File structure for a non-volatile block-erasable semiconductor flash memory

• US 5,592,669 A
• Filed: 12/01/1995
• Issued: 01/07/1997
• Est. Priority Date: 12/31/1990
• Status: Expired due to Term

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Elbert, Dale K., Robinson, Kurt B., Levy, Markus A.
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): Lintz, Paul R.
• Application Number:
  US08/565,929
• Time in Patent Office: 403 Days
• Field of Search: 395/600, 395/800, 348/231, 348/232
• US Class Current: 1/1
• CPC Class Codes: G06F 12/023 Free address space management
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 12/0638 Combination of memories, e.g. ROM and RAM such as to permit replacement or supplementing of words in one module by words in another module address formation of the next microinstruction G06F9/26; masking faults in memories by using spares or by reconfiguring G11C29/70
• CPC Class Codes: G06F 2212/7211 Wear leveling
• CPC Class Codes: G06F 3/0601 Interfaces specially adapted for storage systems
• CPC Class Codes: G06F 3/0664 at device level, e.g. emulation of a storage device or system
• CPC Class Codes: G11C 16/349 Arrangements for evaluating degradation, retention or wearout, e.g. by counting erase cycles

Abstract

A non-volatile semiconductor memory that is erasable only in blocks is described. Each bit of the non-volatile semiconductor memory cannot be overwritten from a first logical state to a second logical state without a prior erasure. Each bit of the non-volatile semiconductor memory can be overwritten from a second logical state to a first logical state without a prior erasure. The non-volatile semiconductor memory comprises an active block for storing a first file, a reserve block for storing a second file, and a directory block. The second file is a copy of the first file. The copy is made during a clean-up operation prior to erasure of the active block. The directory block comprises a directory entry for identifying the first file.

Claims

1. A processor-controlled method of file management for a nonvolatile semiconductor memory with a plurality of physical erase blocks, wherein bits of the memory cannot be overwritten from a first logical state to a second logical state without a prior erasure, wherein erasure is by physical erase block and not on an individual byte basis, the method comprising the steps of:

(1) allocating a first portion of the memory in a first physical erase block for storing an active file and a deleted file;

(2) allocating a second portion of the memory in a second physical erase block for storing a copy of the active file;

(3) storing in an allocated third portion of the memory information as to whether a portion of the memory has been allocated to store the active and deleted files or allocated to store the copy of the active file;

(4) reclaiming memory space by storing in the second portion of the memory the copy of the active file and by erasing the first physical erase block including the first portion of the memory in order to permit reuse of the first portion of the memory for storage;

(5) storing data in the first and second portions of the memory in a inked-list variable file structure.

2. The processor-controlled method of claim 1, further comprising the steps of:

(7) reallocating the second portion of the memory for storing the active file and the deleted file;

(8) reallocating the first portion of the memory for storing the copy of the active file.

3. The processor-controlled method of claim 1, further comprising the step of storing in an allocated fourth portion of the memory an indication as to whether a portion of the memory is in use or not in use.

4. The processor-controlled method of claim 1, further comprising the step of storing in an allocated fourth portion of the memory an indication as to whether a portion of the memory is defective or not defective.

5. The processor-controlled method of claim 1, wherein the first and second portions of the memory are allocated to have a variable-length file structure.

6. The processor-controlled method of claim 5, further comprising the step of storing in an allocated fourth portion of the memory information concerning the file structure of the memory.

7. The processor-controlled method of claim 6, wherein the information concerning the file structure comprises a file structure type.

8. The processor-controlled method of claim 6, wherein the information concerning the file structure comprises a file name.

9. The processor-controlled method of claim 6, wherein the information concerning the file structure comprises information concerning whether a file is active or deleted.

10. The processor-controlled method of claim 1, wherein the active file comprises a linked list.

11. A processor-controlled method of file management for a nonvolatile semiconductor memory with a plurality of physical erase blocks, wherein bits of the memory cannot be overwritten from a first logical state to a second logical state without a prior erasure, wherein erasure is by physical erase block and not on an individual byte basis, the method comprising the steps of:

(1) reclaiming memory space by copying active files and not deleted files from a first portion of a first physical erase block of the memory to a second portion of a second physical erase block of the memory and then erasing the first physical erase block including the first portion;

(2) storing in a third portion of the memory information as to whether a portion of the memory is free for further data storage or in use;

(3) storing data in memory free space in a sectored file structure.

12. The processor-controlled method of claim 11, further comprising the steps of:

(1) tracking a number of times a portion of the memory has been cycled and storing the number as a cycle count in an allocated fourth portion of the memory;

(2) minimizing cycling distributions between physical erase blocks of the memory by choosing for reclamation a portion of the memory with a lowest cycle count.

13. The processor-controlled method of claim 11, further comprising the step of storing in a fourth portion of the memory information as to a total number of physical erase blocks within the memory.

14. The processor-controlled method of claim 11, further comprising the step of storing in a fourth portion of the memory a checksum.

15. The processor-controlled method of claim 11, further comprising the step of storing in a fourth portion of the memory information regarding erase and write voltages.

16. A processor-controlled method of file management for a nonvolatile semiconductor first memory with a plurality of physical erase blocks, wherein bits of the first memory cannot be overwritten from a first logical state to a second logical state without a prior erasure, wherein erasure is by physical erase block and not on an individual byte basis, the method comprising the steps of:

(1) reclaiming memory space of the first memory by copying active files and not deleted files from a first portion of a first physical erase block of the first memory to a random access memory, then erasing the first physical erase block including the first portion, and then copying active files from the random access memory back to free space of the first physical erase block of the first memory;

(2) storing in a second portion of the first memory information as to whether a portion of the first memory is free for further data storage or in use;

(3) storing data in free space of the first memory in a sectored file structure.