Siemens SINAMICS S120 Commissioning Manual page 41

Figure 1-6
The type of transmission is characterized by a PDO's parameter for transmission type.
For synchronous TPDOs the transmission type also identifies the transmission rate as a
factor of the SYNC object transmission intervals. Here, the transmission type "1" means that
the message will be transmitted in every SYNC object cycle. The transmission type "n"
means that the message will be transmitted in every nth SYNC object cycle.
Asynchronous TPDOs are transmitted without reference to the SYNC signal.
Data from synchronous RPDOs which are received after a SYNC signal are transmitted to
the application only 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
Data from asynchronous RPDOs is passed on to the application directly.
PDO services
Transmission via PDO services takes place according to the producer/consumer principle:
● PDO number: PDO number [1..512] for each user type of a device
● User type: One of the values {consumer, producer}
● Data type: According to the PDO mapping
Write PDO
The "Write PDO" service follows the push model. There are either none or several
consumers for a PDO.
The PDO has exactly one producer.
Using this service, the PDO producer transmits the data of the mapped application object to
the individual consumers. The operational sequence for this service is as follows:
CANopen interface
Commissioning Manual, (IH2), V2.6, 10/2008 Edition, 6SL3097-2AA00-0BP3
Principle of synchronous and asynchronous transmission
Add infeed
1.13 PDO services
41