80
FX
3U
/FX
3UC
Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
4 Devices in Detail
4.5 Timer [T]
4.5.3
Set value specification method
1. Specifying a constant (K)
T10 is on 100 ms (0.1 sec) type.
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
Write the contents of an indirectly specified data register
in advance in a program, or receive them in advance by
a digital switch.
Note that the set value at latched (battery backed) type
resister can become indefinite when the battery voltage
is 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 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.
4.5.5
Details of timer operation and timer accuracy
A timer (except interrupt execution type) starts counting when a coil is driven, and its output contact turns on
when the first coil instruction is executed after the timer has reached timeout.
As shown in the above operation diagram, the accuracy of operation of the timer contact after the coil is
driven until the contact turns on is shown in the following outline:
If the contact is programmed before the timer coil, "+2T
0
" is obtained in the worst case.
When the timer set value is "0", the output contact turns on when a coil instruction is executed in the next
cycle. An interrupt execution type timer for 1 ms pulses counts clock pulses of 1 ms as an interrupt
processing after a coil instruction has been executed.
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
X010
T 0
K12
T 0
Y010
Input processing X010 = OFF
→
ON
Counting operation (If the operation cycle is long,
it automatically counts two or more clocks.)
Contact is not
activated at this point
T 0
Contact is
activated
2nd cycle
"n"th cycle
"n+1"th cycle
Y010
ON
Timer starts counting
1st cycle
1.2 sec
time-
out
α
: 0.001 sec (timer for 1 ms), 0.01 sec (timer for 10 ms) or 0.1 sec (timer for 100 ms)
T : Timer set value (sec)
T
0
: Operation cycle (sec)
T
+T
0
−α
