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6 RAS FUNCTIONS
6.1 Scan Monitoring Function
Precautions
The following lists the precautions on the scan monitoring function.
Measurement error of watchdog timer
Since the watchdog timer produces an error within the range of 0 to 10ms, take this into consideration when setting the scan
time monitoring time. For example, if the scan time monitoring time is set to 100ms, an error will occur when the scan time
falls within the range 100ms < t < 110ms.
Resetting the watchdog timer when repeatedly executing a program
The watchdog timer can be reset by executing the WDT reset instruction from the program. If the watchdog timer counts up
while a program is being repeatedly executed by the FOR instruction and NEXT instruction, use the WDT reset instruction to
reset the watchdog timer.
Scan time when the WDT reset instruction is used
Even when the watchdog timer is reset by the WDT reset instruction, the scan time is not reset. The scan time is accumulated
until the END instruction is executed.
FOR K1000
WDT
NEXT
M0
Program which processes data repeatedly
Reset the watchdog
timer.
1000 times
of repeats
END 0 END 0
Internal processing time Program Internal processing time
Scan execution
program A
Scan execution
program B
Watchdog timer reset
(internal processing by the CPU module)
Scan execution
program A
Scan time
Watchdog timer measurement time
Next scan time
Watchdog timer reset
(internal processing by the CPU module)
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