RSLogix 5000 TONR won't work in SFC

[Robert Richter]

I have found the TONR instruction resets, the RTOR doesn't reset, but won't update the timer on the first scan of an N rung or a P1 rung. So, in both cases, TimerEnable is effectively false when calling RTOR or TONR from an SFC on a P1 or the first scan of an N even though the bit itself is true.

Create a simple loop that guarantees that an N only runs for one scan and then the step moves on. Put a RTOR in this step's N action and watch the timer never get updated.

 

[Robert Richter]

As suspected, I created a loop where I used RTOR with and updated it with the N action. The loop is fast enough so that each step is only active a few scans. The timer is running slower than it should because the N actions that are called when the step first becomes active do not update, so the timer stops on those steps.

 

[Robert Richter]

Subroutines are also affected. If I call a structured text subroutine only from a p1 action, I cannot use either tonr or rtor in that subroutine.