Automation System - Siemens SIMATIC PCS 7 Function Manual

Fault-tolerant process control systems (v8.0)
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● Following a prompt from the user program via an acknowledgement signal, for example,
● After pulling/plugging a module
● Following a diagnostic interrupt (e.g. wire break, measured value)
Additional information
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6.2

Automation system

6.2.1
Failure of the master CPU
Functionality
The initial situation is that the S7-400H is in "Redundant" system mode. The processing of the
user program is synchronized on both CPUs of the H system and, for example, CPU0 is the
master CPU and CPU1 is the backup CPU. Event-driven synchronization ensures that the
backup CPU will always continue processing without interruption if the master CPU fails.
Example: Failure of the master CPU
If CPU0 fails, for example, the following LEDs light up on CPU1:
● REDF = Redundancy loss
● IFM1F = Interface fault interface module 1
● IFM2F = Interface fault interface module 2
The H system switches to "Solo" system mode. CPU1 ensures uninterrupted processing of
the user program. CPU1 is now the master CPU. The H system is no longer in "Redundant"
system mode.
Example: Reintegration of the failed master CPU
When the failed CPU0 is reintegrated, it does not become the master CPU. The master CPU
automatically performs the link-up and update of the reintegrated CPU0. Both processes are
necessary in order to check and synchronize the data in the memory of the master CPU and
the backup CPU. CPU0 then goes to RUN mode. Now the system is once again in "Redundant"
mode.
Fault-tolerant Process Control Systems (V8.0)
Function Manual, 03/2012, A5E02779471-02
on an OS with a "Depassivation" button at the block
STEP 7
Automation System S7-400H; Fault-tolerant Systems
Process Control System PCS 7; PCS 7 OS Process Control
This indicates the first fiber-optic cable of the synchronization line.
This indicates the second fiber-optic cable of the synchronization line.
Failure, Switchover and Return of Fault-tolerant Components
6.2 Automation system
177

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