Siemens SCALANCE X-200 Configuration Manual page 30

IRT communication with X-200
Note
Firmware versions
In IRT mode, all X-200 IE switches in a plant must either have firmware version V3.1 or
older, or they must have firmware version V4.0 or newer. Operating an IRT plant containing
both devices with firmware V3.1 and older and devices with V4.0 and newer is not possible.
Where necessary, install firmware V3.1 on the devices. You will find the firmware on the
accompanying CD in the following directory:
\FW\SCALANCE X-200IRT Isochronous Real-Time\
You should remember the following restrictions: The XF204IRT and the X201-3P IRT PRO
are not compatible with firmware V3.1. This firmware version must therefore not be used for
these two modules.
Note
The use of the SCALANCE X-200IRT as a redundant sync master is only permitted for IRT
with the "High Performance" option.
Constant bus cycle and isochronous real time also available with PROFINET
The possibilities available for constant bus cycles and isochronous real time with PROFIBUS
DP are now available for PROFINET IO.
When using the constant bus cycle functionality in PROFIBUS DP, all nodes are
synchronized by a global control signal generated by the DP master. In PROFINET IO with
IRT, a sync master generates a signal with which the sync slaves synchronize themselves.
The sync master and sync slaves belong to a sync domain that is assigned a name during
project engineering. In principle, both an IO controller and an IO device can adopt the role of
sync master. A sync domain has exactly one sync master.
Relationship: Sync domain and IO systems
The important point is that sync domains do not need to be restricted to a PROFINET IO
system: The devices of several IO systems can be synchronized by a single sync master as
long as they are connected to the same Ethernet subnet.
On the other hand: A IO system may only belong to one sync domain.
Signal delays must be taken into account
If you use extremely precise synchronization intervals, the cable lengths and the associated
delay times must be taken into account. With the aid of a Topology Editor, you can enter the
properties of the cables between the ports of the switches. Based on this information and the
other configuration data, STEP 7 calculates the optimized sequence of the IRT
communication and the resulting update time.
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Configuration Manual, 03/2015, C79000-G8976-C285-06
SCALANCE X-200