Run length limited encoding/decoding with robust resync

An encoder for producing a run length limited (RLL) code of binary bit signals from a series of unconstrained binary source signals in a structurally constrained environment, said code having a minimum of (d) and a maximum of (k) "0"s between adjacent "1" bits, comprising:

• a source for receiving said binary source signals;
• and
• an RLL encoder coupled to said source for receiving groups of said binary source signals and responding to said source groups of said binary source signals to provide RLL channel groups of binary signals encoded in said RLL code, said RLL channel groups comprising a stream of bits excluding the following patterns:
• 1) patterns having fewer "0" bits than said RLL (d) constraint;
• 2) patterns having more "0" bits than said RLL (k) constraint;
• 3) a Resync pattern having at least one string of consecutive "0" bits exceeding said RLL (k) constraint;
• and
• 4) patterns representing a bit shift from said Resync pattern comprising shifts of one or both "1" bits adjacent to said occurrence of at least one string of consecutive "0" bits, shifted to shorten said Resync pattern to within said (k) constraint.

A method for decoding a run length limited (d,k) encoded channel bit stream having at least one Resync pattern therein, said Resync pattern having a string of consecutive "0"s exceeding said (k) constraint of said RLL code, comprising:

• receiving said encoded channel bit stream;
• grouping said encoded channel bit stream into predetermined length sliding block groups;
• responding to said groups to decode patterns of said received bit stream;
• and
• detecting said Resync pattern and resolving bit shifts from said Resync pattern of one or both "1" bits adjacent to said occurrence of at least one string of consecutive "0" bits, shifted to shorten said Resync pattern to within said (k) constraint in favor of said Resync pattern, said detected Resync pattern synchronizing said sliding block groups.

A decoder for decoding a run length limited (d,k) encoded bit stream having at least one Resync pattern therein, said Resync pattern having a string of consecutive "0"s exceeding said (k) constraint of said RLL code, and for recovering said Resync pattern, comprising:

• an input for receiving said encoded bit stream;
• a sliding block decoder coupled to said input for decoding said encoded bit stream;
• and
• a Resync detector coupled to said input for recovering said Resync pattern, said Resync detector resolving patterns of said received bit stream which include said string of consecutive "0"s and one or two bit shorter strings of consecutive "0"s in favor of said Resync pattern to accommodate bit shifts from said Resync pattern of one or both "1" bits adjacent to said occurrence of at least one string of consecutive "0" bits, shifted to shorten said Resync pattern to within said (k) constraint.

An encoder/decoder for generating a robust Resync pattern into a channel bit stream of run length limited (d,k) bit signals, and for recovering said Resync pattern from said run length limited (d,k) encoded channel bit stream having at least one Resync pattern therein, comprising:

• a Resync generator for producing said Resync pattern, including at least one string of consecutive "0"s exceeding said RLL (k) constraint, into said channel bit stream;
• an RLL encoder for encoding said RLL (d,k) binary bit signals in said channel bit stream from a series of unconstrained binary source signals, said encoder excluding certain patterns from said RLL (d,k) channel bit stream, said certain patterns representing a bit shift from said Resync pattern of one or both "1" bits adjacent to said occurrence of at least one string of consecutive "0" bits, shifted to shorten said Resync pattern to within said (k) constraint;
• a channel coupled to said Resync generator and said RLL encoder for transmitting said encoded bit stream and for receiving said encoded bit stream;
• a data decoder coupled to said channel for decoding said encoded bit stream;
• and
• a Resync detector coupled to said channel for recovering said Resync pattern, said Resync detector resolving patterns of said received bit stream which include said string of consecutive "0"s and one or two bit shorter strings of consecutive "0"s in favor of said Resync pattern to accommodate bit shifts from said Resync pattern of one or both "1" bits adjacent to said occurrence of at least one string of consecutive "0" bits, shifted to shorten said Resync pattern to within said (k) constraint.

A data recording encoder/decoder for generating a robust Resync pattern into a data recording bit stream of run length limited (d,k) bit signals, and for recovering said Resync pattern from said recorded run length limited (d,k)encoded bit stream having at least one Resync pattern therein, comprising:

• a Resync generator for producing said Resync pattern, including at least one string of consecutive "0"s exceeding said RLL (k) constraint, into said channel bit stream;
• an RLL encoder for encoding said RLL (d,k) binary bit signals in said channel bit stream from a series of unconstrained binary source signals, said encoder excluding certain patterns from said RLL (d,k) channel bit stream, said certain patterns comprising said Resync pattern and patterns representing a bit shift from said Resync pattern of one or both "1" bits adjacent to said occurrence at least one string of consecutive "0" bits, shifted to shorten said Resync pattern to within said (k) constraint;
• a data storage device coupled to said Resync generator and said RLL encoder for recording said encoded bit stream and for retrieving said recorded encoded bit stream;
• a data decoder coupled to said data storage device for decoding said retrieved encoded bit stream;
• and
• a Resync detector coupled to said data storage device for recovering said Resync pattern, said Resync detector resolving patterns of said received bit stream which include said string of consecutive "0"s and one or two bit shorter strings of consecutive "0"s in favor of said Resync pattern to accommodate bit shifts from said Resync pattern of one or both "1" bits adjacent to said occurrence of at least one string of consecutive "0" bits, shifted to shorten said Resync pattern to within said (k) constraint.

A data recording medium having recorded binary signals, comprising:

• a recording medium;
• recorded streams of run length limited (d,k) constrained groups of binary signals excluding the following patterns:
• 1) patterns having fewer "0" bits than said RLL (d) constraint;
• 2) patterns having more "0" bits than said RLL (k) constraint;
• 3) a Resync pattern having at least one string of consecutive "0" bits exceeding said RLL (k) constraint;
• and
• 4) at least one pattern representing a bit shift from said Resync pattern comprising shifts of one or both "1" bits adjacent to said occurrence of at least one string of "0" bits, shifted to shorten said Resync pattern to within said (k) constraint;
• and
• at least one recorded said Resync pattern interspersed in said recorded streams of binary signals.