Mitsubishi MELSEC System Q User Manual

4.7.7 Pulse-triggered execution of operations
In PLC programs you will often need to detect and respond to the rising or falling edge of a bit
device’s switching signal. A rising edge indicates a switch of the device value from “0” to “1”, a
falling edge indicates a switch from “1” to “0”.
During program execution operations that respond to rising and falling pulses only deliver a
value of “1” when the signal state of the referenced device changes.
When do you need to use this? For example, suppose you have a conveyor belt with a sensor
switch that activates to increment a counter every time a package passes it on the belt. If you
don’t use a pulse-triggered function you will get incorrect results because the counter will
increment by 1 in every program cycle in which the switch registers as set. If you only register
the rising pulse of the switch signal the counter will be incremented correctly, increasing by 1
for each package.
NOTE Most applied instructions can also be executed by pulse signals.For details see chapter 6.
4–22 MITSUBISHI ELECTRIC
The Basic Instruction Set An Introduction to Programming
Instruction Function Ladder Diagram IEC Instruction List
LDP
Load Pulse, loads on the rising edge of
the device’s signal
—
LDF
Load Falling Pulse, loads on the falling
edge of the device’s signal
—
ANDP
AND Pulse, logical AND operation on the
rising edge of the device’s signal
ANDP_M
ANDF
AND Falling Pulse, logical AND operation
on the falling edge of the device’s signal
ANDF_M
ORP
OR Pulse, logical OR operation on the
rising edge of the device’s signal
ORP_M
ORF
OR Falling Pulse, logical OR operation
on the falling edge of the device’s signal
ORF_M

Mitsubishi MELSEC System Q Specifications

General

Brand	Mitsubishi
Model	MELSEC System Q
Category	Controller
Language	English