Method of writing, erasing, and controlling memory for memory device

• US 6,584,579 B1
• Filed: 10/17/2000
• Issued: 06/24/2003
• Est. Priority Date: 10/01/1993
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Itoh, Hiroyuki, Takehara, Masaru, Hayashi, Tomohiro, Komatsu, Shinpei, Shibazaki, Shogo, Ishii, Yumi
• Primary Examiner(s): Beausoliel, Robert
• Assistant Examiner(s): Bonzo, Bryce P.
• Application Number:
  US09/688,858
• Time in Patent Office: 980 Days
• Field of Search: 714/7, 714/8, 714/710
• US Class Current: 714/6.32
• CPC Class Codes: G11C 29/76 using address translation or modifications
• CPC Class Codes: G11C 29/765 in solid state disks
• CPC Class Codes: G11C 29/82 for EEPROMs

Abstract

Data transferred from a host computer to a memory device is written into sectors whose addresses in a memory area are decoded by a decode tab. Old data to be updated by the above data is erased or marked with erase flags. At a predetermined point of time, in order to create free areas, necessary data is evacuated to a primary memory media and unnecessary data indicated by erase flags is erased by a unit of predetermined memory size. Part of the memory media which has become defective is marked with a defect flag, and is replaced by an alternate area. In doing so, the decode table is rewritten to rearrange the memory area.

Claims

1. A management method of writing data in a memory device with a memory area unable to be overwritten on a bit-specific basis, the memory area having a plurality of sectors and said memory device erasing and writing data by a unit of one sector, said method comprising:

writing data of N logical addresses to N+1 sectors by leaving one of the N+1 sectors as a free sector;

finding, from the N+1 sectors, a sector that stores data having a specified logical address;

erasing the sector that stores the data having the specified logical address; and

writing new data having the specified logical address to the free sector, and designating the erased sector as a free sector for subsequent data writing.

2. The management method as claimed in claim 1, wherein a decode table manages said N+1 sectors as one block.

3. The management method as claimed in claim 2, wherein said decode table has information for each of said N+1 sectors about a sector arrangement.

4. The management method as claimed in claim 2, wherein said decode table is rewritten when one of the sectors becomes defective, a block containing said one of the sectors being replaced by a block of a backup area.

5. The management method as claimed in claim 3, wherein said decode table is rewritten when one of the sectors becomes defective, said one of the sectors being replaced by a sector of a backup area.

6. The management method as claimed in claim 1, wherein a decode table managing said N+1 sectors has information for each of said N+1 sectors about a sector arrangement.

7. The management method as claimed in claim 6, wherein said decode table is rewritten when one of the sectors becomes defective, said one of the sectors being replaced by a sector of a backup area.

8. A management method of writing data in a memory device with a memory area unable to be overwritten on a bit-specific basis, the memory area having a plurality of sectors and said memory device erasing and writing data by a unit of one sector, said method comprising:

writing data into a free sector among N+1 sectors which are provided for and shared by N sector numbers;

managing said N+1 sectors using a decode table having information for each of said N+1 sectors about a sector arrangement; and

rewriting said decode table when one of the sectors becomes defective, said one of the sectors being replaced by a sector of a backup area, and the remaining N sectors of said N+1 sectors being shared by N−

1 sector numbers.

9. The management method as claimed in claim 8, wherein said decode table is reconstructed so as to decrease a free area.

18. The method as claimed in claim 9, wherein the memory device has a plurality of chips, and each chip is provided with a plurality of work blocks indicating some of said blocks to be used for writing data, one of said work blocks being made obsolete when said one of said work blocks becomes defective.

10. A management method of writing data in a memory device with a memory area unable to be overwritten on a bit-specific basis, the memory area having a plurality of sectors and said memory device erasing and writing data by a unit of one sector, said method comprising:

writing data into a free sector among N+1 sectors which are provided for and shared by N sector numbers;

managing said N+1 sectors as one block using a decode table, wherein said decode table has information for each of said N+1 sectors about a sector arrangement; and

rewriting said decode table when one of the sectors becomes defective, said one of the sectors being replaced by a sector of a backup area, and the remaining N sectors of said N+1 sectors being shared by N−

1 sector numbers.

11. The management method as claimed in claim 10, wherein said decode table is reconstructed so as to decrease a free area.

12. A management method of writing data in a memory device with a memory area unable to be overwritten on a bit-specific basis, the memory area having a plurality of sectors and said memory device erasing and writing data by a unit of one sector, said method comprising:

writing data into a free sector among N+1 sectors which are provided for and shared by N sector numbers;

managing said N+1 sectors as one block using a decode table; and

rewriting said decode table when one of the sectors becomes defective, a block containing said one of the sectors being replaced by a block of a backup area,

wherein said decode table is reconstructed so as to decrease a free area.

13. A management method of writing data in a memory device with a memory area unable to be overwritten on a bit-specific basis, the memory area having a plurality of sectors and said memory device erasing and writing data by a unit of one sector, said method comprising:

writing data into a free sector among N+1 sectors which are provided for and shared by N sector numbers;

managing said N+1 sectors using a decode table having information for each of said N+1 sectors about a sector arrangement; and

rewriting said decode table when one of the sectors becomes defective, said one of the sectors being replaced by a sector of a backup area,

wherein said decode table is reconstructed so as to decrease a free area.

14. A management method of writing data in a memory device with a memory area unable to be overwritten on a bit-specific basis, the memory area having a plurality of sectors and said memory device erasing and writing data by a unit of one sector, said method comprising:

writing data into a free sector among N+1 sectors which are provided for and shared by N sector numbers;

managing said N+1 sectors as one block using a decode table, wherein said decode table has information for each of said N+1 sectors about a sector arrangement; and

rewriting said decode table when one of the sectors becomes defective, said one of the sectors being replaced by a sector of a backup area,

wherein said decode table is reconstructed so as to decrease a free area.

15. A management method of writing data in a memory device with a memory area unable to be overwritten on a bit-specific basis, the memory area having a plurality of sectors and said memory device erasing and writing data by a unit of one sector, said method comprising:

writing data into a free sector among N+1 sectors which are provided for and shared by N sector numbers;

managing said N+1 sectors using a decode table having information for each of said N+1 sectors about a sector arrangement; and

rewriting said decode table when one of the sectors becomes defective, said one of the sectors being replaced by a sector of a backup area,

wherein said memory area is newly divided into a free area and a new backup area by reconstructing said decode table when said backup area is used up.

16. A management method of writing data in a memory device with a memory area unable to be overwritten on a bit-specific basis, the memory area having a plurality of sectors and said memory device erasing and writing data by a unit of one sector, said method comprising:

writing data into a free sector among N+1 sectors which are provided for and shared by N sector numbers;

managing said N+1 sectors as one block using a decode table, wherein said decode table has information for each of said N+1 sectors about a sector arrangement; and

rewriting said decode table when one of the sectors becomes defective, said one of the sectors being replaced by a sector of a backup area,

wherein said memory area is newly divided into a free area and a new backup area by reconstructing said decode table when said backup area is used up.

17. A method of managing a memory device having a memory area with portions that become destroyed after a specific number of erasures, and having a rewritable decoder that indicates locations where data are stored in said memory area, the method comprising:

arranging a first decoder and a second decoder in series to form the decoder; and

rewriting at least one of the first decoder and the second decoder when part of the memory area or part of the first decoder or the second decoder is destroyed, said rewriting making the destroyed part inaccessible.