Rockwell Automation Publication 1756-UM001M-EN-P - February 2012 161
Develop Applications Chapter 10
Task Priority
Each task in the controller has a priority level. The operating system uses the
priority level to determine which task to execute when multiple tasks are
triggered. A higher priority task will interrupt any lower priority task. The
continuous task has the lowest priority and is always interrupted by a periodic or
event task.
You can configure periodic tasks to execute from the lowest priority of 15 up to
the highest priority of 1. Configure the task priority using the Task Properties
dialog box.
Figure 27 - Configure Task Priority
Programs
The controller operating system is a preemptive multitasking system that is IEC
1131-3 compliant. This system provides the following:
• Programs to group data and logic
• Routines to encapsulate executable code written in a single programming
language
Each program contains the following:
• Program tags
• A main executable routine
• Other routines
• An optional fault routine
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