Glossary
133
I/O response time The time required for an output signal to be sent from the PC in response to an
input signal received from an external device.
I/O Terminal A Remote I/O Unit connected in a Wired Remote I/O System to provide a limited
number of I/O points at one location. There are several types of I/O Terminals.
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 specifications.
I/O Units do not include Special I/O Units, Link Units, etc.
I/O verification error An error generated by a disagreement between the Units registered in the I/O
table and the Units actually mounted to the PC.
I/O word 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 A computer that has similar architecture to, that is logically compatible with, and
that can run software designed for an IBM PC/AT computer.
initialize 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 An external device that sends signals into the PC System.
input point 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 An I/O Terminal that provides input points.
instruction 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 A Rack-mounting Unit used to input external interrupts into a PC System.
IOIF An acronym for I/O Interface Unit.
To Next Page
Loading...
Need help?
General
