IEC 61158-6-4 Ed. 3.0 en:2019

IEC 61158-6-4-:2019(E) defines the protocol provided to define the wire-representation of the service primitives defined in IEC 61158-5-4, and define the externally visible behavior associated with their transfer. This standard specifies the protocol of the Type 4 fieldbus application layer, in conformance with the OSI Basic Reference Model (ISO/IEC 7498-1) and the OSI application layer structure (ISO/IEC 9545).