Beckhoff FC5101, Documentation

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Product Overview
FC5101 and FC5102 11 Version: 2.0
2.3 CANopen Introduction
Fig. 4: CANopenLogo
CANopen is a widely used CAN application layer, developed by the CAN-in-Automation association (CiA,
http://www.can-cia.org ), and which has meanwhile been adopted for international standardization.
Device Model
CANopen consists of the protocol definitions (communication profile) and of the device profiles that
standardize the data contents for the various device classes.
Process data objects (PDO) [ } 44] 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),
synchronization, error messages and so on.
Fig. 5: CANopen Device Model
Communication Types
CANopen defines a number of communication classes for the input and output data (process data objects):
• Event driven [ } 46] : Telegrams are sent as soon as their contents have changed. This means that the
process image as a whole is not continuously transmitted, only its changes.
• Cyclic synchronous [
}
46] : A SYNC telegram causes the modules to accept the output data that was
previously received, and to send new input data.
• Requested (polled) [
}
44] : A CAN data request telegram causes the modules to send their input data.
The desired communication type is set by the Transmission Type [ } 44] parameter.