6 658 438

6,658,438 Title:

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

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.

What is claimed is:

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 memorycells, 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 thefile; 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; wherein the write-oncememory array comprises a three-dimensional memory array, 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 layerssubstantially simultaneously.

2. A method for deleting stored digital data from an installed memory device, said method comprising; (a) identifying the installed memory device as one of a write-once memory device and a re-writable memory device; (b) receiving a deletecommand associated with a digital file stored in the installed memory device; (c) when the installed memory device is a write-once memory device, over-writing at least a portion of the stored digital file with a destructive pattern, said patternswitching at least some memory cells associated with the digital file to a programmed digital state, and (d) when the installed memory device is a re-writable memory device, implementing the delete command differently than in (c).

3. The method of claim 2 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 isover-written in (c) consists essentially of the addressing information.

4. The method of claim 2 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.

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

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

7. The method of claim 2 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.

8. The method of claim 2 wherein the delete command is implemented in (d) by clearing at least a portion of the stored digital file.

9. 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 andothers 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 comnmand associated with the file; and then (c) over-writing at least a portion of the storeddigital 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; wherein the stored digital file comprises addressing information that identifies memorycell 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.

10. 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 andothers 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 storeddigital 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; 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.

11. 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 andothers 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 storeddigital 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; wherein (c) comprises over-writing a plurality of memory cells associated with the storeddigital file substantially simultaneously.

12. 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 andothers 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 storeddigital 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; wherein said pattern switches substantially all of the over-written memory cellsassociated with the digital file to the programmed digital state.

13. 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 andothers 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 storeddigital 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; 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.

14. The method of claim 1 wherein the plurality of memory cells in different layers that are over-written substantially simultaneously share a given row and column address.