Mitsubishi Electric FX3G SERIES Programming Manual page 241

FX /FX /FX Series Programmable Controllers
3G 3U 3UC
Programming Manual - Basic & Applied Instruction Edition
2. The watchdog timer time can be changed.
By overwriting the contents of D8000 (watchdog timer time), the watchdog timer detection time (initial value: 200 ms)
can be changed.
By inputting the program shown below, the sequence program after this insertion is monitored by a new watchdog
timer time.
M8002
0
Initial pulse
Program examples
1. When the operation cycle is long and causes an error
For example, by dividing a program whose operation cycle is 240 ms into two portions and inserting WDT instruction
between them, the operation cycle becomes less than 200 ms in both the former half portion and the latter half portion.
Program
whose
operation cycle
is 240 ms
2. When a label (P) of CJ instruction is located in a step number smaller than the step number of CJ
instruction
Put WDT instruction after the label (P).
M8000
Label
Pn
RUN monitor
Command
3. When FOR/NEXT instruction is repeated many times
Put WDT instruction between FOR and NEXT instructions.
→ For details on changing watchdog timer time, refer to Subsection 37.2.2.
FNC 12
K300
MOV
Watchdog timer refresh
FNC 07
If WDT (FNC 07) instruction is not programmed, the value of
WDT
D8000 is valid during END processing.
END
FNC 07
WDT
When the command
Program
contact turns ON
FNC00
Pn
CJ
FNC 08
K30000
FOR
Program
FNC 07
WDT
FNC 09
NEXT
8 Program Flow – FNC 00 to FNC 09
8.8 FNC 07 – WDT / Watchdog Timer Refresh
Watchdog timer time: 300 ms
D8000
Program whose
operation cycle
is 120 ms
FNC07
WDT
Program whose
operation cycle
is 120 ms
END
If an input relay (X) is used as the command
contact, input refresh is disabled, so the
program execution cannot be returned from
the area between P and CJ.
As the command contact, use such device
that can be set to OFF in a program being
jumped.
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