Memory system
AssigneeToshiba Memory Corporation
InventorsTsukasa Tokutomi, Masanobu Shirakawa
Life of this patent
Estimating the term…
Abstract
According to one embodiment, a controller is configured to write four-bit data in each of memory cells, and read first data item from the memory cells through application of a first voltage to a word line. The controller is configured to read second data items by repeating a first operation of reading data including data of respective first bits of the memory cells through application of two voltages to the word line at different timings while changing the two voltages in each first operation from the two voltages in another first operation. The controller is configured to mask part of each of the second data items using the first data.
Claims13
A memory system comprising:
- a semiconductor memory including memory cells and a word line coupled to the memory cells;
- and
- a controller configured to:
- write four-bit data in each of the memory cells,
- read first data item from the memory cells through application of a first voltage to the word line,
- read a plurality of second data items by repeating a first operation of reading data including data of respective first bits of the memory cells through application of two voltages to the word line at different timings while changing the two voltages in each first operation from the two voltages in another first operation, and
- mask part of each of the second data items using the first data.
A memory system comprising:
- a semiconductor memory including memory cells and a word line coupled to the memory cells;
- and
- a controller configured to:
- write p-bit (where p is a natural number not lower smaller than 2) data in each of the memory cells,
- read a plurality of first data items by repeating a first operation of reading data including data in the memory cells through application of a first voltage to the word line at different timings while changing the first voltage in each first operation from the first voltage in another first operation,
- determine a plurality of first counts of memory cells estimated to have threshold voltages respectively corresponding to a plurality of voltages within a first range based on the first data items,
- detect, from the first counts, one or two or more second counts that are local minimum within the first range,
- select, when the two or more second counts are detected, a third count from the two or more second counts that are nearest to a number of the memory cells×Y/2p (where Y is a natural number not more than 2p), and
- use a voltage corresponding to the third count to determine whether a threshold voltage of one of the memory cells is higher than a Yth lowest boundary voltage of 2p−1 boundary voltages.
Dependencies are inferred from the claim text.