IEC 61158-4-4:2023

Overview

IEC 61158-4-4:2023 is an international standard that specifies the data-link layer protocol for a Type 4 fieldbus in industrial communication networks. It defines the procedures and message structures required for the timely transfer of data and control information between peer data-link user entities and among the data-link entities that make up the distributed data-link service provider. The standard also describes the structure and physical representation of fieldbus DLPDUs (Data-Link Protocol Data Units) and PhIDUs (Physical Interface Data Units).

Key Topics

• Data-link layer protocol definition: functional classes, DLL functions and service assumptions from the physical layer (PhL).
• DLPDU and PhIDU structure: encoding, frame check sequences and common/ specific PDUs (confirmed, unconfirmed, acknowledge, immediate-reply).
• State machines and procedures: DLE (Data-Link Entity) state diagrams for transmit/receive behavior, confirmed vs unconfirmed transfers, and acknowledgement handling.
• Routing and link access: Type 4-route formats (Simple, Extended, Complex, Immediate, IP), DL-route generation and link-access mechanisms.
• Operational elements: local variables, counters and queues used by the protocol (e.g., retry limits, bit rate, indication delay).
• Protocol extensions: edition 4 includes an extended data size option for DLS-user data restricted to nodes on a P‑NET IP network.

Applications

IEC 61158-4-4:2023 is applied wherever robust, deterministic data-link communication is required in industrial automation and process control:

• Designing and implementing fieldbus device firmware and data-link stacks.
• Specifying device-to-device communication behavior for sensors, actuators, and controllers.
• Integrating fieldbus networks in manufacturing systems, distributed I/O installations, and process plants.
• Developing test suites, conformance tests and interoperability validation for Type 4 fieldbus implementations.

Who Uses This Standard

• Industrial network architects and system integrators
• Embedded firmware and protocol stack developers
• Device manufacturers and OEMs building fieldbus-enabled equipment
• Test laboratories, certification bodies and compliance engineers

Related Standards

• IEC 61158 series (fieldbus specifications) - general framework and other protocol parts
• IEC 61158-1 (fieldbus reference model, three-layer model)
• IEC 61784-1 / IEC 61784-2 (protocol type combinations and profiles)

Keywords: IEC 61158-4-4:2023, data-link layer protocol, fieldbus DLPDU, PhIDU, industrial communication networks, P‑NET IP, Type 4 fieldbus, link access, routing.