Defines common elements for basic time-critical and non-time-critical messaging communications between application programs in an automation environment and material specific to Type 16 fieldbus. The term "time-critical" is used to represent the presence of a time-window, within which one or more specified actions are required to be completed with some defined level of certainty.

IEC 61158-6-16:2007 describes the fieldbus application layer (FAL) which provides user programs with a means to access the fieldbus communication environment. In this respect, the FAL can be viewed as a \'window between corresponding application programs\'. It specifies the protocol of the Type 16 fieldbus application layer, in conformance with the OSI Basic Reference Model (ISO/IEC 7498) and the OSI application layer structure (ISO/IEC 9545). This first edition and its companion parts of the IEC 61158-6 subseries cancel and replace IEC 61158-6:2003. This publication, together with its companion parts for Type 16, also partially replaces IEC 61491:2002. It includes the following changes:
- deletion of the former Type 6 fieldbus for lack of market relevance;
- addition of new types of fieldbuses;
- partition of part 6 of the third edition into multiple parts numbered -6 2, -6 3,... This bilingual version (2013-09) corresponds to the monolingual English version, published in 2007-12.