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How does Sercos III work?
In order to fully meet the demands of modern industrial automation, Sercos provides a high performance protocol. This protocol combines the openness of standard Ethernet with the need for real-time accuracy in automation engineering.
SSI (Synchronous Serial Interface) is an interface for position sensors. It enables specific information about the position (position information) to be obtained on the basis of serial data transmission. SSI was originally developed by Max Stegmann GmbH (part of the Sick Group since 2002) but is used by a range of other manufacturers. The interface is particularly suitable for applications which require reliability and robustness in an industrial environment. Furthermore, it is constructed in a very simple and low-cost manner. Only two pairs of cables for the cycle and the data are necessary for transmission, and little more than a shift register and a multivibrator are needed to control it. SSI also enables the connection of up to three encoders on one unique cycle so that it is also possible to read several sensors at the same time.
The open BiSS interface (bidrectional/serial/sychronized) is a serial interface protocol for the isochronos, fast and secure reading of sensor data, writing of actuator data in real time and simultaneous access to the register of participants (slaves). BiSS is compatible with SSI interfaces and includes numerous improvements relating to speed and adjustments to cable lengths, among other things. In addition to the SSI and BiSS open interfaces, there are also proprietary encoder interfaces, for example, EnDat (Heidenhain Company) or Hiperface (High Performance Interface, Sick-Stegmann Company). The interfaces are constantly being developed further and adapted to meet new requirements.Gateways are used to connect SSI encoders to field buses or real-time Ethernet systems. With a Sercos SSI Gateway which supports the Sercos encoder profile, any number of SSI encoders can be integrated into a Sercos network. At the same time, the SSI encoder behaves identically to an encoder with an integrated Sercos interface. Alternatively, SSI bus terminals can be used in conjunction with a modular I/O system and a corresponding bus couplerHowever, in addition to specific encoder interfaces, more and more absolute encoders also support standard field buses or real-time Ethernet protocols. This means that encoders can be directly connected to a control via a standard bus system. Corresponding gateways become obsolete, meaning that hardware costs and the amount of cabling work are reduced significantly.