Glossary · Distributed automation and IEC 61499
Adapter interface
Also known as: Adapter (IEC 61499), Adapter interface type, Plug and socket (IEC 61499)
German: Adapterschnittstelle
In IEC 61499, an adapter interface is a reusable bundle of event and data inputs and outputs, defined as an adapter interface type, that connects two function blocks through a single adapter connection: the providing block exposes it as a plug, the accepting block as a socket, and events and data flow in both directions.
- IEC 61499
- Standards
In one sentence
An IEC 61499 adapter interface bundles events and data in both directions into one plug-to-socket connection between two function blocks.
Example
An adapter type AXIS carries the events MOVE and DONE and the data TARGET_POS and ACT_POS; the motion block has an AXIS plug, the drive block an AXIS socket, and one adapter connection replaces eight single lines.
How it applies
- Structure: An adapter interface type declares event inputs and outputs, data inputs and outputs and their WITH associations, like the interface of a Function block type, but it has no behavior of its own. The type is written from the plug's point of view; at the socket the directions are mirrored, so what the plug sends is what the socket receives.
- Plugs and sockets: A function block that provides the interface has a plug, a block that accepts it has a socket. An adapter connection always joins exactly one plug with one socket of the same adapter type. Inside a Composite function block the plugs and sockets appear as blocks that can be wired to the internal network; since the second edition of IEC 61499-1, a Basic function block can also use adapters, and its ECC and algorithms read and write the adapter's events and variables.
- Engineering: Adapters turn a handshake that needs many parallel event and data lines into one typed connection. Typical uses are interfaces between a conveyor segment and its neighbor, between a motion block and a drive, or between a machine module and the line. Changing the adapter type changes every plug and socket that uses it.
- Behavior contract: Because the adapter type has no ECC, the expected order of events (request, confirmation, error) must be agreed separately. Service sequence diagrams, which IEC 61499-1 allows for all interface types, are the standard way to write that contract down.
- Documentation: Document each adapter type once: its events and data with direction seen from the plug, the WITH associations, the service sequences and the blocks that provide or accept it. Application diagrams then only need to show the connection and name the type.
Adapter interface vs. single event and data connections
Single connections link one output to one input and must be drawn and checked one by one. An adapter interface groups a bidirectional set of events and data under one type, so the two ends always match. The adapter connection is a design-time bundle; at runtime the same events and data are exchanged as if they had been connected individually.