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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.
terminator The code comprising an asterisk and a carriage return (* CR) which indicates the
end of a block of data, whether it is a single-frame or multi-frame block. Frames
within a multi-frame block are separated by delimiters.
timer A location in memory accessed through a TC bit and used to time down from the
timer’s set value. Timers are turned ON and reset according to their execution
conditions.
TM area A memory area used to store the results of a trace.
transmission distance The distance that a signal can be transmitted.
TR area A data area used to store execution conditions so that they can be reloaded later
for use with other instructions.
trace An operation whereby the program is executed and the resulting data is stored in
TM memory to enable step-by-step analysis and debugging.
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 transfer
is not changed.
trigger address An address in the program that defines the beginning point for tracing. The actu-
al 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 being
currently executed.
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.
unit number A number assigned to some Link Units and Special I/O Units to facilitate identifi-
cation when assigning words or other operating parameters to it.
watchdog timer A timer within the system that ensures that the cycle 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.
Wired Slave Rack A Slave Rack connected through a Wired Remote I/O Slave Unit.
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.
word multiplier A value between 0 and 3 that is assigned to a Master in a Remote I/O System so
that words can be allocated to non-Rack-mounting Units within the System. The