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Siemens SINUMERIK Controller
Communication · Intermediate · 30-120 minutes
Siemens 28009 - NCU link: conflict in bus parameters of NCU
Alarm 28009 occurs when the NCU link module detects a mismatch between the PROFIBUS DP cycle time (MD 10100: NCU_LINK_CYCLE_TIME) configured on the local NCU and the corresponding parameter settings on the remote NCU. This bus parameter conflict prevents proper synchronization of the NCU link communication and blocks system initialization.
28009
Siemens 28009 - NCU link: conflict in bus parameters of NCU
NCU link: conflict in bus parameters 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 bus 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 28009 occurs when the NCU link module detects a mismatch between the PROFIBUS DP cycle time (MD 10100: NCU_LINK_CYCLE_TIME) configured on the local NCU and the corresponding parameter settings on the remote NCU. This bus parameter conflict prevents proper synchronization of the NCU link communication and blocks system initialization.
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 Diagnostics > System Information > NCU link status to identify which remote NCU (shown in alarm parameter %1) has the conflicting configuration.
- 2
On the local NCU, navigate to Machine > Parameters > Servo > NCU link and verify MD 10100 (NCU_LINK_CYCLE_TIME) value. Standard values are typically 12.8ms, 25.6ms, or 51.2ms.
- 3
Connect to the remote NCU (alarm parameter %1) and verify its MD 10100 matches the local setting exactly. Use Service > System Editor to compare both values.
Cycle time changes require a complete system power cycle; partial reboots will not apply changes.
- 4
After aligning MD 10100 on both NCUs, perform a full power-down for 30 seconds, then power-up to allow PROFIBUS DP re-initialization.
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