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Glossary
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Duplex System
A C2000H PC System that uses a Duplex CPU.
Duplex Unit
The Unit that coordinates the CPU activities of a Duplex System.
electrical noise
Random variations of one or more electrical characteristics such as voltage,
current, and data, which might interfere with the normal operation of a de-
vice.
error code
A numeric code generated to indicate that an error exists, and something
about the nature of the error. Some error codes are generated by the system;
others are defined in the program by the operator.
exclusive OR
A logic operation whereby the result is true if one, and only one, of the prem-
ises is true. In ladder-diagram programming the premises are usually the ON/
OFF states of bits, or the logical combination of such states, called execution
conditions.
exclusive NOR
A logic operation whereby the result is true if both of the premises are true or
both of the premises are false. In ladder-diagram programming the premises
are usually the ON/OFF states of bits, or the logical combination of such
states, called execution conditions.
exection condition
The ON or OFF status under which an instruction is executed. The execution
condition is determined by the logical combination of conditions on the same
instruction line and up to the instruction currently being executed.
execution time
The time required for the CPU to execute either an individual instruction or
an entire program.
Expansion I/O Backplane
A Backplane which is used to create an Expansion I/O Rack.
Expansion I/O Rack
Part of a building-block PC, an Expansion I/O Rack is connected to either a
CPU Rack or another Expansion I/O Rack to increase the number of slots
available for mounting Units.
extended counter
A counter created in a program by using two or more count instructions in
succession. Such a counter is capable of counting higher than any of the
standard counters provided by the individual instructions.
extended timer
A timer created in a program by using two or more timers in succession.
Such a timer is capable of timing longer than any of the standard timers pro-
vided by the individual instructions.
Factory Intelligent Terminal
A programming device provided with advanced programming and debugging
capabilities to facilitate PC operation. The Factory Intelligent Terminal also
provides various interfaces for external devices, such as floppy disk drives.
fatal error
An error that stops PC operation and requires correction before operation
can continue.
FIT
Abbreviation for Factory Intelligent Terminal.
flag
A dedicated bit in memory that is set by the system to indicate some type of
operating status. Some flags, such as the carry flag, can also be set by the
operator or via the program.