Data reading method, storage controller and storage device

A storage controller, for controlling a storage device disposed with a rewritable non-volatile memory module, the storage controller comprises:

• a connection interface unit, configured to couple to a host system;
• a memory interface control circuit, configured to couple to the rewritable non-volatile memory module, wherein the rewritable non-volatile memory module comprises a plurality of word lines, each of the word lines is coupled to a plurality of memory cells, each of the memory cells comprises a plurality of physical pages, and each of the physical pages is configured to be programmed to have a bit value;
• a read assisting circuit unit;
• an error checking and correcting circuit;
• and
• a processor, coupled to the connection interface circuit, the memory interface control circuit, the read assisting circuit unit and the error checking and correcting circuit,
• wherein the processor is configured to select a target physical page of a target word line to perform a read operation on a target codeword stored by the target physical page, wherein a plurality of target memory cells of the target physical page are configured to respectively store a plurality of target bit values of the target codeword,
• wherein the processor is further configured to use a predetermined read voltage corresponding to the target physical page to read the target physical page to obtain a read codeword corresponding to the target physical page, wherein the error checking and correcting circuit is configured to perform a preset decoding operation on the read codeword to obtain a plurality of read codeword syndromes corresponding to the read codeword, wherein the read assisting circuit unit is configured to store the read codeword in a codeword buffer area and store a first one of the read codeword syndromes in a syndrome buffer area,
• wherein in response to the determination that a plurality of bit values of a last one of the read codeword syndromes are not all zero, the processor is further configured to use a first adjust read voltage corresponding to the predetermined read voltage to read again the target physical page to obtain a first adjust codeword corresponding to the target physical page, wherein the error checking and correcting circuit is further configured to perform the preset decoding operation on the first adjust codeword to obtain a plurality of first adjust codeword syndromes corresponding to the first adjust codeword, wherein the read assisting circuit unit is configured to store the first adjust codeword in the codeword buffer area and store a first one of the first adjust codeword syndromes in the syndrome buffer area,
• wherein in response to the determination that the bit values of the last one of the first adjust codeword syndromes are not all zero, the read assisting circuit unit is further configured to generate soft information of each of the target memory cells according to a plurality of codewords corresponding to the read operation in the codeword buffer area,
• wherein the read assisting circuit unit is further configured to identify a target confidence table corresponding to a size relative relation from a plurality of confidence tables corresponding to the target physical page according to the size relative relation among a plurality of syndromes in the syndrome buffer area, wherein the confidence tables respectively correspond to a plurality of modes of the size relative relation, and each of the confidence tables has a plurality of predetermined confidence values respectively corresponding to a plurality of soft information patterns,
• wherein the read assisting circuit unit is further configured to find a confidence value of each of the target memory cells from the target confidence table according to the plurality of soft information of the target memory cells,
• wherein the read assisting circuit unit is further configured to use the confidence values of the target memory cells to replace a plurality of log likelihood ratios corresponding to the target memory cells, and the error checking and correcting circuit is further configured to perform an adjusted preset decoding operation having the replaced log likelihood ratios on the plurality of soft information, so as to obtain a valid codeword corresponding to the target physical page and complete the read operation.

A storage device, comprising:

• a rewritable non-volatile memory module, wherein the rewritable non-volatile memory module comprises a plurality of word lines, and each of the word lines is coupled to a plurality of memory cells, each of the memory cells comprises a plurality of physical pages, and each of the physical pages is configured to be programmed to have a bit value;
• a memory interface control circuit, configured to couple to the rewritable non-volatile memory module,
• a processor, coupled to the memory interface control circuit, wherein the processor loads and executes a read assisting program code module to perform a data reading method, comprising steps of:
• selecting a target physical page of a target word line, so as to perform a read operation on a target codeword stored by the target physical page, wherein a plurality of target memory cells of the target physical page are configured to respectively store a plurality of target bit values of the target codeword;
• using a predetermined read voltage corresponding to the target physical page to read the target physical page to obtain a read codeword corresponding to the target physical page and performing a preset decoding operation on the read codeword to obtain a plurality of read codeword syndromes corresponding to the read codeword, wherein the read codeword is stored in a codeword buffer area, and a first one of the read codeword syndromes is stored in a syndrome buffer area;
• in response to the determination that a plurality of bit values of a last one of the read codeword syndromes are not all zero, using a first adjust read voltage corresponding to the predetermined read voltage to read again the target physical page to obtain a first adjust codeword corresponding to the target physical page and performing the preset decoding operation on the first adjust codeword to obtain a plurality of first adjust codeword syndromes corresponding to the first adjust codeword, wherein the first adjust codeword is stored in the codeword buffer area, and a first one of the first adjust codeword syndromes is stored in the syndrome buffer area;
• in response to the determination that a plurality of bit values of a last one of the first adjust codeword syndromes are not all zero, generating soft information of each of the target memory cells according to a plurality of codewords corresponding to the read operation in the codeword buffer area;
• identifying a target confidence table corresponding to a size relative relation from a plurality of confidence tables corresponding to the target physical page according to the size relative relation among a plurality of syndromes in the syndrome buffer area, wherein the confidence tables respectively correspond to a plurality of modes of the size relative relation, and each of the confidence tables has a plurality of predetermined confidence values respectively corresponding to a plurality of soft information patterns;
• finding a confidence value of each of the target memory cells from the target confidence table according to the plurality of soft information of the target memory cells;
• and
• using the confidence values of the target memory cells to replace a plurality of log likelihood ratios corresponding to the target memory cells in the preset decoding operation and performing an adjusted preset decoding operation having the replaced log likelihood ratios on the plurality of soft information, so as to obtain a valid codeword corresponding to the target physical page and complete the read operation.