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Siemens SINUMERIK Controller
Communication · Intermediate · 30-120 minutes
Siemens 28008 - NCU link: conflict in timer setting of NCU
Alarm 28008 indicates the local NCU detected a mismatch between its own NCU link timer configuration and the timer settings of the remote NCU specified in the alarm parameter. This conflict prevents synchronization of the dual-channel NCU link communication protocol, which requires identical timer values across all linked NCUs in the system.
28008
Siemens 28008 - NCU link: conflict in timer setting of NCU
NCU link: conflict in timer setting of NCU
Error message of the NCU link module. When the NCU link was powered up, the local NCU (indicated by the alarm) detected a conflict between its timer configuration and the configuration of the NCU in the alarm parameter Control reaction: NC not ready. Channel not ready. NC Start disable in this channel. Interface signals are set. Alarm display. NC Stop on alarm.
Root Cause Summary
Alarm 28008 indicates the local NCU detected a mismatch between its own NCU link timer configuration and the timer settings of the remote NCU specified in the alarm parameter. This conflict prevents synchronization of the dual-channel NCU link communication protocol, which requires identical timer values across all linked NCUs in the system.
Safety
- Only qualified personnel should diagnose and clear control alarms; follow the machine builder's safety procedures and lockout/tagout where hardware work is required.
Causes and Fixes
- 1
Access the local NCU's Parameter menu: Press [PARAM] → [MD] → search MD20100 (NCU Link Timer Setting). Document the displayed value.
Do not modify yet; first verify remote NCU configuration.
- 2
Connect to the remote NCU (the one specified in alarm %1) via separate HMI or OPC connection. Navigate to [PARAM] → [MD] → MD20100 and compare the value to the local NCU.
Ensure you are accessing the correct remote NCU; verify via machine nameplate or system documentation.
- 3
If values differ, modify the remote NCU's MD20100 to match the local NCU's setting. Typically use the value specified in the machine builder's NCU Link configuration documentation (commonly 20ms or 50ms).
- 4
Power-cycle both NCUs sequentially (local first, then remote) and verify alarm clears. Confirm NCU link status LED transitions to green on both control units.
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