Modifying the System During Operation
11-45
Automation System S7-400H Fault-tolerant Systems
A5E00068197-07
11.6.4 Step D: Switch to CPU with Modified Configuration
Initial situation
The modified hardware configuration is loaded into the standby CPU.
Procedure
1. In SIMATIC Manager, select a CPU of the fault-tolerant system, and choose the
PLC > Operating Mode menu command.
2. In the Operating Mode dialog box, click the Toggle button.
3. In the Toggle dialog box, select the option with modified configuration and
click the Toggle button.
4. Confirm the query that follows with OK.
Result
The standby CPU links up, is updated and becomes the master. The former
master CPU switches to STOP mode, the fault-tolerant system continues to work
in single mode.
Behavior of the I/O
Type of I/O One-way I/O of previous
master CPU
One-way I/O of new
master CPU
Switched I/O
I/O modules Are no longer addressed
by the CPU.
Output modules output the
configured substitute or
holding values.
Are re-parameterized
1)
and updated by the CPU.
Continue to work without
interruption.
1) Central modules are first reset in addition. Output modules briefly output 0 during this time (instead of the
substitute or holding values configured).
Response if monitoring times are exceeded
If one of the monitored times exceeds the maximum value configured the update is
interrupted and no change of master takes place. The fault-tolerant system
remains in single mode with the previous master CPU and in certain conditions
attempts to perform the change of master later. For more details refer to
Section 6.3.
If the values for the monitoring times in the CPUs are different then the higher
value always applies.
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