Method for identifying memory cells storing replacement data on a memory device

• US 6,820,185 B2
• Filed: 09/23/2002
• Issued: 11/16/2004
• Est. Priority Date: 09/15/2000
• Status: Expired due to Term

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: Matrix Semiconductor, Inc. (Western Digital Corporation)
• Inventors: Moore, Christopher S., Brown, Daniel T., March, Roger W.
• Primary Examiner(s): PORTKA, GARY J
• Application Number:
  US10/253,048
• Publication Number:
  US 20030023820A1
• Time in Patent Office: 785 Days
• Field of Search: 707/200, 707/205, 711/102, 711/103, 711/154, 711/201, 711/212, 711/220
• US Class Current: 711/201
• CPC Class Codes: G06F 11/1008 in individual solid state devices G06F11/1004 takes precedence
• CPC Class Codes: G06F 2003/0697 device management, e.g. handlers, drivers, I/O schedulers
• CPC Class Codes: G06F 3/0601 Interfaces specially adapted for storage systems
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/0631 by allocating resources to storage systems
• CPC Class Codes: G06F 3/0643 Management of files
• CPC Class Codes: G06F 3/0679 Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]
• CPC Class Codes: G06F 3/08 from or to individual record carriers, e.g. punched card , memory card, integrated circuit [IC] card or smart card
• CPC Class Codes: G11C 17/00 Read-only memories programmable only once; Semi-permanent stores, e.g. manually-replaceable information cards
• CPC Class Codes: Y10S 707/99934 Query formulation, input preparation, or translation
• CPC Class Codes: Y10S 707/99943 Generating database or data structure, e.g. via user interface
• CPC Class Codes: Y10S 707/99953 Recoverability
• CPC Class Codes: Y10S 707/99956 File allocation

Abstract

The preferred embodiments described herein provide a memory device and methods for use therewith. In one preferred embodiment, a method is presented for using a file system to dynamically respond to variability in an indicated minimum number of memory cells of first and second write-once memory devices. In another preferred embodiment, a method for overwriting data in a memory device is described in which an error code is disregarded after a destructive pattern is written. In yet another preferred embodiment, a method is presented in which, after a block of memory has been allocated for a file to be stored in a memory device, available lines in that block are determined. Another preferred embodiment relates to reserving at least one memory cell in a memory device for file structures or file system structures. A memory device is also provided in which file system structures of at least two file systems are stored in the same memory partition. Additionally, methods for permanently preventing modification of data stored in a memory device and for identifying memory cells storing data are disclosed.

Claims

1. A method for identifying memory cells storing replacement data in a memory device, the method comprising:

(a) providing a memory device comprising a plurality of memory cells, wherein some of the plurality of memory cells store previously-stored data and wherein memory cells adjacent to the memory cells that store the previously-stored data store an identification pattern;

(b) storing replacement data to replace the previously-stored data by overwriting some of the memory cells storing the identification pattern with the replacement data, wherein the remaining memory cells storing the identification pattern are adjacent to the memory cells storing the replacement data;

(c) identifying the memory cells storing the replacement data by identifying the remaining memory cells that are adjacent to the memory cells storing the identification pattern; and

(d) reading the replacement data instead of the previously-stored data;

wherein a set of memory cells storing the identification pattern are between the previously-stored data and the replacement data, and wherein (c) comprises identifying the memory cells storing the replacement data by identifying memory cells that are between the set of memory cells storing the identification pattern and the memory cells storing the identification pattern that are adjacent to the memory cells storing the replacement data.

2. A method for identifying memory cells storing replacement data in a memory device, the method comprising:

(a) providing a memory device comprising a plurality of memory cells, wherein some of the plurality of memory cells store previously-stored data and wherein memory cells adjacent to the memory cells that store the previously-stored data store an identification pattern;

(b) storing replacement data to replace the previously-stored data by overwriting some of the memory cells storing the identification pattern with the replacement data, wherein the remaining memory cells storing the identification pattern are adjacent to the memory cells storing the replacement data;

(c) identifying the memory cells storing the replacement data by identifying the remaining memory cells that are adjacent to the memory cells storing the identification pattern; and

(d) reading the replacement data instead of the previously-stored data;

wherein the replacement data is between a set of memory cells storing a predetermined pattern of data and memory cells storing the identification pattern, and wherein (c) comprises identifying the memory cells storing the replacement data by identifying memory cells that are between the set of memory cells storing the predetermined pattern of data and the memory cells storing the identification pattern that are adjacent to the replacement data.

3. A method for identifying memory cells storing replacement data in a memory device, the method comprising:

(a) providing a memory device comprising a plurality of memory cells, wherein some of the plurality of memory cells store previously-stored data;

(b) storing replacement data to replace the previously-stored data;

(c) storing an identifier in a set of memory cells contiguous with the memory cells that store the replacement data, the identifier indicating a number of memory cells contiguous with the identifier that store the replacement data;

(d) identifying the memory cells storing the replacement data by identifying the number of memory cells that are contiguous with the identifier; and

(e) reading the replacement data instead of the previously-stored data by reading the number of memory cells that are contiguous with the identifier.

4. The method of claim 3, wherein the identifier is stored at an end of the replacement data.

5. The method of claim 3, wherein the replacement data is stored before and after the identifier.

6. The method of claim 3, wherein the identifier is fixed.

7. The method of claim 3, wherein the identifier is dynamic.

8. The method of claim 3, wherein the identifier indicates whether the replacement data is valid.

9. A method for locating a pointer, the method comprising:

(a) providing a memory array comprising a plurality of lines of un-programmed memory cells;

(b) writing a first pointer pointing to a first location in the memory array, wherein the first pointer is written in a first line of un-programmed memory cells;

(c) writing a second pointer pointing to a second location in the memory array, wherein the second pointer is written in a second line of un-programmed memory cells, wherein the second line is adjacent to the first line and is adjacent to a third line of un-programmed memory cells, and wherein the second pointer replaces the first pointer; and

(d) locating the second pointer by identifying a line of programmed memory cells that is adjacent to the third line of un-programmed memory cells,

wherein each line comprises a minimum number of memory cells that can be written into during a write operation, and wherein the first and second pointers are each written in no more than one line.

10. The method of claim 9, wherein each line comprises a data region and an error code region.

11. The method of claim 10, wherein the error code region is hidden from a file system, whereby the file system writes data only in the data region and not in the error code region.

12. The method of claim 9, wherein the first location comprises a first file, and wherein the second location comprises a second file that replaces the first file.

13. The method of claim 9, wherein the first location comprises a description of a file, and wherein the second location comprises a new description of the file.

14. The method of claim 9, wherein the first location comprises a description of an entry to a calendar application, and wherein the second location comprises an updated entry to the calendar application.

15. The method of claim 9, wherein the first location comprises a description of a picture stored by a picture editing application, and wherein the second location comprises a replacement picture.

16. The method of claim 9, wherein the memory array comprises write-once memory cells.

17. The method of claim 9, wherein the memory array comprises a three-dimensional memory array.

18. The method of claim 9 further comprising, in response to a request to read the first memory location, reading the second memory location instead of the first memory location.