Memory controller, memory system and memory control method

A memory system comprising:

• a non-volatile memory configured to store a code word;
• a memory interface configured to control reading/writing data from/into the non-volatile memory and perform a first reading and second reading, the first reading being reading the code word from the non-volatile memory by using a read voltage including a hard decision voltage which is a voltage used to make a hard decision of the code word stored in the non-volatile memory, the second reading being reading the code word from the non-volatile memory using a plurality of read voltages within a predetermined voltage range;
• a conversion unit configured to convert a reading result by the first reading into first likelihood information and convert a reading result by the second reading into second likelihood information;
• a decoding unit configured to perform decoding based on the first likelihood information or the second likelihood information;
• and
• a controller configured to make the memory interface perform the first reading, make the decoding unit perform the decoding based on the first likelihood information, and make the memory interface perform the second reading and make the decoding unit perform the decoding based on the second likelihood information in a case where the decoding based on the first likelihood information has been failed.