Siemens SIMATIC S7-400H System Manual page 241

Procedure
Do the following in the sequence given:
Step What has to be done?
1 Switch the standby CPU to STOP using the PG.
2 Replace the existing memory card in the standby CPU
with a new one of the required type.
3 Reset the standby CPU using the PG.
4 Download the program data to the standby CPU in
STEP 7 by selecting the "Download User Program to
Memory Card" command. Notice: Select the correct
CPU from the selection dialog.
5 Start the standby CPU with the menu command
"PLC > Mode > Switch to CPU ... with altered
configuration".
6 Modify the memory configuration of the second CPU
as you did for the first CPU in step 2.
7 Download the user program and the hardware
configuration to the second CPU.
8 Start the second CPU from the PG.
NOTICE
If you want to change to FLASH cards, you can load them with the user program and
hardware configuration in advance without inserting them in the CPU. Steps 4 and 7 can
then be omitted.
However, the memory cards in both CPUs must be loaded in the same sequence.
Changing the order of blocks in the load memories will lead to a link-up abort.
S7-400H
System Manual, 09/2007, A5E00267695-03
System modifications in operation
14.8 Changing the CPU memory configuration
How does the system react?
The system is now operating in single mode.
Standby CPU requests memory reset.
–
–
The standby CPU links up, is updated and
•
becomes the master.
Previous master CPU changes to STOP.
•
System operates in single mode.
•
–
–
The second CPU is linked up and updated.
•
The system is now operating again in redundant
•
mode.
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