Glossary
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data link Allows for the connection of up to 32 PCs in a Net Link System where each is
contributing information to a common memory area. Data links may be estab-
lished in the LR and/or DM memory areas.
debugging The process of checking for errors in a program.
default condition The original condition of a function or system. For example, the FIT’s default
condition is to start from its hard drive, but this default condition can be changed
so that it starts from a floppy disk drive.
distributed control An automation concept in which control of each portion of an automated system
is located near the devices actually being controlled, i.e., control is decentralized
and “distributed” over the system. Distributed control is a concept basic to PC
Systems.
EEPROM [E(lectrically) E(rasable) P(rogrammable) R(ead) O(nly) M(emory)] A type of
ROM in which stored data can be erased and reprogrammed. This is accom-
plished using a special control lead connected to the EEPROM chip and can be
done without having to remove the EEPROM chip from the device in which it is
mounted.
electrical noise Electric ‘static’ that can disturb electronic communications. The ‘snow’ that can
appear on a TV screen is an example of the effects of electrical noise.
EPROM [E(rasable) P(rogrammable) R(ead) O(nly) M(emory)] A type of ROM in which
stored data can be erased, by ultraviolet light or other means, and repro-
grammed.
Expansion I/O Unit An I/O Unit for a Package-type PC that provides more I/O points to the PC.
factory computer A general-purpose computer, usually quite similar to a business computer, that
is used in automated factory control.
flag A bit that is turned ON and OFF automatically by the system in order to provide
status information.
High-speed Counter A Special I/O Unit. A High Speed Counter Unit counts independently of the PC’s
cycle time. This allows counting of very short, fast signals.
host computer A computer that is used to transfer data to or receive data from a PC in a Host
Link system. The host computer is used for data management and overall sys-
tem control. Host computers are generally small personal or business comput-
ers.
A computer that has similar architecture to, and is logically compatible with an
IBM PC/XT computer; and that can run software designed for that computer.
instruction line A succession of instructions which begins with a load instruction at the left bus
bar and ends at a right bus bar.
interface An interface is the conceptual boundary between systems or devices and usual-
ly 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
IBM AT/PC or compatible
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