IEC 61158-6-23:2023

Overview

IEC 61158-6-23:2023 - part of the IEC 61158 fieldbus series - defines the application layer protocol specification for Type 23 elements in industrial communication networks. It provides the common elements used for both basic time‑critical and non‑time‑critical messaging between application programs in automation environments. The standard describes syntax, message (PDU) types and semantic elements needed to implement interoperable application‑layer behavior on Type 23 fieldbus devices while addressing the requirement that some actions must complete within a defined time window to avoid operational or safety risks.

Key Topics and Technical Requirements

• Application layer protocol elements: Abstract syntax and encoding rules for FAL (Fieldbus Application Layer) PDUs, including types C, F, and T as defined in the document.
• FALPDU types and message sets: Detailed PDU families (examples listed in the standard) such as Connect, ConnectAck, Scan, Collect, Token, MyStatus, CyclicData, Persuasion, Setup, F‑Token, Transient, TestData and many SLMP (Seamless Message Protocol) related PDUs.
• Time‑critical vs non‑time‑critical messaging: Definitions and handling guidance where time windows impose deterministic delivery or action requirements.
• Data type assignments: Specifications for data types used by the application layer for Type 23 PDUs.
• Protocol syntax and state machines: Formal descriptions for encoding, state transitions and conventions (e.g., reserved bits, abstract syntax descriptions).
• Conformance and normative references: References to related ISO/IEC and IEC documents used for terms, encoding conventions and verification of conformance.

Practical Applications

• Implementing the application layer in Type 23 fieldbus devices (controllers, I/O modules, gateways).
• Designing deterministic messaging for industrial automation, process control and safety‑relevant applications where missing time windows could affect equipment or personnel.
• Developing device firmware and network stacks that must interoperate with other fieldbus nodes using the Type 23 application profile.
• Integrating SLMP‑based services, cyclic and acyclic data exchange, and PTP (Precision Time Protocol) related messaging referenced in the PDU lists.

Who Should Use This Standard

• Industrial automation engineers and control system architects
• Device manufacturers and firmware developers for fieldbus equipment
• System integrators and control panel designers
• Test and conformance labs validating Type 23 implementations
• Safety and functional‑safety specialists concerned with time‑critical messaging

Related Standards

• Other parts of the IEC 61158 family (fieldbus specifications)
• Referenced documents such as ISO/IEC 7498‑1 and ISO/IEC 8822 for networking terminology and layer concepts

Keywords: IEC 61158-6-23, fieldbus, application layer protocol, Type 23, industrial communication networks, time-critical messaging, FALPDU, SLMP, automation.