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 Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
7 Basic Instruction
7.14 NOP
1
In
trodu
ct
ion
2
O
ver
vi
ew
3
In
st
ru
ct
ion 
Li
st
4
D
evices 
in D
etail
5
Specifi
ed t
he
D
evice &
 
C
onst
ant
6
Bef
ore 
Pr
ogr
am
m
ing
7
B
asic 
In
st
ru
ct
ion
8
FNC0
0-F
NC0
9
Pr
ogr
am
 Flow
9
FN
C
10-FN
C
19
Mo
ve
 &
 Co
mp
are
10
FNC2
0-F
NC2
9
Ar
ith.
 &
 Logic 
O
per
ati
on
7.14
NOP
Outline
NOP instruction specifies no operation.
When a program is erased completely, all steps are replaced with NOP instructions.
When NOP instruction is located between general instructions, PLCs ignore NOP instruction.
If NOP instructions are put in the middle of a program, fluctuation of step numbers is minimized when the program is
changed or added.  But excessive program steps are required.
Note that circuits are considerably changed if already written instructions are replaced with NOP instructions.
1. Instruction format
2. Applicable devices
Explanation of function and operation
1. NOP instruction (no operation or null step)
NOP instruction specifies no operation.
If NOP operation is written in the middle of a program, PLCs ignore it in executing the program.
When an existing program is replaced with NOP instructions, it means that former instructions are deleted.
Instruc-
tion
Bit Devices
Word Devices
Others
System User
Digit Specification
System User
Special 
Unit
Index
Con-
stant
Real 
Number
Charac-
ter String
Pointer
X Y M T C S D….b KnX KnY KnM KnS T C D R U…\G… V Z Modify K H
E
"…"
P
NOP
There are no applicable devices.
NOP
No Operation
Basic Instruction
NOP
Continuous
Operation
Pulse (Single)
Operation
Mnemonic
Operation Condition
1 step
AND 
→ NOP
ANI 
→ NOP
Contact becomes
short-circuit.
OR 
→ NOP
Circuit is
disconnected.
ORI 
→ NOP
OUT 
→ NOP (error)