Siemens SIMATIC PCS 7 CPU 410-5H System Manual page 108

Operator controls and operating modes of the CPU 410-5H
7.2 System states of the redundant CPU 410-5H
Self-test
Malfunctions or errors must be detected, localized and reported as quickly as possible.
Consequently, extensive self-test functions have been implemented in the S7-400H that run
automatically and entirely in the background.
The following components and functions are tested:
● Coupling of the central controllers
● Processor
● Internal memory of the CPU
● I/O bus
If the self-test detects an error, the fault-tolerant system tries to eliminate it or to suppress its
effects.
A description of the self-test is available in Chapter Self-test (Page 116).
System operation without STOP
To best meet the requirements of the process industry for system operation without STOP,
PCS 7 intercepts as many possible STOP causes as possible. The CPU 410H-PA has been
enhanced such that, as a redundant system, it reaches the RUN Redundant operating state
automatically on every occasion if possible. A change in the operating state is only possible
through an engineering system command. The diagnostic information always indicates the
RUN switch position.
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CPU 410-5H Process Automation
System Manual, 09/2014, A5E31622160-AB