IEC 61158-5-20:2014

Overview

IEC 61158-5-20:2014 is an international standard developed by the International Electrotechnical Commission (IEC) focusing on industrial communication networks, specifically fieldbus specifications. This part, titled "Application layer service definition – Type 20 elements," defines application layer services provided to users and system management in fieldbus environments. It aligns with the OSI Basic Reference Model (ISO/IEC 7498-1) and the OSI application layer structure (ISO/IEC 9545), ensuring compatibility and interoperability within industrial automation networks.

This third edition updates and replaces the 2010 version by incorporating new data types and services, revising normative references, terms, and definitions, and fixing editorial issues to reflect the latest technological advances. It is foundational for ensuring effective communication between automation applications via fieldbus systems, supporting both time-critical and non-time-critical messaging in industrial settings.

Key Topics

• Fieldbus Application Layer (FAL) Services: The standard specifies how application programs access and communicate over the fieldbus, serving as a window between corresponding applications. This includes defining abstract models for application resources (objects) that can be manipulated.

• Time-Critical Messaging: Addresses communications requiring actions within specific time windows to avoid risks in equipment, plant operations, or safety, underscoring the importance of real-time communication in industrial processes.

• Data Types and Service Definitions: Detailed formal definitions of data type objects and associated services are provided to standardize the behavior and structure of communications at the application layer.

• Communication Model Specification: Provides parameters, classes, and service roles, including Abstract Service Elements (ASEs) and Application Resources (ARs), defining how entities interact in the network.

• Standards Compliance: Fully compliant with OSI model principles, promoting layered architecture that separates communication concerns for scalability and maintainability.

Applications

IEC 61158-5-20:2014 is crucial for organizations and engineers involved in designing, implementing, and maintaining industrial automation systems where fieldbus communication plays a central role. Key practical applications include:

• Industrial Automation Systems: Supporting reliable and timely information exchange between sensors, actuators, controllers, and other devices on a fieldbus network.

• Process Control Environments: Ensuring timely and safe operations in complex manufacturing or chemical processing plants through deterministic messaging services.

• Safety-Critical Systems: Facilitating communication protocols that honor strict deadlines essential to protect equipment and human operators from potential hazards.

• System Integration: Assisting engineers with standardized application layer interfaces that enable interoperability between devices and systems from multiple vendors.

• Industrial Network Management: Defining services not only for application communication but also for system management functions, helping monitor and maintain network health.

Related Standards

IEC 61158-5-20 is part of the broader IEC 61158 series on industrial communication networks and fieldbus specifications. Related standards include:

• IEC 61158-1: Defines the fieldbus reference model, including overall system architecture and layer structure.

• IEC 61158-5-x (other parts): Cover application layer service definitions for different protocol types, helping support diverse industrial network profiles.

• IEC 61784-1 and IEC 61784-2: Specify combinations of protocol types, including the mapping and use of Type 20 elements in industrial protocols.

• ISO/IEC 7498-1 and ISO/IEC 9545: The foundational OSI model documents referenced for layering and abstract service definition.

• IEC 61158-6: Specifies data link layer services to complement the application services defined in IEC 61158-5-20, ensuring a complete protocol stack for fieldbus communication.

The IEC 61158-5-20:2014 standard serves as a cornerstone for industrial communication network design, enabling robust, interoperable, and deterministic application layer communication essential for modern automated and safety-critical industrial systems. Implementing this standard helps achieve harmonized communication protocols facilitating system integration, operational efficiency, and network reliability.