IEC 61158-6-19:2019

Overview

IEC 61158-6-19:2019 is part of the IEC 61158 fieldbus specifications and defines the application layer protocol elements for Type 19. It provides common elements for both time‑critical and non‑time‑critical messaging between application programs in automation systems and includes material specific to Type 2 fieldbus. The standard defines the wire representation of service primitives and the externally visible behavior associated with their transfer, aligned with the OSI Basic Reference Model (ISO/IEC 7498‑1) and OSI application layer structure (ISO/IEC 9545).

Key Topics

• Application layer protocol: Definition of service primitives, transfer syntax and wire representation for Type 19 elements.
• Time‑critical messaging: Concepts of time‑windows and required certainty levels for completing actions; implications for safety and system reliability.
• Protocol machines and state machines: Formal descriptions of AP context state machines, FAL service protocol machine (FSPM), Application Relationship Protocol Machine (ARPM) for master/slave, and DLL mapping protocol machine (DMPM).
• Primitives and PDUs: Specification of RTC PDU attribute formats and mapping between application and data link layers.
• Operational features: Hot‑plug support, redundancy handling, phase switching, and enhanced error handling - significant improvements in the 4th edition.
• Conformance and interoperability: Rules for externally visible behavior and conformance to ensure consistent implementations across devices and vendors.

Applications

IEC 61158-6-19 is used to design, implement and verify application layer behavior in industrial communication systems where reliable messaging and interoperability are required. Typical practical applications include:

• Fieldbus device firmware and stack development (application layer implementation)
• System integrator configuration for distributed automation and control systems
• Network architecture design where time‑bound actions are critical (e.g., motion control, process protection)
• Implementing hot‑plug and redundancy strategies for continuous plant operation
• Diagnostic and error‑handling mechanisms within fieldbus networks

Who should use this standard

• Automation and control engineers
• Industrial communication protocol developers and stack vendors
• Device manufacturers seeking interoperability and conformance
• System integrators and OEMs designing safety‑critical or time‑sensitive systems
• Network architects responsible for redundancy and hot‑plug capabilities

Related standards

• ISO/IEC 7498‑1 (OSI Basic Reference Model)
• ISO/IEC 9545 (OSI application layer structure)
• Other parts of IEC 61158 (fieldbus specifications)
• IEC 61784‑1 and IEC 61784‑2 (protocol type combinations and profiles)

Keywords: IEC 61158-6-19, fieldbus, application layer, Type 19, time-critical messaging, hotplug, redundancy, OSI, industrial communication networks, protocol state machine.