4 Fundamentals ToC Previous Next

4.1 Introduction to Sercos ToC Previous Next

Sercos (Serial Realtime Communication System) is a digital automation bus that interconnects motion controls, drives, I/Os, sensors and actuators for numerically controlled or motion controlled machines and systems. It is designed for high-speed serial communication of standardized real-time data over a noise-immune, fiber optic ring (Sercos I & II) or Industrial Ethernet cable (Sercos III). Sercos is an international standard defined in the IEC61784/ 61158 standard series.

Sercos III is the open, IEC-standardized third-generation of Sercos that uses Industrial Ethernet for real-time control, combining the best of both Ethernet and previous Sercos designs to provide the highly deterministic bi-directional real time motion and I/O control required by modern production equipment. It overcomes the wasted bandwidth in other TCP/IP-based Ethernet bus solutions, because it is based directly on Ethernet frames, defining a new, registered EtherType for Sercos. In addition to real-time communications between all drives and the motion control, Sercos III provides rich I/O communication capabilities, while also enabling other protocols, such as EtherNet/IP, TCP/IP, UDP and others, to be transmitted over the same Ethernet network efficiently in parallel with Sercos real-time communication or even without Sercos real-time communication.

Sercos Parameters can be accessed in different ways, e.g. by using:

  • a Sercos master device and the Sercos real-time protocol providing cyclic and acyclic services to exchange data with Sercos (slave) devices,
  • an S/IP client and the S/IP protocol providing access to all data of Sercos devices which incorporate an S/IP server using the TCP/IP and UDP/IP protocol, not requiring a Sercos master and the Sercos real-time protocol, but also working in parallel to the Sercos real-time protocol,
  • an OPC UA server integrated in a Sercos (slave) device to provide direct OPC UA access to a Sercos device, not requiring a Sercos master and the Sercos real-time protocol, but also working in parallel to the Sercos real-time protocol.

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