periodic Task

I testing a simple periodic task. it has only one Rung consisting of an upcounter.
I expect that the counter counts any time the periodic task is executed. however it doesn't. is there anything else that I should be doing.

Logix 5000 ver 19.

Thanks

Always a learner

use an ADD instruction on an unconditional rung instead ...

Source A = test
Source B = 1
Destination = test

the Counter needs to see a "transition" from FALSE to TRUE in order to make a count ... the ADD doesn't ...

Remember that Counters execute only on a false-to-true transition of the rung conditions preceding them.

The ADD instruction, by contrast, will execute every scan if the rung conditions preceding it are true.

One way to make the Counter count every program scan is to place a rung after the counter that un-latches the .CU (Count Up) bit.

Thank you. That was very helpful. I can't believe I forgot such a simple fact about the counters operation.

An ADD is a better approach.

However, to use a counter you can just unconditionally unlatch the Counter.CU bit on a rung right after the counter. The .CU bit is how the counter detects a false to true transition of the rung. Clearing it lets the counter increment again on the next scan.