Glossary · Distributed automation and IEC 61499
Event output
Also known as: Output event
German: Ereignisausgang
In IEC 61499, an event output is an output of a function block interface through which the block emits events to signal that an operation has completed or a condition has occurred; associated data outputs are valid when the event is emitted.
- IEC 61499
- Standards
In one sentence
An IEC 61499 event output signals that a function block finished an operation; associated data outputs are then valid.
Example
After its algorithm finishes, a block emits the event output CNF, which triggers the next block in the chain to read the result.
How it applies
- Engineering: Event outputs chain blocks together. Common names are INITO (initialization confirmed), CNF (confirmation of a request) and IND (indication of an unsolicited event). In basic function blocks, ECC states emit event outputs as actions.
- Design: An event output can be connected to several event inputs, but the resulting execution order should not be relied on unless the runtime defines it. Splitting blocks such as E_SPLIT make the order explicit.
- Testing: Tests check that each request event is answered with the expected output event and data.
- Documentation: Document the meaning of each event output and the data outputs valid with it. Interface tables for IEC 61499 block types always need both event and data columns.
Event output vs. data output
An event output says that something happened. A Data output (IEC 61499) says what the result is. Downstream blocks react to the event and read the data associated with it.