Flash memory device employing unused cell arrays to update files

• US 5,566,314 A
• Filed: 08/30/1993
• Issued: 10/15/1996
• Est. Priority Date: 08/30/1993
• Status: Expired due to Term

• Current Assignee: Agere Systems Incorporated (Broadcom, Inc.)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: DeMarco, Robert W., Dempsey, Peter A. A., Sarkar, Chandan
• Primary Examiner(s): Robertson, David L.
• Application Number:
  US08/114,553
• Time in Patent Office: 1,142 Days
• Field of Search: 395/425, 395/430, 395/412, 395/421.11
• US Class Current: 711/103
• CPC Class Codes: G06F 11/1435 using file system or storage system metadata
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory

Abstract

Disclosed is a circuit and method for utilizing FLASH devices as nonvolatile storage elements. Information is modified by adding a new block of data at another location in the memory rather than writing over the outdated information. An address pointer locates the latest information for each data file.

Claims

1. A circuit comprising:

a nonvolatile FLASH memory device comprising arrays of memory cells;

means for writing a plurality of first data files into a number of said arrays of cells;

means for storing a series of file pointers each locating the position of the cell array which includes a particular one of the first files;

means for writing a new data file at a previously unused cell array in order to update the information in one of the first data files; and

means for modifying the pointer locating the updated first file to locate the new file.

2. The circuit according to claim 1 wherein the file pointers are stored in designated arrays of cells.

3. The circuit according to claim 1 wherein the file pointers are stored in a random access memory.

4. The circuit according to claim 1 further comprising a second FLASH memory to function as a back-up memory when the FLASH memory device approaches full capacity.

5. The circuit according to claim 1 wherein the means for writing the data files and modifying the file pointers comprises a microprocessor.

6. The circuit according to claim 1 wherein the circuit is adapted for storing data files in contiguous cell arrays and for placing new files in an unused array which is contiguous with an array already including a file.

7. The circuit according to claim 1 wherein the circuit is adapted to write a new file in a previously unused cell array each time it is desired to update an existing file.

8. The circuit according to claim 1 wherein the circuit is adapted to add a new file which does not update an existing file in a previously unused cell array which is contiguous with a cell array including an existing file.

9. A method for writing and storing information in a nonvolatile FLASH memory device which includes arrays of memory cells comprising the steps of:

writing a plurality of first data files into a number of said arrays of cells;

storing a series of file pointers, each locating the position of the cell array including a particular one of the first files;

writing a new data file at a previously unused cell array in order to update the information in one of the first data files; and

modifying the file pointer locating the updated first file to locate the new file.

10. The method according to claim 9 wherein the file pointers are stored in the FLASH memory device.

11. The method according to claim 9 wherein the file pointers are stored in a random access memory.

12. The method according to claim 9 wherein the data files are also written into a second FLASH memory device when the FLASH device approaches full capacity.

13. The method according to claim 9 wherein the writing of the data files and modifying the file pointers are performed by a microprocessor.

14. The method according to claim 9 wherein the first data files are stored in contiguous arrays of memory cells, and the new data file is written into a memory cell which is contiguous with the last written data file.

15. The method according to claim 9 wherein a new file is written into a previously unused cell array each time it is desired to update an existing file.

16. The method according to claim 9 wherein a new file which does not update an existing file is written into a previously unused cell array which is contiguous with a cell array including an existing file.