Data transfer
Structure of the CAN telegram
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EDSMF2178IB EN 3.0
User data
The user data area of the CAN telegram either contains network management data, process
dataor parameter data:
ƒ Network management data (NMT data)
Network management data contain information on the establishment of
communication via the CAN network (^ 45).
ƒ Process data (PDO, Process Data Objects)
– Process data are transferred via the process data channel (see also chapter "Process
data transfer", ^ 48).
– Process data serve to control the controller (slave).
– Process data are transferred between the host and the controllers to ensure a
continuous exchange of current input and output data.
– The host has direct access to process data. In the PLC, the data are, for instance,
directly assigned to the I/O area. An exchange between host and controller is
required as fast as possible. Small amounts of data can be transferred cyclically.
– Process data are not saved in the controller.
– Process data are, for instance, control words, status words, setpoints and actual
values.
ƒ Parameter data (SDO, Service Data Objects)
– Parameter data are transmitted as SDOs via the parameter data channel and
acknowledged by the receiver, i.e.the sender gets a feedback about the
transmission being successful or not (see also chapter "parameter data transfer",
^ 69).
– The parameter data channel enables access to all Lenze codes and CANopen
indices.
– The parameters for instance are set for the initial system set−up during
commissioning or when material is changed on the production machine.
– In general, the parameter data transfer is not time−critical.
– Parameter changes are automatically stored in the controller.
– Parameter data for example are operating parameters, diagnostics information,
and motor data.
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