Memory Checksum Error
Memory checksum error indicates that the PLC's internal memory (program memory or data memory) has been corrupted or modified. This fault prevents the processor from executing the stored program and forces the PLC into STOP mode to prevent unpredictable machine behavior.
Error Code
F00100
Severity
Fault
Equipment
PLC Controller
Manufacturer
Siemens
PLC LED indicator showing red STOP light with no blinking
Display or HMI showing error code F00100 with memory fault message
PLC fails to transition from STOP to RUN mode regardless of selector switch position
No response to input signals; outputs remain in safe state (de-energized)
Occasional memory corruption with program upload/download operations observed before failure
CPU module becomes warm or hot to touch, indicating continuous error checking cycles
Corrupted program memory due to incomplete or interrupted firmware download during maintenance
Faulty battery backup module (CMOS battery) allowing SRAM data loss during power cycles
Defective memory module (RAM or flash memory IC) with manufacturing defect or aging degradation
Electrical noise or voltage spike during power-on sequence corrupting memory contents
Corrupted SD card memory module or faulty MMC interface on CPU
PLC powered down during active write cycle to non-volatile memory
Power cycle the PLC: Turn off main power supply for 30 seconds, then restore power while monitoring LED status
Verify power supply voltage is stable at 24VDC ±5% using multimeter; check for loose terminal connections at power input module
Attempt memory reset using manufacturer tool: Connect engineering workstation via Ethernet/serial, access SIMATIC automation tool, initiate 'Clear All User Data' function to restore factory defaults
Inspect and test CMOS backup battery if accessible (typically CR2032 or similar); measure voltage should exceed 2.8V; replace if below threshold
Re-download the application program from verified source using SIMATIC Step 7 or TIA Portal: erase old program first, then perform complete upload to eliminate residual corrupted data
If memory reset fails, remove and reseat the CPU module in its slot, ensuring proper contact alignment and full seating (listen for audible click); power on and observe boot sequence
Test external memory cards or SD modules by removing and reinserting; if error persists, replace the memory module with genuine Siemens replacement part
Contact Synchronics Electronics for professional module replacement if PLC continues F00100 error after all steps; hardware memory failure likely requires CPU module swap
Safety First: Always isolate power and follow LOTO (Lockout/Tagout) procedures before working on electrical components. If unsure, contact a certified repair technician.
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