Method and apparatus for viterbi detection of generalized partial response signals including two-way add/compare/select for improved channel speed

Abstract

Apparatus is provided for implementing high-speed and area efficient architectures for Viterbi detection of generalized partial response signals including two-way add/compare/select for improved channel speed. The two-way add/compare/select includes a two-way compare for comparing first and second state metric input values and a pair of two-way adds in parallel with the two-way compare for respectively adding the first and second state metric input values with a second input value. The second input value includes a time varying term or a constant term. The time varying terms are expressed as outputs Z of a partial matched filter or as outputs W of a matched filter. A multiplexer is coupled to the pair of two-way adds, the multiplexer receiving a selectable input controlled by the two-way compare. A pair of shifts coupled between the pair of two-way adds and the multiplexer receive a shift control input for providing metric bounding to avoid underflow. The two-way compare for comparing first and second state metric input values can include a hard shift for providing an add for the first state metric input value and then a compare between a resultant first state metric input value and the second state metric input value.