Справочник Пользователя для Mitsubishi Electronics FXCPU
7 Applied Instructions (Program Flow)
7.8 WDT / Watchdog Timer Refresh
125
FXCPU Structured Programming Manual
[Basic & Applied Instruction]
1
O
utlin
e
e
2
Instruc
tion Li
st
3
Configurati
on of
Instruction
4
Ho
w t
o R
ea
d
Explanati
on of
Ins
truction
truction
s
5
B
asic
Instruction
6
Step Ladder
Instruct
ions
7
Ap
pl
ied Inst
ruct
io
io
ns
(Program Flow)
8
Appl
ied
ied
In
stru
cti
cti
ons
(Mov
e and
C
omp
are)
are)
9
App
lie
lie
d Instr
uction
s
s
(Ari
thm
eti
thm
eti
c and
Lo
gic
al O
per
at
ion)
10
App
lied Inst
lied Inst
ructi
ons
ons
(Rot
ati
ati
on and
Shift O
perati
on)
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.
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
FX
3U(C)
FX
3G(C)
FX
3S
FX
2N(C)
FX
1N(C)
FX
1S
FX
U
/FX
2C
FX
0N
FX
0(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
variable
EN
Execution condition
Bit
Output
variable
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
X Y M T C S D
.b KnX KnY KnM KnS T C D R U
\G
V Z Modifier 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.
executed.
Command
contact
contact
WDTP
EN
ENO
Each scan is
executed.
executed.
Command
contact
contact
WDT
EN
ENO
Command
input
input
Command
input
input