IEC 61499-1:2012 defines a generic architecture and presents guidelines for the use of function blocks in distributed industrial-process measurement and control systems (IPMCSs). This architecture is presented in terms of implementable reference models, textual syntax and graphical representations. The models given in this standard are intended to be generic, domain independent and extensible to the definition and use of function blocks in other standards or for particular applications or application domains. It is intended that specifications written according to the rules given in this standard be concise, implementable, complete, unambiguous, and consistent. This second edition cancels and replaces the first edition published in 2005 an constitutes a technical revision. It includes the significant technical changes with respect to the previous edition related to: Execution control, Temporary variables, Service sequences, the syntax for mapping of FB instances, the Syntax for definition of segment types, the Function block types for interoperation with programmable controllers and the READ/WRITE management commands.