Communication
14.2 Basics and terminology of fault-tolerant communication
S7-400H
234 System Manual, 03/2012, A5E00267695-11
If the active subconnection fails, the already established second subconnection automatically
takes over communication.
Resource requirements of fault-tolerant S7 connections
The fault-tolerant CPU supports operation of 62/46 (see the technical specifications) fault-
tolerant S7 connections. Each connection needs a connection resource on the CPU;
subconnections do not need any additional connection resources. On the CP, on the other
hand, each subconnection needs a connection resource.
NOTICE
If you have configured several fault-tolerant S7 connections for a fault-tolerant station,
establishing them may take a considerable time. If the configured maximum communication
delay is set too short, link-up and updating is canceled and the redundant system mode is
no longer reached (see section Time monitoring (Page 155)).
E
ach C
PU provides the connection resources according to its configuration, which means
that a CPU 417-5H that was configured as CPU 412-5H only provides the connection
resources of a CPU 412-5H.
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