Chapter 6. CPU Function
6-6
6.3.2 Troubleshooting
(1) Trouble types
Trouble occurs due to PLC itself, system configuration error or abnormal operation result detected. Trouble is
divided into trouble mode stopping operation for the safety and warning mode generating alert to user with a
mode in trouble.
The causes troubling PLC system are as follows.
(a)
PLC hardware trouble
(b) System configuration error
(c) Operation error while operating user program
(d) Error detected owing to external device in trouble
(2) Operation mode if trouble occurs
PLC system logs any trouble occurred in flag and determines whether to stop or resume operation depending on
trouble mode.
(a) PLC hardware trouble
In case an error occurs so that PLC such as CPU module and power module may not work normally, the
system is halted, but any warning may not interfere with the operation.
(b)
Operation error while operating user program
Representing an error occurred during operation of user program, in case of numeric operation error, it
displays the error in error flag but the system resumes operating. However, if the operation time exceeds by
the operation monitoring time limit and I/O module does not control it normally, the system is halted.
(c)
Error detected owing to external device in trouble
Representing the detection of external device to be controlled by users program of PLC, if an error is
detected, the system is halted, but any warning may not interfere with the operation.
Remark
(1) If any trouble occurs, the trouble content is saved in a special relay %FD1.
(2) For details of flag, refer to the appendix 1 Flag List.
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