Allen-Bradley LOGIX 5000 Reference Manual page 106

Chapter 1 Process Control Instructions
Description
The POSP instruction usually receives the desired position setpoint from a PID
instruction output.
Scaling the Position and Setpoint Values
The PositionPercent and SPPercent outputs are updated each time the instruction
is executed. If either of these values is out of range (less than 0% or greater than
100%), the appropriate bit in Status is set, but the values are not limited. The
instruction uses these formulas to calculate whether the values are in range:
How the POSP Instruction Uses the Internal Cycle Timer
The instruction uses CycleTime to determine how often to recalculate the
duration of Open and Close output pulses. An internal timer is maintained and
updated by DeltaT. DeltaT is the elapsed time since the instruction last executed.
Whenever the internal timer equals or exceeds the programmed CycleTime (cycle
time expires) the Open and Close outputs are recalculated.
You can change the CycleTime at any time.
If CycleTime = 0, the internal timer is cleared to 0, OpenOut is cleared to false
and CloseOut is cleared to false.
106 Rockwell Automation Publication 1756-RM006K-EN-P - November 2018