Glossary · Distributed automation and IEC 61499
Data output (IEC 61499)
Also known as: Data output variable
German: Datenausgang
In IEC 61499, a data output is an output of a function block interface that provides a typed data value to connected blocks; it is associated through a WITH qualifier with the event outputs that signal that the value is valid.
- IEC 61499
- Standards
In one sentence
An IEC 61499 data output provides a typed value to connected blocks, signaled as valid by its associated event output.
Example
A measurement block updates its data output VALUE and then fires the event output IND, which tells the connected blocks to read the new value.
How it applies
- Engineering: Data outputs carry results such as calculated values, statuses or commands. The associated event output tells downstream blocks when to sample the value, so data and event connections are designed together.
- Distribution: When a data output is connected to a block on another device, the value travels with the event over the network, typically through communication function blocks. Network delays then affect timing.
- Testing: Tests check that the data output holds the expected value at the moment the associated event is emitted.
- Documentation: Document each data output with type, unit, meaning and associated events. For outputs that feed other systems, the description is part of the interface specification.
Data output vs. event output
A data output carries a value. An Event output carries only the fact that something happened. In IEC 61499, the two work as a pair, linked by the Event-data association.