Patent ID: 6308195
Filing Date: 2001-10-23
Classification: G06F

Abstract:
A 4-2 compressor circuit for calculating the sum of first through fourth inputs and a carry input applied thereto and for furnishing the summation result and first and second carries generated during said calculation of the sum, said 4-2 compressor circuit comprising:input value inverting means for inverting said third and fourth inputs only if the third input is logic 0 and the fourth input is logic 1;summation means for calculating the logical exclusive OR of any two of said first through fourth inputs and said carry input applied to said 4-2 compressor, the logical exclusive OR of any two of the first logical exclusive OR and the remaining three inputs, the logical exclusive OR of any two of the second logical exclusive OR and the remainder, and the logical exclusive OR of the third logical exclusive OR and the remainder, and for furnishing the fourth logical exclusive OR as said summation result;carry calculating means for calculating said first carry from said first, third, and fourth inputs, and for furnishing said first carry; andselecting means for selecting either said carry input or said second input according to the logical exclusive OR of the logical exclusive OR of any two of said first through fourth inputs and the logical exclusive OR of the remainder, and for furnishing the selected one as said second carry.