Siemens Simatic S7-300 CPU 31xC and CPU 31x S7-300 User Manual

Page 72

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Memory concept

4.1 Memory areas and retentivity

CPU 31xC and CPU 31x, Technical data

4-10

Manual, Edition 08/2004, A5E00105475-05

MMC copy protection

Your MMC has an internal serial number that provides copy protection at user level. You can

read this serial number from the SSL partial list 011C

index 8 using SFC 51 "RDSYSST."

You can then program a STOP command, for example, in a copy-protected block if the

expected and actual serial numbers of your MCC do not tally.

Reference

•

SSL partial list in the instruction list, or

•

in the manual

System and Standard Functions.Information on CPU memory reset:

Operating instructions CPU 31xC and CPU31x, Commissioning, Commissioning

Modules, CPU Memory Reset by means of Mode Selector Switch

Useful life of an MMC

The useful life of an MMC depends mainly on following criteria:
1. The number of delete or programming operations,
2. External influences such as ambient temperature.
At ambient temperatures up to 60 °C, a maximum of 100,000 delete/write operations can be

performed on an MMC.

Caution
To prevent loss of data, always make sure that you do not exceed the maximum number of

delete/write operations.