Chapter 5 Program Configuration and Operation Method
5.1.4 Scan Watchdog timer
WDT (Watchdog Timer) is the function to detect the program congestion by the error of hardware and software of
PLC CPU module.
(1) WDT is the timer used to detect the operation delay by user program error. The detection time of WDT is
set in Basic parameter of XG5000.
(2) If WDT detects the excess of detection setting time while watching the elapsed time of scan
during operation, it stops the operation of PLC immediately and keeps or clears the output according
to parameter setting
(3) If the excess of Scan Watchdog Time is expected in the program processing of specific part while
performing the user program (FOR ~ NEXT instruction, CALL instruction), clear the timer by using
‘WDT_RST’ Function
‘WDT_RST’ Function initializes the elapsed time of Scan Watchdog Timer and starts the time measurement
from 0 again.
(For further information of WDT_RST Function, please refer to Instruction.)
(4) To clear the error state of watchdog, we can use the following method : power re-supply, PLC reset,
mode conversion to STOP mode.
Remark
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