Encoder and a method of encoding for partial response channels

An encoder and a method of encoding successive data words into successive code words for transmission through a channel is provided. The encoder maps a first portion of each successive data word unchanged into a first portion of a corresponding one of the successive code words and maps a second portion of each successive data word into a second portion of a corresponding one of the code words according to a selected code. The successive code words are concatenated to form an encoded bit stream having a plurality of bit positions. The selected code imposes a run length constraint on the successive code words such that the encoded bit stream has a maximum possible run of ten consecutive binary zeroes in adjacent ones of the plurality of bit positions and imposes an interleave constraint on the selected code words such that the encoded bit stream has a maximum possible run of ten consecutive binary zeroes in every other one of the plurality of bit positions.