NORD Drivesystems BU0260 - Manual (Page 105)

8 Additional information
BU 0260 GB Subject to technical amendments 105
8.3 CANopen technology and protocol
The CAN bus is a high-speed standardised bus system. Because of its structure it is possible to design a bus
structure without a central master, i.e. with partners with entirely equal rights. With the aid of the CANopen
system, based on CAN and the defined profiles for communication and application categories which it contains
(I/O profile or Drive profile), this system is comparatively easy to configure.
A wide variety of field devices can therefore be easily interlinked. In case of failure of individual field devices,
data transfer to the remaining bus subscribers continues uninterrupted.
8.3.1 Overview /Protocol architecture
The ISO/OSI layer model describes the communication between the individual subscribers (nodes) of a
communication or automation system. Of the seven defined OSI layers, CANopen uses the layers 1, 2 and 7.
 Layer 1 Physical layer defines the hardware, coding, speed etc. of data transfer
 Layer 2 Connection layer describes the bus access procedure including data security, i.e. it
defines the physics of transfer
 Layer 7 Application layer defines the interface to the application program with the
application-orientated commands.
Here, in addition to the communication profile (DS301), CANopen
also defines various device profiles (e.g.: DS402)
Layer 2 of the ISO/OSI model includes
 the general format for data transfer telegrams
 the bus access mechanisms
 the security mechanisms
 the times to be complied with
 possible transfer services.
CANopen
CAN
ISO/OSI Layer 1 (physical layer)
ISO/OSI Layer 2 (connection layer)
ISO/OSI Layer 7 (application layer) CAL, DS301
Device profile
DS401
I/O Modules
Device profile
DS402
Drives
…
ISO/OSI Layer model