E94AYCCA communication manual (CANopen®)
Data transfer
Structure of the CAN data telegram
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EDS94AYCCA EN 5.0 - 06/2012
7.1.2
User data
All nodes communicate with each other by exchanging data telegrams via the system bus
(CANopen). The user data area of the CAN telegram contains network management data,
parameter data or process data:
Network management data
(NMT data)
Control information on start, stop, reset, etc. of communication to certain or all nodes
of the CAN network.
Process data
(PDOs – Process Data Objects)
Process data are transferred via the process data channel.
The controller can be controlled using process data.
Process data are not saved in the controller.
Process data are transferred between the host and the nodes to ensure a continuous
exchange of current input and output data.
Process data usually are unscaled/scalable raw data
Process data are, for instance, setpoints and actual values.
Parameter data
(SDOs – Service Data Objects)
Parameter data are the CANopen indexes or, in the case of Lenze devices, the codes.
The parameters are, for instance, set for the initial system set-up during
commissioning or when material is changed on the production machine.
Parameter data are transmitted as SDOs via the parameter data channel. They are
acknowledged by the receiver, i.e. the sender receives a feedback about the
transmission being successful or not.
The parameter data channel enables access to all Lenze parameters (codes) and
CANopen indexes.
Parameter changes are automatically saved in the controller until the mains is
switched.
In general, the parameter transfer is not time-critical.
Parameter data are, for instance, operating parameters, diagnostic information and
motor data.