Fnc 07 - Wdt / Watchdog Timer Refresh - Mitsubishi Electric MELSEC FX3U Programming Manual

FX /FX /FX Series Programmable Controllers
3G 3U 3UC
Programming Manual - Basic & Applied Instruction Edition
8.8 FNC 07 – WDT / Watchdog Timer Refresh
Outline
This instruction refreshes the watchdog timer in a sequence program.
1. Instruction format
FNC 07
WDT
2. Set data
Operand type
–
3. Applicable devices
Bit Devices
Oper-
and System User
Type
X Y M T C S D .b KnX KnY KnM KnS T C D R U \G
–
Explanation of function and operation
When the operation cycle (time until END or FEND instruction is executed after the step 0) of a PLC exceeds
200 ms, a watchdog timer error (indicating abnormal operation) occurs; The CPU error LED lights, and the
PLC stops.
When the operation cycle is long, insert WDT instruction in the middle of the program to avoid the watchdog
timer error.
Command
input
FNC 07
WDTP
Command
input
FNC 07
WDT
Related device
Device
D8000 Watchdog timer time
246
Mnemonic
Independent Inst.
P
WDT
1 step
WDTP
There is no set data.
Digit Specification
Command
contact
Command
contact
Name
Up to 32767 ms can be set in units of ms (initial value: 200 ms).
8.8 FNC 07 – WDT / Watchdog Timer Refresh
Operation Condition
Continuous
Operation
Pulse (Single)
Operation
Description
Word Devices
Special
System User
Unit
V Z Modify K H
There are no applicable devices.
One scan is executed.
Each scan is
executed.
Description
8 Program Flow – FNC 00 to FNC 09
Data type
Others
Con- Real Charac-
Index
stant Number ter String
E " "
–
Pointer
P