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Rockwell Automation Publication 1756-UM001O-EN-P - October 2014 151

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 interrupts any lower priority task. The

continuous task has the lowest priority and a periodic or event task interrupts it.

You can configure periodic and event tasks to execute from the lowest priority of

15 up to the highest priority of 1. Configure the task priority by using the Task

Properties dialog box.

Figure 31 - Configure Task Priority

Programs

The controller operating system is a preemptive multitasking system that is in

compliance with IEC 1131-3. This system provides the following:

• Programs to group data and logic

• Routines to encapsulate executable code that is written in one

programming language

Each program contains the following:

• Local Tags

• Parameters

• A main executable routine

• Other routines

• An optional fault routine

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Allen-Bradley ControlLogix Manual de usuario Pagina 151