Glossary · Distributed automation and IEC 61499
Event-data association
Also known as: WITH qualifier, WITH association
German: Ereignis-Daten-Zuordnung
In IEC 61499, an event-data association, declared with the WITH qualifier, links data inputs or outputs of a function block to specific event inputs or outputs, so that the data is sampled or provided together with that event.
- IEC 61499
- Standards
In one sentence
An IEC 61499 event-data association (WITH) links data inputs or outputs to events, so data is sampled or sent with that event.
Example
The data inputs SPEED and DIRECTION are declared WITH the event input REQ, so the block reads both values only when a request arrives.
How it applies
- Engineering: WITH associations define data consistency in IEC 61499. When an event arrives, all associated data inputs are sampled together, and when an event is emitted, all associated data outputs are valid together. This matters especially when data travels between devices.
- Design errors: Missing associations are a common mistake: a data input not associated with any event may never be updated, and an output not associated with its event may not be transmitted over communication blocks.
- Testing: Tests should include cases where data changes without an event, to confirm that the block ignores it until the next associated event.
- Documentation: Show WITH associations in interface diagrams (usually as lines connecting event and data pins) and in interface tables. Readers need them to understand when values take effect.
Event-data association vs. data connection
A data connection links an output of one block to an input of another. The event-data association links a data pin to an event pin within one block's interface and decides when the connected value is used.