EtherCAT interoperability removes industrial networking barriers

Ethernet Insights

• EtherCAT has become popular with users because it has one version that has been enhanced with extensions and emphasizes interoperability.
• EtherCAT conformance testing and plugfest events ensures device interoperability and ease of use. This Ethernet protocol design includes extensions for functional safety and power.

Selecting the right communication technology is one of the most important decisions engineers make, and interoperability helps with that decision. In many ways, industrial communication is even more important than the machine controller. Fieldbus communications directly determine whether the field devices can match the controller’s performance and which devices can be used.  

The EtherCAT Technology Group (ETG) takes conformance and interoperability of devices seriously. Facilitating interoperability among all devices is complex and requires diligence on the part of the trade organization. The ETG’s motivation is not to gather licenses, agreements, or members, but to ensure proper design, development and successful EtherCAT device use. 

Device interoperability is where EtherCAT shines for two reasons.  

First, there is only one EtherCAT protocol version. The EtherCAT technology has never changed; it has been enhanced with extensions. Having a stable base specification means new devices can be used in existing systems without problems or version control concerns. It also provides a firm foundation for EtherCAT extensions, including Safety over EtherCAT (FSoE) for integrated functional safety, EtherCAT P for power and communication in one cable, and EtherCAT G/G10, which provide 1 Gbit/s and 10 Gbit/s communication rates, respectively. There will continue to be enhancements, but they will not change the base technology of EtherCAT Version 1. 

Figure 1: EtherCAT has added several extensions for power and communication in one cable and Gigabit communication, but the core technology remains unchanged. Courtesy: EtherCAT Technology Group

The second primary reason for ensuring interoperability is the ETG member policy surrounding conformance. It is the obligation of all EtherCAT device vendors to follow the ETG conformance policy. 

Figure 2: The ETG has more than 3,000 registered device manufacturers. Courtesy: EtherCAT Technology Group

EtherCAT conformance test tool (CTT)

The CTT is an in-house test of EtherCAT devices and a powerful development tool. An EtherCAT device developer can run the CTT during development to catch possible interoperability issues before market release. This is like compiling control programming code often: It’s best to identify issues early and fix them right away rather than compiling code at the end to see problems pile up.  

All EtherCAT device developers are required to maintain a CTT subscription. The tool is continuously refined to accommodate industry-specific test cases and other changes. Legacy fieldbus systems used to suffer – and still do – from static testing mechanisms that became outdated very quickly. Early on, ETG members decided to have a continuously updated conformance test tool. 

All EtherCAT device vendors are required to have their EtherCAT devices pass a conformance test before market release. The test results do not have to be submitted, but must be available upon request. The CTT, combined with the EtherCAT slave controller (ESC), strives to ensure EtherCAT devices will always work with the network architecture and not adversely affect its performance, reliability or functionality. 

Figure 3: Interoperability in action is demonstrated with use of the EtherCAT Conformance Test Tool. Courtesy: EtherCAT Technology Group

EtherCAT test centers

An optional conformance check can be done at an EtherCAT Test Center. CTT results are checked along with verifying proper exterior markings and LED handling, which cannot be determined by the test tool. It is common for end users to request a vendor to perform an optional conformance test at a recognized EtherCAT test center. There are five test centers around the world, including a North American site in Minneapolis. The results of the optional test are secure, and after completion, vendors can advertise successful completion of the optional test. 

Figure 4: An EtherCAT product verified at an EtherCAT Test Center gets this notation in the ETG product guide: EtherCAT Technology Group | Product Guide. Vendors can advertise a successful compliance test. Courtesy: EtherCAT Technology Group

FSoE conformance test

Fail-safe over EtherCAT (FSoE) provides a mathematically verified safe communications channel over EtherCAT and meets the standards to transfer safety data reliably and in a very timely matter. With FSoE, functional safety features such as door interlocks, e-stops or safety drives can communicate over the same communication system that also handles all other process data.  

The ETG has streamlined the process for FSoE compliance and conformance assessment, including working with a so-called notified body, which eases the burden on the vendor. There are safety controllers and safety devices from more than 40 vendors. Users can pick and choose the best safety device for their application without worrying about interoperability among devices. This is unprecedented in safety circles where users are largely constrained to one vendor for safety components. 

EtherCAT PlugFests

PlugFests parallel omnipresent standards like USB. Put many EtherCAT devices in a room with various EtherCAT controllers and hook them up. EtherCAT Conformance Test Tool experts are on hand to answer questions. During the event, all EtherCAT devices are connected to the participating controller offerings. At the end, all EtherCAT devices are connected, and each EtherCAT controller is connected to the overall system. By that time, all devices are in place and working in harmony.  

Figure 5: ETG hosts PlugFests around the world to ensure interoperability between EtherCAT devices. Courtesy: EtherCAT Technology Group

Interoperability helps industrial Ethernet communications

Any fieldbus or communication technology is useless without viable interoperability. EtherCAT is designed to integrate field devices that work with a variety of controllers so users don’t have to worry about how they will work together. This is intended to benefit all users as a result.  

Robert Trask, P.E., is North America representative of the EtherCAT Technology Group, a CFE Media and Technology content partner. Edited by Chris Vavra, web content manager, Control Engineering, CFE Media and Technology, cvavra@cfemedia.com. 

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