6F3B0253
Basic Hardware and Function 211
7. Instructions
FUN 143 WDT Watchdog timer reset
Expression
Input −[ WDT n ]− Output
Function
When the input is ON, this instruction extend the scan time over detection time by 200 ms.
Normally, T1/T1S detects the scan time-over if a scan is not finished within 200 ms. This instruction
can be used to extend the detection time.
Execution condition
Input Operation Output
OFF No execution OFF
ON Execution ON
Operand
Name Device Register Constant Index
X Y R S T. C. XWYWRWSW T C D I J K
nExtend time 1 - 100
Example
When R020 is ON, the scan time detection time is extended by 200 ms. The operand n has no
effect on the extended time. It is fixed as 200 ms.
Normal detection point Extended point
0 50 100 150 200 250 300 (ms)
Extended by 200 ms
Scan
WDT instruction
execution
Note
• As f or the upper T-series PLCs, the operand n specifies the extended time. Ho we ver in the
T1/T1S, it is fixed as 200 ms regardless of the operand n.