System modifications during operation
17.8 Changing the CPU memory configuration
S7-400H
System Manual, 03/2012, A5E00267695-11
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17.8
Changing the CPU memory configuration
17.8.1
Changing the CPU memory configuration
The redundant system state is only possible if both CPUs have the same memory
configuration. For this the following condition must be met:
●
The size and type of load memory (RAM or FLASH) on both CPUs must match.
The memory configuration of the CPUs can be modified in operation. Possible modifications
of S7-400H memory:
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Expanding load memory
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Changing the type of load memory
17.8.2
Expanding load memory
The following methods of memory expansion are possible:
●
Upgrade the load memory by inserting a memory card with more memory space
●
Upgrade the load memory by inserting a RAM card, if no memory card was previously
inserted
If you change memory in this way, the entire user program is copied from the master CPU to
the reserve CPU during the link-up process (see section Update sequence (Page 149)).
Restrictions
Memory should preferably be expanded using RAM cards, because this will ensure that the
user program is copied to load memory of the reserve CPU in the link-up process.
In principle, it is also possible to use FLASH Cards to expand load memory. However, it is
then your responsibility to download the entire user program and the hardware configuration
to the new FLASH Card (see procedure in section Changing the type of load memory
Starting situation
The fault-tolerant system is operating in redundant system mode.
