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Pilot Light indicator light typically used represent condition a
machine process.
The PLC scan involves updating the status inputs, executing
the user program, performing diagnostic and communication
functions, and updating the status outputs.
New Position
Old Position
Plug-In Unit
. PLC scan is
repetitively executed.
RUN Pilot Light On
Motor Running Motor Stopped
STOP Pilot Light On
PLC Scan complete execution cycle programmable logic controller.
PLC Scan
R
e
a
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Inputs
U
p
d
a
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O
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tputs
Execu
t
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P
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o
g
r
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Diagnos
t
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c
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Communi
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o
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Plug-in Busway Busway that incorporates plug-in units, called bus plugs, to
allow loads distributed over the length the run
