IEC 61158-5-2:2023

Overview

IEC 61158-5-2:2023 is part of the IEC 61158 fieldbus specifications and defines the application layer service definition - Type 2 elements for industrial communication networks. The standard provides common elements for both time‑critical and non‑time‑critical messaging between application programs in automation systems and supplies material specific to Type 2 fieldbus implementations. It clarifies the meaning of “time‑critical” as actions that must complete within defined time windows to avoid risks to equipment, plant or people.

Key topics and technical requirements

• Application service elements (ASEs) - formal definitions for ASE classes (e.g., object management ASE, connection manager ASE, connection ASE) and their services and state machines.
• Communication model - object-oriented communication model including naming, addressing (MAC, class, instance, attribute IDs), and relationships between ASEs and ARs.
• Data types and data modelling - FAL defined data types (fixed-length, strings, structures), type conversion rules and formal data type ASE services.
• Connection and transport services - definitions for connection setup, binding of producers/consumers, transport ARs (including UCMM and Transport AR formal models), fragmentation and session management.
• Time synchronization - Type 2 time synchronization concepts (PTP-related clock models, group startup sequences) for deterministic, time‑critical operations.
• Diagnostics and management - diagnostic connection points, object/parameter state transition diagrams, status codes and management services (Get/Set Attributes, Create/Delete, Start/Stop).
• Operational behavior - timers (transmission trigger, inactivity watchdog, production inhibit), acknowledge handling, and message routing behavior for acknowledged/unacknowledged data production.
• Conformance and normative references - includes conventions, terms aligned with ISO/IEC profiles and conformance statements to ensure interoperability.

Applications and who uses it

IEC 61158-5-2 is intended for:

• Control system architects and automation engineers designing deterministic messaging for manufacturing, process and safety‑critical plants.
• Device and fieldbus stack vendors implementing Type 2 application-layer services and ensuring interoperability.
• System integrators configuring connections, time synchronization and diagnostic services across heterogeneous devices.
• Safety engineers and operations teams requiring documented timing guarantees for time‑critical control actions.

Practical uses include deterministic I/O exchange, clock synchronization in distributed controllers, engineered connection setup for PROFINET/Fieldbus-like networks, and diagnostic/management tooling integration.

Related standards

• IEC 61158 (overall Fieldbus specifications series)
• IEC 61158-5 (other Part 5 family documents for different Type elements)
• ISO/IEC communications and data modelling standards referenced within the document (terminology and service models)

Keywords: IEC 61158-5-2:2023, fieldbus, application layer, Type 2, industrial communication networks, time‑critical messaging, time synchronization, ASE, AR, connection manager, data types, automation.