Definition of the execution model used in the Fuber IEC 61499 runtime environment

The buffered sequential execution model (BSENI) for IEC 61499 function block applications is presented. Before the execution of the application the composite function blocks are flattened. The resulting application containing the basic and service interface function blocks is executed. The basic function blocks are put in the ready queue in the same order that they receive the input events, hence the word “sequential” in the name. Each basic function block keeps a queue of incoming events with their associated data, hence the word “buffered” in the name. Scheduling policy of the blocks is in the scheduling function while the execution policy of the received events is in the function block instance. The extended finite automata models suitable for formal verification of the proposed execution model’s behavior are presented. The model may be analyzed using a discrete event systems tool called Supremica. The presented execution model is implemented in the Fuber runtime environment.