What is BS EN 61158-3-7 - Data-link layer service definition — Type 7 elements about?
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:
- The primitive actions and events of the service
- The parameters associated with each primitive action and event, and the form in which they take
- The interrelationship between these actions and events, and their valid sequences
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.
Who is BS EN 61158-3-7 - Data-link layer service definition — Type 7 elements for?
BS EN 61158-3-7 on data-link layer service definition is useful for:
- Small scale automation industries
- Large scale automation industries
- Network controlling companies
- Transport companies
Why should you use BS EN 61158-3-7 - Data-link layer service definition — Type 7 elements?
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.
What’s changed since the last update?
BS EN 61158-3-7:2008 supersedes BS EN 61158-3:2004 which is withdrawn.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:
- Deletion of Type 6 Fieldbus, and the placeholder for a Type 5 Fieldbus data-link layer, for lack of market relevance
- Addition of new Fieldbus types
- Partition into multiple parts numbered 3-1, 3-2, …, 3-19
