Mitsubishi MELSEC System Q User Manual

4.7.12 Operation result into pulse conversion
The MEP and MEF instructions are used without devices. They generate one output pulse with
the rising respectively falling edge of the input signal i.e. operation result which was valid
before the execution of these instructions. The next pulse is generated with the next rising resp.
falling edge.
The following figure shows the signal sequence for the above example:
These two instructions are especially suitable for multiple contacts connections. For example,
multiple normally open contacts connected in series would maintain the operation result 1 if
they were all closed. If a relay was set by this operation result, it could not be reset. With a MEP
instruction connected in series with these NO contacts the relay could be reset because the
instruction outputs one pulse only, if the series connection result of all contacts changes from 0
to 1.
MELSEC System Q Beginners Manual 4 – 31
An Introduction to Programming The Basic Instruction Set
Instruction Function Ladder Diagram IEC Instruction List
MEP
Pulse generation at the rising edge of
operation result
MEP_M
MEF
Pulse generation at the falling edge of
operation result
MEF_M
Ladder Diagram
MELSEC Instruction List
LD X1
AND X2
MEP
OUT M100
IEC Instruction List
LD X1
AND X2
MEP_M
ST M100
M100
X1
t
0
1
0
1
X2
0
1
0
1
Operation result before the
MEP instruction
Operation result after the
MEP instruction
Relay M100 is only switched on for the duration of a single
program cycle

Mitsubishi MELSEC System Q Specifications

General

Brand	Mitsubishi
Model	MELSEC System Q
Category	Controller
Language	English