ALMD MinDuractionACC not accumulating

[Wildesy]

Hi all,

Can anyone tell me why the MinDuractionACC isn't accumulating in the example below? Is it just a visual bug?

I've tried in multiple different controllers and programs, but it never visually accumulates in the ALMD or in the actual tag. I swear I've seen them accumulating in the past and that's clearly how they are meant to work so I'm obviously missing something. The ALMD will go into alarm after the MinDurationPRE is completed so it is clearly keeping track of the accumulated time in alarm, just not displaying it.

Thanks

 

[drbitboy]

From Logix 5000 manual (https://literature.rockwellautomation.com/idc/groups/literature/documents/rm/1756-rm003_-en-p.pdf#%5B%7B%22num%22%3A138%2C%22gen%22%3A0%7D%2C%7B%22name%22%3A%22XYZ%22%7D%2C46%2C745%2Cnull%5D, page 51):

 

[Wildesy]

Wow, I swear it used to! Did it get bombed in the transition from Rslogix to Studio...?

Why would they keep it as part of the data type if it's not even used?

 

[drbitboy]

The 1756-RM003P manual ca. December 2014 manual still has it as used; the 1756-RM003Q manual ca. July 2016 does not.

 

[drbitboy]

This is probably why the value is not displayed in Logix/Studio 5000. 31 bits of a millisecond counter is just over half an hour [update: whoops! no, it's just under 25d], so the issue should have been pretty rare. Changing the internal behavior would have broken backward compatibility if anyone was using the value in the PLC in 2014 and replaced it after 2016, so I wonder if it is actually changing under the hood. Try COPying it to a UDINT buffer tag and see if the buffer tag's display changes?

You would think there is another 32-bits, somewhere in the structure, that is incrementing. Perhaps you can COP the entire structure to somewhere else and see what is changing.