Counter won't count on First Pass?

AB Micrologix 1500.
In the following you see scan 1 and scan 2 using single step. Clearly the bit in the logic for the first counter is on during scan 1 as is the ote on rung 1. The XIO for First Scan is not shown as on... My question is why does the counter not count up?

not sure just what you’re trying to accomplish here - but this might help -

if the counter’s CU (Count Up) bit was left in a 1 state when the processor was either “shut down” or placed in the “program” mode, then the counter will not count up the next time it is executed with true logic -

Big idea: the CU bit is the processor’s way of reminding itself that it has already counted a particular true condition - think of it as something along the lines of a “built-in” One-Shot which keeps the counter from incrementing on each and every true scan -

experiment with this idea and see if things start to make sense -

  S:1/15           C5:0/CU

---] [--------------(U)---

sorry, out of time,

Thanks so much for your reply.

I was just trying to verify the rung got fired by using a counter to count each time it happened. That's when I saw that the counter on the first pass rung did not count up...


Thanks
John

... more fun ...

... verify the rung got fired ...

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