Examples Of The Reaction Of The Fault-Tolerant System To Faults - Siemens SIMATIC S7-400H System Manual

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4.4 Examples of the reaction of the fault-tolerant system to faults

4.4 Examples of the reaction of the fault-tolerant system to faults
Example 1: Failure of a CPU or of a power supply module
Initial situation: The S7-400H is in redundant mode.
1. Simulate a CPU0 failure by turning off the power supply.
2. Turn the power supply back on.
Example 2: Failure of a fiber-optic cable
Initial situation: The S7-400H is in redundant mode. The mode selector switch of each CPU
is set to RUN.
1. Disconnect one of the fiber-optic cables.
2. Reconnect the fiber-optic cable.
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Result: The LEDs REDF, IFM1F and IFM2F light up on CPU1. CPU1 goes into single
mode and continues to process the user program.
Result:
– CPU0 performs an automatic LINK-UP and UPDATE.
– CPU0 changes to RUN, and now operates in standby mode.
– The S7-400H is in redundant mode.
Result: The LEDs REDF and IFM1F or IFM2F (depending on which fiber-optic cable was
disconnected) now light up on both CPUs. The standby CPU changes to the
TROUBLESHOOTING mode. The other CPU remains master and continues operation in
single mode.
Result: The standby CPU performs starts a LINK-UP and UPDATE. The S7-400H resumes
redundant mode.
System Manual, 09/2007, A5E00267695-03
S7-400H