Max-Log-MAP equivalence log likelihood ratio generation soft Viterbi architecture system and method

A Viterbi detector, comprising:

• an input terminal configured to receive a signal that represents a sequence of values;
• a register;
• and
• a circuit coupled to the input terminal and to the register, the circuit configured to,
• calculate a first set of branch lengths between first and second sets of possible sequence states according to a first set of branches, each branch originating from a respective state that represents a first sequence parity,
• calculate a second set of branch lengths between third and fourth sets of possible sequence states according to a second set of branches, each branch ending on a respective state that represents a second sequence parity,
• recover the sequence of values from the first and second sets of branch lengths, and
• load the recovered sequence into the register.

A disk-drive system comprising:

• a data-storage disk having a surface and configured to store information values;
• a motor coupled to the data-storage disk and configured to rotate the data-storage disk;
• a read head configured to generate a read signal;
• a read-head positioning assembly configured to move the read head over the surface of the data-storage disk;
• and
• a Viterbi detector coupled to the read head and configured to recover a sequence of the stored information values from the read signal by calculating a branch length between first and second potential states of the sequence, the first potential state representing a first parity of the sequence and the second potential state representing a second parity of the sequence.

A method comprising:

• receiving a signal that represents a sequence of values at an input terminal of a Viterbi detector;
• operating a circuit of the Viterbi detector for recovering the sequence of values from the signal by calculating a branch length between a first potential state of the sequence of values representing a first sequence parity and a second potential state of the sequence of values representing a second sequence parity;
• and
• operating the circuit of the Viterbi detector for loading the recovered sequence of values into a register of the Viterbi detector.

A disk-drive system comprising:

• a data-storage disk having a surface and configured to store information values;
• a motor coupled to the data-storage disk and configured to rotate the data-storage disk;
• a read head configured to generate a read signal;
• a read-head positioning assembly configured to move the read head over the surface of the data-storage disk;
• and
• a Viterbi detector coupled to the read head and comprising
• an input terminal configured to receive a signal that represents a sequence of values,
• a register, and
• a circuit coupled to the input terminal and to the register, the circuit configured to
• recover the sequence of values from the signal by calculating a branch length between a first potential state of the sequence of values representing a first sequence parity, and a second potential state of the sequence of values representing a second sequence parity, and
• load the recovered sequence of values into the register.