IEC 61158-4-2:2019

Overview

IEC 61158-4-2:2019 - Industrial communication networks - Fieldbus specifications - Part 4-2 - is the international standard that defines the data-link layer protocol (Type 2 elements) for fieldbus systems. This fourth edition (2019) replaces the 2014 edition and specifies procedures for the timely transfer of data and control information between data-link user entities, the structure and encoding of DLPDUs (Data-Link Protocol Data Units) and their representation as physical interface data units. It formalizes media access, addressing, QoS and scheduling mechanisms used by Type 2 fieldbus implementations.

Key topics and technical requirements

• Data-link services: connected and connectionless transfer, queue maintenance, tag filtering, synchronization and event reporting.
• DLPDU and Lpacket structure: definitions for DLPDU components, preamble, delimiters, Lpackets and Frame Check Sequence (FCS) handling.
• Addressing and identifiers: MAC ID, generic and fixed tag addressing and DL-address structure.
• Media access & scheduling: Access Control Machine (ACM), moderator behavior, sending/receiving scheduled and unscheduled DLPDUs.
• Station management objects: standardized objects and attributes including ControlNet, DeviceNet, TCP/IP interface, Ethernet Link, CCO, DLR, Port and keeper objects.
• Redundancy and mapping: additions for PRP/HSR protocol and PRP/HSR node tables; PRP/HSR protocol mapping; DLR protocol extensions.
• Interoperability & PhL interface: DLL-to-physical-layer assumptions, data encoding rules and physical interface data units (PhIDUs).
• Quality of Service (QoS) and indicator behavior updates (A.2.2 / A.2.4) and other editorial and clarifying changes compared to the previous edition.

Applications and who uses this standard

IEC 61158-4-2 is used where deterministic, timely and interoperable fieldbus data-link services are required:

• Automation engineers and control system architects designing industrial networks and deterministic communications.
• Device manufacturers and embedded systems developers implementing fieldbus data-link firmware (DLPDU/Lpacket handling, MAC logic).
• Network integrators and system vendors deploying networks using ControlNet, DeviceNet, Ethernet Link, DLR, PRP/HSR and TCP/IP interfaces.
• Test laboratories and certification bodies verifying conformance to data-link layer specifications.
• OEMs and asset owners who require standardized interoperability, redundancy (PRP/HSR) and resilience in industrial communication networks.

Related standards

• Part of the IEC 61158 fieldbus series (other parts cover physical layers, station management and application mappings).
• References to industry technologies such as ControlNet, DeviceNet, Ethernet Link, DLR and PRP/HSR are incorporated into the data-link specification to enable practical protocol mappings and interoperability.

Keywords: IEC 61158-4-2:2019, fieldbus, data-link layer, DLPDU, Lpacket, ControlNet, DeviceNet, PRP, HSR, DLR, Ethernet, TCP/IP, industrial communication networks.