Flashers logic

I just come across this logic. Needless to say i am not a expert. Can someone explain how this logic works . I have attached the pdf.

Flashing logic pdf

That is truly weird.

It looks like it must be called, periodically, every ten milliseconds, if the labels are to be believed.

To understand the counters think of the last have of the previous scan. By providing an 'Always Off' enable the CU (Count Up) bit is cleared. Now in the first half of the next scan of this logic the 'Always On' triggers one count.

They are generating toggling by examining the accumulators of the counters. But I don't think the toggle outputs (bottom section) or the counter resets are correct.

I have no idea why they used counters. Simple ADD instructions would have been far simpler to see and would work fine in a periodic task. Instead of "RES, you would just MOV a 0 into the tag. I agree that the output controls are incorrect, particularly rungs 10 and 12.