Basics of Absolute Encoders with BiSS (EN)

email: sales@impulseautomation.co.uk web: www.impulseautomation.co.uk Information shown in these data sheets are for guidance purposes only, no liability is accepted for any errors or omissions. The designer or user is solely responsible for the safe and proper use of these parts, assemblies or equipment described. GENERAL INFORMATION TRANSFER SEQUENCE Block diagram of a BiSS Master-Slave configuration Configuration Basics of Absolute Encoders ACURO Open Digital Sensor Interface (BiSS) The bidirectional digital sensor interface follows on from this.

Just four unidirectional BiSS safeguards communication between RS422 data lines are required; the slave position encoders or measuring devices electronics, kept to an absolute minimum, and industrial controls, such as a drive are incorporated on the sensor ICs. control, for example, and if necessary can When the master sends a clock pulse on transmit measurement values from up to line MA, the slave answers directly on 8 sensors simultaneously. return line SL with the recorded position For 1 to 8 subscribers the interface master data.

Commands and parameters can be provides a clock signal for the simultaneous swapped on a PWM pulse form; this is, capture of all position data and for the syn- however, not necessary to start the BiSS chronous-serial data transmission which protocol. With each data cycle the master learns and catered for. Bidirectional parameter com- compensates for line delays, thus permit- munication for device configuration - also ting clock rates of up to 10 Mbit/s even for applicable to what are known as OEM cable lengths of up to 100 m.

Changes in line parameters - is usually consigned to the conditions which occur during cable drag, register data section, with rapidly changing for example, are corrected. The precision of angle data being assigned to the sensor synchronization among several position data section. encoders along various axes is less than Control cycle times of less than 100 µs are 1 microsecond; the master also makes the thus not a problem, even for data words of up signal delay it has recorded accessible to 64 bits in length. There is enough room in to the control unit, allowing further opti- the protocol for redundancy; this space is mization.

normally used to implement a CRC (cyclic The BiSS protocol classifies each subscri- redundancy check). Framed by just one ber in the following data sections: sensor start and one stop bit, the sensor data is data, register data. These data sections transmitted at the best-possible core data have various setups with regard to access rate. Permanent monitoring of the position and transmission performance so that a and operation of the encoder is possible number of different sensor applications are without interfering with the control cycle. BiSS connection diagram with uni-directional conductions (one sensor, e.g.

with several slave levels) Specific product developments of individual users are not restricted or made unnecessarily expensive by a compulsory compatibility. A BiSS subscriber is described with just a few parameters and the XML-descriptive file included with the delivery simplifies start up of the control system. Doc No: EP0001 Rev: 001 Impulse Automation Limited United Kingdom Company Registration 665193 Page 2015-03-10 1 catered for. Bidirectional parameter com- munication for device configuration - also applicable to what are known as OEM parameters - is usually consigned to the register data section, with rapidly changing angle data being assigned to the sensor data section.

Control cycle times of less than 100 µs are thus not a problem, even for data words of up to 64 bits in length. There is enough room in the protocol for redundancy; this space is normally used to implement a CRC (cyclic redundancy check). Framed by just one start and one stop bit, the sensor data is transmitted at the best-possible core data rate. Permanent monitoring of the position and operation of the encoder is possible without interfering with the control cycle. BiSS connection diagram with uni-directional conductions (one sensor, e.g. with several slave levels)

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