The Step 7 User Program; The User Program - Siemens SIMATIC CPU 410 System Manual

Supplementary information

18.5 The STEP 7 user program

When this connection type is configured, the application automatically determines the
number of possible subconnections:
● If two independent but identical subnets are available and they are suitable for a fault-
tolerant S7 connection, two subconnections are used. In practice, they are usually
electrical networks, one network connection in each subnet:
● If only one subnet is available, four subconnectors are used for a connection between two
fault-tolerant stations. All network connections are located in this subnet:
Only the integrated PROFINET IO interfaces or only the CPs are used for subconnections
within a fault-tolerant S7 connection. But multiple fault-tolerant stations in one subnet may
have different interfaces; they only have to be identical within the station.
Downloading the network configuration into a fault-tolerant station
The complete network configuration can be downloaded into the fault-tolerant station in one
operation. The same requirements that apply for downloads into standard stations must be
met.
18.5 The STEP 7 user program
18.5.1

The user program

The rules of developing and programming the user program for the standard S7-400 system
also apply to the S7-400H.
In terms of user program execution, the S7-400H behaves in exactly the same manner as a
standard system. The integral synchronization functions of the operating system are
executed automatically in the background. You do not need to consider these functions in
your user program.
In redundant operation, the user programs are stored identically on both CPUs and are
executed in event-synchronous mode.
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CPU 410 Process Automation/CPU 410 SMART
System Manual, 05/2017, A5E31622160-AC