Glossary - Siemens SIMATIC S7-400H Manual

Glossary

1–out–of–2 system
See two-channel fault-tolerant system
Comparison error
An error that may occur while memories are being compared on a fault-tolerant
system.
ERROR-SEARCH
An operating mode of the standby CPU of a fault-tolerant system in which the
CPU performs a complete self-test.
Fail-safe systems
Fail-safe systems are characterized by the fact that they remain in a safe state
when certain failures occur or go directly to another safe state.
Fault-tolerant system
Fault-tolerant system consisting of at least two central processing units (master
and standby). The user program is processed in an identical manner in both the
master and standby CPUs.
Fault-tolerant systems
Fault-tolerant systems are designed to reduce production stoppages. Availability
can be enhanced, for example, by means of component redundancy.
H station
Fault-tolerant station containing two central processing units (master and
standby).
I/O, one-sided
We speak of a one-sided I/O when an input/output module can be accessed by
only one of the redundant central processing units. It may be single-channel or
multi-channel (redundant).
S7-400H Programmable Controller Fault-Tolerant Systems
A5E00068197-04
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