Method of testing a modified booth multiplier, modified booth multiplier

Abstract

A modified Booth multiplier for multiplying an m-bit number X by an n-bit number Y comprises a Booth encoder for converter the number Y in groups of 3 bits which overlap by 1 bit into a series Y' of multiplication values whose number is equal to or substantially equal to half the number of bits of Y. There is also provided a multiplex circuit for forming partial products from the number X and said series Y' and a matrix configuration of full adders for adding the partial products in incremental positions. The design is such that the constituent components and the operation of the modified Booth multiplier can be tested by means of a very small number of test patterns which are generated in the Booth multiplier after application of a specific series of X,Y-values. Test patterns are generated for establishing static as well as dynamic errors in the combination formed by the Booth encoder and the multiplex circuit and also test patterns which are formed by specific partial products in order to establish static errors in the matrix configuration. In practice the modified Booth multiplier is usually constructed as a multiplier accumulator; in that case test patterns formed by partial products are also used for establishing static errors in the accumulator section.