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Old February 8th, 2019, 10:39 PM   #1
delforum
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Post RSLogix 1756-L71 Read Only Tamperproof Tags

Hello PLCTalk Experts,

I am looking for an elegant solution to allow viewing of the tags current real values in the database by an unauthorized user, but also prevents the other RSLogix user from ever changing the array of real numbers in that tag.
Do you have any suggestions on how to setup the ladder or AOI using source protection to lock the routine?
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Old February 9th, 2019, 12:52 AM   #2
James Mcquade
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I can understand why you would want to keep maintenance from making program changes, but WHY would you want to keep another programmer from making changes?

my coworker trust each other and we make changes all the time.
we discuss the program changes the next morning.

please explain your application in more detail.

regards,
james
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Old February 9th, 2019, 08:48 AM   #3
collinsd70
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Quote:
Originally Posted by delforum View Post
Hello PLCTalk Experts,

I am looking for an elegant solution to allow viewing of the tags current real values in the database by an unauthorized user, but also prevents the other RSLogix user from ever changing the array of real numbers in that tag.
Do you have any suggestions on how to setup the ladder or AOI using source protection to lock the routine?
Why not just write a constant value to a tag? This stops any changing of values during runtime or choose the 'constant' propery in the Controller Tags?


Regards

Daniel
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Old February 10th, 2019, 10:01 AM   #4
delforum
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Safety of the equipment is the main concern. If those tags change the equipment could be damaged by higher than rated pressures. Adjustments need to be made but infrequently and only by trained service.

With the constant property marked, what steps would be needed to change the register value? Can it be changed while in remote run online?
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Old February 10th, 2019, 10:02 AM   #5
collinsd70
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Quote:
Originally Posted by delforum View Post
Safety of the equipment is the main concern. If those tags change the equipment could be damaged by higher than rated pressures. Adjustments need to be made but infrequently and only by trained service.

With the constant property marked, what steps would be needed to change the register value? Can it be changed while in remote run online?
I believe the constant tag value has to be amended offline and downloaded complete but im not 100% sure on this.


Regards

Daniel
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Old February 10th, 2019, 12:23 PM   #6
collinsd70
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Quote:
Originally Posted by delforum View Post
Safety of the equipment is the main concern. If those tags change the equipment could be damaged by higher than rated pressures. Adjustments need to be made but infrequently and only by trained service.

With the constant property marked, what steps would be needed to change the register value? Can it be changed while in remote run online?
Hi Delform.

I have checked this for you on Emulate 5000, so the constant is declared via a Constant 'checkbox' in the Controller Tags and the value can be freely ammended offline/ online using the monitor tags window.

If an attempt is made to write to a constant tag through a routine; a compiler error is generated, so basically the value can only be updated directly.


Regards

Daniel
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Old February 10th, 2019, 01:51 PM   #7
Phrog30
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If it's that important, hard code the values in a move instruction in a protected routine. Only give the source key to the ones that you want to change. Anyone can still view in the tag database.
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Old February 10th, 2019, 03:05 PM   #8
delforum
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Thank you Daniel, James and Phrog for your insights. The constant tag may work well if I can put it in a protected AOI local tag database. Then in authorized persons couldn't change that tag value. How would I get that value from an AOI tag into my main task's routine?

Putting move instructions in a source protected routine seems like the simplest solution. A person with the correct protection key could edit the rung online, while others could only view the values.
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Old February 10th, 2019, 03:11 PM   #9
dmroeder
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I would go with source protection rather than AIO, If you put them into an AOI, you are going to have to download every time you want to make changes.
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