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3
General information
3.1
Absolute encoders
For an absolute encoder each angular position is assigned a coded position value�
This is generated by a coded disc with several parallel fine code segments which
are detected individually� For singleturn encoders, i�e� an encoder producing
absolute positions within one revolution, the absolute position information is
repeated with every revolution� A multiturn encoder can also distinguish between
revolutions via a gearbox containing magnets which are individually detected
by Hall elements� The number of the individual revolutions is determined by the
resolution of the multiturn detection and is repeated after the total resolution has
been reached�
3.2
CANopen technology
The CANopen communication profile is based on the CAN Application Layer
(CAL) specification from CiA (CAN in Automation)� CANopen is considered as a
robust fieldbus with highly flexible configuration options� It is used in many various
applications which are based on different application profiles� CANopen comprises
a concept to configure and communicate real-time data using synchronous and
asynchronous messages� Four message types (objects) are distinguished�
1�
Administration messages (layer management, network management and
identifier distribution)
2�
Service data messages (SDO)
3�
Process data messages (PDO)
4�
Predefined messages (synchronisation, time stamp, emergency)
You can find more information in the CANopen specification�
3.2.1
Certification of CANopen products
To achieve interoperability and a suitable device functionality CANopen products
are approved by external notified bodies� A copy of the certificate is attached to
this manual�
3.3
References
http://www�can-cia�org
CAN Application Layer, DS 201...207
CAL based communication profile, DS 301
Device profiles for encoders, DS 406
CAN specification version 2�0 A
CANary CAN controller
CANopen encoder
CiA
CiA
CiA
Robert Bosch GmbH
Atmel
UK
5
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