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Glossary
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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 devices
The devices to which terminals on I/O Units or Special I/O Units, or other
Units are connected. I/O devices may be either part of the Control System, if
they function to help control other devices, or they may be part of the con-
trolled system.
I/O Interface Unit
A Unit mounted to an Expansion I/O Rack in certain PCs to interface the Ex-
pansion I/O Rack to the CPU Rack.
I/O Link
Created in an Optical Remote I/O System to enable input/output of one or
two IR words directly between PCs. The words are input/output between the
PC controlling the Master and a PC connected to the Remote I/O System
through an I/O Link Unit or an I/O Link Rack.
I/O Link Unit
A Unit used with certain PCs to create an I/O Link in an Optical Remote I/O
System.
I/O point
The place at which an input signal enters the PC System, or at which an out-
put signal leaves the PC System. In physical terms, I/O points correspond to
terminals or connector pins on a Unit; in terms of programming, an I/O points
correspond to I/O bits in the IR area.
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 table
A table created within the memory of the PC that lists the IR area words allo-
cated to each Unit in the PC System. The I/O table can be created by, or mo-
dified from, a Programming Device.
I/O Unit
The most basic type of Unit mounted to a backplane to create a Rack. 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 word
A word in the IR area that is allocated to a Unit in the PC System.
IR area
A data area whose principal function is to hold the status of inputs coming
into the system and that of outputs that are to be set out of the system. Bits
and words in the IR that are used this way are called I/O bits and I/O words.
The remaining bits in the IR area are work bits.
JIS
Acronym for Japanese Industrial Standards.
jump
A type of programming where execution moves directly from one point in a
program to another, without sequentially executing any instructions inbe-
tween. Jumps are usually conditional on an execution condition.
jump number
A definer used with a jump that defines the points from and to which a jump
is to be made.
ladder diagram (program)
A form of program arising out of relay-based control systems that uses cir-
cuit-type diagrams to represent the logic flow of programming instructions.
The appearance of the program is similar to a ladder, and thus the name.