Using a Functional Global (LabVIEW 2-Style Global) to Increase Determinism.

This example demonstrates how you can use a functional global variable, instead of a standard global variable, to increase the determinism of your time-critical code. This example includes the following three VIs:
1. Time Critical Priority Loop VI - This VI, set to time-critical priority, reads from the Global VI every second. If the Global VI is busy, the Time Critical Priority Loop VI skips it. Right-click on the Global VI placed inside of the Time Critical Priority Loop VI to see that the option "Skip Subroutine Call if Busy" has been selected.
2. Normal Priority Loop VI - This VI, set to normal priority, reads from the Global VI as quickly as it can. The Normal Priority Loop VI does not skip the Global VI if the Global VI is busy.
3. Global VI - This VI acts as a Functional Global, which is also called a LabVIEW 2-Style Global. The Global VI is set to subroutine priority which allows other VIs to skip the Global VI if the Global VI is busy. When the other VIs skip the Global VI, the Global VI returns the front panel indicator default values. The default for the "Skipped?" output of the Boolean front panel indicator is True.
Run the Time Critical Priority Loop VI and the Normal Priority Loop VI at the same time.

Requirements

Filename: functional_globals.zip

Software Requirements

Application Software: LabVIEW Full Development System 5.0
Language(s): LabVIEW

Reader Comments | Submit a comment »