Technical information

Tasks

EIO0000000638 04/2012

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:

z a higher priority task will preempt a lower priority task

z 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

unpredictable. For more information, Task Priorities (see page 43).

Type 4 types of task are available:

z Cyclic (see page 40)

z Freewheeling (see page 41)

z Event (see page 41)

Watchdog

(see page 42)

To configure the watchdog, you must define two parameters:

z Time: enter the timeout before watchdog execution.

z Sensitivity: defines the number of expirations of the watchdog timer before the

Controller stops in Exception mode.

POUs (see SoMachine,

Programming Guide)

The list of POUs (Programming Organization Units) controlled by the task is defined in the

task configuration window

z To add a POU linked to the task, use the command Add Pou and select the POU in the

Input Assistant editor.

z To remove a POU from the list, use the command Remove POU.

z The command Open POU opens the currently selected POU editor.

z To replace the currently selected POU of the list by another one, use the command

Change POU...

z 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.