Glossary
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gramming devices, such as Programming Consoles, and there are non-dedi-
cated programming devices, such as a host computer.
PROM
[P(rogrammable) R(ead) O(nly) M(emory)] A type of ROM into which the pro-
gram or data may be written after manufacture, by a customer, but which is fixed
from that time on.
PROM Writer
A PROM Writer is a device used to write data to ROM, PROM, and EPROM stor-
age chips.
Proximity Switch
A switch that uses magnetic induction to measure the distance of a metallic ob-
ject from the front of the switch.
Rack PC
A PC that is composed of Units mounted to one or more Racks. This configura-
tion is the most flexible, and most large PCs are Rack PCs. A Rack PC is the
opposite of a Package-type PC, which has all of the basic I/O, storage, and con-
trol functions built into a single package.
RAM
[R(andom) A(ccess) M(emory)] RAM will not retain data when power is discon-
nected. Therefore data should not be stored in RAM.
register/registered
Storing text and graphics in the RAM/ROM card from a personal computer or the
ASCII Unit. Graphics that have been written to the RAM/ROM card are referred
to as registered messages.
Remote I/O Unit
A Unit that extends the distance an Expansion I/O Unit can be from the CPU Unit.
ROM
[R(ead) O(nly) M(emory)] A type of digital storage that cannot be written to. A
ROM chip is manufactured with its program or data already stored in it, and it can
never be changed. However, the program or data can be read as many times as
desired.
switching capacity
The voltage/current that relay can switch ON and OFF.
stepping motor
An output device that rotates according to signals from the Control System. The
rotation is very precise and occurs in pre-defined “steps.”
switch
An input device that sends either an ON or OFF signal to the Control System. A
switch can be operated either by a person or by the movement of a piece of
equipment or material.
system configuration
The arrangement in which Units in a System are connected. This term refers to
the conceptual arrangement and wiring together of all the devices needed to
comprise the System. In OMRON terminology, system configuration is used to
describe the arrangement and connection of the Units comprising a Control Sys-
tem that includes one or more PCs.
Unit
In OMRON PC terminology, the word Unit is capitalized to indicate any product
sold for a PC System. though most of the names of these products end with the
word Unit, not all do, e.g., a Remote Terminal is referred to in a collective sense
as a Unit. Context generally makes any limitations of this word clear.
watchdog timer
A special timer inside the CPU Unit that monitors the PC’s cycle time. The watch-
dog timer sets a flag if the cycle time becomes longer than a certain specified
value. This is useful if the correct operation of your System depends on a certain
maximum cycle time.
word
In digital circuits, a group of bits. Usually a word consists of four, eight, or sixteen
bits. In C-series PCs, a word consists of sixteen bits. Words can be used to store
data, or they can be used for I/O.
work bits
Bits in the IR area that are not being used for input or output. These bits can be
used in the program in any way desired.
