The Multi-Task System
Operating Manual XCA 1100 / XCA 1200
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Version 12/17
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9
The Multi-Task System
9.1
Overview
This is based on a real-time operating system controlled by task
priorities. A program is assigned to a task in the MULTIPROG
programming system . The tasks in turn are assigned to different
priority levels and times that ensure the order and duration of the
processing according to their importance.
There are three priority levels for tasks (
Figure122:
Multi-Task-System, priority
levels
Supervisor task
The supervisor task is a specially protected operating system task
that operates on the highest priority level. It detects errors such as
division by zero and task time overrun, and activates the
appropriate operating system task.
User and default tasks
All tasks that are inserted by the user run on the user and default
level. Certain important firmware tasks that have to be considered
when parameterizing user tasks also run on this level. See section
"Task Priorities", page 129. The user tasks are time-monitored
(Watchdog).
▪
Cyclical tasks
execute the programs assigned to them within a defined interval
under a user-defined priority. The task with the highest priority is
called first.
▪
Event tasks
are started by the controller operating system when particular
events occur, for example interrupt signal, CANopen task or
interpolation task.
▪
The default task
is the user task with the lowest priority. It is not time-monitored
and is activated as a background task when no higher priority
user task is active at the time.
Operating system tasks
Tasks for communication, debugging, memory management and
system control run unaffected by the user on the priority level for
the operating system task.
