Implementing Function Block Adapters

Function Block Adapters (FBAs) are new modeling elements, responsible for the connection of UML capsules and function blocks of the IEC 61131-3 standard. FBAs contain an interface to capsules as well as to function blocks and a description of the mapping between these interfaces. In this paper we discuss implementation issues of FBAs. While the specification of FBAs is completely platform-independent, we show that different hardware solutions force highly platform-dependent implementation models. In most cases a FBA is implemented in two programming languages an object oriented language and a language out of IEC 61131-3. While object oriented programs mostly implement an event-driven execution semantic, PLC programs are executed cyclically. Especially this heterogeneous implementation environment was the motivation for developing Function Block Adapters.