Patent ID: 6085212
Filing Date: 2000-07-04
Classification: G06F,H03M

Abstract:
A method for performing effective subtraction for a pair of floating point input values having an absolute exponent difference less than or equal to one, comprising:receiving a first mantissa portion corresponding to a first floating point input value and an inverted version of a second mantissa portion corresponding to a second floating point input value;adding said first mantissa portion and said inverted version of said second mantissa portion in order to produce a first output value and a second output value, wherein said first output value is equal to said first mantissa portion plus said inverted version of said second mantissa portion, and wherein said second output value is equal to said first output value plus one;generating a first plurality of preliminary selection signals indicative of either said first output value or said second output value, wherein each of said first plurality of preliminary selection signals is generated according to at least a portion of each of said first and second floating point input values;generating a first set of control signals using a carry in signal corresponding to a most significant bit position of said first output value;selecting one of said first plurality of preliminary selection signals as a final select value by utilizing said first set of control signals;selecting either said first output value or said second output value as a preliminary subtraction result according to said final select value.