e30bk813.10
Figure 4: Example of Star Topology
2.8.4
Ring Topology
Ring topology enables the same simpler cabling and reduced cabling costs as line topology, but also reduces the damage caused by a
single cable failure in a similar manner as star topology.
NOTICE
When ring topology is used, take precautions to avoid timeout in the PLC when more than 8 drives or power converters are
installed in series. Each drive or power converter in the network adds a small delay to the communication due to the built-in
Ethernet switch. When the update time is too short, the delay can lead to a timeout in the PLC.
l
Set the update time as shown in the table. The numbers given are typical values and can vary from installation to installation.
Number of units connected in series
Minimum update time [ms]
<8
2
8–16
4
16–32
8
33–50
16
>50
Not recommended
The ring topology protocol depends on the protocol in use. For PROFINET, the Media Redundancy Protocol (MRP) is used. The MRP
is designed to react deterministically on a cable failure. One of the nodes in the network has the role of Media Redundancy Manager
(MRM), which observes and controls the ring topology to react to network faults. Usually this device is a PLC or network switch.
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Operating Guide | iC7-Marine PROFINET
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