Memory system and control method thereof

Abstract

A memory system includes a nonvolatile memory including blocks as data erase units, a measuring unit which measures an erase time at which data in each block is erased, a block controller having a block table which associates a state value indicating one of a free state and a used state with the erase time for each block, a detector which detects blocks in which rewrite has collectively occurred within a short period, a first selector which selects a free block having an old erase time as a first block, a second selector which selects a block in use having an old erase time as a second block, and a leveling unit which moves data in the second block to the first block if the first block is included in the blocks detected by the detector.

1 . A memory system comprising:
 a nonvolatile memory including a plurality of blocks as data erase units;   a measuring unit which measures an erase time at which data in each block is erased;   a block controller having a block table which associates a state value indicating one of a free state and a used state with the erase time for each block;   a detector which detects blocks in each of which rewrite has frequently occurred within a short period;   a first selector which selects a free block having an old erase time as a first block, on the basis of an information in the block table;   a second selector which selects a block in use having an old erase time as a second block, on the basis of the information in the block table; and   a leveling unit which moves data in the second block to the first block if the first block is included in the blocks detected by the detector.