Siemens SINAMICS DCM Operating Instructions Manual page 380

Descriptions of functions
10.3 PROFINET IO
RT
RT communication is based on standard Ethernet. The data is transferred via prioritized
Ethernet telegrams. Because standard Ethernet does not support any synchronization
mechanisms, isochronous operation is not possible using PROFINET IO with RT. The real-
time capability is comparable with the present 12-MBaud PROFIBUS DP solutions, i.e. a
sufficiently large bandwidth portion is available for transmitting IT services in parallel on the
same line.
The real update time during which cyclic data are exchanged depends on the bus load, the
devices used, and the quantity structure of the I/O data. The update time is a multiple of the
send cycle.
IRT
Two options are available with this RT class:
● IRT "high flexibility"
● IRT "high performance".
Software preconditions for configuring IRT:
● STEP 7 5.4 SP4 (HW Config)
Note
For further information about configuring the PROFINET interface for the I/O controller and
I/O device, please refer to the following document: SIMOTION SCOUT Communication
System Manual.
IRT "high flexibility"
The telegrams are sent cyclically in a deterministic cycle (Isochronous Real Time). The
telegrams are exchanged in a bandwidth reserved by the hardware. One IRT time interval
and one standard Ethernet time interval are created for each cycle.
Note
IRT "high flexibility" cannot be used for isochronous applications.
IRT "high performance"
In addition to reserving the appropriate bandwidth, telegram traffic can be further optimized
by defining the topology when configuring the system. This enhances the performance
during data exchange and the deterministic behavior. The IRT time interval can thus be
further optimized or minimized with respect to IRT "high flexibility".
378
Operating Instructions, 1.2012, C98130-A7066-A1-05-7619
SINAMICS DCM DC Converter