Coding method and apparatus using quaternary codes

A method for digital transmission of data over a partial response channel using a quaternary alphabet, comprising:

• (A) encoding k-bit data bytes to be transmitted into m-symbol code words by:
• forming a v-state machine according to a v-state transition diagram generating a first set of quaternary symbol sequences that is part of a second set of quaternary symbol sequences derived from a u-state transition diagram, the running digital sum of the sequences of said second set assuming values from a finite set of integers, such that each of the v states is associated with 2.sup.k transitions, each transition corresponding to an m-symbol code word, the number of consecutive identical symbols in any sequence of said m-symbol words being limited to a first given value, and the running digital sum in a sequence of such m-symbol codes words being limited to one of a plurality of second given values, thereby enforcing a spectral null in the code spectrum;
• encoding in said v-state machine a k-bit data byte into an m-symbol code word;
• and
• generating a next state of said v-state machine depending on its current state and the last encoded byte;
• (B) transmitting said encoded data over said channel;
• and
• (C) decoding said transmitted data by:
• generating the most likely sequence of m-symbol words that can be derived from said u-state transition diagram;
• and
• mapping said m-symbol words into k-bit data bytes.

A method for storing data in a multi-level memory using a quaternary alphabet, comprising:

• (A) encoding k-bit data bytes to be stored into m-symbol code words by:
• forming a v-state machine according to a v-state transition diagram generating a first set of quaternary symbol sequences that is part of a second set of quaternary symbol sequences derived from a u-state transition diagram, the running digital sum of the sequences of said second set assuming values from a finite set of integers, such that each of the v states is associated with 2.sup.k transitions, each transition corresponding to an m-symbol code word, the number of consecutive identical symbols in any sequence of said m-symbol code words being limited to a first given value, and the running digital sum in a sequence of such m-symbol code words being limited to one of a plurality of second given values, thereby enforcing a spectral null in the code spectrum;
• encoding in said v-state machine a k-bit data byte into an m-symbol code word;
• and
• generating a next state of said v-state machine depending on its current state and the last encoded byte;
• (B) storing said encoded data in said multi-level memory;
• and
• (C) upon reading said memory, decoding said stored data by:
• generating the most likely sequence of m-symbol words that can be derived from said u-state transition diagram;
• and
• mapping said m-symbol words into k-bit data bytes.

An encoder for encoding k-bit data bytes into m-symbol quaternary code words wherein a v-state machine formed according to a v-state transition diagram generates a first set of quaternary symbol sequences that are included in a second set of quaternary symbol sequences derived from a u-state transition diagram, the running digital sum of said sequences of the second set assuming values from a finite set of integers, such that each of the v states is associated with 2K transitions, each transition corresponding to an m-symbol quaternary code word, said encoder comprising:

• input means for receiving and storing at least one k-bit data byte to be encoded;
• encoding means for encoding said k-bit data bytes into 2 m-bit bytes, said 2 m-bit bytes being associated with transitions corresponding to said m-symbol quaternary code words;
• and
• converter means for converting said 2 m-bit bytes into m-symbol quaternary code words.

A digital transmission system for transmission of data over a partial response channel utilizing a quaternary alphabet, said data encoded in a v-state machine formed according to a v-state transition diagram which generates a first set of quaternary symbol sequences that are included in a second set of quaternary symbol sequences derived from a u-state transition diagram, the running digital sum of said sequences of the second set assuming values from a finite set of integers, such that each of the v states is associated with 2K transitions, each transition corresponding to an m-symbol quaternary code word, said digital transmission system comprising:

• input means for receiving and storing at least one k-bit data byte to be encoded;
• encoding means for encoding said k-bit data bytes into 2 m-bit bytes, said 2 m-bit bytes being associated with transitions corresponding to said m-symbol quaternary code words;
• converter means for converting said 2 m-bit bytes into m-symbol quaternary code words;
• a partial response channel for transmission of sequences of said m-symbol quaternary code words;
• detector means for generating from received channel output samples the most likely sequence of m-symbol quaternary words that can be derived from said u-state transition diagram and transforming said m-symbol quaternary words into 2 m-bit words;
• and
• decoder means coupled to an output of said detector means for mapping said 2 m-bit words into k-bit data bytes.

A storage system for storing data in a multi-level memory utilizing a quaternary alphabet, said data encoded in a v-state machine formed according to a v-state transition diagram which generates a first set of quaternary symbol sequences that are included in a second set of quaternary symbol sequences derived from a u-state transition diagram, the running digital sum of said sequences of the second set assuming values from a finite set of integers, such that each of the v states is associated with 2K transitions, each transition corresponding to an m-symbol quaternary code word, said storage system comprising:

• input means for receiving and storing at least one k-bit data byte to be encoded;
• encoding means for encoding said k-bit data bytes into 2 m-bit bytes, said 2 m-bit bytes being associated with transitions corresponding to said m-symbol quaternary code words;
• converter means for converting said 2 m-bit bytes into m-symbol quaternary code words;
• a multi-level memory means for storing sequences of said m-symbol quaternary code words;
• detector means for generating from received memory means output samples the most likely sequence of m-symbol quaternary words that can be derived from said u-state transition diagram and transforming said m-symbol quaternary words into 2 m-bit words;
• and
• decoder means coupled to an output of said detector means for mapping said 2 m-bit words into k-bit data bytes.

A method for digital transmission of data over a partial response channel using a quaternary alphabet, comprising:

• (A) encoding k-bit data bytes to be transmitted into m-symbol code words by:
• forming a v-state machine according to a v-state transition diagram generating a first set of quaternary symbol sequences that is part of a second set of quaternary symbol sequences derived from a u-state transition diagram, the running digital sum of the sequences of said second set assuming values from a finite set of integers, such that each of the v states is associated with 2.sup.k transitions, each transition corresponding to an m-symbol code word;
• encoding in said v-state machine a k-bit data byte into an m-symbol code word;
• and
• generating a next state of said v-state machine depending on its current state and the last encoded byte;
• (B) transmitting said encoded data over said channel;
• and
• (C) decoding said transmitted data by:
• generating and detecting the most likely sequence of m-symbol words that can be derived from said u-state transition diagram;
• and
• block decoding and mapping said generated and detected m-symbol words into k-bit data bytes.

A method for storing data in a multi-level memory using a quaternary alphabet, comprising:

• (A) encoding k-bit data bytes to be stored into m-symbol code words by:
• forming a v-state machine according to a v-state transition diagram generating a first set of quaternary symbol sequences that is part of a second set of quaternary symbol sequences derived from a u-state transition diagram, the running digital sum of the sequences of said second set assuming values from a finite set of integers, such that each of the v states is associated with 2.sup.k transitions, each transition corresponding to an m-symbol code word;
• encoding in said v-state machine a k-bit data byte into an m-symbol code word;
• and
• generating a next state of said v-state machine depending on its current state and the last encoded byte;
• (B) storing said encoded data in said multi-level memory;
• and
• (C) upon reading said multi-level memory, decoding said stored data by:
• generating and detecting the most likely sequence of m-symbol words that can be derived from said u-state transition diagram;
• and
• block decoding and mapping said generated and detected m-symbol code words into k-bit data bytes.