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2-2-2. Arithmetic principle
The arithmetic principle is explained with the
circuit shown in the figure on the right as an
XI
x2
x3
x4
XI
x2
x3
x 4
'
\
example.
The program for this circuit is as follows with
MELSEC-K.
The execution process for the circuit example
(a) is shown in (b).
InpuUoutput
Step number
Instructions
number
(a) Circuit example
0
LD
x1
Input of the on-off status of X1
Input of the on-off statusof X2 and OR operation with
X l . X l + X 2
1
'
OR
x2
2
AND
x 3
Input of the on-off status of X3 and AND operation
with (X1
+
X2). (X1
+
X2). X3
3
Output of the operation result (X1
+
X2) X3 to Y14.
o u
r r
Y
14
Input (X)
Output (Y)
.
n
X I
x 2
x3
x4
x1
+x2
I
. ,
0
i I L ,
XI
'
1
OK' x2
(
x1 sxz
)
0x3,
/
( X I
+xz
)
0x3
.y
11
Y
12
y
13
Y
14
I1
'12
13
14
3
OT!T
Y14
2 AND
X3
X: Input selection part
Y: Output selection part
A: Register
A
(answer register)
B: Register B (auxiliary register)
'Fig. 2-5. Arithmetic principle
.LU: Logic processing unit
J
IR: Instructions register
.(b) Execution process
Explanation of the arithmetic principle
The execution process for this program and this hardware compostion is as follows.
Step
0 LD X1
@The program number 0 is read from the memory, the instruction LD is stored in the instructions
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