Precautions - Mitsubishi Electric MELSEC iQ-R-R00CPU User Manual

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.
Program which processes data repeatedly
M0
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.
Internal processing time
END
Watchdog timer reset
(internal processing by the CPU module)
6 RAS FUNCTIONS
126
6.1 Scan Monitoring Function
FOR K1000
Reset the watchdog
WDT
timer.
NEXT
Program
Scan execution
program A
0
Scan time
Watchdog timer measurement time
1000 times
of repeats
Internal processing time
Scan execution
program B
END
Watchdog timer reset
(internal processing by the CPU module)
Scan execution
program A
0
Next scan time