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

7 FUNCTION

7.12 Self-Diagnosis Function

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(1) What is Self-Diagnosis Function?
(a) The self-diagnosis is a function performed by Basic model QCPU itself to
diagnose whether there is an error in the Basic model QCPU.
(b) The self-diagnosis function's objective is to prevent Basic model QCPU
erroneous operation and as preventive maintenance.
The self-diagnosis processing detects and displays the error when an error
occurs when the Basic model QCPU power is turned on or during Basic
model QCPU RUN mode. It also stops Basic model QCPU calculations.
(2) Processing for Error Detection
(a) When Basic model QCPU detects an error, it turns on ERR. LEDs. When
an error is detected, special relays (SM0, SM1) are turned ON and an error
code of the error is stored in the special register SD0. When multiple errors
are detected, error codes of the latest errors are stored in the special
register SD0. For error detection, use special relays and special registers in
program so that these devices can interlock with sequencers and
mechanical systems.
(b) Basic model QCPU stores 16 latest error codes. (Refer to Section 7.13.)
The failure history can be checked in the GX Developer function PLC
diagnostics mode.
The failure history can be stored even when the power is shut off using the
battery backup.
(3) Basic model QCPU operation at the time of error detection
(a) When an error is detected from the self-diagnosis, there are two types of
modes that the Basic model QCPU operation can change to.
1) Basic model QCPU calculation stop mode
Stops the calculation at the point when the error is detected, and turns
off all output (Y).
2) Basic model QCPU calculation continue mode
When an error is detected, the program (Instruction) area where the
error occurred is skipped and the rest of the program is executed.
(b) The following errors can set the calculation "continue/stop" in the parameter
mode PLC RAS.
(All parameter defaults are set at "Stop".)
1) Operation error
2) Expanded command error
3) Fuse blown
4) I/O unit comparison
5) Intelligent function module program execution error
For example, when the I/O module verification error is set to "continues",
the calculations are continued in the I/O address before the error occurred.
MELSEC-Q
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