The 6ES7952-1AK00 is a 1 MB RAM memory card for SIMATIC S7-400 controllers. It is the entry-level RAM card for the S7-400 platform — compact in capacity but identical in capability to every other RAM card in the 1A series. It supports RUN-mode program downloads, online block editing, and CFC chart monitoring. It merges with the CPU's internal load memory to form a single contiguous storage area. And it requires a backup battery — the one maintenance item that buys you the flexibility to change your program without stopping your process.

Who needs 1 MB of RAM load memory?

Engineers maintaining legacy S7-400 installations where the program is compact and stable — a small material handling system, a filter control station, a simple pump sequencing application. The program fits in 1 MB and has done so for years. What these users need is not more capacity; it is the ability to make an occasional online correction — adjust a timer value, modify an interlock condition, add a diagnostic message — without shutting down. The 1 MB RAM card delivers exactly that capability at the lowest cost in the RAM card lineup.

What are the battery requirements for the 1 MB card?

Same as every other RAM card in the 1A series. The S7-400 CPU's internal battery or an external supply on the EXT.BATT socket must maintain backup voltage whenever system power is off. The card draws microamperes of backup current — battery life is determined primarily by the CPU and ambient temperature, not by the card. Siemens recommends battery replacement every 1–2 years. The CPU diagnostics will warn you well before the battery is depleted.

Frequently Asked Questions

Can I use this card in an S7-400H CPU?

Yes — but both CPUs in the redundant pair must use identical RAM cards. You cannot pair a 1 MB card in CPU A with a 2 MB card in CPU B.

Is there a functional difference between the 1AK00 and the older RAM cards?

No. All RAM cards in the 6ES7952-1A series share the same architecture, voltage, and feature set. The only variable is capacity. A 1 MB RAM card behaves identically to an 8 MB card — the CPU simply sees a different total load memory size.