Rewrite RSLogix 5000 tag description

Hey all,

I'm writing a small historian project where I'm recording 6 events that occur in my PLC logic. I've left the tags sort of vanilla (Alarm01, Alarm02).

While I could create descriptions for the alarms/events in each tag, it'd be super cool to be able to create some logic to be able to enter in a specific description while online.

Anyone have a method for doing that? Haven't looked into it much yet, but wanted to save some time to see if someone has some ideas I can tinker with.

Thanks for your thoughts!

I tried once to use dynamic alarm messages with FTAE, and had less then satisfactory results. For one thing, the message(s) aren't actually exposed for program manipulation, so I thought, okay, I'll just use embedded tags in the messages!

Well, that doesn't work either very well. Say, for example, you have an ADD instruction at the beginning of every rung in your alarm routine, that starts from zero every scan through...Using that value is useless in the FTAE messages, as there is a definable (and random) time lag between firing off an FTAE instruction, and it actually building the message, yielding essentially junk.

Now, on Roll-Your-Own alarming, it is entirely possible to build your own messages dynamically, and even be able to change them from an HMI. When doing that, the typical approach is to use an array for the actual alarm conditions, a matching array for the actual alarm latches, and another array for the alarm messages.

Then you use indexed addressing to keep them lined up.

The simplest way is two arrays of BOOL, and an array of STRING. With some more complicated math for the index management, you might choose to use arrays of DINTs, which makes checking to see if any alarm is present easier, or add additional arrays of BOOL to handle individual resetting, and show Unacknowledged/Acknowledged status.

Not for the faint of heart

rdrast said:

For one thing, the message(s) aren't actually exposed for program manipulation....

Click to expand...

What could theoretically be done (not that I recommend it) is to create UDTs that have the same data structure(-ish) as the ALMD and ALMA tags, and COP the ALMD into the UDT, manipulate its string (since as a UDT, it would be exposed to the PLC) then COP it back.

Getting the right number of bytes, in the right order, is not an easy task, but is possible.

Aardwizz said:

What could theoretically be done (not that I recommend it) is to create UDTs that have the same data structure(-ish) as the ALMD and ALMA tags, and COP the ALMD into the UDT, manipulate its string (since as a UDT, it would be exposed to the PLC) then COP it back.

Getting the right number of bytes, in the right order, is not an easy task, but is possible.

Click to expand...

...
Ouch.
I really think it is easier to just roll your own, actually. Or use an SCADA (like Ignition) that handles alarming exceptionally well just from the HMI.