Glossary
G–5
program file: The area within a processor file that contains the ladder logic
program.
program mode: When the controller is not executing the processor file and all
outputs are de-energized.
program scan: A part of the controller’s operating cycle. During the scan the
ladder program is executed and the Output data file is updated based on the program
and the Input data file.
programming device: Executable programming package used to develop ladder
diagrams.
protocol: The packaging of information that is transmitted across a network.
read: To acquire data from a storage place. For example, the processor READs
information from the input data file to solve the ladder program.
relay: An electrically operated device that mechanically switches electrical circuits.
relay logic: A representation of the program or other logic in a form normally used
for relays.
REM Run mode: REMote run mode during which the processor scans or executes
the ladder program, monitors input devices, energizes output devices, and acts on
enabled I/O forces.
restore: To download (transfer) a program from a personal computer to a
controller.
reserved bit: A status file location that the user should not read or write to.
retentive data: Information associated with data files (timers, counters, inputs, and
outputs) in a program that is preserved through power cycles. Program files 2–15
are not effected by retentive data.
RS-232: An EIA standard that specifies electrical, mechanical, and functional
characteristics for serial binary communication circuits. A single-ended serial
communication interface.
run mode: When the processor file in the controller is being executed, inputs are
read, the program is scanned, and outputs are energized and de-energized.
rung: Ladder logic is comprised of a set of rungs. A rung contains input and
output instructions. During Run mode, the inputs on a rung are evaluated to be true
or false. If a path of true logic exists, the outputs are made true. If all paths are
false, the outputs are made false.
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