Glossary
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interface An interface is the conceptual boundary between systems or devices and
usually involves changes in the way the communicated data is represented.
Interface devices such as NSBs perform operations such as changing the
coding, format, or speed of data.
I/O devices The devices which are connected to the terminals on I/O Units, Special I/O
Units, or Intelligent I/O Units. I/O devices may be part of the Control System if
they function to help control other devices, or they may be part of the con-
trolled system if they interact directly with it.
I/O point The place at which an input signal enters the PC System or an output signal
leaves the PC System. In physical terms, an I/O point corresponds to termi-
nals or connector pins on a Unit; in terms of programming, an I/O point corre-
sponds to an I/O bit in the IR area.
I/O table Diagram written to the IR memory area listing the type of I/O units controlled
by a PC. It must be cleared before programming or when I/O units are
changed. Tables can be read, verified, or transferred to a EPROM.
I/O Unit The most basic type of Unit mounted to a Backplane. I/O Units include Input
Units and Output Units, each of which is available in a range of specifica-
tions. I/O Units do not include Special I/O Units, Link Units, etc.
Limit Switch A switch that detects when an object has reached the limit of its movement
by actually making contact with the object. Limit Switches are fitted to electric
elevators, traveling cranes, etc. to indicate when a certain part of the equip-
ment has traveled to the specified limit.
Link Unit Any of the Units used to connect a PC to a Link System. These are Remote
I/O Units, I/O Link Units, PC Link Units, Host Link Units, and Net Link Units.
operating mode The Display Terminal Unit can operate in five different modes: Page Read,
Terminal, Dynamic Scan, Read/Write, and Self-Diagnosis.
page One complete Display Terminal Unit screen. Two hundred screens can be
stored on one RAM card.
parallel interface The parallel interface uses the RS-232 connector, but is not serial communi-
cation. When parallel mode is selected as the communication mode, up to 16
Display Terminal Units can be connected to a PC in parallel.
PC
An acronym for Programmable Controller.
PCB An acronym for printed circuit board.
PC Link Unit A Unit used to connect two or more PCs together so that they can exchange
data through their LR areas.
Photoelectric Switch A switch that uses light to detect the presence of an object.
Power Supply A Unit that mounts to a Backplane in a Rack PC. It provides power at the
voltage required by the other Units on the Rack.
printed circuit board A board onto which electrical circuits are printed for mounting into a comput-
er or electrical device.
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