Mitsubishi Q2ACPU User Manual page 159

9. MAINTENANCE FUNCTION
(3) Processing when the watchdog timer times out
When the scan time exceeds the set value of the watchdog timer, a watchdog timer
error occurs and the PLC operates as follows.
(a) All PLC outputs are turned OFF.
(b) The RUN LED on the front of the CPU module goes off and the ERROR LED
flickers.
(c) SM1 turns ON and the error code is stored in SD0.
REMARK
The watchdog timer can be reset by a WDT instruction in the sequence program.
However, the scan time value is not reset and scan time is measured up to the END
instruction.
POINT
An error occurs within 0ms to 10ms in the measured time for watchdog timer.
9 - 3