300 Rockwell Automation Publication 1766-UM001O-EN-P - September 2021
Glossary
output device A device, such as a pilot light or a motor starter coil, that is controlled by the
controller.
processor A Central Processing Unit. See CPU (Central Processing Unit).
processor file The set of program and data files used by the controller to control output
devices. Only one processor file may be stored in the controller at a time.
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.
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.
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 This is an executing mode during which the controller scans or executes the
ladder program, monitors input devices, energizes output devices, and acts on
enabled I/O forces.
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.
save To upload (transfer) a program stored in memory from a controller to a
personal computer; OR to save a program to a computer hard disk.
scan time The time required for the controller to execute the instructions in the program.
The scan time may vary depending on the instructions and each instruction’s
status during the scan.
sinking A term used to describe current flow between an I/O device and controller I/O
circuit — typically, a sinking device or circuit provides a path to ground, low,
or negative side of power supply.
sourcing A term used to describe current flow between an I/O device and controller I/O
circuit — typically, a sourcing device or circuit provides a path to the source,
high, or positive side of power supply.
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