Changing The Memory Components Of The Cpu; Expanding The Main And/Or Load Memory - Siemens SIMATIC S7-400H Manual

11.7

Changing the Memory Components of the CPU

Redundant system mode is only possible if the two CPUs have the same memory
components. For this, the following conditions must be met:
• The main memory of the two CPUs must be the same size.
• The load memory of the two CPUs must be the same size and of the same type
(RAM or FLASH).
The memory components of the CPUs can be modified during operation. Possible
memory modifications in S7-400H are:
• Expansion of the main memory and/or load memory
• Changing the type of load memory
11.7.1

Expanding the Main and/or Load Memory

The following methods of memory expansion are possible:
• expanding the main memory by plugging in additional or larger memory
modules
• expanding the load memory by plugging in a larger memory card of the same
type instead of the existing one
• expanding the load memory by plugging in a RAM card if no memory card was
plugged in previously
With this type of memory change the complete user program is copied from the
master CPU to the standby CPU on link-up (see Section 6.2.1).
Restrictions
Expanding the load memory is only meaningful in the case of RAM Cards, since
only then can the user program be copied to the load memory of the standby CPU
on link-up.
In principle it is also possible to expand the load memory in the form of FLASH
cards, but it is then the user's responsibility to load the complete user program and
the hardware configuration into the new FLASH card (see procedure in
Section 11.7.2).
Initial situation
The fault-tolerant system is working in redundant system mode.
Automation System S7-400H Fault-tolerant Systems
A5E00068197-07
Modifying the System During Operation
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