Step E: Transition To Redundant System Mode - Siemens SIMATIC S7-400H Manual

Modifying the System During Operation
11.6.5

Step E: Transition to Redundant System Mode

Initial situation
The fault-tolerant system works with the modified CPU parameters in single mode.
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, select the standby CPU and click the
Restart (warm restart) button.
Result
Standby CPU links up again and is updated. The fault-tolerant system is working in
redundant system mode.
Behavior of the I/O
Type of I/O One-way I/O of standby
I/O modules Are re-parameterized
and updated by the CPU.
1) Central modules are additionally first reset. Output modules briefly output 0 during this time (instead of the
configured substitute or holding values).
Response if monitoring times are exceeded
If one of the monitored times exceeds the maximum value configured the update is
interrupted. The fault-tolerant system remains in single mode with the previous
master CPU and in certain conditions attempts to perform the link-up and update
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.
11-46
One-way I/O of master
CPU
1)
Continue to work without interruption.
CPU
Automation System S7-400H Fault-tolerant Systems
Switched I/O
A5E00068197-07