Siemens SIMATIC S7-400H System Manual page 290

System modifications during operation
17.3 Adding components in PCS 7
Reaction of the I/O
Type of I/O
Added I/O
modules
I/O modules still
present
Added DP stations are not addressed by the
The central modules are first reset. Output modules briefly output 0 during this time (instead of the
1)
configured substitute or hold values).
Reaction to monitoring timeout
The update is canceled and no change of master takes place if one of the monitored times
exceeds the configured maximum. The fault-tolerant system remains in single mode with the
previous master CPU and, assuming certain conditions are met, attempts the master
changeover later. For additional information, refer to section Time monitoring (Page 155).
290
One-sided I/O of
previous master CPU
are not addressed by the
CPU.
are no longer addressed
by the CPU.
Output modules output
the configured substitute
or holding values.
CPU.
One-sided I/O of new
master CPU
are given new parameter settings and updated by
the CPU.
Driver blocks are not yet present. Process or
diagnostic interrupts are detected, but are not
reported.
are given new parameter
settings and updated by
1)
the CPU.
as for added I/O modules (see above)
System Manual, 03/2012, A5E00267695-11
Switched I/O
continue operation
without interruption.
S7-400H