IEC 62026-2:2008

Overview

IEC 62026-2:2008 - "Low-voltage switchgear and controlgear - Controller-device interfaces (CDIs) - Part 2: Actuator Sensor Interface (AS‑i)" defines the communication method and interoperability rules for a single control device (master) and its switching elements (slaves). This 2008 second edition updates the 2000 edition and introduces two major changes: doubling the number of slaves from 31 to 62 by using sub‑addresses, and the introduction of the AS‑i safety system. IEC 62026-2 is part of the IEC 62026 series for controller‑device interfaces (CDIs) used in industrial automation.

Key topics and requirements

The standard contains detailed technical requirements and test procedures covering:

• Communication and transactions
  • Master/slave request‑response structures, single and combined transactions, addressing modes (standard/extended), and error detection.
• Signal characteristics and transmission
  • Physical signal definitions, coding, timing diagrams and topology models for the AS‑i bus.
• Power and data distribution
  • AS‑i power supply, cabling (field and cabinet), repeaters and decoupling circuits.
• Topology and components
  • System architecture, master, slave and repeater roles, interface definitions and connector/cable guidance.
• Slave and master requirements
  • Functional behaviour, state machines, I/O mapping and profiles (Annex A/B contain slave and master profiles).
• Safety and diagnostics
  • Introduction of the AS‑i safety system and requirements for diagnosis and status reporting.
• Electromagnetic compatibility (EMC)
  • EMC requirements and impedance/symmetry tests to ensure reliable field operation.
• Testing and conformity
  • Extensive test methods, test circuits and procedures for interoperability, performance, symmetry, noise emission and component validation.

Applications

IEC 62026-2 (AS‑i) is widely used in industrial and machine‑level automation where simple, robust, low‑cost I/O networks are required. Typical applications include:

• Sensor and actuator networks on production lines
• Discrete manufacturing machines and conveyor systems
• Machine builders and OEMs integrating distributed I/O
• Safety‑related applications using the AS‑i safety extension for emergency stop and safety sensors
• Retrofit and modular systems where interoperability between vendors is essential

Who should use this standard

• Control engineers and system integrators specifying AS‑i networks
• Component manufacturers (masters, slaves, repeaters, power supplies) for product design and compliance
• Test labs and certification bodies validating EMC and interoperability
• Maintenance and commissioning teams implementing wiring, diagnostics and troubleshooting

Related standards

• Part of the IEC 62026 CDI series (controller‑device interfaces). Users should refer to other parts of the series and related IEC standards for complementary guidance on low‑voltage switchgear, safety and system integration.

Keywords: IEC 62026-2, AS‑i, Actuator Sensor Interface, controller-device interfaces, CDIs, low-voltage switchgear, industrial automation, AS‑i safety, master/slave, interoperability.