IC697CPX935 Replacement Checks: Memory, Ports, and Rack Power

Replacing a GE Fanuc IC697CPX935 is not just a matter of finding another 96 MHz Series 90-70 CPU. The part number identifies a particular memory architecture, I/O ceiling and serial-port arrangement. Firmware and rack power records matter just as much as the front-panel label.

What the IC697CPX935 Actually Is

GE Fanuc datasheet GFK-1435F identifies IC697CPX935 as a single-slot Series 90-70 CPU with a 96 MHz 80486DX4 processor, 32-bit floating-point execution and 1 Mbyte of battery-backed fast CMOS user memory. It also includes 256 Kbytes of optional non-volatile user flash memory.

The CPU supports up to 12K discrete inputs and outputs in any mix, plus up to 8K analog I/O. Its stated Boolean execution time is 0.4 microseconds per function. Those figures describe controller capacity; they do not prove that a replacement will accept an existing application without a configuration and firmware review.

Do Not Confuse Memory Size with Memory Type

Several 96 MHz CPX CPUs share a similar front panel. Their memory arrangements are not the same. IC697CPX782 provides 1 Mbyte of standard memory. IC697CPX928 provides 6 Mbytes of medium-speed memory. IC697CPX935 provides 1 Mbyte of fast memory. The active IC697CPX928 product page is useful for comparing the 6 Mbyte model, but it should not be treated as an automatic substitute.

Before removing the installed CPU, record the full catalog number and hardware suffix. Save the PLC program, hardware configuration, register data, fault tables and any site-specific commissioning files. If the machine has recipe storage or Bulk Memory Area use, confirm the required memory allocation rather than comparing only program size.

Firmware Changes the Replacement Checklist

The CPX935 supports Bulk Memory Area in release 7.92 and later. Starting with firmware release 8.00, Ports 1 and 2 added program Load/Store operations and Datagrams, and Break-Free SNP became the default protocol on those ports.

That creates two practical risks. First, an older programming package might not support the installed firmware or configuration features. Second, a serial programmer can lose communication after a stored port configuration changes baud rate, parity or protocol behavior. Record the current port settings and software version before a CPU exchange.

The operating-system firmware is stored in flash and can be upgraded through a serial port. A firmware upgrade is not a substitute for verifying hardware suffixes, application dependencies and the site backup. Treat it as a controlled maintenance action with a rollback plan.

Serial Ports: Three Connectors, Different Electrical Interfaces

IC697CPX935 has three independent serial ports:

• Port 1: RS-232 compatible, using a 6-pin female RJ-11 connector.
• Port 2: isolated RS-485 compatible interface on a 15-pin female D-connector.
• Port 3: non-isolated RS-485 compatible interface on a 15-pin female D-connector.

All three ports support SNP Slave. Ports 1 and 2 support Break-Free SNP from firmware 8.00; Port 3 does not. The datasheet lists no SNPX or RTU support. Ethernet programming needs a separate Series 90-70 Ethernet interface. Do not infer an onboard Ethernet port from a networked installation.

Rack Power and Cooling Are Part of CPU Selection

The datasheet specifies 3.1 A nominal from the 5 V backplane bus, equivalent to 15.5 W of 5 V load. Add that load to every module in the rack and compare the total with the installed supply. The IC697PWR710 power-supply page and the related IC697PWR710 load-budget guide show why a CPU replacement should include a rack-level calculation.

From 0 to 50°C, the CPU can operate at full rack power without forced air. From 50 to 60°C, GE gives two choices: provide 70 CFM forced air for the full rack rating, or limit total rack power to 70 W without forced air. A replacement that works on the bench can still fail in a hot, fully loaded cabinet if this limit is ignored.

I/O Support Does Not Mean Unrestricted Substitution

The CPX935 communicates with IC697 discrete and analog I/O over the rack backplane. It can also work with IC660 or IC661 I/O through the appropriate bus controller. For example, the IC697BEM731 Genius bus controller provides a separate distributed-I/O network function; it is not built into the CPU.

Record installed LAN interfaces, communications modules, bus controllers, coprocessors and I/O Link hardware. The replacement CPU checks the physical rack configuration against the stored configuration at power-up and during operation. A mismatch can become a configuration fault even when the processor itself is healthy.

Battery and Start-Up Sequence

IC697ACC701 is the specified lithium battery. GE lists five years of shelf life at 20°C and six months nominal memory retention without rack power. Install the new battery before disconnecting the old one.

With rack power off, install the CPU in slot 1 of rack 0. Start with the mode switch in STOP and memory protection off. After power-up diagnostics, confirm the OK LED remains on and that RUN, EN and MEM PROTECT reflect the intended state. Restore the application only after the rack configuration and firmware are confirmed.

What Remains Site-Specific

OEM documents define the CPU limits. They cannot identify the firmware, hardware suffix, program image, port settings, rack load or option-module revisions in a particular plant. Those facts must come from the installed system and its maintenance records. A procurement decision is complete only when the replacement matches both the catalog specification and the recorded site configuration.

Source Basis

OEM facts in this article were checked against GE Fanuc IC697CPX935 datasheet GFK-1435F (May 2000), the Series 90-70 data-sheet manual GFK-0600F, and IC697CPX935 product update GFK-1436E. Statements about backup, rollback and site-record checks are editorial maintenance guidance based on the limits in those documents.