Overview
IEC 61131-5:2000 - Programmable controllers: Part 5 Communications defines the communication aspects of a programmable controller (PC) within the IEC 61131 series. It specifies, from the viewpoint of the programmable controller, how any device can communicate with the PC as a server and how the PC application can communicate with devices. The standard describes PC behavior when providing services for other devices and the services a PC application may request. This bilingual (2012) edition corresponds to the English 2000 publication.
Keywords: IEC 61131-5, programmable controllers, communications, PLC communications, industrial automation, PC communication services, function blocks.
Key topics and technical requirements
- Communication models: Defines PC network communication, functional, hardware and software models to standardize interactions between controllers and devices.
- PC communication services: Specifies subsystems, status reporting, and application-specific functions for communications management.
- Communication function blocks: Standardized function blocks (e.g., STATUS, READ, WRITE, SEND, RCV, USEND/URCV, BSEND/BRCV, CONNECT, ALARM, NOTIFY) for implementing device verification, polled and programmed data acquisition, parametric and interlocked control, alarm reporting and connection management.
- Status and diagnostics: Detailed status types, signaling, timing diagrams and state machines for consistent error, status and health reporting across implementations.
- Compliance and implementer features: Tables and clauses for compliance testing and a mechanism for implementer-specific parameters and features.
- Mapping to other standards: Normative annexes include mapping to ISO/IEC 9506 (MMS) and guidance on PC behavior using ISO/IEC 9506-2.
Practical applications and who uses it
- Automation vendors and PLC manufacturers use IEC 61131-5 to implement standard communication services and function blocks in controller firmware.
- Control-system integrators and OEMs adopt the standard to ensure predictable communications between PLCs and I/O devices, HMIs, SCADA and enterprise systems.
- Control and software engineers use the defined function blocks and models to design interoperable, maintainable control programs for data acquisition, alarm reporting and remote control.
- Test labs and compliance teams rely on the compliance tables and state-diagram specifications when validating device behavior and interoperability.
Related standards
- IEC 61131 series (programming and architecture of programmable controllers)
- ISO/IEC 9506 (MMS) - normative mappings provided in Annex A/B for interoperability with MMS-based systems
IEC 61131-5 is essential for consistent PLC communications design-improving interoperability, diagnostics, and maintainability in industrial automation networks.
