IEC 61158-6-13:2014 defines the protocol provided to define the wire-representation of the service primitives defined in IEC 61158-5-13, and define the externally visible behavior associated with their transfer. This standard specifies the protocol of the Type 13 fieldbus application layer, in conformance with the OSI Basic Reference Model (ISO/IEC 7498-1) and the OSI application layer structure (ISO/IEC 9545). This secod edition cancels and replaces the first edition published in 2007 and constitutes a technical revision. The main changes are: addition of synchronization feature, corrections and editorial improvements.