Mitsubishi MELSEC-F FX-TRN-BEG-E, User Manual, Page: 51 / 164

FX-TRN-BEG-E B: Let’s Study the Basics 2
B-23
2.4.3 Points of training and control specifications
1) Input rising / falling edge detection instruction
Let’s learn programs which operate only when an input is set to ON or OFF.
The rising / falling edge detection instruction captures the alternate status of ON to OFF and
OFF to ON.
It is used for control where the input signal should not be kept either ON or OFF.
Example
• X024 is an alternate switch which is
a l way s e i t h e r O N o r O F F. H ow eve r,
because the PLS instruction is used here,
the OUT instruction M0 is operated only on
the rising edge of input X024 for a single
scan cycle.
• X020 is a momentary pushbutton switch
which turns ON when pressed. However,
because the PLF instruction is used here,
the OUT instruction M1 is operated on the
falling edge of input X020 for a single scan
cycle.
* Even if inputs X024 or X020 are set ON or OFF by the PLS or PLF instruction, the latched
output instruction program for Y000, Y001 and Y006 can be shut down by the input of
X021.
2) Contact type rising/falling edge detection instruction
There is another type of rising/falling edge detection instruction which turns a contact only
for a moment.
Example
• The program shown on the left performs
the same operation with the program
shown above in which the PLS and PLF
instructions are used for rising/falling edge
detection.
M0
Y001
Y001
X021
M1
Y000
Y000
X021
X024
M0 PLS
X020
M1 PLF
Y006
X024
Y001
Y000
X021
X020
Y000
Y001
X021
Y006
rising edge
detection
falling edge
detection