Glossary
nonfatal error
NOT
A
hardware or software error that produces a warning but does not stop the PC
from operating.
A logic operation which inverts the status of the operand. For example, AND
NOT indicates an AND operation with the opposite of the actual status of the op
-
erand bit.
octal
OFF
A
number system where all numbers are expressed in base 8, i.e., numbers are
written using only numerals 0 through 7.
The status of an input or output when a signal is said not to be present. The OFF
state is generally represented by a low voltage or by non-conductivity, but can be
defined as the opposite of either.
OFF delay
The delay between the time when a signal is switched OFF (e.g., by an input
device or PC) and the time when the signal reaches a state readable as an OFF
signal (i.e., as no signal) by a receiving party (e.g., output device or PC).
offset
ON
A positive or negative value added to a base value such as an address to specify
a desired value.
The status of an input or output when a signal is said to be present. The ON state
is generally represented by a high voltage or by conductivity, but can be defined
as the opposite of either.
ON delay
The delay between the time when an ON signal is initiated (e.g., by an input de
vice or PC) and the time when the signal reaches a state readable as an ON sig
nal by a receiving party (e.g., output device or PC).
-
-
on-line removal
operand
Removing
eration.
a
Rack-mounted Unit for replacement or maintenance during PC op
-
The values designated as the data to be used for an instruction. An operand can
be input as a constant expressing the actual numeric value to be used or as an
address to express the location in memory of the data to be used.
operating error
An error that occurs during actual PC operation as opposed to an initialization
error, which occurs before actual operations can begin.
optical connector
optical fiber cable
OR
A connector designed to be connected to an optical fiber cable.
Cable made from light conducting filaments used to transmit signals.
A
logic operation whereby the result is true if either of two premises is true, or if
both are true. In ladder-diagram programming the premises are usually ON/OFF
states of bits or the logical combination of such states called execution condi-
tions.
output
The signal sent from the PC to an external device. The term output is often used
abstractly or collectively to refer to outgoing signals.
Output Block
A Unit used in combination with a Remote Interface to create an I/O Terminal. An
Output Block provides mounting positions for replaceable relays. Each relay can
be selected according to specific output requirements.
output device
output point
An external device that receives signals from the PC System.
The point at which an output leaves the PC System. Output points correspond
physically to terminals or connector pins.
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