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35 Interrupt Function and Pulse Catch Function
813
FXCPU Structured Programming Manual
[Basic & Applied Instruction]
31
Appl
ied
 In
stru
cti
ons 
(Da
ta
 T
rans
fer 
3)
32
Ap
plied
 Instru
ctio
ns 
(High S
peed 
Process
ing 2)
33
App
lied Instr
ucti
ons 
(Exte
nsion File 
Regis
ter C
ontrol
)
34
Ap
pl
ied In
struct
ions 
(FX
3U
-C
F-
AD
P)
35
Int
errupt
 Fun
cti
on 
and Puls
e Cat
ch 
Functi
on
A
Re
lation
sh
ip
be
tw
ee
n de
vic
es
 
an
d ad
dre
ss
es
B
Ap
plie
In
structio
n List
35.8 Pulse width/Pulse period measurement function [M8075 to M8083, D8074 to D8097]
35.8
Pulse width/Pulse period measurement function [M8075 to M8083, 
D8074 to D8097]
This function is supported only in FX
3G
 PLC (Ver.1.10 or later) and FX
3GC
.
The pulse width/pulse period measurement function stores the values of 1/6 
μs ring counters at the input
signal rising edge and falling edge to special data registers. This function also divides by "60" the difference in
the counter value (pulse width) between the rising edge and the falling edge or the difference in the counter
value (pulse period) between the previous rising edge and the current rising edge, and stores the obtained
pulse width or pulse period in units of 10 
μs to special data registers.
The pulse width/pulse period measurement function becomes valid when a program is described using
M8075 as a contact. Specify the pulse width measurement flag in the subsequent OUT instruction, and set an
input terminal to be used.
When the pulse width/pulse period measurement function is valid, it always operates while the PLC mode is
RUN.
Assignment of special auxiliary relays and special data registers
*1.
Cleared when the PLC mode switches from STOP to RUN.
*2.
The measurable pulse width is 10 
μs minimum and 100 s maximum.
The measurable pulse period is 20 
μs minimum and 100 s maximum.
1. Program example
1) Pulse width measurement
The pulse width of the input signal from X000 is measured.
Pulse input
Pulse width/ Pulse 
period measurement 
flag
Pulse period 
measurement mode
Ring counter value 
for rising edge
*1
 
[Unit: 1/6 
μs]
Ring counter value 
for falling edge
*1
 
[Unit: 1/6 
μs]
Pulse width /Pulse 
period
*1*2
 
[Unit: 10 
μs]
X000
M8076
M8080
D8075, D8074
D8077, D8076
D8079, D8078
X001
M8077
M8081
D8081, D8080
D8083, D8082
D8085, D8084
X003
M8078
M8082
D8087, D8086
D8089, D8088
D8091, D8090
X004
M8079
M8083
D8093, D8092
D8095, D8094
D8097, D8096
This duration is measured.
ON
OFF
X000
EN ENO
EI
DMOV
[Main program]
[Interrupt program]
(Event: I000)
X000 Falling edge
interrupt
*1. VAR_01 is a global label and is defined as D8078.
*2. VAR_02 is a global label and is defined as D0.
X000 is used for the pulse width/pulse period
measurement function.
When the interrupt routine is executed at the
falling edge of the input signal from X000, the
pulse width of input signal from X000 stored in
D8078 and D8079 is transferred to D1 and D0.
M8075
M8000
RUN monitor
VAR_01
*1
VAR_02
*2
Pulse width/Pulse
period measurement
setting flag
M8076
EN
ENO
s
d
User program