Siemens SINAMICS G120 Operating Instructions Manual page 144

Configuring the fieldbus
8.5 Communication via CANopen
Synchronous data transmission
In order for the devices on the CANopen bus to remain synchronized during transmission, a
synchronization object (SYNC object) must be transmitted at periodic intervals.
Each PDO that is transferred as a synchronous object must be assigned a transmission type
1 ... n. The following is applicable:
● Transmission type 1: the PDO is transferred in every SYNC cycle.
● Transmission type n: the PDO is transferred in every nth SYNC cycle.
The following diagram shows the principle of synchronous and asynchronous transmission:
Figure 8-17
For synchronous TPDOs, the transmission mode also identifies the transmission rate as a
factor of the SYNC object transmission intervals. Here, transmission type "1" means that the
message will be transmitted in every SYNC object cycle. Transmission type "n" means that
the message will be transmitted in every nth SYNC object cycle.
Data from synchronous RPDOs that are received after a SYNC signal is not transmitted to
the application until after the next SYNC signal.
Note
The SYNC signal does not synchronize the applications in the SINAMICS drive, only the
communication on the CANopen bus
Asynchronous data transmission
Asynchronous PDOs are transferred - cyclically or acyclically - without reference to the
SYNC signal.
142
Principle of synchronous and asynchronous transmission
SINAMICS G120C frequency converter
Operating Instructions, 03/2012, FW V4.5, A5E02999804B AB