Sercos

Sercos, short for Serial Real-Time Communication System, is a family of open, vendor-neutral standards for real-time communication in automation and motion control. It enables controllers, servo drives, and I/O devices to exchange cyclic process data with deterministic timing, supporting synchronized operation across complex production lines.

Developed in the 1990s by a consortium of European automation providers led by Siemens and Robert Bosch, SERCOS is now administered by SERCOS International GmbH. The family comprises three generations: SERCOS I, SERCOS II, and SERCOS III. SERCOS I and II are serial-bus interfaces designed for deterministic real-time exchange of process and I/O data, while SERCOS III uses standard Ethernet networks with real-time extensions to preserve determinism on off-the-shelf hardware.

Key features include cyclic data transfer of process data, non-cyclic service data, time synchronization with a global cycle reference, deterministic latency, and optional fault-tolerance options. The protocol employs a master-slave communication model, defined data mappings, and a fixed cycle time to guarantee timely updates of all connected devices.

Historically dominant in CNC machines, machine tools, robotics, and other automated equipment in Europe, SERCOS is used to connect motion controllers to servo drives and I/O modules. SERCOS III, in particular, seeks to combine real-time performance with the flexibility of Ethernet, while still maintaining certification and interoperability across vendors. Adoption varies among industries and regions, with ongoing development and certification maintained by the SERCOS International organization.