Siemens LOGO! Series Manual page 98

Programming LOGO!
3.7 Writing and starting the circuit program
What is meant by: "LOGO! is in RUN"?
In RUN mode, LOGO! executes the circuit program. To do so, LOGO! first reads the status
at the inputs, determines the status of the outputs by means of the circuit program, and
switches these on or off according to your settings.
This is how LOGO! indicates the I/O status:
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Manual, 04/2011, A5E03556174-01
LOGO!