If a Logic program is configured to have an Execution Method setting of On Interval, you can configure the system to automatically execute the program whenever one of the program’s inputs changes value. This is useful, as it means you can set a Logic program to execute on a timed basis, but only if its inputs have changed value.
To choose whether a Logic program executes only when its inputs have changed, you need to use the Input Change Detection check box on the Logic tab of Logic Program Form:
- If you check the Input Change Detection check box, the system will only execute the program if one of the program's inputs changes. This means that if the program is scheduled to be executed, but none of its inputs have changed value, the program will not be executed.
If your Logic program is designed to use database values in a calculation, and then write the result to a point, you should consider enabling the Execute on Quality Change feature (see Define whether a Logic Program Executes when the Quality of an Input Changes).
- If you clear the Input Change Detection check box, the system will execute the program according to its Interval settings (see Define the Interval Settings for a Logic Program). The program will still be executed even if the program's input values have not changed since it was last executed. The program will have updated events etc. relating to the execution.
Further Information
Display the Logic Program Form: see Configure an ST Program, Ladder Diagram, SFC or FBD.