Patent ID: 9460781
Filing Date: 2016-10-04
CPC Classification: G06F,G11C

Claim Text:
1. A memory system comprising: a non-volatile memory that includes four planes configured to be operable in a parallel, the plane including a plurality of word lines, each of the plurality of word lines being coupled to a plurality of memory cells, each of the plurality of the memory cells being capable of storing two bits of a first bit and a second bit, the first bit corresponding to a first page, the second bit corresponding to a second page; a memory interface configured to control reading and writing of data to the non-volatile memory; an encoder configured to generate eight code words; and a control unit configured to cause the memory interface to perform a first writing, a second writing after the first writing, and a fifth writing after the second writing, the fifth writing being configured to repeatedly perform a third writing and a fourth writing in sequence, wherein the first writing is configured to write a symbol included in one code word among the eight code words to the first page in a first word line among the plurality of word lines, the second writing is configured to write a symbol included in a code word identical to the code word used for the first writing to the first page in a word line adjacent to the first word line, the symbol being a symbol different from the symbol written by the first writing, the third writing is configured to write a symbol included in a code word different from a code word used for a writing performed immediately before among the first or the fourth writing to the second page in a word line on which writing to the first page has been executed oldest among word lines to which the second page has not been written, and the fourth writing is configured to write a symbol included in a code word identical to the code word used for the third writing to the first page in a word line adjacent to the word line adjacent to a word line in the third writing, the symbol being a symbol different from the symbol for the third writing, the word line being a word line to which data has not been written.