The 6ES7952-1KY00 is a 64 MB Flash EPROM memory card for SIMATIC S7-400 controllers — the largest FEPROM card available for the S7-400 platform. It stores the user program, hardware configuration, and data blocks in non-volatile 5V Flash. On every CPU power-up, the program is automatically copied from the card into the CPU's work memory. The card's extended load memory operates independently from the built-in load memory, providing a separate, removable storage volume that does not consume the CPU's internal memory budget.

Flash EPROM versus RAM — why no battery?

Unlike S7-400 RAM cards, which require a backup battery to retain data through a power cycle, the Flash EPROM card is inherently non-volatile. Remove it from the CPU, store it on a shelf for years, plug it back into any compatible S7-400 — the program is still there. This makes FEPROM cards the standard choice for applications where battery maintenance is impractical, where power interruptions are expected, or where the program must be archived inside the PLC itself without relying on external storage.

Why choose 64 MB over 32 MB?

The 6ES7952-1KY00 doubles the capacity of the 6ES7952-1KT00 (32 MB). If your S7-400 program, data blocks, and recipes fit within 32 MB, the 1KT00 is sufficient and more economical. If your project approaches or exceeds that threshold — common in large process automation systems with thousands of data points, extensive recipe databases, or integrated HMI data structures — the 64 MB card provides the necessary headroom. Both cards share the same 5V Flash EPROM technology and long-design form factor.

Frequently Asked Questions

Which S7-400 CPUs support this card?

All standard S7-400 CPUs with a memory card slot — including the S7-412, S7-414, S7-416, and S7-417 families, plus the S7-400H high-availability series. Each CPU in a redundant H-system pair requires its own memory card. Some early S7-400 CPUs manufactured before 1998 may require a firmware update for full 64 MB support.

Can I read this card in a programming device outside the PLC?

Yes. Insert the card into a compatible Siemens PG (programming device) with a memory card slot to view, copy, or archive user programs without connecting to the CPU. This is a standard workflow for program backup and duplication across multiple machines.