Allen-Bradley LOGIX 5000 Reference Manual page 109

Process Control Instructions
Execution
Function Block
Condition/State
Prescan
Tag.EnableIn is false
Tag.EnableIn is true
Instruction first run
Instruction first scan
Postscan
Structured Text
Condition/State
Prescan
Normal Execution
Postscan
Examples
Example 1
In this example, the POSP instruction opens or closes a motor-operated valve
based on the CVEU output of the PIDE instruction. The actual valve position is
wired into the Position input and optional limit switches, which show if the valve
is fully opened or closed, are wired into the OpenedFB and ClosedFB inputs. The
OpenOut and CloseOut outputs are wired to the open and close contacts on the
motor-operated valve.
Rockwell Automation Publication 1756-RM006K-EN-P - November 2018
Action Taken
EnableIn and EnableOut bits are cleared to false.
EnableIn and EnableOut bits are cleared to false.
EnableIn and EnableOut bits are set to true.
The instruction executes.
N/A
OpenTime and CloseTime are cleared to 0.0.
EnableIn and EnableOut bits are cleared to false.
Action Taken
See Prescan in the Function Block table.
See Tag.EnableIn is true in the Function Block
table.
See Postscan in the Function Block table.
Chapter 1
109