BECKHOFF FC5101 - Manual (Page 9)

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9
CANopen Introduction
CANopen is a widely used CAN application layer, developed by the CAN in Automation association, and which
has meanwhile been adopted for international standardisation.
Device Model
CANopen consists of the protocol definitions (communication profile) and of the device profiles that standardise
the data contents for the various device classes. Process data objects (PDO).are used for fast communication
of input and output data. The CANopen device parameters and process data are stored in a structured object
directory. Any data in this object directory is accessed via service data objects (SDO). There are, additionally, a
few special objects (such as telegram types) for network management (NMT), synchronisation, error messages
and so on.
Communication Types
CANopen defines a number of communication classes for the input and output data (process data objects):
· Event driven: Telegrams are sent as soon as their contents have changed. This means that the proc-
ess image as a whole is not continuously transmitted, only its changes.
· Cyclic synchronous: A SYNC telegram causes the modules to accept the output data that was previ-
ously received, and to send new input data.
· Requested: A CAN data request telegram causes the modules to send their input data.
The desired communication type is set by the "Transmission Type" parameter.
Device Profile
The Beckhoff CANopen devices support all types of I/O communication, and correspond to the device profile for
digital and analog input/output modules (DS401).
The default mapping has not been adapted to the profile version DS401 V2 because of the downward compati-
bility.
Transmission Rates
Nine transmission rates from 10 kbaud up to 1 Mbaud are available for different bus lengths. The effective utili-
sation of the bus bandwidth allows CANopen to achieve short system reaction times at relatively low data rates.