Overview
IEC 61158-6-24:2023 is part of the IEC 61158 fieldbus family and specifies the application layer protocol elements for Type 24 fieldbus systems. The standard defines common elements for both time‑critical and non‑time‑critical messaging between application programs in industrial automation. It explains abstract and transfer syntaxes, APDU structures, device profiles and the behavior of protocol state machines to ensure deterministic, interoperable application‑level communication between controllers, field devices, monitors and messaging services.
Key topics and technical requirements
- Application layer protocol (FAL): Definitions of APDU types, FDC (Field Device Control) and MSG (Message) services, plus detailed PDU formats (short, long, enhanced, subcommand types).
- Time‑critical messaging: Concepts of time windows and deterministic behavior required for actions that, if not completed in time, risk equipment, plant or human safety.
- Protocol state machines: Formal statecharts and transition rules for APC (AP‑context), FDCPM (Field Device Control Protocol Machine), MSGPM (Message Protocol Machine), ARPM (Application Relationship Protocol Machine) and DMPM (DLL mapping).
- Transfer syntax and encoding rules: Encoding for INTEGER, REAL, BIT STRING, OCTET STRING, SEQUENCE and arrays used in APDUs.
- Device profile & virtual memory: Virtual memory map, device information and device ID area specifying how device data and configuration are represented.
- Conformance and interoperability: Rules for conformance testing and mappings to ensure multi‑vendor interoperability in Type 24 fieldbus networks.
- Normative references: Incorporates references to ISO/IEC foundational models (e.g., ISO/IEC 7498‑1, 9545) for terms and conventions.
Applications and who should use it
- Automation engineers designing deterministic communication for process and factory automation.
- Device manufacturers implementing fieldbus stacks, firmware and device profiles for sensors, actuators and intelligent field devices.
- System integrators and control‑system architects building multi‑vendor networks that require time‑critical and event‑driven messaging.
- Safety and validation engineers needing protocol behavior, timing and conformance guidance.
- Software developers creating application‑layer protocol implementations, gateways, and diagnostic tools interoperable with Type 24 fieldbus devices.
Related standards
- IEC 61158 series (other parts for physical/link layers and different Type classifications)
- IEC 61784 (profile and functional safety frameworks) - relevant for industrial communication profiles and safety integration
- ISO/IEC foundational documents referenced for terms and syntax (ISO/IEC 7498‑1, 9545, 8824‑1, etc.)
IEC 61158-6-24 is essential for professionals who need a precise, standardized application‑layer description to achieve deterministic, interoperable, and safe communications on Type 24 fieldbus networks.