Siemens S7-300 appendix Properties of the Micro Memory Card MMC, MMC as memory module for the CPU

Memory concept 4.1 Memory areas and retentivity

4.1.5Properties of the Micro Memory Card (MMC)

The MMC as memory module for the CPU

The memory module used on your CPU is a SIMATIC Micro Memory Card (MMC.) You can use MMCs as load memory or as a portable storage medium.

Note

The CPU requires the MMC for operation.

Data stored on the MMC:

•User programs (all blocks)

•Archives and recipes

•Configuration data (STEP 7 projects)

•Data for operating system update and backup

Note

You can either store user and configuration data or the operating system on the MMC.

Properties of an MMC

The MMC ensures maintenance-free and retentive operation of these CPUs.

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 MMC on your PG, or format the card in the CPU. Never remove an MMC in RUN mode. Always remove it when power is off, or when the CPU is in STOP state, and when the PG is not a 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.

CPU 31xC and CPU 31x, Technical data	4-9
Manual, Edition 08/2004, A5E00105475-05