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6.17
Self-diagnostic Function
(1) Definition
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.
(2) 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.
(3) Checking errors
(a) LED status
When the CPU module detects an error, the ERR. LED turns on.
(b)
Storage location of error information and error check
When the CPU module detects an error, the special relays (SM0, SM1) turn on and the error information (error
code) are stored in the special register (SD0).
When several errors are detected, the latest error code is stored in SD0.
Use the special relays and special register in a program as an interlock for the programmable controller and
mechanical system.
(4) Checking error history
To check the latest error code, select [Diagnostics]
The error history are backed up using a battery even after the programmable controller is powered off.
[PLC diagnostics]
"Error log" in GX Developer.
CHAPTER6 FUNCTIONS
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