Glossary
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Expansion I/O Backplane A Backplane used to create an Expansion I/O Rack.
Expansion I/O Rack Part of a Rack PC, an Expansion I/O Rack is connected to a CPU Rack to
increase the number of slots available for mounting Units.
Expansion I/O Unit An I/O Unit for a Package-type PC that provides more I/O points to the PC.
expansion slot Allows FIT to be modified by addition of optional circuit cards. These circuit
cards are made by OMRON and other companies to customize systems for
particular functions.
flag A bit that is turned ON and OFF automatically by the system in order to pro-
vide status information.
hardware error An error originating in the hardware structure (electronic components) of the
PC, as opposed to a software error, which originates in software (i.e., pro-
grams).
hexadecimal Number system used to represent numbers in base 16 with digits
0,1,2...9,A,B...F.
increment Increasing a numeric value.
indirect address An address whose contents indicates another address. The contents of the
second address will be used as the operand. Indirect addressing is possible
in the DM area only.
instruction execution time The time required to execute an instruction. The execution time for any one
instruction can vary with the execution conditions for the instruction and the
operands used within it.
instruction line A group of conditions that lie together on the same horizontal line of a ladder
diagram. Instruction lines can branch apart or join together to form instruction
blocks.
interface An interface is the conceptual boundary between systems or devices and
usually involves changes in the way the communicated data is represented.
Interface devices such as NSBs perform operations like changing the coding,
format, or speed of the data.
I/O capacity The number of inputs and outputs that a PC is able to handle. This number
ranges from around one hundred for smaller PCs to two thousand for the
largest ones.
I/O Control Unit A Unit mounted to the CPU Rack in certain PCs to monitor and control I/O
points on Expansion I/O Units.
I/O point The place at which an input signal enters the PC System or an output signal
leaves the PC System. In physical terms, an I/O point corresponds to termi-
nals or connector pins on a Unit; in terms of programming, an I/O point corre-
sponds to an I/O bit in the IR area.
I/O Unit The most basic type of Unit mounted to a Backplane. I/O Units include Input
Units and Output Units, each of which is available in a range of specifica-
tions. I/O Units do not include Special I/O Units, Link Units, etc.
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