Rockwell Automation 1747-PTxx Getting Started Guide for HHT - Manual (Page 70)

Glossary
Getting Started Guide
for HHT
G–3
program file: The area within a processor file that contains the ladder logic
program.
program mode: When the SLC is not executing the processor file and all
outputs are de–energized.
program scan: A part of the SLC’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.
rack (chassis): A hardware assembly that houses devices such as I/O
modules, processor modules, and power supplies.
read: To acquire data from a storage place. For example, the processor
READs information from the input data file to solve the ladder program.
restore: To download (transfer) a program from the HHT to an SLC.
run mode: When the processor file in the SLC 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.
SLC (Small Logic Controller): A controller that comes in one of two
styles: fixed or modular.
slot: The area in a rack that a module plugs into.
software: Executable programming package used to develop SLC ladder
diagrams.
status: The condition of a circuit or system, represented as logic 0 (OFF) or
1 (ON).
terminal: A point on an I/O module that external I/O devices, such as a
pushbutton or pilot light, are wired to.
true: The status of an instruction that provides a continuous logical path on
a ladder rung.
upload: To transfer a program from an SLC to the HHT memory.
WHO: A utility in the HHT that lets you view the devices on your DH–485
network.
write: To copy data to a storage device. For example, the processor
WRITEs the information from the output data file to the output modules.
eXamine If Closed (XIC): An input instruction that is logically true when
the status of the bit located at its address is a 1; false when it’s a 0.
eXamine If Open (XIO): An input instruction that is logically true when
the status of the bit located at its address is a 0; false when it’s a 1.