siemens S7 ROM & RAM


Thread Starter



When we click download the program , where the program is saved? Is it ROM?

There are two options in PLC 1) copy RAM to ROM and 2) transfer the program to memory card what is the difference?

If the CPU of PLc have a MMC memory card, when you download the program is saved on MMC.

Copy RAM To Rom is valid for CPU with EPROM on Board.

Save the program on MMC is referred to a Prommer connected to PG/PC.

Wiwi Hartono


When you go online with the PLC and before you download, you would be able to see that there are SFCs and SFBs, These are system function and blocks in build-in ROM which come with each model PLC. Each PLC would have different set of system blocks.

When you download to PLC, you would download to build-in RAM by default, not the build-in ROM. Build-in ROM would have you the OS(firmware) and the System Blocks.

You could have 'EEPROM' module insert to your CPU, this is additional memory for you to store your program and you could reuse the 'EEPROM' in other PLC.

1. Copy RAM to ROM - ROM is referred to the EEPROM.

Alternatively, you are able to drag and drop within the simatic manager instead using the menu options.

2. If you are using the Simatic PG (Siemens Industrial laptop), this is slot for you to insert EEPROM.

This option is meant for you to copy to this inserted EEPROM.

Hope this help.