Abstract: A method for encoding a sequence of 16 bit digital data words into a sequence of 17 bit codewords in consonance with predetermined minimum zero run length (d), predetermined maximum zero run length (G) and maximum interleave zero run length (I) coding constraints of (d=0, G=6/I=7) for recording upon a magnetic medium within a magnetic recording channel is disclosed. The method includes dividing the 16 bit data word into an 8-bit A byte: a1, a2, a3, a4, a5, a6, a7, a8; and an 8-bit B byte b1, b2, b3, b4, b5, b6, b7, b8; separately testing the A and B bytes for violation of coding constraints, generating P and Q code bytes from the A and B bytes and inserting a center bit C of value one or zero between the P and Q code bytes to form the 17 bit codeword of a form p1, p2, p3, p4, p5, p6, p7, p8, C, q8, q7, q6, q5, q4, q3, q2, q1, in a manner minimizing hardware logic implementation.

Abstract: An EPR4 detector comprises a PR4 Viterbi detector and an EPR4 post-processor for improving estimated output sequence at an output of the PR4 Viterbi. The PR4 Viterbi detector produces digital estimates of coded digital information values into the channel in accordance with a path through a PR4 trellis and produces other path information relating to other paths through the PR4 trellis.