Appeal No. 1997-1416
Application 08/277,386
The invention pertains to an apparatus for subtracting or
adding two thermometer coded words which each include a
plurality of bytes. In thermometer coding, the value of a
number is represented by a number of right justified “1" bits.
For example, the number “3" would be represented as 0111 in a
four bit system. Obviously, as the number to be represented
increases, the number of bits required to represent the number
grows rapidly. One way to reduce the amount of circuitry
necessary to operate on thermometer coded numbers is to code
each digit or byte of a number as a separate thermometer coded
value. For example, in the same four bit system, the number
“31" would be represented as 0111 0001 with each digit coded
separately.
Representative claim 17 is reproduced as follows:
17. A computer implemented method of subtracting two
thermometer coded words, comprising:
detecting a first borrowing condition in response to a
first word and a second word;
detecting a second borrowing condition in response to
said first and second words;
decreasing a value of a first most significant byte
corresponding to said first word in response to said first
borrowing condition;
-2-
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