There are a lot of reason make to plc causes, hardware and software errors make to crashes.
(1) I/O channeling, PLC automatically detect I/O errors, enter STOP mode.
(2) I/O damaged,Program can not execute the command.
(3) PLC connection module And the address assignment module failed.
(4) power Interferenceor failure.
(5) address assignment PLC connection module and a module failure.
(6) the cable fault.
2, the software
(1) infinite loop.
(2) the program changed the contents of the system parameters area, but no initialization section.
(3) protection program starts
(4) data overflow, the step is too large, the watchdog (can be modified DOG time) action.