Media Redundancy - Siemens Sinamics S120 Function Manual

Communication
10.3 Communication via PROFINET IO
10.3.2.1

Media redundancy

To increase the availability of PROFINET, you can create a ring topology for redundancy
purposes. If the ring is interrupted at one point, the data paths between the devices are
automatically reconfigured. Following reconfiguration, the devices can once again be
accessed in the resulting new topology.
To create a ring topology with media redundancy, route the two ends of a line-type
PROFINET topology into one device, the Scalance device. Closing the linear bus topology is
realized using two ports (ring ports) of the Scalance device. The Scalance device is the
redundancy manager. The redundancy manager monitors the data telegrams in the
PROFINET ring. All other connected PROFINET nodes are redundant clients.
The Media Redundancy Protocol (MRP) is the standard procedure for media redundancy.
Using this technique, a maximum of 50 devices can participate in each ring. In the case of an
interrupted cable, data transfer is only briefly interrupted as the system switches over to the
redundant data path.
If a short-term interruption is not permitted, data transfer must be set to IRT High
Performance. The uninterruptible MRRT is automatically set.
The two integrated PROFINET IO interfaces of the Control Units CU320-2 PN and CU310-2
PN can be configured as redundant clients.
From a CBE20, only the first two ports are capable of establishing a ring topology. Routing
between the integrated PROFINET IO interfaces and a CBE20 is not possible.
Configuring media redundancy
The ring topology is configured by appropriately configuring the participating devices
individually in STEP7.
10.3.3 RT classes for PROFINET IO
PROFINET IO is a scalable realtime communication system based on Ethernet technology.
The scalable approach is expressed with three realtime classes.
RT
RT communication is based on standard Ethernet. The data are transferred via prioritized
Ethernet telegrams. Because standard Ethernet does not support any synchronization
mechanisms, isochronous operation is not possible with PROFINET IO with RT! The real-
time capability is comparable with the present PROFIBUS DP solutions with 12 MBaud, i.e. a
sufficiently large bandwidth portion is available for the parallel transmission of IT services on
the same line.
The real update cycle in which cyclic data are exchanged depends on the bus load, the
devices used and the quantity framework of the I/O data. The update cycle is a multiple of
the send cycle.
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Function Manual, (FH1), 01/2012, 6SL3097-4AB00-0BP2
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