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Glossary
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SV Short for set value.
switching capacity The voltage/current that a relay can switch on and off.
syntax error An error in the way in which a program is written. Syntax errors can include
‘spelling’ mistakes (i.e., a function code that does not exit), mistakes in speci-
fying operands within acceptable parameters (e.g., specifying unwritable SR
bits as a destination), and mistakes in actual application of instructions (e.g.,
a call to a subroutine that does not exist).
system error An error generated by the system as opposed to one resulting from execu-
tion of an instruction designed to generate an error.
system error message An error message generated by the system as opposed to one resulting from
execution of an instruction designed to generate a message.
TC area A data area that can be used only for timers and counters. Each bit in the TC
area serves as the access point for the SV, PV, and Completion flag for the
timer or counter defined with that bit.
TC number A definer that corresponds to a bit in the TC area and used to define the bit
as either a timer or a counter.
terminal instruction An instruction placed on the right side of a ladder diagram that uses the final
execution condition on an instruction line(s).
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 ex-
ecution 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.
transfer The process of moving data from one location to another within the PC or
between 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.
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 prod-
uct 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 col-
lective 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 assign words
and sometimes other operating parameters to it.
watchdog timer A timer within the system that ensures that the cycle time stays within speci-
fied limits. When limits are reached, either warnings are given or PC opera-
tion is stopped depending on the particular limit that is reached. Although a
default value of 130 ms is automatically set for the basic time limit, this value
can be extended by the program.