The BiSS protocol was introduced in 2002 by ASiC manufacturer iC-Haus as an open source interface for automation technology. The aim was to achieve fast bidirectional sensor-actuator communication with simultaneous hardware compatibility with the established SSI interface (synchronous, serial). In addition to technical details, there are three prerequisites for today's globally used standard: the free license for applications, the stability and continuity of the protocol since its introduction and the physical layer compatibility with existing standard interfaces.

As far as the integrability and hardware realization of the user application are concerned, the electrical realization of the BiSS interface requires only two unidirectionally controlled lines in both the sensor and the drive (master). The use of standard RS422 transceivers ensures high interference immunity with low hardware costs.

Technical background

"BiSS Safety is a manufacturer-independent protocol for safe data that will help many users, as a broad base of sensors will implement the interface," explains Lothar Kübler, Managing Director of Fritz Kübler.

© Fritz Kübler

BiSS makes it possible to send commands from the master to slaves without interrupting the sensor data flow, for example in a drive control system. Fast digital controls such as motor feedback systems benefit from this in particular. The interface uses an in-band protocol for this purpose and forwards fractions of a data word to the connected slaves with each cycle on the clock line. The bidirectional communication with in-band protocols can also be used in a variety of ways, for example for maintenance (condition monitoring) and temperature information (encoder and motor temperature).

BiSS defines standard information content such as serial number, manufacturer and product identification and an electronic nameplate (EDS) for encoders, which also offers the user the option of storing and reading out their own data - for example motor data - in the encoder. This standardization means that encoders from different manufacturers can be used interchangeably in control systems; there is no interface-related binding to specific component manufacturers. The BiSS interface has been released as an open standard and is disclosed as a manufacturer-neutral protocol definition. Processes and designs with BiSS are patented by iC-Haus and are part of the free license for BiSS device manufacturers. This license includes the use of the BiSS brand and the BiSS IPs as source code. More than 380 licenses have now been issued to manufacturers of encoders and controllers, among others.

Safety' growth market

Sin/cos analog transmissions combined with digital absolute information are usually found on the market for safety encoders. More complex protocols from the market leaders and proprietary solutions are also available.

The further development of BiSS for safety-relevant applications (BiSS Safety) was based on two requirements: firstly, to achieve SIL2 and SIL3 with the existing BiSS protocol and secondly, to maintain the physical interface for using existing and new sensors in current system developments. The first drives and encoders have already been announced by various manufacturers for 2016.

BiSS Safety is 100% based on BiSS C and uses all protocol options. The identification features, electronic data sheets and diagnostic options are fully retained.