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.

• An additional constraint is that each event input of a simple FB type shall have exactly one correspondingly named simple state and vice versa.

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

• You can Add a simple EC state to the ECC directly from a list of available event input names in the Add State submenu of the ECC's popup menu.
• You can Edit a simple EC state in the EC State Dialog.
  • In addition to the error messages for duplicate names and invalid name syntax, the dialog will display an error message if you attempt to create a simple EC state with the name of an event input that is already in use in an EC transition condition.
• The list of event input names in the EC Transition Dialog is limited to those that are not currently in use as the names of simple EC states.
• If the ECC contains only simple states, the text under the XML and src tabs is adjusted to match the syntax defined for simple FB types.
• The Java™ code generated via the File Save dialog includes special provisions for efficient execution of simple EC states. You can use the FBDK to compare and contrast the generated code for the functionally equivalent Basic FB types Basic0T and Basic1T, and the Simple FB type Simple2T.

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.