Siemens ESM - Manual (Page 39)

Network Topologies with OSM/ESM
Industrial Ethernet OSM/ESM
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The connection between two network segments is on two separate paths. Two of
the OSMs/ESMs in a ring are connected together via a connecting cable (ITP-XP
standard cable 9/9 with a maximum length of 40 m) and inform each other of their
operating states. One of these OSMs/ESMs is assigned the redundant function
using the DIP switch setting "Stby on" (standby slave). The other OSM takes over
the function of the standby master (DIP switch setting "Stby off").
Immediately following the failure of the main transmission path, the standby slave
enables the redundant path. If the main path is OK again, the standby master
informs the standby slave. The main path is enabled and the redundant path
disabled again. The reconfiguration time of the redundant ring coupling is less than
0.3 s.
Port Assignment in the Standby Mode
On the standby master and standby slave only port 1 (standby port) can be used
for the coupling to the neighboring ring. Ports 2 - 6 can be used just as normal
OSM ports.
With network management, it is also possible to configure ports other than port 1
as standby ports (see also OSM/ESM Network Management User Manual /1/).
Simultaneous Standby and Redundancy Manager Operation
A standby master or standby slave can adopt the function of a redundancy
manager at the same time.
Replacing the Standby Master During Operation
When replacing a standby master during operation, the following order is
necessary to prevent an interruption on the network:
1. Remove the terminal block for the power supply on the standby master
2. Remove the signal lines and the standby connecting cable from the standby
master.
3. Connect the signal lines to the standby connecting cable on the replacement
device.
4. Plug in the terminal block for the power supply on the replacement device.
When replacing a standby slave, no special measures are necessary. You must
simply make sure that the standby master is active.