Siemens SIMATIC S7-400H System Manual page 104

Link-up and update
9.3 Link-up and update
RAM
The following components are transferred from the RAM of the master CPU to the standby
CPU:
● Contents of all data blocks assigned the same interface time stamp in both load memories
● Data blocks generated in the master CPU by SFCs.
● Process images, timers, counters and memory markers
● Diagnostics buffer
If there is insufficient memory, link-up is cancelled with an entry in the diagnostics buffer.
The status of SFB instances of S7 Communication contained in modified data blocks is
restored to the status prior to their initial call.
Note
When changing over to a CPU with modified configuration, the size of load memories in the
master and standby may be different.
Switch to CPU with expanded memory configuration
You may have expanded the load memory on the standby CPU. The memory media for
storing load memory must be identical, i.e. either RAM cards or FLASH cards. If you
expanded with FLASH cards, their contents must be identical.
NOTICE
Assuming you have implemented a different type of load memory module or operating
system on the standby CPU, this CPU does not go into RUN, but rather returns to STOP
and writes a corresponding message to the diagnostics buffer.
Assuming you have not expanded load memory on the standby CPU, this CPU does not go
into RUN, but rather returns to STOP and writes a corresponding message to the
diagnostics buffer.
The system does not perform a master/standby changeover, and the previous master CPU
remains in RUN.
For information on changing the type of memory module or on load memory expansions,
refer to section Failure and replacement of components during operation (Page 185).
When you initiate a link-up and update with the "Switch to CPU with expanded memory
configuration" option in STEP 7, the system reacts as follows with respect to the handling of
memory contents.
104
and having the attributes "read only" and "unlinked".
The DBs generated in the standby CPU by means of SFC are deleted.
If a data block with the same number is also found in the load memory of the standby CPU,
link-up is cancelled with an entry in the diagnostics buffer.
If the configured size of the diagnostics buffer of the standby CPU is smaller than that of
the master CPU, only the number of entries configured for the standby CPU are transferred.
The most recent entries are selected from the master CPU.
System Manual, 09/2007, A5E00267695-03
S7-400H