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Glossary
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slot A position on a Rack (Backplane) to which a Unit can be mounted.
software error An error that originates in a software program.
software protect A means of protecting data from being changed that uses software as opposed
to a physical switch or other hardware setting.
source The location from which data is taken for use in an instruction, as opposed to the
location to which the result of an instruction is to be written. The latter is called
the destination.
Special I/O Unit A dedicated Unit that is designed for a specific purpose. Special I/O Units in-
clude Position Control Units, High-Speed Counter Units, Analog I/O Units, etc.
SR area A data area in a PC used mainly for flags, control bits, and other information pro-
vided about PC operation. The status of only certain SR bits may be controlled
by the operator, i.e., most SR bits can only be read.
SSS Abbreviation for SYSMAC Support Software.
subroutine A group of instructions placed after the main program and executed only if called
from the main program or activated by an interrupt.
subroutine number A definer used to identify the subroutine that a subroutine call or interrupt acti-
vates.
SV Abbreviation for set value.
switching capacity The maximum voltage/current that a relay can safely 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 exist), mistakes in specify-
ing operands within acceptable parameters (e.g., specifying reserved SR bits as
a destination), and mistakes in actual application of instructions (e.g., a call to a
subroutine that does not exist).
SYSMAC Support Software A software package installed on a IBM PC/AT or compatible computer to func-
tion as a Programming Device.
system configuration The arrangement in which Units in a system are connected.
system error An error generated by the system, as opposed to one resulting from execution 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 ex-
ecution 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.