What causes Siemens SINUMERIK alarm 16956?

Global start disable (_N_STRTLK) parameter is active, preventing any program execution. Machine operator or maintenance personnel set global start disable via HMI or parameter interface. Safety interlock or emergency stop sequence left global start disable engaged. Parameter _N_STRTLK was set during troubleshooting and not cleared. Alarm mask bit 6 of $MN_ENABLE_ALARM_MASK is enabled, causing the alarm to trigger.

How do I fix Siemens SINUMERIK alarm 16956?

1. Verify global start disable status by checking parameter _N_STRTLK value; if set to 1, this is blocking program execution 2. Clear the global start disable by setting parameter _N_STRTUL to 1 or using the HMI interface to remove the start lock 3. Confirm the machine is not in emergency stop or safety interlock condition before clearing the disable 4. If alarm persists after clearing _N_STRTUL, verify bit 6 of parameter $MN_ENABLE_ALARM_MASK is correctly configured for your application 5. Attempt to restart the selected program once global start disable is removed and alarm is cleared

Siemens SINUMERIK codes

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Siemens SINUMERIK Controller

Servo/Axis · Basic · 5-15 minutes

Alarm 16956

Siemens 840D 16956 - Channel program cannot be started due to global start disable.

The program selected in this channel cannot be started as "Global start disable" had been set. Note: PI "_N_STRTLK" sets the "Global start disable" and PI "_N_STRTUL" deletes the "Global start disable". The alarm is switched on with $MN_ENABLE_ALARM_MASK bit 6.

Siemens SINUMERIKServo/AxisBasic5-15 minutes

16956

Siemens 840D 16956 - Channel program cannot be started due to global start disable.

Channel program cannot be started due to global start disable.

Safety

Refer to Siemens documentation
Ensure qualified technician performs repairs

Common Causes

Global start disable (_N_STRTLK) parameter is active, preventing any program execution
Machine operator or maintenance personnel set global start disable via HMI or parameter interface
Safety interlock or emergency stop sequence left global start disable engaged
Parameter _N_STRTLK was set during troubleshooting and not cleared
Alarm mask bit 6 of $MN_ENABLE_ALARM_MASK is enabled, causing the alarm to trigger

Troubleshooting Steps

1Verify global start disable status by checking parameter _N_STRTLK value; if set to 1, this is blocking program execution
2Clear the global start disable by setting parameter _N_STRTUL to 1 or using the HMI interface to remove the start lock
3Confirm the machine is not in emergency stop or safety interlock condition before clearing the disable
4If alarm persists after clearing _N_STRTUL, verify bit 6 of parameter $MN_ENABLE_ALARM_MASK is correctly configured for your application
5Attempt to restart the selected program once global start disable is removed and alarm is cleared

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