IEC 61804-2:2018 specifies FB (function blocks)  by using the result of a harmonization work as regards several elements.
a) The device model which defines the components of an IEC 61804-2 conformant device.
b) Conceptual specifications of FBs for measurement, actuation and processing. This includes general rules for the essential features to support control, whilst avoiding details which stop innovation as well as specialization for different industrial sectors.
c) The electronic device description (EDD) technology, which enables the integration of real product details using the tools of the engineering life cycle.
This third edition cancels and replaces the second edition published in 2006 and integrates parts of IEC 61804-1 which was withdrawn in January 2013. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) added command communication mapping in Clause 8,
b) moved and reword compatibility level definition from IEC 62804-1 to new Annex B and terms and definitions,
c) added proxy concept in new Annex C.