Failure and Replacement of Components During Operation
10-3
Automation System S7-400H Fault-tolerant Systems
A5E00068197-07
10.1.1 Failure and Replacement of a Central Processing Unit
(Fault-Tolerant CPU)
Complete replacement of the CPU is not always necessary. If the failure affects
only the load memory, all you have to do is replace the memory card concerned.
Both cases are described below.
Starting situation for replacement of the complete CPU
Failure How Does the System React?
The S7-400H is in redundant system mode
and a CPU fails.
• Partner CPU switches to single mode.
• Partner CPU reports the event in the
diagnostics buffer and via OB 72.
Requirements for a replacement
The module replacement described below is possible only if the “new” central
processing unit
• has the same operating system version as the failed CPU and
• the same main memory and load memory as the failed CPU.
Notice
New CPUs are always delivered with the latest operating system version. To be
able to use this type of CPU as a replacement module, you must create an
operating system update card for the operating system version of the failed CPU
and use it to transfer the operating system to the replacement CPU.
Procedure
To change a central processing unit, perform the following steps:
Step What Has To Be Done? How Does the System React?
1 Turn off the power supply module. • Entire subsystem is turned off
(system operating in single mode).
2 Replace the central processing unit. -
3 Plug in the synchronization
submodules. Make sure the rack
number is set correctly.
-
4 Plug in the fiber-optic cable connections
of the synchronization submodules.
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