Справочник Пользователя для Mitsubishi Electronics MELSEC -Q/L

7  APPLICATION INSTRUCTIONS
7.19  Other Instructions

Processing details

 • Resets watchdog timer during the execution of a sequence program.
 • Used in cases where the scan time exceeds the value set for the watchdog timer due to prevailing conditions. If the scan 

time exceeds the watchdog timer setting value on every scan, change the watchdog timer settings at the parameter 
settings of a programming tool.

 • Make sure that the setting for t1 from step 0 to the WDT instruction and the setting for t2 from the WDT instruction to the 

END (FEND) instruction do not exceed the setting value of the watchdog timer.

 • The WDT instruction can be used two or more times during a single scan, but care should be taken in such cases, because 

of the time required until the output goes OFF during the generation of an error.

 • Scan time values stored at the special register will not be cleared even if the WDT or WDTP instruction is executed. 

Accordingly, there are times when the value for the scan time for the special register is greater than the value of the 
watchdog timer set at the parameters.

Operation error

 • There is no operation error in the WDT(P) instruction.

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Command

WDT

WDTP

Command

END (FEND)

WDT

t1

t2

Step 0