What Is Safety over EtherCAT (FSoE)?

Safety over EtherCAT, commonly known as FSoE, provides a way to transmit safety-related information within an EtherCAT environment.

FSoE uses a "black channel" approach. Safety-related data is packaged with additional information used to verify its integrity and transported through the standard communication system.

The safety communication includes mechanisms designed to help:

• Detect corrupted safety data
• Identify communication errors
• Verify safety communication partners
• Monitor message timing
• Detect missing safety information
• Trigger predictable responses when communication faults occur

FSoE is standardized in IEC 61784-3 and can support safety communication up to SIL 3.

Why FSoE Matters in Functional Safety

EtherCAT is widely used in applications requiring fast and deterministic communication, particularly where multiple axes, precise synchronization, and sophisticated motion control are involved.

But fast communication alone doesn't make a system functionally safe.

FSoE adds a safety communication layer that allows safety-related information to be transmitted within the control architecture while providing mechanisms for detecting communication faults.

For motion systems, this can support safety functions involving:

• Safe position monitoring
• Safe speed monitoring
• Safe direction monitoring
• Safe motion
• Safe stopping functions

This makes FSoE particularly relevant for sophisticated automation and motion systems where safety and machine control must work closely together.

EtherCAT vs Safety over EtherCAT  

Standard EtherCAT provides high-performance industrial Ethernet communication for automation and motion control.

It is designed to efficiently transmit standard process and control information but is not inherently a functional safety protocol.

FSoE adds safety-related communication to the architecture.

Safety data is packaged within safety containers that include additional information used to verify the integrity of the data. These containers can then be transmitted through the standard communication system.

This allows standard and safety-related information to use the same communication infrastructure while the safety layer independently monitors the integrity of the safety data.

FSoE and Motion Feedback

Encoders provide position, speed, and motion information that can be critical to a machine's safety system.

An FSoE-compatible safety encoder can communicate safety-related motion information to a compatible safety controller, helping the system determine whether equipment is operating within defined safe parameters.

Depending on the encoder and safety architecture, this information may be used to monitor:

• Position
• Speed
• Direction
• Movement

When an unsafe condition or communication fault is detected, the safety controller can initiate the response defined by the machine's safety design.

Note: Supported safety functions, certifications, and safety levels depend on the specific encoder, controller, system architecture, and implementation.

Planning for Safety over EtherCAT

If FSoE is part of your safety architecture, consider these requirements early in the machine design:

• What safety functions are required?
• What SIL or Performance Level must be achieved?
• Is the machine already using EtherCAT?
• Which safety controller will be used?
• What safety-related motion information is required?
• Is single-turn or multi-turn position feedback needed?
• What encoder resolution is required?
• What mechanical configuration fits the application?
• What environmental conditions will the encoder experience?
• What diagnostics and fault responses are required?

Early planning can help simplify encoder selection, system integration, validation, and documentation.

Safety over EtherCAT FAQ

EPC's Safety over EtherCAT Encoder