Communications Via Fault-Tolerant S7 Connections - Siemens SIMATIC S7-400H System Manual

Communication

11.5 Communications via fault-tolerant S7 connections

11.5 Communications via fault-tolerant S7 connections
Availability of communicating systems
Fault-tolerant communication expands the overall SIMATIC system by additional, redundant
communication components, such as CPs and bus cables. To illustrate the actual availability
of communicating systems when using an optical or electrical network, a description is given
below of the possibilities for communication redundancy.
Requirements
The essential requirement for the configuration of fault-tolerant connections with STEP 7 is a
configured hardware installation.
The hardware configuration in both subsystems of the redundant systems must be identical.
This applies in particular to the slots.
Depending on the network you are using, CPs can be used for fault-tolerant and fail-safe
communication, see Appendix Function modules and communication processors supported
by the S7-400H (Page 333) .
Only Industrial Ethernet with the ISO protocol is supported.
To be able to use fault-tolerant S7 connections between a fault-tolerant system and a PC,
you must install the "S7-REDCONNECT" software package on the PC. Please refer to the
Product Information on "S7-REDCONNECT" to learn more about the CPs you can use at the
PC end.
Configuration
The availability of the system, including the communication, is set during configuration. Refer
to the STEP 7 documentation to find out how to configure connections.
Only S7 communication is used for fault-tolerant S7 connections. To set this up, open the
"New Connection" dialog box, then select "S7 Connection Fault-Tolerant" as the type.
The number of required redundant connections is determined by STEP 7 as a function of the
redundancy nodes. Up to four redundant connections will be generated, if supported by the
network. Higher redundancy can not be achieved even by using more CPs.
In the "Properties - Connection" dialog box you can also modify specific properties of a
fault-tolerant connection if necessary. When using more than one CP, you can also route the
connections in this dialog box. This may be practical, because by default all connections are
routed initially through the first CP. If all the connections are busy there, any further
connections are routed via the second CP, etc.
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