Mitsubishi Electric MELSEC-Q/L - Other Instructions; Watchdog Timer Reset

752
7 APPLICATION INSTRUCTIONS
7.19 Other Instructions
7.19 Other Instructions
Watchdog timer reset
WDT(P)
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.
Setting
data
Internal device R, ZR J\ U\G Zn Constant Others
Bit Word Bit Word

Basic
Process
High
performance
Redundant Universal LCPU
Command
WDT
WDTP
Command
WDT
WDTP
END (FEND)
WDT
t1
t2
Step 0