Decoding method, memory storage device and memory control circuit unit

Patent metadata

Field	Value
Publication number	US-9715429-B1
Application number	US-201615249487-A
Country	US
Kind code	B1
Filing date	Aug 29, 2016
Priority date	Jul 7, 2016
Publication date	Jul 25, 2017
Grant date	Jul 25, 2017

Abstract

A decoding method, a memory storage device and a memory control circuit unit are provided. The decoding method includes: reading first data from a plurality of first memory cells of a rewritable non-volatile memory module based on a first read voltage level and performing a first decoding operation; estimating a channel status of the rewritable non-volatile memory module and obtaining a second read voltage level according to the channel status if the first decoding operation fails, and the second read voltage level is different from the first read voltage level, and the second read voltage level is different from an optimal read voltage level; and reading second data from the plurality of first memory cells based on the second read voltage level and performing a second decoding operation. Therefore, an encoding efficiency can be improved.

First claim

What is claimed is:

1. A decoding method for a rewritable non-volatile memory module comprising a plurality of memory cells, the decoding method comprising:
reading first data from a plurality of first memory cells among the plurality of memory cells based on a first read voltage level;
performing a first decoding operation on the first data;
estimating a channel status of the rewritable non-volatile memory module and obtaining a second read voltage level according to the channel status if the first decoding operation fails, wherein the second read voltage level is different from the first read voltage level, and the second read voltage level is different from an optimal read voltage level;
reading second data from the plurality of first memory cells based on the second read voltage level; and
performing a second decoding operation on the second data.

2. The decoding method of claim 1 , wherein the step of estimating the channel status of the rewritable non-volatile memory module and obtaining the second read voltage level according to the channel status comprises:
obtaining a first number of a memory cell among the plurality of first memory cells meeting a default condition; and
determining the second read voltage level according to the first number.

3. The decoding method of claim 2 , wherein the step of obtaining the first number of the memory cell among the plurality of first memory cells meeting the default condition comprises:
obtaining the first number of the memory cell among the plurality of first memory cells meeting the default condition according to a first type data of the first data.

4. The decoding method of claim 2 , wherein the step of determining the second read voltage level according to the first number comprises:
obtaining a ratio of the first number and a total number of the plurality of first memory cells; and
determining the second read voltage level according to the ratio.

5. The decoding method of claim 2 , wherein a value of the first number is positively correlated to a voltage difference value between the first read voltage level and the second read voltage level.

6. The decoding method of claim 1 , further comprising:
performing an optimal read voltage level tracking operation to obtain the optimal read voltage level if the second decoding operation fails;
reading third data from the plurality of first memory cells based on the optimal read voltage level, wherein a total number of an error bit of the third data is less than a total number of an error bit of the second data; and
performing a third decoding operation on the third data.

7. The decoding method of claim 1 , wherein the decoding method is adapted to the rewritable non-volatile memory module having a three-dimensional memory cell array.

8. The decoding method of claim 1 , wherein a first voltage difference value between a threshold read voltage level of the rewritable non-volatile memory module and a predetermined read voltage level of the rewritable non-volatile memory module is greater than half of a second voltage difference value,
wherein the second voltage difference value is a voltage difference value between a threshold voltage upper terminal and a threshold voltage lower terminal corresponding to a state of an initial threshold voltage distribution of the plurality of first memory cells,
wherein a total number of an error hit comprised by data read from the plurality of first memory cells based on the threshold read voltage level approaches an error bit number corresponding to a maximum error correction capability of a memory control circuit unit for controlling the rewritable non-volatile memory module.

9. A memory storage device, comprising:
a connection interface unit, configured to couple to a host system;
a rewritable non-volatile memory module, comprising a plurality of memory cells; and
a memory control circuit unit, coupled to the connection interface unit and the rewritable non-volatile memory module,
wherein the memory control circuit unit is configured to transmit a first read command sequence which instructs reading first data from a plurality of first memory cells among the plurality of memory cells based on a first read voltage level,
wherein the memory control circuit unit is further configured to perform a first decoding operation on the first data,
wherein the memory control circuit unit is further configured to estimate a channel status of the rewritable non-volatile memory module and obtaining a second read voltage level according to the channel status if the first decoding operation fails, wherein the second read voltage level is different from the first read voltage level, and the second read voltage level is different from an optimal read voltage level,
wherein the memory control circuit unit is further configured to transmit a second read command sequence which instructs reading second data from the plurality of first memory cells based on the second read voltage level,
wherein the memory control circuit unit is further configured to perform a second decoding operation on the second data.

10. The memory storage device of claim 9 , wherein the operation of the memory control circuit unit estimating the channel status of the rewritable non-volatile memory module and obtaining the second read voltage level according to the channel status comprises:
obtaining a first number of a memory cell among the plurality of first memory cells meeting a default condition; and
determining the second read voltage level according to the first number.

11. The memory storage device of claim 10 , wherein the operation of the memory control circuit unit obtaining the first number of the memory cell among the plurality of first memory cells meeting the default condition comprises:
obtaining the first number of the memory cell meeting the default condition according to a first type data of the first data.

12. The memory storage device of claim 10 , wherein the operation of the memory control circuit unit determining the second read voltage level according to the first number comprises:
obtaining a ratio of the first number and a total number of the plurality of first memory cells; and
determining the second read voltage level according to the ratio.

13. The memory storage device of claim 10 , wherein a value of the first number is positively correlated to a voltage difference value between the first read voltage level and the second read voltage level.

14. The memory storage device of claim 9 , wherein the memory control circuit unit is further configured to perform an optimal read voltage level tracking operation to obtain the optimal read voltage level if the second decoding operation fails,
wherein the memory control circuit unit is further configured to transmit a third read command sequence which instructs reading third data from the plurality of first memory cells based on the optimal read voltage level, wherein a total number of an error bit of the third data is less than a total number of an error bit of the second data,
wherein the memory control circuit unit is further configured to perform a third decoding operation on the third data.

15. The memory storage device of claim 9 , wherein the rewritable non-volatile memory module has a three-dimensional memory cell array.

16. The memory storage device of claim 9 , wherein a first voltage difference value between a threshold read voltage level of the rewritable non-volatile memory module and a predetermined read voltage level of the rewritable non-volatile memory module is greater than half of a second vol

Assignees

• Phison Electronics Corp

Inventors

• Lin Wei

Classifications

• G06F11/1048 Primary

  using arrangements adapted for a specific error detection or correction feature · CPC title

• G06F3/064

  Management of blocks · CPC title

• G06F11/1068 Primary

  in sector programmable memories, e.g. flash disk (G06F11/1072 takes precedence) · CPC title

• G11C29/52

  Protection of memory contents; Detection of errors in memory contents · CPC title

• G11C16/26

  Sensing or reading circuits; Data output circuits · CPC title