BS EN 61158-6-20:2014

What is BS EN 61158-6-20 – Type 20 application layer protocol specification about?

BS EN 61158-6-20 is one of a series produced to facilitate the interconnection of automation system components. BS EN 61158-6-20 is related to other standards in the set as defined by the “three-layer” fieldbus reference model described in IEC 61158-1.

BS EN 61158-6-20 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 20 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 61158-6-20 defines in an abstract way the externally visible behaviour provided by type 20 of the fieldbus application layer in terms of:

• The abstract syntax defining the application layer protocol data units conveyed between communicating application entities
• The transfer syntax defining the application layer protocol data units conveyed between communicating application entities
• The application context state machine defining the application service behaviour visible between communicating application entities
• The application relationship states machines defining the communication behaviour visible between communicating application entities

Who is BS EN 61158-6-20 – Type 20 application layer protocol specification for?

BS EN 61158-6-20 on industrial communication networks is useful for:

• The IT industry / Software programmers 
• The automation industry
• Networking sectors
• Implementors and designers of industrial automation systems

Why should you use BS EN 61158-6-20 – Type 20 application layer protocol specification?

The application protocol provides the application service by making use of the services available from the data link or other immediately lower layer.

BS EN 61158-6-20 provides you with a set of rules for communication expressed in terms of the procedures to be carried out by peer application entities (AEs) at the time of communication. These rules for communication are intended to provide a sound basis for development in order to serve a variety of purposes:

• As a guide for implementors and designers
• For use in the testing and procurement of equipment
• As part of an agreement for the admittance of systems into the open systems environment
• As a refinement to the understanding of time-critical communications within OSI

Overall, by using BS EN 61158-6-20 together with other standards positioned within the OSI or fieldbus reference models, otherwise incompatible systems may work together in any combination.