Glossary
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unit number A number assigned to some Link Units and Special I/O Units to assign words
and sometimes other operating parameters to it.
watchdog timer A timer within the system that ensures that the scan time stays within speci-
fied limits. When limits are reached, either warnings are given or PC opera-
tion is stopped depending on the particular limit that is reached. Although a
default value of 130 ms is automatically set for the basic time limit, this value
can be extended by the program.
Wired Slave Rack A Slave Rack connected through a Wired Remote I/O Slave Unit.
word A unit of storage in memory that consists of 16 bits. All data areas consists of
words. Some data areas can be accessed by words; others, by either words
or bits.
word address The location in memory where a word of data is stored. A word address must
specify (sometimes by default) the data area and the number of the word that
is being addressed.
work bit A bit in a work word.
work word A word that can be used for data calculation or other manipulation in pro-
gramming, i.e., a ‘work space’ in memory. A large portion of the IR area is
always reserved for work words. Parts of other areas not required for special
purposes may also be used as work words, e.g., I/O words not allocated to
I/O Units.
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