4 memory concept, 1 memory areas and retentivity, 1 cpu memory areas – Siemens Simatic S7-300 CPU 31xC and CPU 31x S7-300 User Manual

Page 63: Memory concept

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

4-1

Memory concept

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.