Glossary
484
Ladder Support Software A
software
package that provides most of the functions of the Factory Intelligent
Terminal on an IBM AT, IBM XT, or compatible computer.
LAN An acronym for local area network.
leftmost (bit/word) The
highest numbered bits of a group of bits, generally of an entire
word, or the
highest
numbered words of a group
of words. These bits/words are often called
most-significant bits/words.
Link Adapter A
Unit used to connect communications lines, either to branch the lines or to con
-
vert between different types of cable. There are two types of Link Adapter:
Branching Link Adapters and Converting Link Adapters.
link A
hardware or software connection formed between two Units.
“Link” can refer
either
to a part of the physical connection between two Units (e.g., optical links in
Wired
Remote I/O Systems) or a software connection created to data existing
at
another location (Network Data Links).
linkable slot A
slot on either a CPU or Expansion I/O Backplane to which a Link Unit can be
mounted. Backplanes differ in the slots to which Link Units can be mounted.
Link System A
system that
includes one or more of the following systems: Remote I/O Sys
-
tem, PC Link System, Host Link System, or Net Link System.
Link Unit Any
of the Units used to connect a
PC to a Link System. These are Remote I/O
Units, I/O Link Units, PC Link Units, Host Link Units, and Net Link Units.
load The
processes of copying data either from an external device or from a storage
area
to an
active portion of the system such as a display buf
fer
. Also, an output
device connected to the PC is called a load.
local area network A network consisting of nodes or positions in a loop arrangement. Each node
can
be any one of a number of
devices, which can transfer data to and from each
other.
logic block A
group of instructions that is logically related in a ladder-diagram program and
that requires logic block instructions to relate it to other instructions or logic
blocks.
logic block instruction An
instruction used to locally
combine the execution condition resulting from a
logic block with a current execution condition. The current execution condition
could
be the
result of a single condition, or of another logic block. AND Load and
OR Load are the two logic block instructions.
logic instruction Instructions
used to logically
combine the content of two words and output the
logical results to a specified result word. The logic instructions combine all the
same-numbered
bits in the two words and output the
result to the bit of the same
number in the specified result word.
loop A
group of instructions that
can be executed more than once in succession (i.e.,
repeated) depending on an execution condition or bit status.
LR area A
data area that is used in a PC Link System so that data can be transferred be
-
tween
two or more PCs.
If a PC Link System is not used, the LR area is available
for use as work bits.
LSS Abbreviation for Ladder Support Software.
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