Simple States, ECCs and FB Types

The concept of a simple state, an EC state that has the same name as an event input and is not used as the source or destination of any EC transition, has been proposed as a possible extension to a future edition of the IEC 61499 Standard. The purpose of this extension is to provide a way to achieve immediate execution of one or more EC actions in a defined sequence upon the occurrence of an event at a specified event input, without otherwise affecting the state of the ECC.

In addition, the proposed extensions to IEC 61499-1 define a simple ECC as an execution control chart consisting solely of a set of simple states, and a simple FB type as a function block type, the behavior of whose instances is defined by a simple ECC. This extends and formalizes the concept of "simple" FB types currently defined in Annex D.2 of IEC 61499-1.

The FBDK now includes the following features to support these extensions:

To accommodate this extension, the online LibraryElement.dtd Document Type Definition (DTD) has been modified to include the new SimpleFB element. Basic FB Types developed with earlier versions of the FBDK are forward-compatible with this DTD.