Siemens alarm 2000: PLC sign-of-life monitoring
SINUMERIK 828D alarm · Siemens 828D
What it means
On the 828D the integrated S7 PLC must toggle a life counter toward the NCK within MD10100 $MN_PLC_CYCLIC_TIMEOUT. If it fails, the NCK sets NC-not-ready and stops the channel, because safe axis control without a live PLC is impossible. The alarm also appears when the PLC is stopped outright.
Likely causes
- PLC user program in a loop or stopped
- Timeout too short for first OB1 cycle after program changes
- PLC stop caused by a second, underlying PLC alarm
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