Siemens SIMATIC S7-400H System Manual page 332

System modifications during operation
17.8 Changing the CPU memory configuration
Procedure
Proceed as follows in the specified sequence:
Step What to do?
1 Switch the reserve CPU to STOP using the
programming device.
2 Replace the existing memory card in the reserve CPU
with a new one of the required type.
3 Reset the reserve CPU using the programming
device.
4 Download the program data to the reserve 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 reserve CPU with the menu command "PLC
> Mode > Switching to CPU with modified
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 termination of the link-up
process.
Writing to a FLASH Card in the fault-tolerant system
You can always write to a FLASH Card while the fault-tolerant system is in RUN, without
having to stop the fault-tolerant system. This is, however, only possible if the online data of
the hardware configuration and the user program in both CPUs and the corresponding offline
data in your engineering station match.
332
How does the system react?
The system is now operating in single mode.
Reserve CPU requests memory reset.
–
–
The reserve 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

system mode.
System Manual, 03/2012, A5E00267695-11
S7-400H