Rockwell Automation 1761 MicroLogix 1000 Programmable Controllers - Manual (Page 401)

Glossary
G–3
input device: A device, such as a push button or a switch, that supplies signals
through input circuits to the controller.
inrush current: The temporary surge current produced when a device or circuit is
initially energized.
instruction: A mnemonic and data address defining an operation to be performed
by the processor. A rung in a program consists of a set of input and output
instructions. The input instructions are evaluated by the controller as being true or
false. In turn, the controller sets the output instructions to true or false.
instruction set: The set of general purpose instructions available with a given
controller.
I/O (Inputs and Outputs): Consists of input and output devices that provide
and/or receive data from the controller.
jump: Change in normal sequence of program execution, by executing an
instruction that alters the program counter (sometimes called a branch). In ladder
programs a JUMP (JMP) instruction causes execution to jump to a labeled rung.
ladder logic: A program written in a format resembling a ladder-like diagram. The
program is used by a programmable controller to control devices.
lease significant bit (LSB): The digit (or bit) in a binary word (code) that carries
the smallest value of weight. For the analog controllers, 16-bit two’s complement
binary codes are used in the I/O image in the card.
LED (Light Emitting Diode): Used as status indicator for processor functions and
inputs and outputs.
LIFO (Last-In–First-Out): The order that data is entered into and retrieved from a
file.
low byte: Bits 0–7 of a word.
logic: A process of solving complex problems through the repeated use of simple
functions that can be either true or false. General term for digital circuits and
programmed instructions to perform required decision making and computational
functions.
Master Control Relay (MCR): A mandatory hardwired relay that can be
de-energized by any series-connected emergency stop switch. Whenever the MCR
is de-energized, its contacts open to de-energize all application I/O devices.
mnemonic: A simple and easy to remember term that is used to represent a
complex or lengthy set of information.