Siemens Simatic S7-300 CPU 31xC and CPU 31x S7-300 - Manual (Page 74)

Memory concept
4.2 Memory functions
CPU 31xC and CPU 31x, Technical data
4-12
Manual, Edition 08/2004, A5E00105475-05
Note
This function is only permitted when the CPU is in STOP mode. Load memory is cleared if
the load operation could not be completed due to power loss or illegal block data.
4.2.3 Handling with modules
4.2.3.1 Download of new blocks or delta downloads
There are two ways to download additional user blocks or download deltas:
•
Download of blocks: You already created a user program and downloaded it to the CPU
via MMC. You then want to add new blocks to the user program. In this case, you do not
need to reload the entire user program to the MMC. Rather, you can download only the
new blocks to the MMC (this reduces download times for highly complex programs).
• Delta download: In this case, you only download the deltas in the blocks of your user
program. In the next step, perform a delta download of the user program, or only of
changed blocks to the MMC, using the PG/PC.
Warning
The delta download of blocks / user programs overwrites all data stored under the same
name on the MMC.
The data of dynamic blocks are transferred to RAM and activated after the block is
downloaded.
4.2.3.2 Uploading blocks
Uploading blocks
Other than download operations, an upload operation is the transfer of specific blocks or a
user program from the CPU to the PG/PC. The block content is here identical with that of the
last download to the CPU. Dynamic DBs form the exception, because their actual values are
transferred. An upload of blocks or of the user program from the CPU in STEP 7 does not
influence CPU memory.