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7 Applied Instructions (Program Flow)
7.8 WDT / Watchdog Timer Refresh
125
FXCPU Structured Programming Manual
[Basic & Applied Instruction]
1
Outline
2
Instruction List
3
Configuration of
Instruction
4
How to Read
Explanation of
Instructions
5
Basic Instruction
6
Step Ladder
Instructions
7
Applied Instructions
(Program Flow)
8
Applied Instructions
(Move and
Compare)
9
Applied Instructions
(Arithmetic and
Logical Operation)
10
Applied Instructions
(Rotation and
Shift Operation)
7.8 WDT / Watchdog Timer Refresh
Outline
This instruction refreshes the watchdog timer in a sequence program.
1. Format and operation, execution form
2. Set data
3. Applicable devices
Function and operation explanation
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.
Related device
FX3U(C) FX3G(C) FX3S FX2N(C) FX1N(C) FX1S FXU/FX2C FX0N FX0(S)
Instruction
name
Operation
Execution
form
Expression in each language
Structured ladder/FBD ST
WDT
16 bits
Continuous WDT(EN);
WDTP Pulse WDTP(EN);
Variable Description Data type
Input
variable
EN Execution condition Bit
Output
variable
ENO Execution state Bit
Operand
type
Bit Devices Word Devices Others
System User Digit Specification
System
User
Special
Unit
Index
Constant
Real
Number
Character
String
Pointer
XYMTCS
D.b
KnX KnY KnM KnS T C D R
U\G
VZModifier K H E
""
P
- No target device is available.
Device Name Description
D8000 Watchdog timer time Up to 32767 ms can be set in units of ms (initial value: 200 ms).
WDT
EN ENO
WDTP
EN ENO
One scan is
executed.
Command
contact
WDTP
EN ENO
Each scan is
executed.
Command
contact
WDT
EN ENO
Command
input
Command
input