Siemens Simatic S7-300 CPU 31xC and CPU 31x S7-300 - Manual (Page 63)

CPU 31xC and CPU 31x, Technical data
Manual, Edition 08/2004, A5E00105475-05
4-1
Memory concept
4
4.1 Memory areas and retentivity
4.1.1 CPU memory areas
The three memory areas of your CPU:
CPU
Loading memory
(located on the MMC)
Memory of the CPU
System memory
Working memory
MMC
Load memory
The load memory is located on a Micro Memory Card (MMC). The size of the load memory
corresponds exactly to the size of the MMC. It is used to store code blocks, data blocks and
system data (configuration, connections, module parameters, etc.). Blocks that are identified
as non runtime-related are stored exclusively in load memory. You can also store all the
configuration data for your project on the MMC.
Note
User programs can only be downloaded and thus the CPU can only be used if the MMC is
inserted in the CPU.