1. A finite impulse response filter, comprising: a plurality of taps arranged to receive and process a sequence of input data samples so as to generate a filter output, each tap comprising: a multiplier operating in ones complement arithmetic, the multiplier being coupled to multiply a respective input sample from the sequence by a respective equalization coefficient; and an adder, which sums an output from the multiplier, the taps being arranged in sequence so that the input sample to each of the taps, except to a first tap in the sequence, is delayed relative to a preceding tap in the sequence; an adjustment-accumulator coupled to receive the filter output and responsive thereto to generate an adjustment that is adapted to correct the filter output to a twos complement result; and an adjustment-adder which sums the adjustment and the filter output to generate a final output.