Overview
IEC 61158-4-24:2019 is an international standard that defines the data-link layer protocol (Type 24 elements) for industrial fieldbus systems. This second edition (2019) replaces the 2014 edition and specifies procedures, frame formats and timing needed for the timely transfer of data and control information between peer data‑link user entities and among the data‑link entities that form a distributed data‑link service. Key updates include a patent declaration, corrections to fixed‑width time slot transmission sequencing, and a technical extension for band sharing between I/O data exchange and message communication.
Key topics and technical requirements
- Data‑link layer procedures: Rules for cyclic and acyclic data transfer, timing sequences and synchronization to guarantee deterministic communication.
- DLPDU structure: Definition of frame formats (basic and short), field encodings, destination/source addressing and PDU types for data and control.
- Timing and slot types: Fixed‑width and configurable time slot cyclic transmission modes, timing charts and requirements for predictable I/O exchange.
- Cyclic Transmission Control (CTC) and Send Receive Control (SRC): Sublayer components, state machines and interfaces that manage cyclic data flow and message handling.
- DL‑management layer (DLM): Primitives, parameters and management state machines (C1/C2 masters, slaves) to support configuration, diagnostics and control.
- Acyclic messaging: Token/message frames and procedures for non‑periodic communication alongside cyclic I/O.
- Delay measurement and synchronization: Frames and procedures for latency measurement and timing alignment across nodes.
- Band sharing extension: Technical provisions to share bandwidth between I/O cyclic exchange and message traffic, improving flexibility in mixed traffic deployments.
Applications and who uses it
IEC 61158-4-24 is intended for organizations and professionals involved in industrial communication and automation:
- Fieldbus and industrial network designers implementing Type 24 data‑link protocols.
- Device manufacturers (I/O modules, controllers, gateways) requiring compliant DLPDU formats and timing behavior.
- System integrators and automation engineers designing deterministic control systems.
- Firmware and protocol stack developers building CTC, SRC and DLM implementations.
- Test labs and certification bodies validating conformance, timing and interoperability.
Related standards
- Part of the IEC 61158 fieldbus family (other Part 4‑xx specifications define other Type elements).
- Typically used alongside application and physical layer specifications within IEC 61158 and complementary industrial network standards.
This standard is essential when deterministic, timely, and interoperable fieldbus data‑link behavior is required-especially for systems that must balance periodic I/O exchange with message traffic.