1. An address generator for generating a sequence of digit reversed signals to be used in conjunction with a transform of N sample points and one or more radix values, the generator comprising: a reversed-field sequence generator for generating a series of binary-coded signals respectively representing the natural sequence of integers, i=0, 1, 2, 3,. .. , N-1, where N is a supplied variable, and wherein the bits in the least significant field of size log.sub.2 N bits of the generated signals are reversed from their natural order; and a digit unreversing unit, operatively coupled to the reversed-field sequence generator for associating subfields of each log.sub.2 N sized field generated by the reversed-field sequence generator with specific reversed digits and unreversing the bits of each such subfield which has a bit-width greater than one, thereby to produce the corresponding digit in nonreversed form; wherein said reversed-field sequence generator comprises: an adder having a first input port, a second input port and an output port for producing a sum signal representing the sum of first and second binary-coded signals applied respectively to the first and second adder input ports, said adder being a forward adder not having an ability to add backwards; feedback means for feeding the sum signal back to the second input port of the adder; a first bus twist for supplying a field-reversed signal whose unreversed version represents the variable value N/2 to the first input port of the adder; and a second bus twist for supplying a field-reversed version of the sum signal as an output of the reversed-field sequence generator.