Logix5000 FOR instruction execution

HI guys!

Will a FOR instruction execute every scan or does it need to see a transition like a counter?

My gut says the former, but it never hurts to check.

Thanks in advance!

Yes the FOR loop executes every scan. As the scan hits the rung where the FOR loop resides, the FOR loop will execute the routine from the initial value to the terminal value. After all loop iterations have completed, the PLC scan will continue to the next rung of logic.

The FOR loop will index itself based on the step size configuration there is no need to trigger the for loop to index.

You could achieve similar function using in-direct addressing with a trigger to a counter to create an index. This method would require a trigger to increase the index, and only a single trigger would be possible per scan. The same operation could occur, just at a much slower rate since it would be a single iteration per PLC scan versus all interactions per scan with the FOR loop.

Thanks, Paully. Like I said, It's pretty much what I figured. Just nice to have that validation!