Hello,

I have question about MMC?

1- When I download my program to PLC, should I save my program to MMC (Load memory) or does that happen automatically??

2- When can I use "copy RAM to ROM"?

3- When can I use "Save To memory Card "?

Thankyou

Hello Hmimed;

The following document explains the memory concept of the different generations of S7-300, you should concentrate on Chapter 4, discussing the S7-300 with a MMC bay (these are the greater number of S7-300 still in use today):

- How can you obtain an overview of the memory concept of SIMATIC S7-300 CPUs and C7 devices?

https://support.industry.siemens.com/cs/ww/en/view/7302326

When you have such an MMC on the CPU, the MMC is the only load memory that you have . Every download (from the program icons or load to memory card instruction) will transfer the program data and code to the MMC.

The document states that you can also use Copy RAM to ROM with these CPUs, but I have never felt the need to use it: the PLC must be set to Stop mode first, and only the complete program can be downaded (no partial downads of a single or multiple blocks, for example).

Hope this helps,

Daniel Chartier