NAND flash memory systems with efficient soft information interface

Patent metadata

Field	Value
Publication number	US-9467170-B2
Application number	US-201414267307-A
Country	US
Kind code	B2
Filing date	May 1, 2014
Priority date	May 17, 2013
Publication date	Oct 11, 2016
Grant date	Oct 11, 2016

Abstract

A controller for a nonvolatile memory device includes a transfer control module and a decoder module. The transfer control module is configured to request a read of data from a flash memory module. The data to be read includes data corresponding to a first codeword. The transfer control module is configured to receive hard decisions corresponding to the first codeword from the flash memory module. The transfer control module is configured to receive soft information corresponding to the first codeword from the flash memory module. Both the hard decisions corresponding to the first codeword and the soft information corresponding to the first codeword are received without receiving any intervening hard decisions or soft information corresponding to another codeword. The decoder module is configured to decode the first codeword using the hard decisions and the soft information corresponding to the first codeword.

First claim

What is claimed is:

1. A controller for a nonvolatile memory device, the controller comprising:
a transfer control module configured to
request a read of data from a flash memory module, wherein the data to be read includes data corresponding to a first codeword,
receive hard decisions corresponding to the first codeword from the flash memory module, and
receive soft information corresponding to the first codeword from the flash memory module,
wherein both the hard decisions corresponding to the first codeword and the soft information corresponding to the first codeword are received without receiving any intervening hard decisions or soft information corresponding to another codeword; and

a decoder module configured to decode the first codeword using (i) the hard decisions corresponding to the first codeword and (ii) the soft information corresponding to the first codeword.

2. The controller of claim 1 , wherein the decoder module is configured to begin decoding the first codeword prior to the transfer control module completing reception of hard decisions and soft information corresponding to a second codeword, wherein the second codeword is immediately subsequent to the first codeword.

3. The controller of claim 1 further comprising a buffer configured to store the hard decisions corresponding to the first codeword and the soft information corresponding to the first codeword, wherein a size of the buffer is smaller than a size of all hard decisions for a page of data.

4. The controller of claim 1 , wherein the decoder module is configured to begin decoding the first codeword after (i) the hard decisions corresponding to the first codeword and (ii) the soft information corresponding to the first codeword are received.

5. The controller of claim 1 , wherein a quantity of the soft information corresponding to the first codeword is an integer multiple of a quantity of the hard decisions corresponding to the first codeword.

6. The controller of claim 1 , wherein the transfer control module is configured to:
select a hard decision buffer of the flash memory module prior to receiving the hard decisions corresponding to the first codeword; and
select a soft information buffer of the flash memory module prior to receiving soft information corresponding to the first codeword.

7. The controller of claim 6 , wherein the transfer control module is configured to:
upon selecting the hard decision buffer of the flash memory module, request the data corresponding to the first codeword; and
upon selecting the soft information buffer of the flash memory module, request the data corresponding to the first codeword.

8. The controller of claim 1 , wherein the transfer control module is configured to:
request the data from the flash memory module at an address corresponding to the hard decisions of the first codeword; and
request the data from the flash memory module at an address corresponding to the soft information of the first codeword.

9. The controller of claim 1 , wherein the transfer control module is configured to instruct the flash memory module to transmit both hard decisions of a codeword and soft information of the codeword together without transmitting any intervening hard decisions or soft information corresponding to another codeword.

10. A nonvolatile memory device comprising:
a storage array of nonvolatile memory cells, wherein the nonvolatile memory cells are grouped into pages;
a buffer; and
an access control module configured to selectively (i) write data to a selected page of the pages or (ii) read data from the selected page into the buffer,
wherein reading data from the selected page includes
making hard decisions about states of nonvolatile memory cells in the selected page,
acquiring soft information about the states of the nonvolatile memory cells in the selected page, and
storing the hard decisions and the soft information into the buffer,

wherein the selected page includes data corresponding to a plurality of codewords, and
wherein the access control module is further configured to, for each codeword of the plurality of codewords, output the hard decisions corresponding to the codeword along with any soft information corresponding to the codeword without outputting any intervening hard decisions or soft information for any other ones of the plurality of codewords.

11. The nonvolatile memory device of claim 10 , wherein the access control module is configured to read data from the selected page in response to a read request from a controller.

12. The nonvolatile memory device of claim 11 , wherein the access control module is configured to identify the selected page in response to the read request, and wherein the access control module is configured to choose a first codeword of the selected page for output according to the read request.

13. A method of operating a controller for a nonvolatile memory device, the method comprising:
requesting a read of data from a flash memory module, wherein the data to be read includes data corresponding to a first codeword;
receiving hard decisions corresponding to the first codeword from the flash memory module;
receiving soft information corresponding to the first codeword from the flash memory module, wherein both the hard decisions corresponding to the first codeword and the soft information corresponding to the first codeword are received without receiving any intervening hard decisions or soft information corresponding to another codeword; and
decoding the first codeword using (i) the hard decisions corresponding to the first codeword and (ii) the soft information corresponding to the first codeword.

14. The method of claim 13 further comprising beginning decoding the first codeword prior to completing reception of hard decisions and soft information corresponding to a second codeword, wherein the second codeword is immediately subsequent to the first codeword.

15. The method of claim 13 further comprising storing the hard decisions corresponding to the first codeword and the soft information corresponding to the first codeword in a buffer, wherein a size of the buffer is smaller than a size of all hard decisions for a page of data.

16. The method of claim 13 further comprising beginning decoding the first codeword after reception is completed of (i) the hard decisions corresponding to the first codeword and (ii) the soft information corresponding to the first codeword.

17. The method of claim 13 , wherein a quantity of the soft information corresponding to the first codeword is an integer multiple of a quantity of the hard decisions corresponding to the first codeword.

18. The method of claim 13 further comprising:
selecting a hard decision buffer of the flash memory module prior to receiving the hard decisions corresponding to the first codeword; and
selecting a soft information buffer of the flash memory module prior to receiving soft information corresponding to the first codeword.

19. The method of claim 18 further comprising:
upon selecting the hard decision buffer of the flash memory module, requesting the data corresponding to the first codeword; and
upon selecting the soft information buffer of the flash memory module, requesting the data corresponding to the first codeword.

20. The method of claim 13 further comprising:
requesting the data from the flash memory module at an address corresponding to the hard decisions of the first codeword; and
requesting the data from the flash memory module at an address corres

Assignees

• Marvell World Trade Ltd

Inventors

• Chilappagari Shashi Kiran
• Burd Gregory

Classifications

• H03M13/3927

  Log-Likelihood Ratio [LLR] computation by combination of forward and backward metrics into LLRs · CPC title

• H03M13/458

  by updating bit probabilities or hard decisions in an iterative fashion for convergence to a final decoding result · CPC title

• H03M13/3746

  with iterative decoding · CPC title

• H03M13/1108

  Hard decision decoding, e.g. bit flipping, modified or weighted bit flipping · CPC title

• H03M13/3738

  with judging correct decoding · CPC title