Siemens alarm 3: PLC stop
SINUMERIK 810/820 legacy alarm · Siemens 810/820
What it means
The integrated S5 PLC is no longer operational, so NC START is inhibited and operation comes to a defined standstill. On the 810/820 this power-on-group alarm frequently appears together with battery or memory problems, or after a crashed user program.
Likely causes
- PLC user program fault (cycle-time overrun, STOP state)
- Memory corruption following a low-battery event
- Hardware fault on the PLC CPU
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