Method of and architecture for controlling system data with automatic wear leveling in a semiconductor non-volatile mass storage memory

• US 5,835,935 A
• Filed: 09/13/1995
• Issued: 11/10/1998
• Est. Priority Date: 09/13/1995
• Status: Expired due to Term

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Lexar Media Incorporated (Micron Technology, Inc.)
• Inventors: Reid, Robert Alan, Estakhri, Petro, Iman, Berhanu, Assar, Mahmud
• Primary Examiner(s): Chan, Eddie P.
• Assistant Examiner(s): Portka, Gary J.
• Application Number:
  US08/527,484
• Time in Patent Office: 1,154 Days
• Field of Search: 395/430, 395/405, 395/419, 395/462, 365/218, 365/185.11, 365/185.29, 365/185.33, 711/103, 711/5, 711/135, 711/209
• US Class Current: 711/103
• CPC Class Codes: G06F 2212/2022 Flash memory
• 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 16/102 External programming circuits, e.g. EPROM programmers; In-circuit programming or reprogramming; EPROM emulators

Abstract

A semiconductor non-volatile mass storage memory is partitioned into user files and system files. The system files partition is further subdivided into clusters, each cluster having a plurality of sectors. Each cluster stores the system file for a single predetermined LBA. As the information within the LBA is changed, the new information is written into an empty sector within the cluster. Once the cluster is filled, the system either erases for recycling the cluster or preferably locates an empty cluster and repeats the process with that new cluster. Once all the clusters are filled, all clusters containing old data are erased for recycling.

Claims

1. A mass storage system comprising:

at least one semiconductor non-volatile memory means having a plurality of individually addressable sector storage locations for storing information; and

a controller circuit coupled to said memory means and operative to define a first partition within said memory means having sector storage locations for storing user files, and a second partition within said memory means having sector storage locations for storing system files, the sector storage locations of said second partition being grouped in a plurality of clusters, each said cluster being uniquely identifiable by a predetermined logical block address, said controller circuit being further operative upon initial access of a particular cluster identified by a particular logical block address to store a first system sector information in one of the sector storage locations of the particular cluster, and upon subsequent accesses of the particular cluster identified by the particular logical block address, the controller circuit further being operative to store replacement system sector information into an empty sector storage location of the particular cluster, leaving intact the system sector information previously stored in the particular cluster, said controller circuit further being operative to generate an indication for subsequently identifying the location of the most recently stored sector information within the cluster,

thereby avoiding the need to erase the memory means every time a cluster identified by a logical block address is re-accessed.

2. The mass storage system as recited in claim 1 wherein the non-volatile memory means includes flash memory devices.

3. The mass storage system as recited in claim 1 wherein upon filling the empty sector storage locations of the particular cluster with replacement system sector information, a subsequent replacement system file is stored in an empty cluster.

4. The mass storage system as recited in claim 1 wherein each of the sector storage locations within a cluster also contains flags indicative of whether the sector information stored in the respective sector storage location is "old."

5. The mass storage system as recited in claim 1 wherein each of the sector storage locations within a cluster also contains a flag indicative of whether the sector information stored in the respective sector storage location is "used."

6. The mass storage system as recited in claim 1 wherein each of the sector storage locations within a cluster further contains a flag indicative of whether the sector information stored in the respective sector storage location is "defective."

7. A mass storage system as recited in claim 1, wherein said indication includes an address of the storage location wherein the mot recently stored sector information resides within the particular cluster.

8. A mass storage system as recited in claim 7 wherein the address of the storage location of the most recently stored sector information stored within the particular cluster is incremented each time the particular cluster identified by the logical block address is re-accessed.

9. A mass storage system as recited in claim 1 wherein each logical block address is stored in a particular one of the sector storage locations of a corresponding cluster.

10. A memory system for storing data comprising:

a semiconductor non-volatile mass storage memory partitioned into at least two areas, one of which includes sector storage locations used to store system files, a predetermined plurality of said sector storage locations of said one area being grouped in clusters, each said cluster being uniquely identifiable by a predetermined logical block address, a first sector storage location of a particular cluster being used for storing system sector information upon initial access of the particular cluster, and upon re-accesses of the particular cluster, prior to erasure of the particular cluster'"'"'s sector information, subsequent sector storage locations of the particular cluster being used for storing replacement system sector information; and

a control circuit coupled to the semiconductor non-volatile mass storage memory for controlling the partitioning thereof, for storing system sector information within the cluster, and for storing replacement system sector information within the cluster while leaving intact the system sector information previously stored in the particular cluster, said control circuit further being operative to generate an indication of the location of the most recent sector information stored within the particular cluster,

thereby avoiding the need to erase the non-volatile mass storage memory every time a cluster identified by a logical block address is re-accessed.

11. The memory system as recited in claim 10 wherein said mass storage memory is flash memory.

12. The memory system as recited in claim 10 wherein a write operation is completed by writing replacement system sector information into an empty sector storage location within the cluster corresponding to an appropriate logical block address.

13. A memory system as recited in claim 10 wherein said semiconductor non-volatile mass storage memory further includes an empty cluster for storing a subsequent replacement system file when a previous cluster is filled.

14. A memory system as recited in claim 10 further including a table storage device for storing a table of information, the table storage device being operative to translate an input logical block address to a corresponding physical block address that can be used to address said mass storage memory.

15. A memory system as recited in claim 14 wherein the table storage device is a random access memory.

16. A memory system as recited in claim 14 wherein the table of information is updated by reading system sector information in clusters identified by logical block addresses and modifying the table entries to reflect current logical block address to physical block address relationships.

17. A memory system as recited in claim 11 wherein each entry within the table contains a flag indicative of whether or not the sector information stored in the respective sector storage location is "used".

18. A memory system as recited in claim 11 wherein each entry within the table contains a flag indicative of whether or not the sector information stored in the respective sector storage location is "defective".

19. A memory system as recited in claim 15 wherein each entry within the table further includes an indication of a current sector within a cluster corresponding to a logical block address.

20. A method of storing information in a semiconductor nonvolatile mass storage memory adapted to store information in sector storage spaces, comprising:

partitioning the memory into a first group of sector storage spaces for storing a plurality of user files and a second group of sector storage spaces for storing a plurality of system files;

combining the sector storage spaces of the second such group into clusters of storage spaces, each such cluster being uniquely identifiable by a logical block address and used for storing a current system sector within one of the sector storage spaces in that cluster;

storing a system file in a particular one of said clusters;

determining which sector storage space in the particular cluster is an empty sector storage space;

writing a replacement system file for the stored system file into the empty sector storage space;

providing an indication for identifying the location of the most recently written sector storage space of the particular cluster; and

marking the particular cluster as old when a last sector storage space within the particular cluster is replaced and there is no remaining empty sector storage space within the particular cluster.

21. A method of storing information as recited in claim 20 further comprising the step of writing a subsequent replacement system sector into an empty cluster when a previous cluster is filled.

22. A method of storing information as recited in claim 20 further comprising the step of erasing any clusters having only "old" system sector information.