PLC Programming

Task Configuration...
may be extended by customer specific events. Possible events are for instance: Stop, Start, Online
Change.
The assignment of system events to POUs is also done in the Task configuration editor. Use the
dialog 'Events', which will be opened as soon as the entry " System-events" is selected in the task
configuration tree:
Table for Assigning POUs to System Events
Each event is represented in a line: Name and Description are displayed as defined in the target file,
in the column called POU you can enter the name of the project POU which should be called and
processed as soon as the event occurs.
For this use the input assistant () or enter manually the name of an already existing POU (e.g.
"PLC_PRG" or "PRG.ACT1"), or insert a name for a not yet existing POU. In order to get this POU
created in the project, press button Create POU. Hereupon the POU will be inserted in the Object
Organizer. The input and output parameters which are required by the event will automatically be
defined in the declaration part of the POU. Below the assignment table the currently selected event is
displayed in a picture, showing the required parameters.
If you actually want the POU to be called by the event, activate the entry in the assignment table ( ).
Activating/deactivating is done by a mouseclick on the control box.
Which task is being processed
For the execution, the following rules apply:
• That task is executed, whose condition has been met; i.e., if its specified time has expired, or after
its condition (event) variable exhibits a rising edge.
• If several tasks have a valid requirement, then the task with the highest priority will be executed.
• If several tasks have valid conditions and equivalent priorities, then the task that has had the
longest waiting time will be executed first.
• The processing of the program calls will be done according to their order (top down) in the task
editor.
Taskconfiguration in Online Mode
In online mode the status and number of passed through cycles of each task will be displayed in the
configuration tree. The time flow is monitored in a diagram. Precondition: the libraries SysTaskInfo.lib
and SysTime.lib must be included in the project to provide functions for the internal evaluation of the
6-38 CoDeSys V2.3