Differences Between Fault-Tolerant Systems And Standard Systems; Additional Functions Of Fault-Systems - Siemens SIMATIC S7-400H Manual

Differences Between Fault-Tolerant
Systems and Standard Systems
When you configure and program a fault-tolerant programmable logic controller
with fault-tolerant CPUs, certain differences to the standard S7-400 CPUs will
become apparent. On the one hand, compared to a standard S7-400 CPU, a
fault-tolerant CPU has additional functions, while on the other hand a fault-tolerant
CPU does not support certain other functions. This has to be taken in account
particularly if you wish to run a program that was created for a standard S7-400
CPU on a fault-tolerant CPU.
The items in which the programming of fault-tolerant systems differs from that for
standard systems are summarized below. You will find further differences in
Appendix B.
If you use one of the calls concerned (OBs and SFCs) in your user program, you
will need to adapt your program accordingly.

Additional functions of fault-systems

Redundancy error OBs
Additional information in OB
start information and in
diagnostics buffer entries
SFC for fault-tolerant
systems
Fault-tolerant
communication connections
Self-test
Switched I/O
Automation System S7-400H Fault-tolerant Systems
A5E00068197-07
Function
•
•
You can find detailed information in the System and
Standard Functions reference manual.
The rack number and the CPU (master/standby) are
specified. You can evaluate this additional information in the
program.
You can control the processes in fault-tolerant systems with
the SFC 90 "H_CTRL".
Fault-tolerant connections are configured, no further
programming is required.
You can use the SFBs for configured connections when
you are using fault-tolerant connections.
The self-test is performed automatically, no further
programming is required,
No additional programming is required, see Section 7.3.
Additional Programming
I/O redundancy error OB (OB 70)
CPU redundancy error OB (OB 72)
D
D-1