Siemens S7-300 appendix General Memory functions, User program download

Memory concept 4.2 Memory functions

4.2Memory functions

4.2.1General: 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 there is... You created a new user program, use a PG/ PC to download the complete program to MMC.

4.2.2Loading user program from Micro Memory Card (MMC) to the CPU

User program download

All user program data are downloaded from your PG/PC to the CPU via 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

PG

Stored on hard disk

Code modules

Data modules

Comments

Symbols

MMC

Loading memory

Code modules

Data modules

CPU

Working memory

Process-relevant

parts of the code

and data modules *

*If not alI of the work memory area is retentive, its retentive area is indicated in the STEP 7 module status as retentive memory (same as on CPU 317). You cannot run the program until all the blocks are downloaded.

CPU 31xC and CPU 31x, Technical data	4-11
Manual, Edition 08/2004, A5E00105475-05