System and Operating Modes of the S7-400H
5-8
Automation System S7-400H Fault-tolerant Systems
A5E00068197-07
5.3.4 Operating State RUN
Except for the additions described below, the CPUs of the S7-400H behave in
exactly the same way in the RUN mode as the standard CPUs on the S7-400 do.
The user program is executed by at least one of the two CPUs in the following
system modes:
• Single Mode
• Link-up, Update
• Redundant mode
Single Mode, Link–up, Update
In the above-named system modes the master CPU is at RUN and executes the
user program on its own.
Redundant System Mode
The master CPU and the standby CPU are at RUN in redundant system mode.
The two CPUs execute the user program in synchronism and perform mutual
checks.
In redundant system mode it is not possible to test the user program with
breakpoints.
Redundant system mode is only possible if both CPUs are of the same release
and the same firmware version. It is quit upon the causes of error listed in
Table 5-3.
Table 5-3 Causes of Error Leading to the Termination of Redundant System Mode
Cause of Error
Reaction
Failure of one CPU Refer to Section 10.1.1
Failure of the redundant link
(synchronization submodule or fiber-optic
cable)
Refer to Section 10.1.5
Error upon comparison of RAM (comparison
error)
Refer to Section 5.3.6
Redundant modules
The following rule applies in Redundant system mode:
Redundantly used modules (for example, DP slave interface module IM 153-2)
must be identical – in other words, they must have the same order number, the
same version, and the same firmware version.
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