Further Understanding AOI RSLogix

[Tharon]

I have noticed that a TON's ACC value increases as long as the input is TRUE. When it reaches the .PRE value, the .DN bit goes true but the .ACC continues to increase. However, a RTO's .ACC value stops increasing once the .DN bit goes TRUE, regardless of the input's state.

The ACCumlator does not continue to accumulate after it reaches the PREset value. Once it reaches the PREset value, it stops.

What you may see is a slight overshoot on the ACC value. But this is due to the way the Timer and the program scan time interact.

If the timer reaches the PREset value before it gets scanned, the ACCumulator will count up a bit more until it is scanned and the Timer is Done. Then it will stop. So you may see, for example, a Timer that is Done with the PREset value of 1000 ms, but the ACCumulator sitting at 1004.

Showshocka, did you find YYY.J_TM used elsewhere in the program? It sounds like somewhere outside the AOI is changing the allowed Jamming time, which is why you are seeing the J_TM value change in your AOI.

 

[rdrast]

The Mystery is how is J_TM is moving while the conveyor is running the only other thing that I can think of is that the variations are coming from a VFD output. I see in the definition of the AOI that the set time is 6000 and it goes up or down from there. The Motor does not have an encoder on it so it must be a value coming from a VDF. Maybe, it has to be. My confusion now is whats the difference between and input/output vs an in/out in the AOI?

The definition has absolutely NOTHING to do with the USAGE of the AOI. You have Inputs to the AOI. The Input values REPLACE THE ONES IN THE DEFINITION.

AOI INPUT: Value is passed into the AOI from an external source via a copy, replacing the default value.
AOI OUTPUT: Value is copied from the AOI to an external destination, replacing the external value.
AOI IN/OUT: Value is directly referenced to the actual tag within the AOI. All operations on the tag within the AOI are immediately reflected in the external tag. All changes in the External tag are immediately reflected within an AOI.