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Code 4065: Buffered memory was restored from backup medium (potential loss of data!)

Issue Description & Safety Warning

The Siemens SINUMERIK 840D CNC has triggered a critical Buffered memory was restored from backup medium (potential loss of data!) alarm. Immediate attention from a qualified operator or maintenance technician is required to prevent secondary damage to the equipment or spoiled parts during the manufacturing cycle. Always ensure standard safety and LOTO procedures are followed before accessing electrical cabinets.

Official Troubleshooting Steps

Definitions: Only occurs with SINUMERIK 840D / 840Di sl / 802D. !! 840Di sl only The user data of the NC and the remanent data of the PLC are stored in the static memory area (SRAM) of the MCI board. The content of the SRAM is backed up as an SRAM image on PCU hard disk at each "NCK POWER ON reset" and each time Windows XP is closed down normally. The previously valid SRAM image then becomes the SRAM backup, which is also stored on the PCU hard disk. The SRAM backup is used and alarm 4065 issued in the following cases: HW serial no SRAM MCI board SRAM image MCI board "OK" "OK" 1. Known No No 2. Unknown Yes No 3. Unknown No No !! Only for 802D The reason for this alarm is that the backup time is exceeded. Make sure that the required operating time of the control corresponds to the specifications in your Installation & Start-up Guide. The current backup copy of the buffered memory has been created by the last internal data backup via the "Save data" softkey on the HMI. Reaction: NC not ready. NC Start disable in this channel. Interface signals are set. Alarm display. Remedy: Make a POWER ON reset. !! 840Di / 840Di sl only: Alarm 4065 also has to be acknowledged on the HMI after a POWER ON reset: HMI: Operating area switchover > Diagnostics > NC/PLC Diagnostics > Diagnostics > "Acknowledge alarm 4065" button Note Press the "ETC" key to change to the secondary softkey bar in order to acknowledge the alarm with a softkey. Program Continuation: Switch control OFF - ON.

Source: SINUMERIK 840D sl / 840Di sl / SINAMICS S120 Diagnostics Manual (DAsl, 03/2009)

Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.

About Siemens SINUMERIK 840D CNC Alarms

Siemens controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code 4065 on the SINUMERIK 840D CNC identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Siemens's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.

Complete Alarm List: 4014 Siemens SINUMERIK 840D CNC codes.

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