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0198441113586, V2.01, 11.2008
IL•1F CANopen DS301 3 Basics
Fieldbus interface 45
Cyclic ad acyclic data transmission Synchronous exchange of messages can be cyclic or acyclic.
Figure 3.27 Cyclic and acyclic transmission
In the case of cyclic transmission, PDO messages are exchanged con-
tinuously in a specified cycle, e.g. with every SYNC message.
If a synchronous PDO message is transmitted acyclically, it can be
transmitted or received at any time; however, it will not be valid until the
next SYNC message.
Cyclic or acyclic behavior of a PDO is specified in the subindex
transmission type (02
h
) of the corresponding PDO parameter,
e.g. in the object 1st receive PDO parameter (1400
h
:02
h
) for
R_PDO1.
COB ID, SYNC object For fast transmission, the SYNC object is transmitted unconfirmed and
with high priority.
The COB ID of the SYNC object is set to the value 128 (80
h
) by default.
The value can be changed after initialization of the network with the ob-
ject COB-ID SYNC Message (1005
h
) .
T_PDO2: cyclical
T_PDO1: acyclical
SYNC