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SW_100301763-Newcomer
3-Newcomer
May 17, 2023
Question

Read and Write to Device Level System Tags with an Allen Bradley PLC

Hello, we do a lot of development on an Allen Bradley PLC and had the question come up wondering if there is a way to read or write to the Device Level System Tags (the ._System tags) that you see in OPC Quick Client. Are there any examples or is there a way to do this? This is a 1756-L72 ControlLogix 5570 with revision 32.11 and using KepServerEx v6.10.659.0, basically the thought is can I create a tag in the PLC that can write to or read to a particular ._System tag? Or anyway to read all of the ._System tags on the PLC side?

10 replies

SlidingDownhill12-Amethyst
12-Amethyst
May 17, 2023

You can map them as static tags within a Kepware channel and then have the PLC read those... You might need "advanced tags" to read the system tags though... not sure about that... but now I'm interested too. 

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cmorehead13-Aquamarine
13-Aquamarine
May 22, 2023

@SW_10030176

 

The default access for System tag read/write permissions is disabled. Please take a look at the knowledge base article in the following link to change the access permissions:

 

https://www.ptc.com/en/support/article/CS280759

 

Thanks,

*Chris

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SW_100301763-NewcomerAuthor
3-Newcomer
May 22, 2023

Thanks for your reply Chris, this is what I received from PTC support ticket as well. I have all the permissions allowed, this does not help me how to setup in the PLC or in the KepServerEx Configuration to make this actually work. Thanks. 

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cmorehead13-Aquamarine
13-Aquamarine
May 22, 2023

@SW_10030176,

 

I'm not sure I follow you. The _System and _Statistic tags are internal to the KEPServerEX application and do not require plc set up. System Tags in KEPServerEX represent server, channel, and device-level properties only and are not connected directly to any PLC programming. Here is a link to complete list of available system tags with Read/Write or Read Only availability :

 

 

https://www.kepware.com/getattachment/e1943820-ef3c-4932-b055-4ef2a80ab863/kepserverex-manual.pdf#page=113

 

Do you have a specific tag or use case you are having trouble with?

 

Thanks,

*Chris

 

 

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SW_100301763-NewcomerAuthor
3-Newcomer
May 22, 2023

My original question is can I read and write to the _System tags that are internal to the KEPServerEx application from a PLC? So on the PLC side I would have a PLC tag where I want to set a _System tag that is read/writeable in KEPServerEx, so an example would be say I want to set the ._System._Enabled kepware tag to 0 from the PLC, can I do that and how? I have the permissions all possible to do that

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SlidingDownhill12-Amethyst
12-Amethyst
May 22, 2023

That's interesting, You want the PLC itself to read/write to the system tags? or any Kepware tags?

The PLC might not be able to even address Kepware tags like you can in a SCADA platform (without using Open Sockets and a lot of work perhaps). 

 

 

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