Glossary
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terminal instruction An instruction placed on the right side of a ladder diagram that uses the final
execution conditions of an instruction line.
timer A location in memory accessed through a TIM/CNT bit and used to time down
from the timer’s set value. Timers are turned ON and reset according to their
execution conditions.
TR area A data area used to store execution conditions so that they can be reloaded
later for use with other instructions.
TR bit A bit in the TR area.
trace An operation whereby the program is executed and the resulting data is stored
to enable step-by-step analysis and debugging.
trace memory A memory area used to store the results of trace operations.
transfer The process of moving data from one location to another within the PC, or be-
tween the PC and external devices. When data is transferred, generally a copy
of the data is sent to the destination, i.e., the content of the source of the trans-
fer is not changed.
transmission distance The distance that a signal can be transmitted.
trigger A signal used to activate some process, e.g., the execution of a trace opera-
tion.
trigger address An address in the program that defines the beginning point for tracing. The ac-
tual beginning point can be altered from the trigger by defining either a positive
or negative delay.
UM area The memory area used to hold the active program, i.e., the program that is be-
ing currently executed.
Unit In OMRON PC terminology, the word Unit is capitalized to indicate any product
sold for a PC System. Most of the names of these products end with the word
Unit.
unit number A number assigned to some Units to facilitate identification when assigning
words or other operating parameters.
unmasked bit A bit whose status is effective. See masked bit.
unsigned binary A binary value that is stored in memory without any indication of whether it is
positive or negative.
uploading The process of transferring a program or data from a lower-level or slave com-
puter to a higher-level or host computer. If a Programming Devices is involved,
the Programming Device is considered the host computer.
watchdog timer A timer within the system that ensures that the scan time stays within specified
limits. When limits are reached, either warnings are given or PC operation is
stopped depending on the particular limit that is reached.
WDT See watchdog timer.
word A unit of data storage in memory that consists of 16 bits. All data areas consists
of words. Some data areas can be accessed only by words; others, by either
words or bits.
word address The location in memory where a word of data is stored. A word address must
specify (sometimes by default) the data area and the number of the word that
is being addressed.
work area A part of memory containing work words/bits.
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