BS EN 61158-3-7 is the seventh subpart of the third part of the multiple series standard that provides common elements for basic time-critical messaging communications between devices in an automation environment. 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.
BS EN 61158-3-7 defines in an abstract way the externally visible service provided by the Type 7 Fieldbus data-link layer in terms of:
Note: 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.
BS EN 61158-3-7 on data-link layer service definition is useful for:
DL-segment, the local link is a set of devices that respect the DL protocol and that are interconnected through a PhL. Only one bus arbitrator is active on a single DL-segment.
BS EN 61158-3-7 defines the services provided to the Type 7 Fieldbus application layer at the boundary between the application and data-link layers of the Fieldbus reference model, and systems management at the boundary between the data-link layer and systems management of the Fieldbus reference model.
The principal objective of BS EN 61158-3-7 is to specify the characteristics of conceptual data-link layer services suitable for time-critical communications, and thus supplement the OSI Basic Reference Model in guiding the development of data-link protocols for time-critical communications and a secondary objective is to provide migration paths from previously-existing industrial communications protocols.
BS EN 61158-3-7:2008 supersedes BS EN 61158-3:2004 which is withdrawn.
With respect to EN 61158-3:2004 the following changes were made:
EN 61158-3-7:2008
IEC 61158-3-7:2007