Omron CS1W-SLK11-21 - 06-2004 Manual page 189

operand
operating error
optical communications
OR
output
Output Block
output device
output point
output signal
Output Terminal
overflow
overwrite
parity
parity check
PLC
PLC configuration
PLC System
PCB
PLC Setup
172
Glossary
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.
An error that occurs during actual PLC operation as opposed to an initialization
error, which occurs before actual operations can begin.
A communications method in which signals are sent over optical fiber cable to
prevent noise interference and increase transmission distance.
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
conditions.
The signal sent from the PLC to an external device. The term output is often
used abstractly or collectively to refer to outgoing signals.
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 re-
lay can be selected according to specific output requirements.
An external device that receives signals from the PLC System.
The point at which an output leaves the PLC System. Output points correspond
physically to terminals or connector pins.
A signal being sent to an external device. Generally an output signal is said to
exist when, for example, a connection point goes from low to high voltage or
from a nonconductive to a conductive state.
An I/O Terminal that provides output points.
The state where the capacity of a data storage location has been exceeded.
Changing the content of a memory location so that the previous content is lost.
Adjustment of the number of ON bits in a word or other unit of data so that the
total is always an even number or always an odd number. Parity is generally
used to check the accuracy of data after being transmitted by confirming that
the number of ON bits is still even or still odd.
Checking parity to ensure that transmitted data has not been corrupted.
An acronym for Programmable Controller.
The arrangement and interconnections of the Units that are put together to
form a functional PLC.
With building-block PLCs, all of the Racks and independent Units connected
directly to them up to, but not including the I/O devices. The boundaries of a
PLC System are the PLC and the program in its CPU at the upper end; and the
I/O Units, Special I/O Units, Optical I/O Units, Remote Terminals, etc., at the
lower end.
An acronym for printed circuit board.
A group of operating parameters set in the PLC from a Programming Device
to control PLC operation.