IEC 61158-5-4:2019

IEC 61158-5-4:2014 defines the services provided to the FAL user at the boundary between the user and the application layer of the fieldbus reference model, and Systems Management at the boundary between the application layer and Systems Management of the fieldbus reference model. This standard specifies the structure and services of the IEC fieldbus application layer, in conformance with the OSI Basic Reference Model (ISO/IEC 7498-1) and the OSI application layer structure (ISO/IEC 9545). This second edition cancels and replaces the first edition published in 2007 and constitutes an editorial revision with minor editorial changes.

IEC 61158-5-4:2023 provides common elements for basic time-critical and non-time-critical messaging communications between application programs in an automation environment and material specific to Type 4 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. Failure to complete specified actions within the time window risks failure of the applications requesting the actions, with attendant risk to equipment, plant and possibly human life.