METHOD AND APPARATUS FOR ARITHMETIC OPERATIONS

摘要

It is an object of the present invention to provide an arithmetic logic unit that can perform a sum-of-products operation in a reduced number of processing cycles without carrying out data transfer and additions even in obtaining a single result from a plurality of divided input data words. Data words X and Y are input. A product of the high-order bits of X and Y is calculated using first decoder 511, first selector 521, first partial product generator 531 and first full adder 541. A product of the low-order bits of X and Y is also calculated using second decoder 512, second selector 522, second partial product generator 532 and second full adder 542. These products are adaptively shifted at a shifter 55 and then added up with a fed back data word Z at a third full adder 56 and a carry-propagation adder 58. In this manner, the data word Z, representing the result of the sum-of-products operation, is obtained. <IMAGE>