Memory system and memory control method

A memory system comprising:

• a non-volatile memory arranged to store an N-dimensional error-correction code in which at least one of symbols constituting a code is protected by N component code groups (N is an integer of 2 or more);
• a read information memory arranged to store read information to be read from the non-volatile memory;
• a syndrome value memory arranged to store a syndrome value corresponding to each of the M component codes (1≤i≤N, ni is the number of component codes included in an i-dimensional component code group, where M is the sum of ni) calculated from the read information stored in the read information memory;
• a correction information memory arranged to store, for the a-th component code (1≤a≤ni) of the i-dimensional component code group, a-th correction information indicating a location corrected by decoding processing of an a-th component code;
• a reliability information memory arranged to store a-th reliability information indicating reliability of a decoded word obtained in the decoding processing of the a-th component code;
• a low-reliability location information memory arranged to store a-th low-reliability location information indicating a location of the read information determined to have low reliability among pieces of the read information for each of the M component codes;
• and
• a memory controller configured to:
• determine the number of pieces of low-reliability location information, the number of pieces of low-reliability location information being the number of pieces of a-th low-reliability location information for each of the M component codes according to a value based on the number of component codes included in the first to N-th dimensional component code groups;
• determine a low-reliability location information address, the low-reliability location information address being an address on the low-reliability location information memory of the a-th low-reliability location information for each of the M component codes based on the number of pieces of the low-reliability location information;
• calculate the a-th low-reliability location information before calculating an a-th soft-input value, the a-th soft-input value being a soft-input value for the a-th component code;
• store the calculated a-th low-reliability location information in the low-reliability location information address of the low-reliability location information memory;
• calculate the a-th soft-input value based on the a-th correction information, the a-th reliability information, a syndrome value of the a-th component code, and the a-th low-reliability location information;
• calculate a decoded word of the a-th component code, the a-th correction information, and the a-th reliability information by inputting the a-th soft-input value and executing the decoding processing of the a-th component code;
• store the calculated a-th correction information and b-th correction information indicating a corrected location of a b-th component code (1≤b≤nj) in a j-th dimension (j≠i, 1≤j≤N) corrected by the decoding processing of the i-th component code in the correction information memory;
• store the calculated a-th reliability information in the reliability information memory;
• and
• output an output decoded word calculated from the read information, the correction information, and M pieces of the a-th reliability information.

A memory control method, for performing by a memory controller configured to control a non-volatile memory storing an N-dimensional error-correction code in which at least one of symbols constituting a code is protected by N component code groups (N is an integer of 2 or more), the method comprising:

• storing read information to be read from the non-volatile memory in a read information memory;
• storing a syndrome value corresponding to each of the M component codes (1≤i≤N, ni is the number of component codes included in an i-dimensional component code group, where M is the sum of ni) calculated from the read information stored in the read information memory in a syndrome value memory;
• storing, for the a-th component code (1≤a≤ni) of the i-dimensional component code group, a-th correction information indicating a location corrected by decoding processing of an a-th component code in a correction information memory;
• storing a-th reliability information indicating reliability of a decoded word obtained in the decoding processing of the a-th component code in a reliability information memory;
• and
• determining the number of pieces of correction information, the number of pieces of correction information being the number of pieces of the a-th correction information for each of the M component codes according to a value based on the number of component codes included in the first to N-th dimensional component code groups;
• determining a correction information address, the correction information address being an address on the correction information memory of the a-th correction information for each of the M component codes based on the number of pieces of the correction information;
• calculating an a-th soft-input value, the a-th soft-input value being a soft-input value for the a-th component code based on the a-th correction information, the a-th reliability information, and a syndrome value of the a-th component code;
• calculating a decoded word of the a-th component code, the a-th correction information, and the a-th reliability information by inputting the a-th soft-input value and executing decoding processing of the a-th component code;
• storing the calculated a-th correction information and b-th correction information indicating a corrected location of the b-th component code (1≤b≤nj) in a j-th dimension (j≠i, 1≤j≤N) corrected by the decoding processing of the i-th component code in the correction information address of the correction information memory;
• storing the calculated a-th reliability information in the reliability information memory;
• and
• outputting an output decoded word calculated from the read information, the correction information, and M pieces of the a-th reliability information.

A memory control method by a memory controller configured to control a non-volatile memory storing an N-dimensional error-correction code in which at least one of symbols constituting a code is protected by N component code groups (N is an integer of 2 or more), the method comprising:

• storing read information to be read from the non-volatile memory in a read information memory;
• storing a syndrome value corresponding to each of the M component codes (1≤i≤N, ni is the number of component codes included in an i-dimensional component code group, where M is the sum of ni) calculated from the read information stored in the read information memory in a syndrome value memory;
• storing, for the a-th component code (1≤a≤ni) of the i-dimensional component code group, a-th correction information indicating a location corrected by decoding processing of an a-th component code in the correction information memory;
• storing a-th reliability information indicating reliability of a decoded word obtained in the decoding processing of the a-th component code in a reliability information memory;
• storing a-th low-reliability location information indicating a location of the read information determined to have low reliability among pieces of the read information in a low-reliability location information memory for each of the M component codes;
• determining the number of pieces of low-reliability location information, the number of pieces of low-reliability location information being the number of pieces of the a-th low-reliability location information for each of the M component codes according to a value based on the number of component codes included in the first to N-th dimensional component code groups;
• determining a low-reliability location information address, the low-reliability location information address being an address on the low-reliability location information memory of the a-th low-reliability location information for each of the M component codes based on the number of pieces of low-reliability location information;
• calculating the a-th low-reliability location information before calculating an a-th soft-input value, the a-th soft-input value being a soft-input value for the a-th component code;
• storing the calculated a-th low-reliability location information in the low-reliability location information address of the low-reliability location information memory;
• calculating the a-th soft-input value based on the a-th correction information, the a-th reliability information, a syndrome value of the a-th component code, and the a-th low-reliability location information;
• calculating a decoded word of the a-th component code, the a-th correction information, and the a-th reliability information by inputting the a-th soft-input value and executing decoding processing of the a-th component code;
• storing the calculated a-th correction information and b-th correction information indicating a corrected location of a b-th component code (1≤b≤nj) in a j-th dimension (j≠i, 1≤j≤N) corrected by the decoding processing of the i-th component code in the correction information memory;
• storing the calculated a-th reliability information in the reliability information memory;
• and
• outputting an output decoded word calculated from the read information, the correction information, and M pieces of the a-th reliability information.