SERCOS daughter boards eliminate the analogue interface in motion systems

Assembly Automation

ISSN: 0144-5154

Article publication date: 1 June 2004



(2004), "SERCOS daughter boards eliminate the analogue interface in motion systems", Assembly Automation, Vol. 24 No. 2.



Emerald Group Publishing Limited

Copyright © 2004, Emerald Group Publishing Limited

SERCOS daughter boards eliminate the analogue interface in motion systems

SERCOS daughter boards eliminate the analogue interface in motion systems

The latest addition to the Trio range of motion control products from Unimatic Engineers is a SERCOS daughter card, which enables high-speed fibre optic communications between drives and motion products. The SERCOS daughter card can be used with Trio's MC206 and MC224 Motion Coordinator products, both of which are supplied and supported by Unimatic (Plate 4).

Unimatic is a strong advocate of SERCOS as a control interface, and has long had SERCOS capability in its drives ranges. SERCOS is an open standard that replaces the traditional mass of wires with a single fibre-optic cable to provide reliable, noise-immune, high-speed data transmission between drives and motion controllers.

Plate 4 The SERCOS daughter card

Specifically designed for drive control applications, the SERCOS interface can transmit cyclic data at high speeds with precise synchronisation. In conjunction with the Trio MC206 or MC224 Motion Coordinators, cycle times down to 250 μs can be achieved for eight axes in a ring system, and up to four SERCOS daughter boards can be used per system. Operating at speeds up to 16 MHz, the board enhances the communications between the motion coordinators and the drives, significantly improving motor performance and positional accuracy.

Trio's SERCOS interface is built around the latest SERCON 816 ASIC – a high-speed chip employing 32 bit technology for enhanced communications in drive systems. As well as carrying the control information, the SERCOS interface can also be used for the distribution of the extensive diagnostics information that modern drives generate, enabling powerful integrated systems to be quickly configured.

The SERCOS daughter board plugs directly into expansion ports on the compatible Trio Motion Coordinators. The MC206 Motion Coordinator provides up to eight axes of stepper or servo control with the SERCOS daughter board installed, whilst the flagship MC224 controller can co-ordinate up to 24 axes simultaneously when used with the SERCOS daughter board.

Drive initialisation files are available for leading brands of drives, including the innovative Pacific Scientific range which Unimatic also supplies.

Combined with Trio's Motion Coordinator controllers, the SERCOS interface board allows the development of extremely flexible yet high performance machines that are easier to maintain and more readily upgradable.

To put simply, SERCOS – the serial real- time communications system – is an open controller-to-intelligent digital drive interface specification, designed for high-speed serial communication of standardised closed-loop data, in real-time, over a fibre-optic cable. The SERCOS interface connects digital drives, actuators, and I/O using one or more fibre-optic rings, with up to 254 devices per ring. This provides noise immunity and simplifies wiring by eliminating dozens of wires required by discrete connections. In addition, the digital interface allows for the exchange of set-up and diagnostic information between the controller and the drive.

With its high-speed data transfer, diagnostic capabilities, cost reduction potential and inherent noise immunity, the SERCOS interface has become the dominant solution for motion control applications, even when compared to more “high profile” standards in drives communication such as Profibus and CAN. Even alternatives such as the various industrial Ethernet implementations, which on the surface promise higher speed, fail to match the real-time capabilities of SERCOS.

Such is its rise in popularity that the SERCOS interface has become the recognised de facto standard for highly dynamic motion control applications, whether multi axis synchronisation is required or not. As well as drives, remote I/O products and actuators from a host of manufacturers currently integrate the standard, making any other fieldbus an unnecessary extra in a host of special purpose machine designs, and making the choice of appropriate fieldbus a much more straightforward affair in more general automation applications.

For further information, contact: Trupti Patel, Unimatic Engineers Ltd, Unimatic House, Granville Road, London, NW2 2LN. Tel: 020 8922 1000; Fax: 020 8922 1066; E-mail:; Web site:

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