The Siemens 6ES7953-8LJ00-0AA0 is a Micro Memory Card (MMC) for S7-300, C7, and ET 200S IM151 CPU systems. It provides 512 kbyte of Flash-EPROM storage for program code, configuration data, and firmware updates, operating at 3.3 V NFlash voltage. This card plugs directly into the MMC slot on compatible CPUs — no external power or adapter needed. The Flash-EPROM type means program retention without battery backup, critical for unattended or remote panels.
Key Specs That Matter for Fit
The 512 kbyte capacity handles medium-size S7-300 programs — enough for a multi-block control logic with several function blocks and data blocks. For larger projects, Siemens offered higher-capacity MMCs (1 MB, 2 MB, 4 MB, 8 MB) in the same form factor. Flash-EPROM memory retains data indefinitely without a battery, so no scheduled battery replacement is needed. This is the standard memory type for S7-300 MMCs.