Redundancy, Functional; Redundant Mode; Redundant Systems; Redundant Link - Siemens SIMATIC S7-400H Manual

Redundancy, functional

Redundancy with which the additional technical means are not only constantly in
operation but also involved in the scheduled function. Synonym: active
redundancy.

Redundant mode

In redundant system mode of a fault–tolerant system the central processing units
are in RUN mode and are synchronized over the redundant link.

Redundant systems

Redundant systems are characterized by the fact that important automation
system components are available more than once (redundant). When a
redundant component fails, processing of the program is not interrupted..

Redundant link

A link between the central processing units of a fault–tolerant system for
synchronization and the exchange of data.
Self-test
In the case of fault–tolerant CPUs defined self–tests are executed during startup,
cyclical processing and when comparison errors occur. They check the contents
and the state of the CPU and the I/Os.
Single mode
In the single system mode of a fault–tolerant system, the master CPU is
in RUN mode, whereas the standby CPU is in the STOP, TROUBLE-
SHOOTING or DEFECTIVE mode.
Single operation
Referring to single operation, we mean the use of a fault-tolerant CPU in a stan-
dard SIMATIC-400 station.
Standby CPU
The redundant central processing unit of a fault–tolerant system that is linked to
the master CPU. It goes to STOP mode when the redundancy connection is lost.
The user program is processed identically in both the master and standby CPUs.
STOP
With fault–tolerant systems: in the Stop system mode of a fault–tolerant system
the central processing units of the fault–tolerant system are in STOP mode.
Automation System S7-400H Fault-tolerant Systems
A5E00068197-07
Glossary
Glossary-3