AB - ONS and FLL

I'm using a CompactLogix L33ER with v24 of Studio 5000. I've been noticing some odd behavior when I trigger a FLL instruction behind an ONS. It looks like the FLL doesn't always fully execute throughout the array.

For example, using a FLL on a DINT[24] to set all values to zero. I still get the odd value ([18] in this example) that doesn't get set to zero.

Any ideas?

What are you setting as source and destination for the FLL? I will usually use 0 for source, the array/structure for destination, and a length of 1.

If it's always the same value, I'd be looking for other things that might be overwriting the data. Look especially for COP or CPS instructions with an incorrect length.

Create a whole new array of the same length and modify your existing logic to point to that array instead of your existing one. Don't change anything else - just the target array - and then see if the symptoms remain.

I'd be very, very surprised to learn of an FLL not "executing properly".

Jeev said:

What are you setting as source and destination for the FLL? I will usually use 0 for source, the array/structure for destination, and a length of 1.

Click to expand...

Source is 0.
Destination is [0] of DINT[24] array.
Length is 24.

As ASF said, I would then check what's able to access that structure.