Siemens alarm 2000: PLC sign-of-life monitoring
SINUMERIK 808D alarm · Siemens 808D
What it means
The PLC must increment a sign-of-life counter on the internal NC/PLC interface within the monitoring time set in MD10100 $MN_PLC_CYCLIC_TIMEOUT. If the counter stops changing, or the PLC enters stop state, the NCK declares the PLC dead and takes the control to 'NC not ready'. This is the classic first alarm seen after a failed PLC start-up, a user-program loop, or an OEM program crash.
Likely causes
- PLC user program stopped or in an endless loop
- Monitoring time in MD10100 too short for the first OB1 cycle
- PLC stop triggered from the commissioning switch or by another PLC alarm
- Internal PLC software fault
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