IEC 61784-3-6:2010

Overview

IEC 61784-3-6:2010 defines a safety communication layer (services and protocol) for CPF 6 (INTERBUS™ Safety) within the IEC 61784 family. It specifies mechanisms for transmitting safety-relevant messages over fieldbus technology (based on IEC 61158 Type 8) in accordance with the functional safety requirements of the IEC 61508 series. This second edition (2010) updates the first edition (2007) and aligns with changes in IEC 61784‑3.

Key topics and technical requirements

• Safety communication layer (SCL): Defines services, protocols and the PDU (safety PDU) format used to exchange safety messages between SCL user (SCLM) and SCL service (SCLS).
• Function blocks: Includes standard safe function blocks such as Input Safe Data, Output Safe Data, and Safe Calculation, and their parameterization.
• Safety measures: Required measures include sequence numbers, time stamps, time expectation, acknowledgement, and connection authentication to ensure data integrity and timely delivery.
• Distinction of messages: Differentiates safety-relevant from non-safety messages, allowing different integrity assurance approaches.
• Connection management: Services for initiate, abort, parameterize device, send application parameter, and Set-Safety-Configuration manage lifecycle and context of safety connections.
• State machines and abort behavior: Specifies SCLM/SCLS state machines, synchronization, abort conditions and handling of errors (including abort of single or all connections).
• System requirements and assessment: Guidance on indicators/switches, installation, safety function response time (including parameterized shutdown time), maintenance, and required safety documentation/manuals.
• Management & configuration: Procedures for starting IEC 61158 Type 8 services and managing safety configuration parameters.

Practical applications and users

IEC 61784-3-6 targets industries that require deterministic, safe communication over fieldbus networks:

• Process control (chemical, oil & gas)
• Manufacturing automation and assembly lines
• Industrial machinery with distributed I/O and safety functions

Primary users and stakeholders:

• Safety engineers and system integrators designing safety-related communication
• Fieldbus device manufacturers implementing CPF 6 safety profiles
• Functional safety assessors and certifying bodies verifying compliance with IEC 61508
• Automation architects planning networked safety systems (INTERBUS Safety implementations)

Related standards

• IEC 61784-1 / IEC 61784-2 (CPF definitions and fieldbus profiles)
• IEC 61784-3 (general principles for functional safety communications)
• IEC 61158 Type 8 (fieldbus data link/physical type)
• IEC 61508 series (functional safety requirements)

Keywords: IEC 61784-3-6, functional safety fieldbus, CPF 6, INTERBUS Safety, safety communication layer, IEC 61158 Type 8, IEC 61508, safety PDU, parameterized shutdown time.