An equal-length encoding and decoding method for unreliable state elimination of flash memory cells

A codec method and flash memory cell technology, applied in the field of solid-state storage, can solve problems such as code length changes, key bit position shifting in stored data, etc.

Active Publication Date: 2022-02-11
HARBIN INST OF TECH
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Problems solved by technology

The existing data modulation method for state elimination is based on variable-length coding, and its defect is that the bit flipping in the flash memory may lead to a change in the code length after decoding, which in turn leads to the change of the position of the key bit in the stored data. verb: move

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  • An equal-length encoding and decoding method for unreliable state elimination of flash memory cells
  • An equal-length encoding and decoding method for unreliable state elimination of flash memory cells
  • An equal-length encoding and decoding method for unreliable state elimination of flash memory cells

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[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them; based on this The embodiments in the invention, and all other embodiments obtained by persons of ordinary skill in the art without creative efforts, all belong to the scope of protection of the present invention.

[0040] The following uses image data as an example to illustrate the importance of key bit-sensitive data types to ensure that key bit positions do not move. figure 1 is a picture of a brand new block written to flash (with write / erase cycles of 0), figure 2 It is the picture recovered from the data read out immediately after writing, and the error between the two is 10 -5 Although the error rate is very low, it can be seen that there is seriou...

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Abstract

The present invention proposes an equal-length encoding and decoding method for eliminating the unreliable state of a flash memory cell. The cell data is preprocessed by an encoder, and then all the states of the multi-level cell are divided into 4 groups, and then according to the code segment The state combination in obtains the remapping encoding method; the information after remapping encoding is stored in different blocks of the flash memory: the decoder reversely maps the 3-cell code segment through step 3 into original data according to the flag bit; the present invention is based on the The characteristics of long coding ensure that the code lengths of all codewords are equal, that is, the original data stream will not fluctuate due to bit flips in the stored modulation data, and realize a data form that eliminates the target state for multi-level cells. A codec method for data storage in flash memory. One state can be eliminated for MLC type flash memory, and two states can be eliminated for TLC type flash memory.

Description

technical field [0001] The invention belongs to the field of solid-state storage, and in particular relates to an equal-length encoding and decoding method for eliminating unreliable states of flash memory cells. Background technique [0002] The current solid-state storage uses two types of multi-level cell NAND flash memory as MLC (Multi-Level Cell, which stores 2 bits of information in each cell) and TLC (Trinary-Level Cell, which stores 3 bits of information in each cell). Mainly, its reliability is closely related to the characteristics of the cell threshold voltage distribution after writing data. The patent of the present invention involves modulating the data form written into NAND flash memory, and optimizing the threshold voltage distribution in the same writing area as much as possible Cell programming to a more reliable state can significantly improve the reliability of NAND flash data storage in a variety of storage application scenarios. [0003] With the deve...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G06F11/10G11C29/42
CPCG06F11/1068G11C29/42
Inventor 魏德宝张京超朴哲龙冯骅乔立岩彭喜元
Owner HARBIN INST OF TECH
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