Siemens SINAMICS S120 Series Function Manual page 128

Communication via PROFINET IO
5.2 RT classes for PROFINET IO
Comparison between RT and IRT
Table 5- 1 Comparison between RT and IRT
Transfer mode
Isochronous application
in the IO controller
Determinism
Reload the network configu-
ration after a change
Maximum switching depth
(number of switches in one
line)
For possible send cycles, see subitem "Send cycles and update cycles for RT classes" in table "Adjustable send cycles
and update cycles"
Set the RT class
The RT class is set by means of the properties of the controller interface of the IO controller.
If RT class IRT "high performance" is set, it is not possible to operate any IRT "high
flexibility" devices on the IO controller and vice versa. IO devices with RT can always be
operated, regardless of the IRT class setting.
You can set the RT class in the HW Config for the associated PROFINET device.
1. In HW Config, double-click item PROFINET interface in the module.
The "Properties" dialog box opens.
2. Select the RT class under RT class on the "Synchronization" tab.
3. Once you have selected "IRT", you can also choose between option "high flexibility" and
"high performance".
4. Confirm with "OK".
126
RT
Switching based on the MAC
address; prioritization of the
RT telegrams possible using
Ethernet-Prio (VLAN tag).
No
Variance of the transmission
duration by started TCP/IP
telegrams.
Not relevant
10 at 1 ms
IRT "high flexibility"
Switching using the MAC
address;
bandwidth reservation by
reserving an IRT "high flexi-
bility" interval in which only
IRT "high flexibility" frames
are transferred but, for ex-
ample, no TCP/IP frames.
No
Guaranteed transmission of
the IRT "high flexibility" tele-
grams in the current cycle by
the reserved bandwidth.
Only when the size of the
IRT "high flexibility" interval
needs to be modified (reser-
vation of position is possi-
ble).
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IRT "high performance"
Path-based switching ac-
cording to a topology-based
plan; no transmission of
TCP/IP frames and IRT "high
flexibility" frames in the IRT
"high performance" interval.
Yes
Exactly planned transfer;
times for transmission and
receiving are guaranteed for
any topologies.
Always when the topology or
the communications relation-
ships change.
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Communication