General
With each type of event processing it is possible to use other input/output channels than those for the event.
As with tasks, exchanges are then performed implicitly by the system before (%I) and after (%Q) application processing.
Operation
The following table describes the exchanges and processing performed.
Phase |
Description |
|---|---|
1 |
The occurrence of an event reroutes the application program to perform the processing associated with the input/output channel which caused the event. |
2 |
All inputs associated with event processing are acquired automatically. |
3 |
The event processing is executed. It must be as short as possible. |
4 |
All the outputs associated with the event processing are updated. |
Premium/Atrium PLCs
The inputs acquired and the outputs updated are:
the inputs associated with the channel which caused the event
the inputs and outputs used during event processing
to a channel (e.g. counting module) or
to a group of channels (discrete module). In this case, if the processing modifies, for example, outputs 2 and 3 of a discrete module, the image of outputs 0 to 7 is then transferred to the module.
Quantum PLCs
The inputs acquired and the outputs updated are selected in the configuration. Only local inputs/outputs can be selected.
Programming Rule
The inputs (and the associated group of channels) exchanged during the execution of event processing are updated (loss of historical values, and thus edges). You should therefore avoid testing fronts on these inputs in the master (MAST), fast (FAST) or auxiliary (AUXi) tasks.