Glossary
data transfer
debug
Moving data from one memory location to another, either within the same device
or between different devices connected via a communications line or network.
A process by which a draft program is corrected until it operates as intended.
Debugging includes both the removal of syntax errors, as well as the fine-tuning
of timing and coordination of control operations.
decimal
A number system where numbers are expressed to the base 10. In a PC all data
is ultimately stored in binary form, four binary bits are often used to represent
one decimal digit, via a system called binary-coded decimal.
decrement
default
Decreasing a numeric value, usually by 1.
A value automatically set by the PC when the user does not specifically set
another value. Many devices will assume such default conditions upon the appli
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cation of power.
destination
The location where an instruction places the data on which it is operating, as op
posed to the location from which data is taken for use in the instruction. The loca
tion from which data is taken is called the source.
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digit
A unit of storage in memory that consists of four bits.
DIN track
A
rail designed to fit into grooves on various devices to allow the devices to be
quickly and easily mounted to it.
DIP switch
Dual in-line package switch, an array of pins in a signal package that is mounted
to a circuit board and is used to set operating parameters.
distributed control
A automation concept in which control of each portion of an automated system is
located near the devices actually being controlled, i.e., control is decentralized
and ‘distributed’ over the system. Distributed control is a concept basic to PC
Systems.
DM Area
A data area used to hold only word data. Words in the DM area cannot be ac-
cessed bit by bit.
DM word
A word in the DM Area.
downloading
The process of transferring a program or data from a higher-level or host com-
puter to a lower-level or slave computer. If a Programming Device is involved,
the Programming Device is considered the host computer.
Dummy I/O Unit
EEPROM
An I/O Unit that has no functional capabilities but that can be mounted to a slot on
a
Rack so that words can be allocated to that slot. Dummy I/O Units can be used
to avoid changing operand addresses in programs by reserving words for a slot
for future use or by filling a slot vacated by a Unit to which words have already
been allocated.
Electrically erasable programmable read-only memory; a type of ROM in which
stored data can be erased and reprogrammed. This is accomplished using a
special control lead connected to the EEPROM chip and can be done without
having to remove the EEPROM chip from the device in which it is mounted.
electrical noise
EM Area
Random variations of one or more electrical characteristics such as voltage, cur
rent, and data, which might interfere with the normal operation of a device.
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Extended Data Memory Area; an area that can be optionally added to certain
PCs to enable greater data storage. Functionally, the EM Area operates like the
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OMRON [ OMRON ELECTRONICS LLC ]
