Glossary
I/O verification error
I/O word
A error generated by a disagreement between the Units registered in the I/O
table and the Units actually mounted to the PC.
A
word in the CIO area that is allocated to a Unit in the PC System and is used to
hold I/O status for that Unit.
IBM PC/AT or compatible
initialize
A computer that has similar architecture to, that is logically compatible with, and
that can run software designed for an IBM PC/AT computer.
Part of the startup process whereby some memory areas are cleared, system
setup is checked, and default values are set.
input
The signal coming from an external device into the PC. The term input is often
used abstractly or collectively to refer to incoming signals.
input bit
A bit in the CIO area that is allocated to hold the status of an input.
Input Block
A Unit used in combination with a Remote Interface to create an I/O Terminal. An
Input Block provides mounting positions for replaceable relays. Each relay can
be selected according to specific input requirements.
input device
input point
An external device that sends signals into the PC System.
The point at which an input enters the PC System. Input points correspond phys
-
ically to terminals or connector pins.
input signal
A
change in the status of a connection entering the PC. Generally an input signal
is said to exist when, for example, a connection point goes from low to high volt
-
age or from a nonconductive to a conductive state.
Input Terminal
instruction
An I/O Terminal that provides input points.
A
direction given in the program that tells the PC of the action to be carried out,
and the data to be used in carrying out the action. Instructions can be used to
simply turn a bit ON or OFF, or they can perform much more complex actions,
such as converting and/or transferring large blocks of data.
interface
An interface is the conceptual boundary between systems or devices and usual-
ly 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.
interrupt (signal)
A signal that stops normal program execution and causes a subroutine to be run
or other processing to take place.
Interrupt Input Unit
IOIF
A Rack-mounting Unit used to input external interrupts into a PC System.
An acronym for I/O Interface Unit.
IOM (Area)
A collective memory area containing all of the memory areas that can be ac-
cessed by bit, including timer and counter Completion Flags. The IOM Area in
-
cludes all memory area memory addresses between 0000 and 0FFF.
JIS
An acronym for Japanese Industrial Standards.
jump
A type of programming where execution moves directly from one point in a pro
-
gram to another, without sequentially executing any instructions in between.
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