Siemens alarm 300101: Bus communications failure
SINUMERIK 840D/810D powerline drive alarm (SIMODRIVE 611D) · SIMODRIVE 611D/611U
What it means
The NC is already running but no drive module has signalled on the drive bus - in practice either the drives are powered later than the NCU, or even the first module on the bus cannot be recognized. It is the power-up counterpart of alarm 300100 (power loss during operation).
Likely causes
- drive power switched on after the NCU (sequencing)
- first drive module has no electronics supply - check its red LED
- equipment-bus ribbon from I/R (or monitoring) unit to first module open or not inserted
- drive bus connector not snapped home or bus terminator missing
- defective first drive module
Triage note: Diagnostic order per Siemens: check module LEDs first, then equipment-bus ribbon, then drive-bus connectors/terminator; replace hardware only last.
Replacement parts
We supply the following units for this alarm — tested, warranty-backed:
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6SN1145-… / 6SN1146-…
infeed · Common cause
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6FX2003-…
cable · Common cause
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6SN1123-…
power-module · Check if others ruled out
Need the part urgently?
Send us alarm 300101 with your machine details — typical RFQ turnaround is 24–48h.