1 , hardware aspects Â
   ( 1 ) I / O power, the PLC automatically detects an I / O error and enters STOP mode. Â
   ( 2 ) I / O is damaged, the program runs to the feedback signal that needs this I / O , and the instruction cannot be executed downward. Â
   ( 3 ) Expansion module ( function type, such as A / D) line interference or open circuit. Â
   ( 4 ) There is interference or malfunction in the power supply section. Â
   ( 5 ) The connection module and address assignment module of the PLC have failed. Â
   ( 6 ) A fault caused by the cable. Â
2 , software aspects Â
   ( 1 ) Triggered an infinite loop. Â
   ( 2 ) The program rewrites the contents of the system parameter area, but there is no initialization part. Â
   ( 3 ) Protection program startup: hardware protection, limited use time ( recovery for payment )
   ( 4 ) Data overflow, too large step size, watchdog ( can modify DOG time ) action.
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