PLCS7-1200Verified · sol.ls-electric.com
S7-1200 16#4400 — Programming error OB121
Trip — immediate stop
CAUSE
Why does it occur?
Runtime programming error — invalid pointer, out-of-range access, etc.
REMEDY · Step by step
How to fix it?
- Add OB121, then debug using the ENO and err variables in OB1
- Validate index/pointer ranges.
Do not reset repeatedly before identifying the cause. Repeated resets while ignoring a trip/alarm can cause secondary damage (IGBT failure, motor winding damage, etc.).
SOURCE
Related manual page
Summary based on the official Siemens AG manual. For accurate and complete information, always consult the official manual.
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