Appendix
Communication interfaces
Control via CAN bus
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SW-HB 13.0002-EN EN 3.0
Processing of CAN messages
The 931E servo positioning controller uses a command interpreter for the CAN messages
received. The command interpreter is called every 1.6 msec. With every call, the command
interpreter can process one SDO or a special message such as a SYNC telegram or an
emergency message. Depending on their complexity, the processing of PDOs may even
take two time slices of the command interpreter. As a result, the processing speed for CAN
objects of the 931E servo positioning controller is subject to certain restrictions :
ƒ
The control must not send PDOs more frequently than every 4 msec. Otherwise, they
might not be registered or evaluated by the 931E servo positioning controller. This
may lead to control jumps or motor jerks.
ƒ
In the worst case, a PDO will only become effective in the controller after 4.8 msec
(e.g. as a speed setpoint). This may be the case, if two time slices are required for
PDO processing and the control sends the PDO directly after the preceding
command interpreter call.
ƒ
There may be 8 msec between sending an SDO and a response from the controller
because the response data must be first compiled in the controller.
Note!
For more detailed information on the 931E servo positioning controller
communication and control via the CANopen interface and information about
the CAN bus wiring, please see the CANopen Manual for the 931E servo
positioning controller.
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