Technical data

Downloading and Uploading
19.1 Downloading from the PG/PC to the Programmable Controller
Programming with STEP 7
420 Manual, 05/2010, A5E02789666-01
19.1.4 Download Methods Dependent on the Load Memory
The division of the load memory of a CPU into RAM and EEPROM areas determines the methods
available for downloading your user program or the blocks in your user program. The following
methods are possible for downloading data to the CPU:
Load Memory Method of Loading Type of Communication between
PG and PLC
Downloading and deleting individual
blocks
Online PG - PLC connection
Downloading and deleting a complete
user program
Online PG - PLC connection
RAM
Reloading individual blocks Online PG - PLC connection
Integrated (S7-300 only) or
plug-in EPROM
Downloading complete user programs Online PG - PLC connection
Plug-in EPROM Downloading complete user programs External loading of the EPROM and
inserting the memory card or via
online connection on the PLC where
the EPROM is inserted.
Downloading to the RAM via Online Connection
In the programmable controller the data are lost if there is a power failure and the RAM is not
backed up. The data in the RAM will then be lost in this case.
Saving to EPROM Memory Card
Blocks or the user program are saved on an EPROM memory card which is then inserted in a slot
on the CPU.
Memory cards are portable data media. They are written by the programming device and then
inserted in the appropriate slot on the CPU.
The data stored on them are retained following power down and when the CPU is reset. The
contents of the EPROM are copied to the RAM area of the CPU memory again when power returns
following a memory reset of the CPU and power down if the RAM is not backed up.
Saving in the Integrated EPROM
For the CPU 312, you can also save the contents of the RAM to the integrated EPROM. The data
in the integrated EPROM are retained during power down. The contents of the integrated EPROM
are copied to the RAM area of the CPU memory again when power returns following power down
and a memory reset of the CPU if the RAM is not backed up.