Rockwell Automation 1747-PTxx Getting Started Guide for HHT - Manual (Page 69)

Glossary
G–2
input device: A device, such as a pushbutton or a switch, that supplies data
through input circuits to a programmable controller.
input scan: A part of the SLC’s operating cycle. Status of the input
modules are loaded into the Input data file.
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 SLC as
being true or false. In turn, the SLC sets the output instructions to true or
false.
ladder logic: A program written in a format resembling a ladder–like
diagram. The program is used by a programmable controller to control
devices.
memory: An area in either an HHT or processor that stores the ladder
program (progam and data files).
memory pak: A circuit board that goes into the back of the HHT containing
the software and language to operate the HHT.
mnemonic: A three–letter abbreviation for a ladder programming
instruction.
modular controller: SLC 500 system consisting of a power supply, racks,
CPU, and input and output modules.
module: An interchangeable plug–in device that may be inserted into a rack.
network: A series of devices connected by a communication medium.
offline: Describes devices not under direct communication. For example,
when programming with an HHT.
online: Describes devices under direct communication. For example, when
the HHT is monitoring the program file in a SLC. Also, a function in the
HHT to establish communications with an SLC after using the WHO screen.
operating cycle: The sequential order of operations performed by the
processor when in the run mode.
OTE (OuTput Energize): An instruction that energizes when a rung is true
and de–energizes when a rung is false.
output device: A device, such as a pilot light or a motor starter coil, that
receives data from the programmable controller.
output scan: A part of the SLC’s operating cycle. During this scan the
output data file information is transferred to the output modules.
processor: See CPU.
processor file: The set of Program and Data Files used by the SLC to
control output devices. Only one processor file may be stored in the SLC at
a time. In HHT terminology program is equivalent to processor file.
processor overhead: An internal portion of the operating cycle used for
house–keeping and set–up purposes.
program: The set of Program and Data Files used by the SLC to control
output devices. Only one processor file may be stored in the SLC at a time.
In HHT terminology program is equivalent to processor file.