Chapter 4 CPU modules MASTER-K
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4.3.4 Error handling
1) Error classification
Error occurs due to various causes such as PLC system errors, system configuration fault
or abnormal operation result. Errors are classified into fatal error that stops system
operation for safety, and ordinary error that continue system operation with informing the
user of error warning.
The causes of system error are as following;
- The hardware error
- System configuration error
- Operation error during execution of user program
- External device malfunction
2) Operation mode at error occurrence
In case of error occurrence, the CPU stores corresponding error code at error flags, and
stop / continue operation according to the error type.
① The hardware error
The system is changed to STOP mode when a fatal error such as CPU defection
occurs. When an ordinary error such as battery error occurs, the system keep its
operation status.
② System configuration error
This error occurs when actual hardware configuration conflicts with the configuration
assigned in parameter setting. The system is changed to the STOP mode.
③ Operation error during execution of user program
When a arithmetic operation error occurs, the system output error code at the
corresponding error flag and continue operating. If a scan time exceeds the watchdog
timer setting value or mounted I/O module is not normally controlled, the system is
switched to the STOP mode.
④ External device malfunction
The CPU can detect an external device malfunction with user program. If a fatal error
detected, the system is stopped. Otherwise, it continues operating.
Remark
1. When an error occurs, the error code is stored at special relay (F006 word).
2. Refer the appendix 1 ‘Flag list’ for details of error flags.
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