The Siemens 6ES7954-8LB00-0AA0 is a SIMATIC S7 memory card for S7-1200 CPUs, providing 2 Mbyte of Flash-EPROM storage at 3.3 V. This card stores the user program, project data, and firmware updates for the S7-1200 controller. The 2 Mbyte capacity is sized for mid-range applications — enough for a control program with moderate tag count and a few HMI faceplates, but not for large recipe libraries or extensive data logging. The Flash-EPROM type means the card retains data without backup battery, and supports in-system programming via the TIA Portal download cycle.
Dimensions are 24 mm wide, 32 mm tall, and only 2.1 mm deep — it inserts into the S7-1200 CPU's memory slot on the front face, not on a DIN rail. The slim profile means it does not affect the CPU's clearance to the enclosure door or adjacent modules.