This 64 KB RAM card provides volatile load memory expansion for SIMATIC S7-400 CPUs. Unlike FEPROM cards, the RAM card appears as a contiguous extension of the CPU internal load memory — the two form one unified storage area. Programs download with a single-click Download in STEP 7, and online block modification is fully supported during RUN.

When is a RAM card the right choice?

RAM cards are the standard for commissioning, program development, and PCS7 projects. They enable three capabilities that FEPROM cards cannot: (1) RUN-mode program downloads without stopping the CPU, (2) CFC online monitoring for process diagnostics, and (3) dynamic block length modification on load memory — required by applications like Route Control. The trade-off is that RAM is volatile: if the CPU backup battery fails and external power is lost, the program is erased and must be reloaded.

What battery backup does this card need?

The RAM card itself has no built-in battery — it relies on the CPU backup battery (or external battery via the EXT.BATT socket on the CPU rack). Ensure the CPU battery is healthy and replaced on schedule. When the battery is depleted and power is removed, both the program and any CPU password are lost.

Key Specifications

Frequently Asked Questions

Can I mix a RAM card with a FEPROM card in the same CPU?

No — the S7-400 CPU accepts only one memory card at a time. The card type determines the overall load memory behavior: RAM mode (unified, battery-backed, online-capable) or FEPROM mode (independent, battery-free, STOP-mode download only).

What happens if the battery fails during operation?

As long as the CPU has external power, the RAM contents are maintained. The program is lost only when both external power is removed AND the backup battery is depleted. If the CPU is running continuously, a dead battery poses no immediate risk — but schedule replacement before the next planned power-down.