46 AM   #6
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Originally Posted by I_Automation View Post
....I have even found settings that are not changeable by the machines HMI - but someone had a PV+ in his locker and would program it to change whatever he wanted on whatever PLC he wanted to.
That person is in the wrong position!

And while you can apply protection to an entire data file, there is not an option to protect a single element within a data file.

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Last edited by Operaghost; April 23rd, 2021 at 10:54 AM.
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Old April 23rd, 2021, 11:12 AM   #7
OkiePC
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If I had to make the change, I would just edit the PLC to use a different address or a literal constant. I have been bit once or twice by an HMI or remote device that was able to write to an address at the exact instant after I limit checked it right before the next instruction made use of it. It might be one in a trillion with your situation, but once bitten, twice shy.
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Old April 23rd, 2021, 11:44 AM   #8
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Agree. I would change the logic to use a new address. Hopefully, it isn't being used in a bunch of places. But change it from F11:17 to some other unused floating-point address.

Then add logic to check and move from the original location to the new location. The HMI can still write to F11:17 but we can check and make sure it is a proper value before moving it to our new address.

If you create a new "F" file you could even add static protection to it to prevent anyone from changing it while online. The logic could still change it, but not an online user in Logix or an HMI.

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Old April 23rd, 2021, 01:01 PM   #9
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Switch PLC to run and remove key from PLC? You must have some smart operators if they know how to hook up to PLC and change addresses, haha. Although they could probably find another key and switch back to remote... Maybe lock the program from being edited, and have password protection if possible? Or give them the plc file, but without any tags.
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Old April 23rd, 2021, 02:20 PM   #10
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Switch PLC to run and remove key from PLC? You must have some smart operators if they know how to hook up to PLC and change addresses, haha. Although they could probably find another key and switch back to remote... Maybe lock the program from being edited, and have password protection if possible? Or give them the plc file, but without any tags.
None of this addresses the OP's issue in the slightest. The program (logic) is not changing, the desire is to remove the ability of the HMI to change a specific value that it currently accesses, without altering the HMI program.
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Old April 23rd, 2021, 03:16 PM   #11
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Quote:
Originally Posted by jds8086 View Post
...
a parameter on the HMI (EZ Automation EZ-T10C-F)that writes back to F11:17 on the PLC (SLC 5/04).
...

The problem is the operator shouldn't be able to change this,
...

Is there a way to make that address "locked" so if they try to change it from the HMI it won't actually write the change?
Worst case I'll change the program so that it uses a different address all together but I'd rather not change the program if i don't have to. Any help is greatly appreciated.

It sounds like the HMI should have been set up to only read that parameter, but instead it was set up to both read and write.


If so, I think you are at the worst case: re-write the PLC program to use a different address internally, and copy that new address into the old location that the HMI is looking at; even if the old location is written by the HMI, the PLC should overwrite it soon enough.


Of course it is probably possible to do what you want without changing the PLC or the HMI code, but it is not worth the effort.
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Old April 26th, 2021, 12:56 PM   #12
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Oh I misread, I thought someone physically went online with the plc and started changing tag values. I was like man, he got some smart operators
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Old April 28th, 2021, 06:04 AM   #13
jds8086
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Oh I misread, I thought someone physically went online with the plc and started changing tag values. I was like man, he got some smart operators

No, i would be pretty surprised if something of that nature ever happens here.


I ended up adding a rung with a NEQ set to the value i want, and a MOV after to change it if it isn't. Thank you guys for your help.
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Old April 29th, 2021, 05:09 AM   #14
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We received a new machine that used an EZ automation touchscreen, after about a year I had a list of complaints from production about things that should be different.

I work for a plant that exclusively uses AB hardware or software, not sure how this one made it through. Long story short I found the software to be extremely cheap (I think it was less than $200) and when I inevitably ran into trouble with the quirks of the software I got a response after hours by email.

This isn’t what you asked for but I struggled to get our parts guys to even order the software, its not “repair and maintenance.” In the end it was $$ well spent and I was able to completely resign the HMI to look more like the rest of our interfaces.

I guess the what I am getting at is I was able to fix the complaints from production, add a few buttons and features to the HMI, and I don't have to worry about being responsible for a piece of hardware that I cannot maintain in the future.

Hope this helps, even if your original problem is solved
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