General

Event processing is used to reduce the response time of the application program to events:

• coming from input/output modules,

• from event timers.

These processing tasks are performed with priority over all other tasks. They are therefore suited to processing tasks requiring a very short response time in relation to the event.

The number of event processing tasks that can be programmed depends on the type of processor.

Structure

An event processing task is monosectional, and made up of a single (unconditioned) section.

It is programmed in either LD, FBD, IL or ST language.

Two types of event are offered:

• I/O event: for events coming from input/output modules

• TIMER event: for events coming from event timers.

Execution

The execution of an event processing task is asynchronous.

The occurrence of an event reroutes the application program to the processing task associated with the input/output channel or event timer which caused the event.

Control

The following system bits and words can be used to control event processing tasks during the execution of the program.