Supplementary information
18.9 Usable networks
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System Manual, 05/2017, A5E31622160-AC
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Resource requirements for fault-tolerant S7 connections
The H-CPU enables the operation of 62 (see 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.
Note
If you have configured multiple fault-tolerant S7 connections for an H station, it may take a
considerable time for them to be established. If the configured maximum communication
delay was set too short, link-up and updating is canceled and the redundant system state is
no longer achieved (see Chapter Time monitoring (Page 120)).
18.9
Usable networks
Your choice of the physical transmission medium depends on the required expansion,
targeted fault tolerance, and transfer rate. The following bus systems are used for
communication with fault-tolerant systems:
●
Industrial Ethernet
●
PROFIBUS
Additional information on the networks that can be used is available in the relevant SIMATIC
NET documentation on PROFIBUS and Ethernet.
18.10
Communication via S7 connections
Communication with standard systems
There is no fault-tolerant communication between a fault-tolerant system and a standard
CPU. The following examples illustrate the actual availability of the communicating systems.
Configuration
S7 connections are configured in STEP 7.
Programming
If S7 communication is used on a fault-tolerant system, all communication functions can be
used for this.
The communication SFBs are used in STEP 7 to program communication.