Memory device and method for storing and reading a file system structure in a write-once memory array

• US 7,003,619 B1
• Filed: 06/08/2001
• Issued: 02/21/2006
• Est. Priority Date: 04/09/2001
• 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., Tringali, J. James, Schneider, James E., March, Roger W.
• Primary Examiner(s): Peikari, B. James
• Assistant Examiner(s): Li, Zhuo H.
• Application Number:
  US09/877,719
• Time in Patent Office: 1,719 Days
• Field of Search: 711102-103, 711/115, 711/4, 711/100, 711/108, 711/154, 711/156, 707202-203, 369/47.1, 369/47.27, 369/47.34, 369/13.01, 714746-747, 365/185.33, 365/185.29, 36518514-18515, 365/189.01, 365/234, 365/236
• US Class Current: 711/102
• CPC Class Codes: G11C 17/146 Write once memory, i.e. allowing changing of memory content by writing additional bits
• CPC Class Codes: G11C 17/16 using electrically-fusible links
• CPC Class Codes: G11C 7/1006 Data managing, e.g. manipulating data before writing or reading out, data bus switches or control circuits therefor
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

The preferred embodiments described herein provide a memory device and method for storing and reading a file system structure in a write-once memory array. In one preferred embodiment, a plurality of bits representing a file system structure is inverted and stored in a write-once memory array. When the inverted plurality of bits is read from the memory array, the bits are inverted to provide the file system structure bits in their original, non-inverted configuration. With this preferred embodiment, a file system structure can be updated to reflect data stored in the memory array after the file system structure was written. Other preferred embodiments are provided, and each of the preferred embodiments described herein can be used alone or in combination with one another.

Claims

1. A method for storing and reading a file system structure in a write-once memory array, the method comprising:

(a) inverting a plurality of bits representing a file system structure irrespective of a number of logic one bits in the plurality of bits;

(b) storing the inverted plurality of bits in a write-once memory array;

(c) reading the inverted plurality of bits from the write-once memory array; and

(d) inverting the inverted plurality of bits read from the write-once memory array.

2. The method of claim 1 further comprising storing an inverted plurality of bits representing an update to the file system structure.

3. The method of claim 1, wherein act (a) is performed by a data storage device coupled with a memory device comprising the write-once memory array.

4. The method of claim 3, wherein the data storage device comprises a device selected from the group consisting of a digital audio player, a digital audio book, an electronic book, a digital camera, a game player, a general-purpose computer, a personal digital assistant, a portable telephone, a printer, and a projector.

5. The method of claim 1, wherein act (a) is performed by a controller of a memory device comprising the write-once memory array.

6. The method of claim 1, wherein act (d) is performed by a data reading device coupled with a memory device comprising the write-once memory array.

7. The method of claim 6, wherein the data reading device comprises a device selected from the group consisting of a digital audio player, a digital audio book, an electronic book, a digital camera, a game player, a general-purpose computer, a personal digital assistant, a portable telephone, a printer, and a projector.

8. The method of claim 1, wherein act (d) is performed by a controller of a memory device comprising the write-once memory array.

9. The method of claim 1, wherein the file system structure comprises a directory.

10. The method of claim 9, wherein the directory comprises a root directory.

11. The method of claim 9, wherein the directory comprises a sub-directory.

12. The method of claim 1, wherein the file system structure comprises a file allocation table.

28. The method of claim 1 or 13, wherein the write-once memory array comprises a three-dimensional memory array.

29. The method of claim 1 or 13, wherein the write-once memory array comprises a two-dimensional memory array.

32. The method of claim 1, wherein the plurality of bits are inverted even when a number of logic one bits in the plurality of bits does not exceed fifty percent of a total number of bits in the plurality of bits.

13. A method for updating a file system structure stored in a write-once memory array, the method comprising:

(a) creating an inverted file system structure by inverting a plurality of bits representing a file system structure irrespective of a number of logic one bits in the plurality of bits;

(b) storing the inverted file system structure in a write-once memory array, the inverted file system structure being associated with data stored in the write-once memory array during a first session;

(c) storing additional data in the write-once memory array during a second session; and

(d) updating the stored inverted file system structure for the additional data stored during the second session.

14. The method of claim 13, wherein the file system structure comprises a directory.

15. The method of claim 14, wherein the directory comprises a root directory.

16. The method of claim 14, wherein the directory comprises a sub-directory.

17. The method of claim 13, wherein the file system structure comprises a file allocation table.

33. The method of claim 13, wherein the plurality of bits are inverted even when a number of logic one bits in the plurality of bits does not exceed fifty percent of a total number of bits in the plurality of bits.

18. A memory device comprising:

a write-once memory array storing a plurality of bits representing an inverted file system structure; and

a controller coupled with the write-once memory array and operative to invert the plurality of bits representing the inverted file system structure irrespective of a number of logic one bits in the plurality of bits when the plurality of bits is read from the write-once memory array.

19. The memory device of claim 18, wherein the controller is further operative to create the inverted file system structure by inverting a plurality of bits representing a file system structure.

20. The memory device of claim 18, wherein the write-once memory array further stores a plurality of data bits, and wherein the controller does not invert the data bits when the data bits are read from the write-once memory array.

21. The memory device of claim 18, wherein the write-once memory array further stores a plurality of data bits, and wherein the controller is further operative to invert the data bits when the data bits are read from the write-once memory array.

22. The memory device of claim 18, wherein the file system structure comprises a directory.

23. The memory device of claim 22, wherein the directory comprises a root directory.

24. The memory device of claim 22, wherein the directory comprises a sub-directory.

25. The memory device of claim 18, wherein the file system structure comprises a file allocation table.

26. The memory device of claim 18, wherein the memory device comprises a solid-state memory device.

27. The memory device of claim 18, wherein the memory device comprises an optical memory device.

30. The memory device of claim 18, wherein the write-once memory array comprises a three-dimensional memory array.

31. The memory device of claim 18, wherein the write-once memory array comprises a two-dimensional memory array.

34. The memory device of claim 18, wherein the controller is operative to invert the plurality of bits even when a number of logic one bits in the plurality of bits does not exceed fifty percent of a total number of bits in the plurality of bits.