Rockwell Automation Publication 5069-UM002A-EN-P - January 2019 185
Develop Control Applications Chapter 8
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 interrupts any lower priority task. The
continuous task has the lowest priority and a periodic or event task interrupts
it.
The continuous task runs whenever a periodic task is not running. Depending
on the application, the continuous task could run more frequently than the
periodic tasks, or much less frequently. There can also be large variability in the
frequency that the task is called, and its scan time (due to the effect of the other
periodic tasks).
You can configure periodic and event tasks to execute from the lowest priority
of 15 up to the highest priority of 1. Use the Task Properties dialog box to
configure the task priority.
Figure 30 - Configure Task Priority
IMPORTANT If you configure multiple tasks with the same priority, the controller
timeslices them, which de-optimizes their application. This is not
recommended.
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