8K CMOS Logic Memory Module for Series Six Model 600/6000 PLC — 8K 16-Bit Words, External Backup Battery Required

What this part is:
This is an 8K CMOS logic memory module for the GE Series Six family of programmable logic controllers, covering the Model 600 and Model 6000 platforms. It is the component that actually holds your ladder program. Series Six processors do not store the program themselves — the CPU board executes, the memory module remembers — so a Series Six CPU rack needs both parts present and matched before it will run a machine.

8K words, not 8K bytes — and why the difference matters:
The published capacity is 8K of 16-bit words, which is a genuine point of confusion in the surplus market because plenty of listings write “8K” and let the buyer assume bytes. In word terms that is twice the storage a byte reading would suggest, and it is the figure that maps onto the Series Six memory map and onto the instruction counts in your program listing. If you are sizing a replacement against a program printout, count words.

This module is logic memory only. There is no separate register block on it. That distinguishes it from the higher-capacity in-family modules such as IC600LX648, which is specified as 32K logic plus 16K register. If your application needs register memory as a distinct allocation, an 8K CM548 is not the part that provides it.

Battery backup: read this before you buy:
CMOS RAM is volatile. The program held on this module is retained only while an external lithium–manganese dioxide backup battery keeps it powered. That battery is not part of the memory module and is not included with this item.

The practical consequence is blunt: a memory module bought without arranging a fresh battery will lose its program the first time the rack is powered down. People discover this during a planned outage, which is the worst possible moment. On Series Six the battery assembly is typically supplied with or mounted on the CPU rack rather than on the memory module itself, so the battery you need may already be in your cabinet — but it may also be a decade past its useful life, and a battery that has been sitting in a rack since the Clinton administration is not a backup, it is a hazard.

We are not publishing a battery part number. The number commonly repeated by dealers for Series Six backup batteries could not be confirmed as correct against any source we trust, and quoting a wrong battery number on a memory listing is how programs get lost. Confirm the battery part number against your own rack documentation or the GE Series Six installation manual before you commission this module.

CPU compatibility:
This module is intended for the Series Six Model 600 and 6000 CPU modules — the IC600CB5xx processor family, which includes IC600CB502, IC600CB512, IC600CB515, IC600CB524, IC600CB525 and IC600CB526. What is not published anywhere we could verify is a definitive per-CPU compatibility matrix stating which processors accept an 8K module and which require a different capacity. Check the memory module against your specific CPU part number and your machine’s parts list rather than assuming family-wide fit. If you are also short a processor, we stock an IC600CB512 Series Six CPU under SKU B-BL3#HU4ZAW; the two parts are routinely bought together because neither works without the other.

Published data and known gaps:
Type: CMOS logic memory module, GE Series SixCapacity: 8K 16-bit words, logic memory onlyRegister memory: none as a separate blockPlatform: Series Six Model 600 and Model 6000 programmable controllersBackup: external lithium–manganese dioxide battery required, not suppliedRevision: A suffix confirmed to exist; a full revision list is not publishedNot published: per-CPU compatibility matrix, backplane load, battery part number

GE, GE Fanuc or GE-Emerson — all the same part:
The IC600 series began as GE Series Six under General Electric, was sold under the GE Fanuc Automation joint venture from 1987, moved to GE Intelligent Platforms, and passed to Emerson in February 2019. Qualitrol and Emerson now label these parts “GE-Emerson.” A module marked GE, one marked GE Fanuc and one catalogued as GE-Emerson under the same IC600CM548A number are the same product under different corporate branding. This is worth stating plainly because buyers search all three names and sometimes conclude they have the wrong part when the silkscreen does not match the purchase order.

Upgrade paths are not substitutes:
The IC600LR6xx and IC600LX6xx ranges are the higher-capacity in-family memory modules, and dealers sometimes offer them as alternatives to an 8K CM548. They are upgrades, not drop-in equivalents. A different capacity means a different memory map, which means reconfiguration of the program allocation rather than a swap. If your only requirement is to restore a working system to its documented configuration, source the 8K part.

Quantity and configuration:
We have four of these on the shelf. On an obsolete memory module that is a real consideration rather than a sales line: with no factory production and no equivalent, availability is the constraint on keeping a Series Six system supportable. Four units lets a single plant buy a lifetime of spares in one transaction, or stock one per line across four production areas, without re-entering a thin surplus market at whatever price it happens to be at in three years. Modules are sold individually; contact us if you want all four.

Interchange guidance:
Equivalent search forms include IC600CM548A, IC600CM548, IC600-CM-548-A and IC600 CM 548. Obsolete with no direct factory equivalent; supply is reman and surplus only.