Frequently Asked Question

There are a number of reasons why a PLC CPU will enter the "Stopped" Mode. This can either be a fatal software error or hardware error.
If the PLC is of a Safety type then the PLC will enter "Stop" Mode if the safety program has been breeched or passivated.
Check The Following:-

• Check power is applied to the PLC.
• Check for "Error" lights on the PLC CPU.
• Check for "Error" lights on I/O cards. NOTE* On safety PLC's the safety cards will show "Error" if the safety program has been breeched

If all of the above are clear and correct, carry out the following:-

• Move the mode switch on the PLC CPU to "STOP".
• Ensure all personnel are clear of any equipment.
• Move the mode switch on the PLC CPU to "RUN".

Once the PLC is back into "RUN", wait for a minute or so for the PLC to start, if the PLC does get to the "RUN" state, reset the system.
If the PLC does NOT get to "RUN" mode, make a note of the PLC CPU status lights and contact S4 Engineering Support.