12 SCAN MONITORING FUNCTION
12.3 Precautions
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12
12.3 Precautions
The following precautions relate to the scan monitoring function.
Watchdog timer reset when executing a program repeatedly
The watchdog timer can be reset by executing the WDT instruction in a program. If the time of the watchdog timer is up while
executing a program repeatedly by the FOR instruction and NEXT instruction, use the WDT instruction to reset the watchdog
timer.
Scan time when the WDT instruction is used
Even though the watchdog timer is reset using the WDT instruction, the scan time value is not reset. The scan timer value is
the value measured up to the END instruction.
FOR K1000
WDT
NEXT
Program repeatedly executed
Resetting of the
watchdog timer
Repeated 1,000 times
M0
Internal
processing time
Program
Internal
processing time
Scan execution
program A
Scan execution
program B
WDT reset (CPU module
internal processing)
END
0 ENDWDT
Scan execution
program A
0
Scan time
Clear
WDT measurement time
WDT
measurement
time
Next scan time
Next WDT measurement
time
WDT reset (CPU module
internal processing)
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