Glossary · Distributed automation and IEC 61499
Event input
Also known as: Input event
German: Ereigniseingang
In IEC 61499, an event input is an input of a function block interface through which the block receives events that trigger its execution; associated data inputs are sampled when the event arrives.
- IEC 61499
- Standards
In one sentence
An IEC 61499 event input receives events that trigger a function block's execution and sampling of associated data inputs.
Example
When the event input REQ of a calculation block receives an event, the block samples its data inputs and runs its algorithm.
How it applies
- Engineering: Event inputs control when a function block acts. Typical names are INIT for initialization and REQ for a request. In basic function blocks, event inputs appear in the transition conditions of the ECC.
- Design: Event chains determine the execution order of an application. Engineers trace event connections to understand what happens after a sensor event, much as they would read a sequence diagram.
- Timing: Event handling depends on the runtime's scheduling. Two events arriving at once are handled in an order defined by the runtime implementation, which should be known for time-critical designs.
- Documentation: For each event input, document what it requests and which data inputs are sampled with it.
IEC 61499 event input vs. event task
An event input triggers a single function block. An Event task in IEC 61131-3 starts a whole program. Both are event-driven, at different granularity. See also Event-driven communication.