Memory concept   
4.2 Memory functions 
  CPU 31xC and CPU 31x, Technical Data 
4-10  Manual, 01/2006 Edition, A5E00105475-06 
4.2  4.2 Memory functions 
4.2.1  General: Memory functions 
Memory functions 
Memory functions are used to generate, modify or delete entire user programs or specific 
blocks. You can also ensure that your project data are retained by archiving these. If you 
created a new user program, use a PG/PC to download the complete program to the 
SIMATIC Micro Memory Card.  
4.2.2  Loading user program from SIMATIC Micro Memory Card (MMC) to the CPU 
User program download 
The entire user program data are downloaded from your PG/PC to the SIMATIC Micro 
Memory Card (MMC). The previous content of the MMC is deleted in the process. Blocks 
use the load memory area as specified under "Load memory requirements" in "General block 
properties".  
The figure shows the load and work memory of the CPU 
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: If not all of the work memory area is retentive, the retentive area is indicated in STEP 7 
module status as retentive memory (same as on CPU 317). You cannot run the program 
until all the blocks are downloaded.