Patent ID: 11893238
Assignee: KIOXIA CORPORATION
Field: Computer technology (Electrical engineering)
Classification: CPC G | IPC G

Claim 0:
1. A method of controlling a nonvolatile semiconductor memory comprising a plurality of blocks, each of the blocks comprising a plurality of memory cells, each of the memory cells being configured to store i-bits data, i being equal to or larger than 2, the method comprising:
performing a write operation in a first mode in response to a request from a host device,
calculating a total amount of valid data written in the memory system based on an amount of valid data stored in each block, the valid data being data assigned to logical addresses,
determining whether to perform a first operation based on a result of the calculation of the total amount of the valid data, the first operation including reading data from one of the blocks written in the first mode and writing the read data to another one of the blocks in a second mode; and
reading data from one of the blocks written in the second mode and writing the read data to another one of the blocks in the second mode, as a second operation, wherein
only j-bits data is written into each of memory cells in the first mode, and
k-bits data is written into each of memory cells in the second mode, k being larger than j and equal to or smaller than i.