9
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6
9.2.1 Input (X)
(1) Definition
The input (X) is used to send commands or data to the CPU module
from external devices such as push-
button switches, selector switches, limit switches, and digital switches.
(2) Concept of input (X)
One input point is assumed to be a virtual relay Xn in the CPU module.
Programs use the normally open or closed contact of Xn.
(3) Allowable number of
normally open or closed contacts
There are no restrictions on the number of normally open or closed contacts of Xn used in a program,
as long as the program capacity is not exceeded.
Figure 9.2 Commands from external devices to a CPU module
Figure 9.3 Concept of input (X)
Figure 9.4 Input (X) used in a program
1
2
3
Push-button switch
Selector switch
Digital switch
Input (X)
Sequence
operation
LS2
PB1
X0
X1
XF
PB16
XF
X1
X0
Virtual relay
Program
Input ladder (external device)
Programmable
controller
X0
Y21
X0
X0
Y20
Y21
Y23
X1
X2
X2
No restrictions on
the quantity used.