Siemens CPU 31 Series Technical Data Manual page 85

CPU 31xC and CPU 31x, Technical Data
Manual, 01/2006 Edition, A5E00105475-06
Note
Active system functions SFC82 to 84 (active access to the SIMATIC Micro Memory Card)
have a distinct influence on PG functions (for example, block status, variable status,
download block, upload, open.) This typically reduces performance (compared to passive
system functions) by the factor 10.
Note
For CPUs with firmware V2.1.0 or higher, you can also generate non-retentive DBs using
SFC 82 (parameter ATTRIB -> NON_RETAIN bit.)
Note
To prevent data losses, do not exceed this maximum of delete/write operations. For
further information, refer to the Technical Data of the SIMATIC Micro Memory in the
General Technical Data of your CPU.
Caution
Data on a SIMATIC Micro Memory Card can be corrupted if you remove the card while it
is being accessed by a write operation. In this case, you may have to delete the SIMATIC
Micro Memory Card on your PG, or format the card in the CPU. Never remove a
SIMATIC Micro Memory Card in RUN mode. Always remove it when power is off, or
when the CPU is in STOP state, and when the PG is not writing to the card. When the
CPU is in STOP mode and you cannot not determine whether or not a PG is writing to
the card (e.g. load/delete block), disconnect the communication lines.
Memory concept
4.2 Memory functions
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