Method for deleting stored digital data from write-once memory device

• US 7,174,351 B2
• Filed: 09/29/2003
• Issued: 02/06/2007
• Est. Priority Date: 08/14/2000
• Status: Expired due to Term

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk 3D LLC (Western Digital Corporation)
• Inventors: Moore, Christopher S., Bosch, Derek J., Tringali, J. James, Steere, Daniel C.
• Primary Examiner(s): Wong; Don
• Assistant Examiner(s): Black; Linh
• Application Number:
  US10/674,289
• Publication Number:
  US 20040098416A1
• Time in Patent Office: 1,226 Days
• Field of Search: 707 1-1041, 707/200
• US Class Current: 1/1
• CPC Class Codes: G06F 16/9017 using directory or table look-up use of a directory or look-up table in file systems G06F16/13
• CPC Class Codes: Y10S 707/99953 Recoverability
• CPC Class Codes: Y10S 707/99956 File allocation

Abstract

A digital storage system is coupled to a write-once memory array. File delete commands are implemented by over-writing a destructive digital pattern to at least a portion of the memory cells associated with the file to be deleted. One disclosed system alters the manner in which a file delete command is implemented, depending upon whether the file is stored in a write-once memory or in a re-writable memory.

Claims

1. A method for deleting stored digital data from a write-once memory device, said method comprising:

(a) providing a write-once memory array comprising a plurality of memory cells, wherein some of the cells are in an original digital state and others of the cells are in a programmed digital state, and wherein the states of the memory cells represent a stored digital file;

(b) receiving a delete command associated with the file; and

then

(c) over-writing at least a portion of the stored digital file with a destructive pattern, said pattern switching at least some of the memory cells associated with the digital file to the programmed digital state.

4. The method of claim 1, 2, or 3 wherein the stored digital file comprises addressing information that identifies memory cell addresses associated with the stored digital file;

and wherein the at least a portion of the stored digital file that is over-written in (c) consists essentially of the addressing information.

5. The method of claim 1, 2, or 3 wherein the at least a portion of the stored digital file that is over-written in (c) consists essentially of the entire stored digital file.

6. The method of claim 1, 2, or 3 wherein (c) comprises over-writing a plurality of memory cells associated with the stored digital file substantially simultaneously.

7. The method of claim 1, 2, or 3 wherein said pattern switches substantially all of the over-written memory cells associated with the digital file to the programmed digital state.

8. The method of claim 1, 2, or 3 wherein the at least a portion of the stored digital file that is over-written in (c) comprises multiple spaced blocks of the memory cells associated with the stored digital file.

2. A method for deleting stored digital data from a three-dimensional memory array, said method comprising:

(a) providing a three-dimensional memory array comprising a plurality of memory cells, wherein some of the cells are in an original digital state and others of the cells are in a programmed digital state, and wherein the states of the memory cells represent a stored digital file;

(b) receiving a delete command associated with the file; and

then

(c) over-writing at least a portion of the stored digital file with a destructive pattern, said pattern switching at least some of the memory cells associated with the digital file to the programmed digital state.

9. The method of claim 2 wherein the memory cells are arrayed in rows, columns, and layers in the three-dimensional memory array, and wherein (c) comprises over-writing a plurality of memory cells in different layers substantially simultaneously.

3. A method for deleting stored digital data from a write-once memory device, said method comprising:

(a) providing a write-once, three-dimensional memory array comprising a plurality of memory cells, wherein some of the cells are in an original digital state and others of the cells are in a programmed digital state, and wherein the states of the memory cells represent a stored digital file;

(b) receiving a delete command associated with the file; and

then

(c) over-writing at least a portion of the stored digital file with a destructive pattern, said pattern switching at least some of the memory cells associated with the digital file to the programmed digital state.