Siemens SINAMICS S150 Operating Instructions Manual page 258

Operation
6.8 PROFINET IO
The scheduled data transfer requires a hardware support for PROFINET IO with IRTtop in
the form of a communication ASIC (Application Specific Integrated Circuit). In order for
scheduled communication not to be put at risk by spontaneously transmitted IT telegrams, a
certain proportion of cyclic communication is reserved exclusively for IRTtop transmission.
This is called bandwidth reservation. The rest of the communication cycle can be used for
RT and IT communication.
Data exchange
Communication is generally also possible via network limits via routers. However,
PROFINET IO with IRTtop only runs within a sync domain.
258
Drive converter cabinet units
Operating Instructions, 07/07, A5E00288214A