Siemens SINAMICS Configuration Manual page 150

Communication
A.1 Communication
3. Once you have selected "IRT", you can also choose between option "high flexibility" and
"high performance".
4. Confirm with "OK".
Synchronization domain
The sum of all devices to be synchronized form a synchronization domain. The whole domain
must be set to a single, specific RT class (real-time class) for synchronization. Different
synchronization domains can communicate with one another via RT.
For IRT, all IO devices and IO controllers must be synchronized with a common
synchronization master.
RT allows an IO controller to communicate with a drive unit outside a synchronization domain
or "through" another synchronization domain. As of version 5.4 SP1, STEP 7 supports multiple
synchronization domains on a single Ethernet subnet.
Example:
● Synchronization domain IRT: SIMOTION2 with SINAMICS
● SINAMICS drive that is assigned to the I/O system of SIMOTION1. This is arranged in the
topology in such a way that its RT communication must be established through the IRT
synchronization domain.
Figure A-21
Update cycles and send cycles for RT classes
Definition of the update time / send cycle:
If we take a single IO device in the PROFINET IO system as an example, this device has been
supplied with new data (outputs) by the IO controller and has transferred new data (inputs) to
the IO controller within the update time. The send cycle is the shortest possible update cycle.
All cyclic data is transferred within the send cycle. The actual send cycle that can be set
depends on various factors:
● Bus load
● Type of devices used
150
RT communication across the limits of synchronization domains
Configuration Manual, 08/2017, A5E36912609A
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