An MR128 memory module can block a new project download when stale project data or an incorrect capacity record remains on the module. The strongest diagnostic evidence is module-specific behavior: the same failure occurs on two Pixel PLCs while other memory modules save normally. Updating the PLC core alone did not correct the fault.
Recognize the MR128 Failure Pattern
The save sequence first reports that the project contains project data and setpoints. After confirmation, the partial-save dialog opens and then reports that the source memory module cannot be found. Other observed failures include “SAVE ERROR!!! ESC to exit”, data reading as NaN or zero, and implausible EEPROM capacity values.
| Observation | Engineering interpretation |
|---|---|
| Available EEPROM reported as 2,147,479,295 | Invalid capacity indication; do not treat it as usable space. |
| Capacity reported as 192256 for a 128K module | Automatic capacity detection is incorrect. |
| 128K modules fail while a 256K module works in the same PLC | The evidence points toward the affected modules or their capacity metadata, not a general PLC write failure. |
| Failure persists on two PLCs | This further isolates the problem to the memory module or the formatting method. |
Do Not Treat a Core Update as the Complete Fix
One test reproduced the problem with core 03.273.008 and again after updating to 3.291.008. A separate case used core 3.291.000 on Pixel controller modification 2511-02-00 and still could not save a minimal program to four 128K modules. These results show that updating an old core is a valid compatibility check, but persistence after the update requires investigation of the module and its detected capacity.
Clear the Module with Capacity Set Manually
A clearing macro improved data access, but its automatic capacity detection produced an incorrect size and did not restore project saving. The successful correction was to override automatic detection and enter the module capacity manually in the clearing project. The evidence does not identify the macro name, field identifier, input units, or exact value entered, so verify those details in the clearing project before writing.
- Connect the suspect MR128 module to a Pixel PLC and inspect the reported EEPROM capacity.
- If the value is implausible or inconsistent with the 128K module, open the available module-clearing project or macro and disable or bypass automatic size detection.
- Enter the correct capacity for the installed module using the units required by that project, then run the clearing operation to completion.
- Write a small PLC project to the module and confirm that the save completes without the source-module or save-error message.
Verify the Repair Before Returning the Module to Service
Confirm both data access and project storage. Successful variable writes and reads alone are insufficient: one cleared module could store application data but still rejected a simple project. Check that the system menu reports a plausible capacity, write and read module data, save a minimal project, and verify that the project can be recovered through the normal workflow. If manual capacity configuration still produces inconsistent size reports or save failures, treat the module as suspect hardware and remove it from service pending manufacturer-supported testing.
FAQ
Why does an MR128 report that the source memory module is missing?
The reported sequence is associated with stale project information or corrupted capacity metadata on the module. If other modules work and the same MR128 fails on two PLCs, clear it with the capacity specified manually.
Will updating the Pixel PLC core fix an MR128 save error?
Not necessarily. The fault persisted after an update from 03.273.008 to 3.291.008, and another case failed on 3.291.000, so use the update as a compatibility check and then verify module capacity detection.
Why can the PLC read MR128 data but not save a project?
Data read/write success does not prove that project storage is valid. One module worked for application data after clearing but still reported 192256 and produced “SAVE ERROR!!!”; manually setting the correct capacity during clearing restored project saving.
