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Siemens SINUMERIK Controller
Servo/Axis · Intermediate · 30-120 minutes
Siemens 27101 - Axis difference in function safe operational stop, NCK: drive:
Alarm 27101 indicates a discrepancy between NCK and drive monitoring channels during safe operational stop (SOS) verification in the 840D safety system. This cross-comparison failure suggests either a communication breakdown, parameter mismatch, or hardware fault in the safety-relevant monitoring chain that prevents both channels from achieving consensus on SOS status.
27101
Siemens 27101 - Axis difference in function safe operational stop, NCK: drive:
Axis difference in function safe operational stop, NCK: drive
During cross-comparison of result list 1 a difference was detected between the NCK and drive monitoring channels in the status of safe operating stop monitoring. Safe operating stop: Bit 0,1 in result list 1 Monitoring status (,): - OFF = Monitoring is inactive in this monitoring channel - OK = Monitoring is active in this monitoring channel, limit values are not violated - L+ = Monitoring is active in this monitoring channel, upper limit exceeded - L- = Monitoring is active in this monitoring channel, lower limit exceeded Control reaction: NC Start disable in this channel. Alarm display. A Stop F was triggered. If safe monitoring was active, STOP B was also triggered automatically. In this case, a power OFF/ON of the control will be required. Alarms.
Root Cause Summary
Alarm 27101 indicates a discrepancy between NCK and drive monitoring channels during safe operational stop (SOS) verification in the 840D safety system. This cross-comparison failure suggests either a communication breakdown, parameter mismatch, or hardware fault in the safety-relevant monitoring chain that prevents both channels from achieving consensus on SOS status.
Safety
- Safety Integrated alarm: work may only be carried out by qualified personnel. After any change to Safety Integrated settings or hardware, repeat the Safety Integrated acceptance test before returning the machine to service.
- Drive/power/encoder circuit: hazardous voltages may remain in the DC link after power-off. Lock out / tag out, wait for discharge per the drive documentation, and use qualified personnel only.
Causes and Fixes
- 1
Access Diagnostics > Alarms > 27101 and note the NCK value (%2) and drive value (%3). Cross-reference against the axis in question.
- 2
In HMI Diagnostics menu, verify MD34200 (SOS enable flag) and MD34201 (SOS monitoring parameters) match the corresponding drive safety module parameters via PROFISAFE telegram or direct drive diagnostics.
Do NOT modify MD34200 during runtime; use offline program verification mode.
- 3
Regenerate and reload the NCK safety program (NC Safety > Compile Safety Data) and resync drive safety configuration using STARTER or SINAMICS commissioning tool to ensure both sides have identical parameter sets.
- 4
Perform a controlled axis reset (M0/M1 stop) followed by power cycle to reinitialize the safety monitoring handshake and clear the cross-comparison buffer.
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