US Patent 8250437 Memory system and control method for the same

A memory system in an embodiment having a host and a memory card, including: a plurality of semiconductor memory cells, each cell being configured to store N-bit coded data based on threshold voltage distributions; an LLR table storage section configured to store a first LLR table that consists of normal LLR data corresponding to predetermined threshold voltages and a second LLR table that consists of LLR data such that two LLRs at each location corresponding to each location in the first LLR table at which a sign is inverted between two adjacent LLRs are “0”; and a decoder configured to perform decoding processing through probability-based repeated calculations using an LLR.