4 MByte MMC for S7-300 racks
The 6ES7953-8LM20-0AA0 is a 4 MByte Micro Memory Card (MMC) for the SIMATIC S7-300 family, including the C7 compact units and ET 200 distributed I/O. It uses 3.3V Nflash technology and is designated as a spare part by Siemens. This card plugs into the MMC slot on the CPU — it is the mandatory program and data storage medium for S7-300 CPUs that lack an integrated load memory. Without it the CPU has no memory to hold the user program.
Capacity and fit
The 4 MByte capacity is enough for mid-sized S7-300 applications — a typical process block library plus a few hundred FCs/FBs fits within this footprint. It is not a high-capacity card; for larger projects the 8 MByte or higher MMCs are needed.
Sourced to order against RFQ through independent distribution.