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IPROGRAMMING
IDescription
of
internal devices
I
I
Inputs
x
I
Using inputs, communication is made between the PLC and external equipment via
the input modules off the PLC system. They are used
to
receive ON/OFF
commands and data from external devices such as push buttons, select switches,
digital switches etc.., for use within the sequence program.
Assuming that one input point incorporates a virtual relay Xn within the PLC, the
normally open contact (NIO) and normally closed contact (NIC) of that input point
can then be used in the program. There is no restriction
to
the number
of
N/O
contacts and N/C contacts used for that one input point.
\
/-;-a
a
I
II
I
Input
circuit (external devtces) Sequence
program
I
OUtDUtS
Y
I
Like inputs, outputs enable communication between the PLC, via output modules in
the PLC system, and external equipment. Outputs provide program control results
to
external devices such as solenoids, magnetic switches, signal lamps, digital
indicators etc.
Assuming that one output point incorporates a virtual relay coil Yn within the
FLC.
The N/O contacts and N/C contacts of this coil can also be used within the program,
with no restriction on the number of times they are used.
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