Chapter 2 Decentral block periphery CAN-Bus CANopen
Manual VIPA System 100V
2-22
HB100E - SM-CAN - Rev. 15/02
If the consumer–producer model of the CANopen PDOs shall be used for
the direct data transfer between nodes (without master), you have to adjust
the identifier allocation, so that the TxPDO identifier of the producer is fitting
with the RxPDO identifier of the consumer:
This procedure is called PDO linking. It enables the easy structure of
electronic gearing, where several slave axis follow the actual value in
TxPDO of the master axis at the same time.
CANopen supports the following possibilities for process data exchange:
•
event triggered
•
polled
•
synchronized
The "event" is the change of an input value, the data is sent directly after an
alteration. Using the event triggering, the bus spread is utilized best,
because you do not transfer the whole process image all the time but only
the alterations of it. At the same time, a short reaction time is received,
because you don't have to wait for a request of another master after the
change of an input value.
The PDOs may also be polled by data request telegrams (Remote
Frames). Thus allows that e.g. the input process image at event triggered
inputs may be brought on the bus also without input changes, for example
a monitor or diagnostic device linked up to the network during runtime.
The VIPA CANopen bus couplers support the request of PDOs via remote
frames - for this is not presupposeable due to the hardware, this
communication type is only recommended partially.
It is convenient not only for drive applications to synchronize the evaluation
of the input information as well as the setting of the outputs. For this,
CANopen supports the SYNC object, a CAN telegram of high priority
without user data, which reception is used as trigger for the reading of the
inputs res. the setting of the outputs by the synchronized nodes.
PDO Linking
PDO communica-
tion types
Event triggered
Polled
Synchronized
