Mitsubishi L02CPU, User Manual, Page: 147 / 340

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CHAPTER 3 CPU MODULE FUNCTIONS
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Self-Diagnostic Function
This function allows the CPU module to diagnose itself to check for errors. This function aims to preventive measures
and prevention of malfunction of the CPU module.
(1) Self-diagnostic timing
When an error occurs at power-on or during the RUN or STOP status of the CPU module, the error is detected
and displayed by the self-diagnostic function, and the CPU module stops an operation. Note that errors cannot be
detected by the function depending on error status or an instruction executed. When the operation is not stopped
by the function, configure a safety circuit external to the programmable controller so that the entire system
operates safely.
(2) Storage location of error information and error check
When the CPU module detects an error, SM0 and SM1 turn on and the error information (error code) are stored in
SD0. When several errors are detected, the latest error code is stored in SD0. Use SM0, SM1, or SD0 in a
program as an interlock for the programmable controller and mechanical system. Also, it can be checked by the
on status of the ERR. LED.
(3) Checking error history
The latest error history (error description) can be checked in the "Error history" area.
[Diagnostics] [PLC Diagnostics]
Errors can also be checked by the display unit. ( Page 188, Section 4.2.1)
Up to 100 module errors
*2
can be stored in the system memory
*1
.
*1 The memory is internally controlled by the system.
*2 Once the memory is full, the oldest stored log is deleted to store a new log.
To clear the module error data, click the button.