Other Instructions - Mitsubishi MELSEC Q Series Programming Manual

7.18

Other instructions

7.18.1
Resetting watchdog timer (WDT(P))
WDT(P)
WDT
WDTP
Setting
Data
––
Function
(1) Resets watchdog timer during the execution of a sequence program.
(2) 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 peripheral device parameter settings.
(3) 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.
(4) 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.
(5) 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.
Command
Command
Internal Devices
R, ZR
Bit Word
Step 0
T1
High
Basic
performance
J \
U \G
Bit Word
––
END (FEND)
WDT
T2
WDT(P)
Process
Redundant Universal LCPU
WDT
WDTP
Zn Constants Other
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