Programming manual M238 | 3 MB - BERGER - POSITEC

Tasks
The following table describes the fields of the Task Configuration screen:
Field Name Definition
Priority You can configure the priority of each task with a number between 0 and 31 (0 is the
highest priority, 31 is the lowest).
Only one task at a time can be running. The priority determines when the task will run:
a higher priority task will preempt a lower priority task
tasks with same priority will run in turn (2 ms time-slice)
NOTE: Do not assign tasks with the same priority. If there are yet other tasks that attempt
to preempt tasks with the same priority, the result could be indeterminate and unpredicable.
For more information, refer to Task Priorities (see page 39).
Type 4 types of task are available:
Cyclic (see page 35)
Freewheeling (see page 36)
Event (see page 36)
External event (see page 37)
Watchdog
(see page 38)
POUs (see SoMachine,
Programming Guide)
To configure the watchdog, you must define two parameters:
Time: enter the timeout before watchdog execution.
Sensitivity: defines the number of expirations of the watchdog timer before the
Controller stops program execution and enters into a HALT state (see page 44).
The list of POUs (Programming Organization Units) controlled by the task is defined in the
task configuration window
To add a POU linked to the task, use the command Add Pou and select the POU in the
Input Assistant editor.
To remove a POU from the list, use the command Remove POU.
The command Open POU opens the currently selected POU editor.
To replace the currently selected POU of the list by another one, use the command
Change POU...
POUs are executed in the order shown in the list. To move the POUs in the list, select
a POU and use the command Move Up or Move Down.
NOTE: You can create as many POUs as you want. An application with several small
POUs, as opposed to one large POU, can improve the refresh time of the variables in
online mode.
34 EIO0000000384 04/2012