Patent ID: 7003545
Filing Date: 2006-02-21
Classification: G06F

Abstract:
1. A method for computing a sum or difference and a carry-out of numbers in product-term based programmable logic comprising the steps of: (A) configuring a plurality of macrocells as a ripple carry chain in each of a plurality of logic blocks of a product-term based programmable logic device, wherein an output of a carry generator multiplexer of a first macrocell of said ripple carry chain in each of said plurality of logic blocks is presented as a carry input to a lookahead carry generator in each of said plurality of logic blocks; (B) generating (i) a portion of said sum or difference and (ii) a lookahead carry output in each of said plurality of logic blocks; (C) communicating said lookahead carry output of each of said logic blocks to a carry input of a next logic block; and (D) presenting said lookahead carry output of a last logic block as said carry-out.