605
WDT, WDTP
1
2
3
4
4
6
7
8
7.18
Ot
her inst
ructions
7.18.1
W
DT, WDT
P
7.18
Other instructions
F
unct
i
on
(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.
Operat
i
on
E
rror
(1) There is no operation error in the WDT(P) instruction.
Program
E
xamp
l
e
(1) The following program has a watchdog timer setting of 200ms, when due to the execution conditions program execution
requires 300ms from step 0 to the END (FEND) instruction.
WDT, WDTP
Watchdog timer reset
7.18.1
WDT, WDTP
Setting
Data
Internal Devices
R, ZR
J \
U \G
Zn
Constants
Other
Bit
Word
Bit
Word
––
––
Basic
Process
High
performance
Redundant Universal
LCPU
Command
WD
T
WD
T
P
Command
WDT
WDTP
Step
0
EN
D
(
FEN
D)
WD
T
T
1
T
2
END
[When WDT instruction is used]
END
WDT
Program
w
here
scan time is
300 ms.
Program
w
here
scan time is
150 ms.
Program
w
here
scan time is
150 ms.