Mitsubishi MELSEC-Q Series User Manual page 160

7 PROCEDURE BEFORE STARTING THE DATA LINK
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From the previous page
The test result is displayed using the "LED"
indicator lamps of the master/local module and
the CPU module.
[When normal]
The CPU "ERR." LED flashes
(to check the operation of the watchdog timer).
[When abnormal]
The "MST" LED lights up and the "ERR."
LED flashes.
Replace the module since there is a hardware
malfunction.
(Check once again to see that the terminal
resistor that comes with the module is
connected between terminals DA and DB.)
POINT
When the RUN/STOP switch of the PLC CPU is set to "RUN" and a hardware test
is performed, the system status become SP. UNIT DOWN and the PLC CPU stops
to check the operation of the watch dog timer function. Make sure that the
RUN/STOP switch of the PLC CPU is set to "STOP" and then perform the
hardware test.
End
MELSEC-Q
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