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 an organisation. The ETG’s aim is not to gather licences, agreements or members, but to ensure the proper design, development and successful use of EtherCAT devices.
EtherCAT excels in device interoperability 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 provides 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.
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.
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 is best to identify issues early, and fix them right away rather than compiling code at the end, just 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 Legacy fieldbus systems used to, and still do, suffer from static testing mechanisms that became outdated very quickly.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.
An optional conformance check can be done at an EtherCAT test centre. CTT results are checked, along with verifying proper exterior markings and LED handling that 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 recognised EtherCAT test centre. There are five test centres 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.
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 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 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. You can 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.
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