When we write the PLC program and debug it (especially in the later maintenance and  maintenance), we often have no way to deal with the occurrence of an error, especially  when there is a fault indicator on the CPU panel  

When we write the PLC program and debug (especially in the later maintenance and  maintenance), we often have no way to deal with an error, especially when there is an  abnormal fault indicator on the CPU panel, we don't know how to deal with it, and  sometimes we use a lot of personnel. After mastering the knowledge of PLC CPU fault  indicators, you can deal with faults through abnormal displays without panic when facing  these abnormal displays.  

So what are the CPU failure indicators of PLC? The number of indicator lights of  different models of CPUs is also different, here is a more complete example for friends - the  panel of CPU318-2 is as follows:  

The corresponding indicator lights and fault meanings in the above picture are as follows:  

The corresponding indicator lights and fault meanings in the figure above are as follows：

I. SF-system error fault is displayed in red: it lights up when the PLC hardware failure or software error;

2. BATF-battery fault is displayed in red: it lights up when the battery voltage is low or there is no battery;

3. The normal indicator of DC 5V-+5V power supply is green: the 5V power supply is lit up when it is normal;

4. FRCE-enforcement is displayed in yellow: at least one 1/0 is enforced when it is enforced;

5. RUN - green during normal operation: it lights up when the CPU is in the RUN state; Shines at 2Hz on reboot; HOLD (single-step) state at a frequency of 0.5Hz;

6. STOP-STOP mode is yellow when stopped: the CPU is always on when it is in STOP or HOLD state;

7. BUSF-bus is displayed in red when it is wrong: when it is off, it means that all configured slaves can be addressed, and when it is solid, it means that the transmission rate of bus hardware failure/DP interface failure/multi-DP master mode is inconsistent, and when it flashes, it means that one or more slaves are faulty, and at least one assigned slave cannot be addressed.

Additional CPU fault LED meanings:

8. INTF - when red is displayed, it indicates internal faults, such as program running timeout;

9. EXTF - when red is displayed, it indicates external faults, such as power supply or module problems;

10. CRST - when yellow is displayed, it indicates a complete reset (cold start). 

I believe that after the above introduction of PLC 318-2 CPU panel and related other CPU panels, friends will have a comprehensive understanding, which will be helpful to your work. If you like to follow me privately, thank you!