Can I edit tags and UDTs in Logix5K without having to reload entire program?

defcon.klaxon · May 16, 2019

Hi all,

I'm working on some Control and Compact Logix A&B PLCs, running Logix5K version 24. I've been doing online edits just fine, but I've noticed that if I want to adjust tags (like changing the size of an existing array), I can't do it. Also, I can't modify UDTs. Obviously if I go offline and reload the whole program to the controller I can do that, but that of course shuts down processes and takes longer. Was wondering if there was any way to make these tag/UDT changes without having to do the whole program reload?

JGax · May 16, 2019

defcon.klaxon said:
Hi all,

I'm working on some Control and Compact Logix A&B PLCs, running Logix5K version 24. I've been doing online edits just fine, but I've noticed that if I want to adjust tags (like changing the size of an existing array), I can't do it. Also, I can't modify UDTs. Obviously if I go offline and reload the whole program to the controller I can do that, but that of course shuts down processes and takes longer. Was wondering if there was any way to make these tag/UDT changes without having to do the whole program reload?

A tag/udt cant be redefined online.

what I do sometimes...

Redefine a new tag/udt.... after just use it on your logic.... if its highly used It would be a pain... if just a few rungs you would be ok...

Once your old tag is not used any more it may be deleted online... not udts...

Regards

jimbom · May 16, 2019

Nope. It's the nature of the beast. Most memory allocation has to be done off line.

defcon.klaxon · May 16, 2019

Thanks guys for the verification, I figured this was the case but wanted to verify so I wasn't missing something.

Ken Roach · May 16, 2019

Changing the definition of structures can't be done online.

That includes changing the datatype of an existing tag, or changing the size of an array, or changing the contents of a User-Defined Data Type.

It's just the nature of the beast. The structure of data types is essential enough to the program that you can't change it while the program is running.

I usually save up my structural changes, then take the opportunity to do the download when something else goes wrong or there's a break in the action.

JaxGTO · May 16, 2019

You can change a UDT online in version 21 and greater, but there can be no tags defined with that type. Some tags can be renamed online as long as it doesn't have an HMI reading that tag.

jstolaruk · May 18, 2019

I like to put "spare" definitions in my UDT, use them while online and before doing a new download, rename the members in the UDT to something making sense. Renaming UDT members will transition through to the routines that use it. Best to rename one at a time compiling between each, I have tried doing too many and the compiler couldn't track it.

I don't recall which version this was allowed, but having the ability to edit the member description while online even with tags defined of that UDT has been a real plus.

Can I edit tags and UDTs in Logix5K without having to reload entire program?

defcon.klaxon

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JGax

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jimbom

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defcon.klaxon

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Ken Roach

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JaxGTO

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jstolaruk

Lifetime Supporting Member

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