Siemens SIMATIC S7-400H System Manual page 148

Using I/Os in S7-400H
10.5 Connecting redundant I/Os
NOTICE
If there are two redundant analog output modules and an error occurs on the second
module, as long as the first module is still passivated the second will not be passivated. If
the first module is repaired and depassivated, only half the current value is output on the
faulty channels until the second module has also been repaired.
Depassivation of modules
Passivated modules are depassivated by the following events:
● When the fault-tolerant system starts up
● When the fault-tolerant system changes over to "redundant" state
● After system modifications in operation
● If you call FC 451 "RED DEPA" and at least one redundant channel or module is
The depassivation is executed in FB 450 "RED IN" after one of these events has occurred.
Completion of the depassivation of all modules is logged in the diagnostic buffer.
When operating redundant I/O on a one-sided central unit or one-sided DP slave, you will
need to depassivate the redundant modules after a station failure/recovery or replacement of
a defective module. You can trigger depassivation of all modules by calling FC 451.
Note
When a redundant module is assigned a process image partition and the corresponding OB
is not available on the CPU, the complete passivation may take approximately 1 minute.
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FB 452 "RED_DIAG" initiates depassivation at the change to redundant mode. This
requires FB 452 to be called in OB 72 (CPU redundancy error). FB 452 "RED_DIAG" also
needs to be called in OB 82 (diagnostic interrupt), in OB 83 (remove/insert module
interrupt) and in OB 85 (program execution error). This ensures correct functioning of the
blocks for the redundant I/O.
passivated.
The functionality and use of FC 451 is described in the corresponding online help.
System Manual, 09/2007, A5E00267695-03
S7-400H