Patent ID: 6560625
Filing Date: 2003-05-06
Classification: G06F

Abstract:
A digital adder for adding a first n-bit operand A and a second n-bit operand B, with n=2m, comprising:a first block calculating couples of signals Pq and Gq based on the bits of rank q, Aq and Bq, of the first and second operands, with Pq=Aq+Bq and Gq=Aqâ€¢Bq; a second block formed of an array of normal elementary cells and auxiliary elementary cells of identical functions arranged in n rows and m columns; the normal elementary cells disposed in (row j, column i) of the second block where j is a set of integers from k2iâˆ’2i-1+1 to k2i, k being the set of integers from 1 to 2m-i, the first input couple to a normal elementary cell is the couple {Pj-1, Gj-1} if the normal elementary cell is located in column 1 of the second block and the output couple coming from the auxiliary elementary cell of column i-1 and of row (kâˆ’1)2i+1 of the second block otherwise, the second input couple to a normal elementary cell being the couple {Pj, Gj} if j=k2iâˆ’2i-1+1 or i=1, or the output couple coming from the normal elementary cell of row j and of column r+1, where r is defined such that 2r+1&lE;jâˆ’(kâˆ’1)2iâˆ’2iâˆ’1&lE;2r+1, otherwise; and the auxiliary elementary cells, disposed in column i, row j of the second block, j is the set of integers between (kâˆ’1)2i+1 and k2iâˆ’2i-1 inclusive, having inputs and outputs connected in parallel with those of the auxiliary elementary cells and normal elementary cells corresponding to a same value of k and of i, wherein: the first input couple of an auxiliary elementary cell is couple {Pj, Gj} if the auxiliary elementary cell is in column 1 of the second block and the output couple coming from the auxiliary elementary cell of column i-1 and of row (k-1)2i+1 of the second block otherwise, and the second input couple of an auxiliary elementary cell is couple {Pj+1, Gj+1} if the auxiliary elementary cell is in column 1 of the second block and the output couple coming from the auxiliary elementary cell of column iâˆ’1 and of row k2iâˆ’2i-1+1 of the second block otherwise.