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99
FX
3G
/FX
3U
/FX
3UC
Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
4 Devices in Detail
4.5 Timer [T]
1
Int
roduct
ion
2
O
ver
view
3
In
str
uc
tion
Li
st
4
D
evices
in D
etail
5
Spec
ified t
he
D
evice &
C
onst
ant
6
Bef
ore
Pr
ogr
am
m
ing
7
B
asic
In
st
ru
ct
io
n
8
FN
C
00-FN
C
09
P
rogr
am
F
low
9
FN
C
10
-FN
C
19
Mo
ve
&
Co
mp
are
10
FNC2
0-F
NC2
9
Ar
ith.
&
Logic
O
per
ation
2) When variable analog potentiometers (expansion board) are used
The value of a variable analog potentiometer
board which can be built in an FX
3G
PLC as an
expansion board can be obtained as numeric
data in the range from 0 to 255 in accordance
with the scale position.
An obtained numeric value can be specified as
the indirectly specified value for a timer to make
a variable potentiometer type analog timer.
Use the FNC85 (VRRD) instruction to take the
value of a variable analog potentiometer into the
PLC.
→
For FNC85(VRRD), refer to Section 16.6.
Use the FNC86 (VRSC) instruction to take the
value of a variable analog potentiometer as a
numeric value in the range from 0 to 10.
→
For FNC86(VRSC), refer to Section 16.7.
4.5.3
Set value specification method
1. Specifying a constant (K)
T10 is a 100 ms (0.1 sec) type timer.
When the constant "100" is specified, T10 works as a
10-second timer (0.1 sec
×
100 = 10 sec).
2. Indirectly specifying a data register
Turns on when T10 reaches the indirectly specified
value of the defined data register, previously set by a
digital switch.
Note that the set value of a latched (battery backed)
type register is not held correctly sometimes when the
battery voltage becomes low.
4.5.4
Cautions on routines
1) Use timers T192 to T199 in subroutines and interrupt routines. These timers execute counting when a
coil instruction or END instruction is executed.
When such a timer reaches the set value, its output contact turns on when a coil instruction or END
instruction is executed.
Because general type timers execute counting only when a coil instruction is executed (Refer to "4.5.5
Details of timer operation and timer accuracy" below.), they do not execute counting and do not operate
normally if they are used in subroutines or interrupt routines in which a coil instruction is executed only in
a certain condition.
2) When a retentive timer for 1 ms pulses (T246 to T249) is used in a subroutine or interrupt routine, note
that its output contact turns on when the first coil instruction is executed after the retentive timer has
reached the set value.
VRRD
Example of application as analog timer
The analog value of the potentiometer No. 0 is converted into
binary 8-bit data, and a numeric value in the range from 0 to 255
is transferred to D0.
In this application example, the value of D0 is used as the set
value of a timer.
volume
number
Read
destination
FNC 85
K0
D0
X000
X001
T0
D0
X003
T10
K100
Constant
(decimal integer)
10-second timer
D5 = K100
10-second
timer
X001
FNC 12
MOV
K100
D 5
X003
T10
D 5