Delta AX-3 Series, Operation Manual

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C h a p t e r 4 B a s ic O p e r a t i o n
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4.4 Task
Task Configuration
You define one or more tasks for controlling and executing the program blocks (POUs) in the PLC. You define a task with
a name, a priority, and a type, which determines which condition triggers the start of the task. You can define this condition
either by time (cyclic-interval, freewheeling) or by the occurrence of an internal or external event to process the task.
A task calls one or more program blocks (POUs). With the combination of priority and condition, you define the order in
which the tasks are processed. You can configure a watchdog for each task.
Rules for the processing order of the defined tasks:
•
If the task condition is satisfied, then the system processes the task.
•
If several tasks satisfy the condition for processing at the same time, then the system processes the tasks with
the highest priority first.
•
If several tasks with the same priority level satisfy the condition for processing at the same time, then the
system processes the longest waiting task first.
•
The program calls are processed in the order they appear in the configuration dialog of the task.
•
If a called program has the same name in the device tree of the application and in a library or project-global in
the POU window, then the application program is used.
Note: Set the priority level from 0 to 31. If the set number is closer to 0, it has higher priority.
4.4.1.1 Task Types
There are five types of task types:

Cyclic Task
：
The system processes the task in cycles. The cycle time of the task is defined in the input field Interval.

Event Task
：
The system starts processing the Event Task as soon as the global variable defined in the input
field Event contains a rising edge.

Freewheeling Task
：
The system starts processing the Freewheeling Task again automatically in a continuous loop at program start and
at the end of a complete pass.

Status Task
：
The system starts Status Task processing as soon as the variable defined in the Event input field yields the
Boolean value TRUE.