Self-Diagnostic Function - Mitsubishi Electric MELSEC Q Series User Manual

11.2

Self-Diagnostic Function

The self-diagnostic function allows the C Controller module to detect its own error during operation, preventing a
malfunction and providing preventive maintenance.
(1) Self-diagnostics timing
When an error occurs at power-on of the C controller module or during RUN/STOP of the C controller module, an
error is detected and displayed, and the operation of the C controller module will be stopped by the self-diagnostic
function.
Note that errors may not be detected by the self-diagnostic function depending on the error occurrence status and the
instruction to be executed. Even if the operation will not be stopped by the self-diagnostics, establish a safety circuit outside
so that the entire system operates safely.
(2) Error checking
(a) LED ON
When the C controller module detects an error, it turns on ERR. LEDs.
For LED status, refer to the following.
 Page 156, (5) in this section
(b) Checking the error details
You may check the error code and error information from the following functions of Setting/monitoring tools for
the C Controller module.
•
[Diagnostics]  [CCPU diagnostics]  <<CCPU diagnostics>>
(c) Checking the event history
Any error that occurred during error detection will be registered to the event history.
You may check the registered event history from the following functions of Setting/monitoring tools for the C
Controller module.
•
[Diagnostics]  [Event history]  <<Event history>>
(3) Processing after error detection
Upon detection of an error, outputs (Y) from the user program and writing to the buffer memory is disabled, and
outputs to output modules, I/O modules, and intelligent function modules are cleared.
For the following items, you may check operations in error detection by using Setting/monitoring tools for the C
Controller module.
(a) Output mode
Whether to clear or retain the output to the module with any error detected can be selected.
For this setting, use the following functions in Setting/monitoring tools for the C Controller module.
•
Project view  "Parameter"  "CCPU Parameter"  <<I/O assignment settings>>
 "Detailed Settings"  "Error Time Output Mode"
154
Q24DHC-V Q24DHC-VG Q24DHC-LS Q26DHC-LS Q12DC-V