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4-2. Types and composition of instruction words
(1)Instruction types
MELSEC instructions are composed with a basic word length of 16 bits (2 bytes
=
1 word),
and according to the instruction type, there are the 3 lengths
of
1 step instructions, 2 step in-
structions, and 3 step instructions.
Corresponding to this, 1, 2, or 3 program memory steps are required.
First step
@
Sequence operation instructions
@
Output instructions
LU
LDI, AND, AN1, O R O R I , AN& ORB
hlC,
M C R SFT, PLS, SET, RST, OUT, C J
Instruction code
@ Data instructions
MOV,
>,
(,
= ,
+,
- , RCD, B I N
M
None
@
Others
NOP, END
M 0-253
None
(2)Composition of the instruction words
(1 step instructions)
-
First step
r
Instruction code
8
8
S , F T , P L S
A N B , ORE3
N O P , E N D
MC,
M C l t
-
Input/output number
Input/output
source
I
O F B # ( K l )
x\
yooo#-
1
F F # ( K 2
)
X.
Y,
M, F
T ,
c ,
No SET, RST for T.
No SET for T.
K
I
'5''
is attached for index use.
I
i
=
0-6 3
(2 step instructions)
O U
T T ,
OU
'r c.
C
J
8
I
Second step
I
8
0
(2 step instructions)
8
7
O U T , T, C
C J
Same
as
1 step
K (constant) or D
instruction OUT
(Data register number)
Instruction code
K (jump destination step)
(3 step instructions)
M O
V, ?,
(, =,
+,
- , B C D , B I N
First step
[I
Data instruction code
I
Auxiliary code (type)
I
Second step
I
Source
[K (constant) or D (data register number)]
I
I
1
7 -
Destination
[K (constant) or D (data register number)]
L
Third step
-21-
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