Failure And Replacement Of A Central Processing Unit Cpu 417-4H - Siemens SIMATIC S7-400H Manual

9.1.1 Failure and Replacement of a Central Processing Unit
CPU 417-4H
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
The S7-400H is in the Redundant system
mode and a CPU fails.
Requirements for a replacement
The module replacement described below is possible only if the "new" central
processing unit
has the same operating system status as the failed CPU (refer to Operating
system update in section 10.8) und
has the same main memory and load memory as the failed CPU.
Procedure
To change a central processing unit, perform the following steps:
Step
1 Turn off the power supply module.
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.
5 Turn the power supply back on.
6 Perform Memory Reset on the replaced
CPU.
7 Start the replaced CPU – for example,
STOP RUN or Start via programming
device.
S7-400H Programmable Controller Fault-Tolerant Systems
A5E00068197-04
Failure and Replacement of Components During Operation
Failure
What Has To Be Done?
How Does the System React?
Partner CPU switches to Solo mode.
Partner CPU reports the event in the
diagnostic buffer and via OB 72.
How Does the System React?
Entire subsystem is turned off
(system operating in Solo mode).
-
-
-
CPU executes the self-tests and
goes to STOP.
-
CPU performs automatic LINK-UP
and UPDATE.
CPU changes to RUN and
operates as the standby CPU.
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