Glossary
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be changed. However, the program or data can be read as many times as de-
sired.
routing table Tables of setting that specify what networks a device is a member of and what
nodes must be passed through to reach other specific networks. See local net-
work table and relay network table.
RS-232C interface An industry standard for serial communications.
RS-422 interface An industry standard for serial communications.
scan The process used to execute a ladder-diagram program. The program is ex-
amined sequentially from start to finish and each instruction is executed in turn
based on execution conditions. The scan also includes peripheral processing,
I/O refreshing, etc. The scan is called the cycle with CV-series PCs.
scan time The time required for a single scan of a ladder-diagram program.
self diagnosis A process whereby the system checks its own operation and generates a warn-
ing or error if an abnormality is discovered.
series A wiring method in which Units are wired consecutively in a string. In Link Sys-
tems wired through Link Adapters, the Units are still functionally wired in series,
even though Units are placed on branch lines.
servicing The process whereby the PC provides data to or receives data from external de-
vices or remote I/O Units, or otherwise handles data transactions for Link Sys-
tems.
set The process of turning a bit or signal ON.
set value The value from which a decrementing counter starts counting down or to which
an incrementing counter counts up (i.e., the maximum count), or the time from
which or for which a timer starts timing. Set value is abbreviated as SV.
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.
software switch See memory switch.
Special I/O Unit A Unit that is designed for a specific purpose. Special I/O Units include Position
Control Units, High-speed Counter Units, Analog I/O Units, etc.
SRAM Static random access memory; a data storage media.
subroutine A group of instructions placed separate from the main program and executed
only when called from the main program or activated by an interrupt.
SV Abbreviation for set value.
synchronous execution Execution of programs and servicing operations in which program execution
and servicing are synchronized so that all servicing operations are executed
each time the programs are executed.
syntax The form of a program statement (as opposed to its meaning). For example, the
two statements, LET A=B+B and LET A=B*2 use different syntaxes, but have
the same meaning.
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