The Siemens 6ES7954-8LL03-0AA0 is a SIMATIC S7 memory card for S7-1X00 CPUs, using 3.3 V Flash-EPROM technology with 256 Mbyte capacity. It stores the user program, configuration data, and firmware updates for the controller. Rated for a minimum of 200 000 write/delete operations, with data retention of 10 years when the delete/write count stays under 20 000; retention drops to 1 year if the count exceeds 180 000 cycles. That endurance profile suits program storage and occasional recipe changes — not a high-frequency data-logging target. The card measures 24 mm wide, 32 mm tall, and only 2.1 mm deep — essentially the thickness of a few stacked credit cards. It plugs directly into the CPU slot; no DIN rail or panel space consumed.
The 256 Mbyte capacity sits in the middle of the S7-1X00 memory card range. If your project needs more headroom for large libraries or HMI integration, the next step up is the 2 Gbyte card (6ES7954-8LL04-0AA0). For minimal programs or a spare to keep in the drawer, the 4 Mbyte card (6ES7954-8LE00-0AA0) covers basic logic.
Integration note
Compatible with S7-1200, S7-1500, and S7-1500T CPUs that accept the SIMATIC memory card form factor. Insertion is keyed; the card seats flush with the CPU face. No external power or wiring — the 3.3 V supply comes from the CPU slot. The Flash-EPROM type means the card retains data without battery backup. Use it to transfer a complete project to a replacement CPU without a PG/PC connection — pull the card from the failed unit, plug into the new one, power cycle.