GE IC697CPM790 | Series 90-70 GMR Central Processor Unit 1MB Memory

🔧 Product Overview

The GE IC697CPM790 is a Series 90-70 Central Processor Unit designed for Genius Modular Redundancy (GMR) and Triple Modular Redundancy (TMR) control systems. It uses a 64 MHz 80486DX2 processor with 32-bit floating-point processing and is installed as a single-slot CPU module.

The module includes 1 MB of battery-backed CMOS RAM on the CPU board. Of this memory, up to 512 KB is available for the user’s application program and data. The memory board is integral to the CPM790 rather than being a separate expansion module.

The CPM790 was specifically developed for redundant control architectures and supports voted I/O configurations as well as Series 90-70 and IC660/IC661 I/O depending on the system configuration. It also provides an RS-422/RS-485-compatible serial interface for programming and communications.

📋 Technical Specifications

Parameter	Specification
Brand	GE / GE Fanuc
Model	IC697CPM790
Product Series	Series 90-70
Product Type	Central Processor Unit
CPU Architecture	32-bit
Processor	Intel 80486DX2
Processor Speed	64 MHz
Floating Point	Yes
On-Board Memory	1 MB battery-backed CMOS RAM
User Program/Data Memory	Up to 512 KB
Memory Backup	Battery-backed
Battery	IC697ACC701
Boolean Execution Speed	0.4 µs per Boolean function
Serial Interface	RS-422/RS-485 compatible
Serial Connector	15-pin D-type
Installation	Single-slot CPU
Discrete I/O	Up to 12,288 points in simplex configuration
Voted Discrete I/O	Up to 2,048 inputs / 2,048 outputs
Analog I/O	Up to 8K inputs / 8K outputs in simplex configuration
Operating Temperature	0 to 60°C with forced air; 0 to 40°C without forced air
Rack Position	Slot 1
System Application	GMR / TMR control systems

The published GE/GE Fanuc documentation identifies the CPM790 as a 64 MHz, 32-bit floating-point CPU with 1 MB memory and a 0.4 µs Boolean execution time.

⚙️ Key Features

64 MHz 80486DX2 processor
32-bit floating-point processing
1 MB integrated battery-backed CMOS memory
Up to 512 KB available for application program and data
Single-slot CPU design
RS-422/RS-485-compatible serial port
Designed for Genius Modular Redundancy systems
Supports Triple Modular Redundancy architectures
Supports voted I/O configurations
In-system firmware upgrade capability
Compatible with Series 90-70 control architectures
Battery-backed calendar/time functions

The CPU uses flash memory for operating-system firmware, while the user program and data are maintained in battery-backed CMOS RAM.

🏭 Typical Applications

The IC697CPM790 is associated with control systems where CPU redundancy and fault tolerance are important.

Typical applications include:

Process control systems
Power generation and utility automation
Emergency shutdown systems
Fire and gas control
Critical industrial process control
Redundant PLC systems
Large Series 90-70 installations
GMR/TMR control architectures
Distributed I/O systems

For GMR applications, the CPM790 works as part of a redundant CPU architecture rather than as a conventional standalone PLC CPU. The GE documentation specifically describes its use with triple PLCs and Genius buses.

🔌 Installation & Configuration Notes

The CPM790 should be installed in the correct Series 90-70 rack configuration, with the CPU occupying Slot 1. Adequate forced-air cooling is required when operating within the full 0–60°C temperature range.

Before commissioning a replacement module:

Confirm the catalog number is IC697CPM790.
Check the CPU revision and firmware version.
Inspect the battery condition.
Verify the rack and backplane condition.
Confirm the CPU is installed in Slot 1.
Check the required cooling arrangement.
Verify the GMR/TMR configuration before loading the application.
Confirm serial communication wiring and programming interface.
Back up the existing application before replacing the CPU whenever possible.

⚠️ Battery Note

The CPM790 uses a battery-backed memory system. GE documentation specifies the IC697ACC701 lithium battery and warns that the new battery should be installed before disconnecting the old one when retaining memory contents.

For a used or surplus CPU, battery condition should therefore be checked before placing the module into service.

🛠 Maintenance & Inspection

For a replacement or spare CPU, inspect:

Front-panel LEDs
CPU housing
Backplane connector
Serial communication connector
Battery compartment and battery condition
Memory protection switch/key position
Module label and catalog number
PCB condition, if inspection is possible
Evidence of corrosion, overheating, or mechanical damage

A functional test should ideally include power-up diagnostics, CPU status verification, communication testing, and application loading/verification in an appropriate Series 90-70 test rack.

❓ Frequently Asked Questions

Q: What is the memory capacity of the IC697CPM790?
A: The module has 1 MB of integrated battery-backed CMOS RAM. Up to 512 KB is available for the user’s application program and data.

Q: Is the IC697CPM790 a standard Series 90-70 CPU?
A: It is a Series 90-70 CPU specifically intended for GMR/TMR architectures. It should be selected according to the system’s redundancy configuration rather than treated as a generic replacement for every Series 90-70 CPU.

Q: What processor does it use?
A: The CPM790 uses a 64 MHz 80486DX2 processor with 32-bit floating-point capability.

Q: Which slot is used for the CPU?
A: The CPM790 is designed for installation in Slot 1 of the appropriate rack.

Q: Does it have Ethernet built in?
A: No. The CPU provides a serial RS-422/RS-485-compatible interface. Ethernet TCP/IP communication requires an appropriate Series 90-70 Ethernet interface module.

📦 Related GE Series 90-70 CPU Models

The following models belong to the same broader Series 90-70 CPU family. They are related models, not automatic drop-in replacements:

IC697CPU788
IC697CPU789
IC697CPM924
IC697CPM925
IC697CPM915
IC697CSE924
IC697CSE925
IC697CPX772
IC697CPX782
IC697CPX935

The exact replacement choice depends on the existing rack, firmware, memory requirements, I/O architecture, and especially whether the system uses GMR/TMR functionality. GE documentation lists the CPM790 separately from the standard CPU788/789 and other Series 90-70 CPU families.

📌 Identification & Ordering Notes

When purchasing an IC697CPM790, verify the following against the physical unit:

Catalog number: IC697CPM790
CPU type: GMR/TMR CPU
64 MHz processor
1 MB onboard memory
Series/revision
Battery condition
Front-panel condition
Serial connector condition
Backplane connector
Included accessories

For used or surplus inventory, the actual firmware revision and battery status should be confirmed from the physical module rather than assumed from the catalog number alone.