Question about PLC S7-300 memory card

Hello Milad;

Your CPUs must be very old, at this time all MCs 951 seem to be in discontinuation phase, and if they csn be found in Siemens' distribution centers they will be very expensive.

SIMATIC S7, MEMORY CARD FOR S7-300, SHORT VERSION, 5V FLASH EPROM, 512 KBYTES

Which memory cards can you use with an S7-300 CPU?

You could try to find these EPROM modules on the web, there are many resellers of automation equipment that hold these items.

For example:

https://www.google.ca/#q=6es7951-0kj00-0aa0^

Hope this helps,

Daniel Chartier