Siemens SIMATIC S7-400H Manual page 120

Failure and Replacement of Components During Operation
Initial situation
Simultaneous failure of the two
synchronization submodules or
fiber-optic cables:
The S7-400H is in the Redundant system
mode and both fiber-optic cables or
synchronization submodules fail.
Procedure
The double error described results in loss of redundancy. In this event proceed as
follows:
Step
1 Switch off a subsystem.
2 Replace the faulty components.
3 Turn the subsystem back on.
4 Start the CPU – for example,
STOP RUN or Start via programming
device.
9-10
Failure
What Has To Be Done?
S7-400H Programmable Controller Fault-Tolerant Systems
How Does the System React?
Both CPUs report the event in the
diagnostic buffer and via OB 72.
Both CPUs become the master CPU and
remain in RUN mode.
How Does the System React?
-
-
LEDs IFM1F and IFMF2F go out. The
standby LED lights.
CPU performs automatic LINK-UP
and UPDATE.
CPU changes to RUN (Redundant
system mode) and now operates
as the standby CPU.
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