BS EN 61158-5-3:2014

What is BS EN 61158-5-3 - Application layer service definition - Type 3 elements about?

BS EN 61158-5-3 is part of the BS EN 61158 series that has been created to facilitate the interconnection of automation system components. The Fieldbus application layer (FAL) 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.”

BS EN 61158-5-3 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 3 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.

BS EN 61158-5-3 defines the externally visible service provided by the Type 3 Fieldbus application layer in terms of:

• An abstract model for defining application resources (objects) capable of being manipulated by users via the use of the FAL service
• 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

BS EN 61158-5-3 defines the services provided to:

• The FAL user at the boundary between the user and the application layer of the Fieldbus reference model
• Systems Management at the boundary between the application layer and Systems Management of the fieldbus reference model

BS EN 61158-5-3 specifies the structure and services of the Type 3 fieldbus application layer, in conformance with the OSI Basic Reference Model (ISO/IEC 7498-1) and the OSI application layer structure (ISO/IEC 9545).

Note: Nevertheless, it is not a formal programming interface, and any such interface will need to address implementation issues not covered by BS EN 61158-5-3, including

• The sizes and octet ordering of various multi-octet service parameters
• The correlation of paired request and confirm, or indication and response, primitives

Who is BS EN 61158-5-3 - Application layer service definition - Type 3 elements for?

BS EN 61158-5-3 on application layer service definition - type 3 elements is useful for:

• The IT industry / Software programmers  
• Internet engineering task forces
• Internet service providers
• Telecommunication companies 
• The automation industry 
• Networking sectors 

Why should you use BS EN 61158-5-3 - Application layer service definition - Type 3 elements?

BS EN 61158-5-3 is one of a series produced to facilitate the interconnection of automation system components. BS EN 61158-5-3 is related to other standards in the set as defined by the “three-layer” Fieldbus reference model described in IEC 61158-1. The application service is provided by the application protocol making use of the services available from the data link or other immediately lower layer. BS EN 61158-5-3 defines the application service characteristics that Fieldbus applications and/or system management may exploit. Throughout the set of Fieldbus standards, the term “service” refers to the abstract capability provided by one layer of the OSI Basic Reference Model to the layer immediately above. Thus, the application layer service defined in this document is a conceptual architectural service, independent of administrative and implementation divisions.

BS EN 61158-5-3 specifies the characteristics of conceptual application layer services suitable for time-critical communications, and thus supplement the OSI Basic Reference Model in guiding the development of application layer protocols for time-critical communications. A secondary objective is to provide migration paths from previously existing industrial communications protocols. It is this latter objective that gives rise to the diversity of services standardized as the various Types of IEC 61158, and the corresponding protocols standardized in IEC 61158-6 (all subparts). BS EN 61158-5-3 is to be used as the basis for formal application programming interfaces.

Using BS EN 61158-5-3 guidelines, you are in a position to facilitate communication between applications and accelerate productivity.