What causes Siemens SINUMERIK alarm 27092?

Parameter or machine data configuration error. Hardware fault on the NC or drive component. Part program error or illegal command. Communication fault between NC and drive or I/O modules. Software or firmware error requiring system restart.

How do I fix Siemens SINUMERIK alarm 27092?

1. Note the complete alarm text including any axis, channel, or block number values. 2. Check for related alarms active simultaneously in the SINUMERIK alarm list. 3. Power cycle the machine to clear transient faults. 4. Review the SINUMERIK machine data for parameters related to the alarm. 5. Consult the Siemens SINUMERIK alarm manual for alarm 27092 detailed remedy.

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Siemens SINUMERIK Controller

Servo/Axis · Intermediate · 30-120 minutes

Alarm 27092

Siemens 840D 27092 - Communication broken off during NCK PLC data cross check, error

Alarm 27092 indicates a loss of synchronous communication between the NCK (Numerical Control Kernel) and PLC subsystems during cyclic data cross-check. The 1-second watchdog timer for the monitoring channel has expired, meaning either the NCK or PLC failed to transmit its expected data packet within the defined cycle time, breaking the real-time handshake protocol required for coordinated axis control and safety functions.

Siemens SINUMERIKServo/AxisIntermediate30-120 minutes

27092

Siemens 840D 27092 - Communication broken off during NCK PLC data cross check, error

Communication broken off during NCK PLC data cross check, error

Root Cause Summary

Alarm 27092 indicates a loss of synchronous communication between the NCK (Numerical Control Kernel) and PLC subsystems during cyclic data cross-check. The 1-second watchdog timer for the monitoring channel has expired, meaning either the NCK or PLC failed to transmit its expected data packet within the defined cycle time, breaking the real-time handshake protocol required for coordinated axis control and safety functions.

Safety

Refer to Siemens documentation
Ensure qualified technician performs repairs

Causes and Fixes

1
In HMI Diagnosis > System Information, verify actual PLC cycle time and NCK cycle time are running nominally. Check MD 37110 (PLC_CYCLE_TIME) and MD 20050 (NCK_CYCLE_TIME) values; typical values are 10-50ms for PLC and 2-8ms for NCK.
Do not modify MD 37110 without documented engineering change; incorrect PLC cycle time can cause loss of axis feedback synchronization.
2
Access PLC Editor > Program > Diagnostics to review PLC scan time histogram. Look for scan times consistently >80% of the configured PLC cycle time, indicating code bloat or inefficient logic that delays the next communication packet.
3
Check NCK load via HMI Diagnostics > System Status > Performance. If NCK CPU load is >90%, reduce active axis count, simplify G-code interpolation complexity, or reduce real-time data logging frequency.
4
Review recent PLC program modifications in the PLC source code version history. Identify any new OBs, FBs, or data structures added that increased cycle time. Recompile and download the PLC program to clear any stale communication buffers.

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