Siemens SINAMICS Configuration Manual page 148

Communication
A.1 Communication
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 the bandwidth reservation, the telegram traffic can be further tuned by configuring
the topology. This enhances the performance during data exchange and the deterministic
behavior. The IRT time interval can thus be further tuned or minimized with respect to IRT
"high flexibility".
In addition to the isochronous data transfer provided by IRT, even the application itself (position
control cycle, IPO cycle) can be isochronous in the devices. This is an essential requirement
for closed-loop axis control and synchronization via the bus. Isochronous data transfer with
cycle times well below one millisecond and with a deviation in the cycle start (jitter) of less than
a microsecond provide sufficient performance reserves for demanding motion control
applications.
In contrast to standard Ethernet and PROFINET IO with RT, the telegrams for PROFINET IO
with IRT are transferred according to a schedule.
Modules
The following modules support the IRT "high performance":
● CU320 in conjunction with the CBE20
● CU320-2 DP in conjunction with the CBE20
● CU320-2 PN
Clock generation via PROFINET IO (isochronous communication)
SINAMICS with CU320‑2 DP/CU320‑2 PN can only assume the role of a synchronization
device within a PROFINET IO network.
For a CU320‑2 DP/CU320‑2 PN with CBE20 module, the following applies:
● Transmission type IRT, IO device is synchronization slave and isochronous, send cycle is
applied to bus: Control Unit synchronizes with the bus and the send cycle becomes the
cycle for the Control Unit.
● RT or IRT (option drive unit "not isochronous") has been configured. SINAMICS uses the
local cycle configured in SINAMICS.
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Configuration Manual, 08/2017, A5E36912609A
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