Memory controller and method of accessing flash memory

A method of accessing a flash memory, for use in a memory controller of a data storage device, the method comprising:

• storing data to the flash memory of the data storage device via a storage program;
• obtaining a channel value read from the flash memory of the data storage device;
• obtaining a codeword difference, and calculating a syndrome according to the codeword difference,
• during each LDPC (low-density parity check) decoding iterative operation, performing the following steps:
• determining a syndrome weight according to the channel value and the syndrome from the check-node circuit;
• obtaining a previous codeword generated by a previous LDPC decoding iterative operation;
• determining a flipping strategy of a bit-flipping algorithm for each codeword bit in the previous codeword according to the syndrome weight and a predetermined threshold, and flipping one or more codeword bits in the previous codeword according to the flipping strategy to generate an updated codeword;
• and
• subtracting the previous codeword from the updated codeword to generate the codeword difference.

A memory controller, for use in a data storage device, the memory controller comprising:

• a variable-node circuit, configured to obtain a channel value read from a flash memory of the data storage device;
• and
• a check-node circuit, configured to obtain a codeword difference from the variable-node circuit, and to calculate a syndrome according to the codeword difference,
• wherein during each LDPC (low-density parity check) decoding iterative operation, the variable-node circuit executes the following steps:
• determining a syndrome weight according to the channel value and the syndrome from the check-node circuit;
• obtaining a previous codeword generated by a previous LDPC decoding iterative operation;
• determining whether each codeword bit in the previous codeword has been flipped according to the channel value and the previous codeword;
• selecting a first flipping-strategy lookup table and a second flipping-strategy lookup table for the codeword bits that have been flipped and the codeword bits that have not been flipped in the previous codeword, wherein the first flipping-strategy lookup table is different from the second flipping-strategy lookup table;
• determining a flipping strategy of a bit-flipping algorithm for each codeword bit in the previous codeword according to the syndrome weight, a predetermined threshold, and the selected first flipping-strategy lookup table or the second flipping-strategy lookup table, and flipping one or more codeword bits in the previous codeword according to the flipping strategy to generate an updated codeword;
• and
• subtracting the previous codeword from the updated codeword to generate the codeword difference.