IEC 61158-6-20:2014

Overview

IEC 61158-6-20:2014 is an international standard from IEC that provides the protocol specification for the application layer of Type 20 fieldbus in industrial communication networks. As part of the broader IEC 61158 series, it plays a key role in defining how automation system components communicate over fieldbus networks, ensuring reliable and interoperable data exchange. This third edition reflects updates in line with new services, upgraded references, and enhanced clarity, further supporting robust industrial automation solutions.

Key Topics

• Fieldbus Application Layer Protocol: IEC 61158-6-20:2014 defines the behavior and structure of the application layer protocol specifically for Type 20 fieldbus networks. It outlines the abstract and transfer syntax for protocol data units exchanged between devices.
• Conformance with OSI Model: The standard aligns with the OSI Basic Reference Model (ISO/IEC 7498-1) and the OSI application layer structure (ISO/IEC 9545), ensuring compatibility with established international communication frameworks.
• Time-Critical and Non-Time-Critical Messaging: Provides mechanisms for both urgent (time-critical) and regular (non-time-critical) communications between automation devices, catering to a range of industrial needs.
• State Machines and Communication Behavior: Specifies the externally visible behavior, including application context and relationship state machines, which governs how application layer services are managed and transferred.
• Technical Updates: This edition adds support for new services (from IEC 61158-5-20), includes newly normative annexes, updates terminology and references, prevents editorial errors, and enhances clarity.

Applications

IEC 61158-6-20:2014 is essential for industries seeking interoperable communication between automation devices such as sensors, actuators, and control systems. Key applications include:

• Process Automation: Ensures consistent and predictable communication in time-sensitive industrial processes, such as chemical, oil & gas, and manufacturing operations.
• Device Integration: Facilitates seamless interworking between devices from different vendors, promoting open system environments and reducing integration costs.
• System Design and Implementation: Used as a reference by designers and implementors for developing hardware and software that interact on Type 20 fieldbus networks.
• Testing and Procurement: Serves as a benchmark for equipment validation, selection, and acceptance in industrial automation projects.
• Safety and Reliability: Supports time-critical operations where delayed or lost messages could result in equipment damage or safety hazards.

By defining clear rules and behaviors for application layer communication, the standard underpins reliable data transfer, system scalability, and future-proof investment in industrial communication networks.

Related Standards

To maximize interoperability and implementation efficiency, IEC 61158-6-20:2014 should be used alongside related standards:

• IEC 61158-1: Overview and guidance for the entire IEC 61158 fieldbus series.
• IEC 61158-5-20: Service definition for the application layer protocol of Type 20, directly referenced in -6-20 for service primitives.
• ISO/IEC 7498-1: OSI Basic Reference Model, foundational for network layer structure.
• ISO/IEC 9545: Defines the structure of the OSI application layer.
• IEC 61784 Series: Profiles for communication networks in industrial systems, specifying protocol combinations and network functionality.

By conforming to these standards, organizations ensure compatibility, scalability, and adherence to global best practices in industrial communication protocols.

Keywords: IEC 61158-6-20, fieldbus specifications, industrial communication networks, application layer protocol, Type 20 fieldbus, OSI model, automation, process control, protocol specification, device interoperability.