Table of Contents
Advertisement
(b) Resetting a watchdog timer when a program is repeatedly executed between the FOR and
NEXT instructions
The watchdog timer can be reset by executing the WDT instruction in the sequence program.
To avoid the time up of watchdog timer while a program is repeatedly executed between the FOR and NEXT
instructions, reset the watchdog timer by the WDT instruction.
MO
Resetting watchdog timer when the a program is executed between the FOR and NEXT instructions
Figure 6.78 Resetting a watchdog timer when the program is executed between the FOR and NEXT instructions
(c) Scan time when using the WDT instruction
The scan time value is not reset even if the watchdog timer is reset in the sequence program.
The scan time is measured up to the END instruction.
Internal processing time
END
WDT reset
(CPU module internal
processing)
●
A scan time is time required for the CPU module to operate the sequence program from step 0 and return
to the step 0 in the sequence program with the same file name.
●
The scan time depends on the execution status of the following:
• Instructions used in the program
• Interrupt program and fixed scan execution type program
To keep the same scan time in every scan, use the constant scan function.
6 - 96
FOR K1000
Program repeatedly executed
WDT
NEXT
Sequence program
Scan execution
Scan execution
0
type program A
type program B
Scan time
WDT measurement time
Figure 6.79 Watchdog timer reset
Repeated in
1,000 times
WDT reset
Internal
processing time
Scan execution
END
0
type program A
Next scan time
WDT reset
(CPU module internal
processing)
(
Section 6.2)
Advertisement
Table of Contents
