What is Sercos?

Sercos is an open international standard for communication between controllers and intelligent digital drives, I/Os, actuators and other peripheral devices.

Sercos I/II are based on an optical ring topology with a time-triggered master-slave communication. The bandwidth is 2, 4, 8 and 16 MBaud with very high protocol efficiency. 
Sercos III is based on standard industrial Ethernet.

Sercos allows very short cycle times (down to 62.5 us for Sercos I/II; 32.25 us for Sercos III) with very low jitter (below 1us) allowing the deterministic real-time data communication required for synchronous multi-axis motion control applications.

Sercos is expandable. It imposes no limit to the number of rings which can be synchronized together. The real limit is with the controller, which will have a limit to the number of axes it can process.

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Who can use Sercos?

There are thousands of digital control systems communicating via Sercos around the world. It is estimated that the majority of Sercos axes in the field today are on non-machine tool applications. Applications with many axes that need to be strictly synchronized benefit from the outstanding performance of the Sercos technology.

Some examples of applications:

Web-fed printing presses; packaging machines, converting & food processing machines; assembly, handling and robots; semiconductor processing equipment; metalforming and welding machines; textile processing; fiber winding; simulators and test equipment; plastics machines and many other types of special machines.

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Sercos development -- History

Sercos was created by a group of drive, control and machine tool manufacturers in 1986 at the request of a machine tool builders' organization, whose members desired an open communication system. The consortium's main aims were:

-- cost-effectiveness
-- "plug & play" interface
-- independence of control and drive technology
-- interoperability
-- cross-vendor compatibility

This activity led to the first release of the Sercos specification in 1989.

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Who maintains the Sercos standard?

The Sercos Technical Working Groups (TWG) in North America and Europe hold meetings 5 to 6 times per year.

Some of their duties are:

-- Specify new functions and ident numbers
-- Extend and improve existing functions
-- Publish technical updates
-- Support manufacturers and users of Sercos products
-- Define compatibility classes and function groups
-- Prepare all information necessary to update the IEC standards

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Sercos in comparison with other servo communication buses

Sercos products must pass a conformance test to ensure that they are compliant to the standard. Thousands of multi-vendor installations prove the cross-vendor compatibility of the Sercos standard.

Updates to the Sercos standard are defined by multi-company Technical Working Groups (TWGs) in both North America and Europe, which ensure that the latest enhancements proposed by Sercos member companies are incorporated into the specifications.

Sercos defines not only the physical layer and the communication protocol but also the semantics of motion control functions by over 500 standardized parameters (IDNs = IDentifier Numbers).

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Where can I get technical help?

Contact any of the Sercos member companies or qualified systems integrators for product-specific information and applications assistance.

Contact a Sercos Competency Center for fee-based services, including training, application support and hot-line telephone support.

To request copies of the Sercos standards, please contact IEC or its partner companies.

For the latest versions of the Sercos specifications (working documents) and the application notes (available in German and English), please contact the Sercos North America office.

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