Method of rewriting data in non-volatile memory, and system therefor

• US 4,517,663 A
• Filed: 12/22/1983
• Issued: 05/14/1985
• Est. Priority Date: 09/04/1979
• Status: Expired due to Fees

• Current Assignee: Fujitsu Fanuc Ltd (Fanuc Corporation)
• Original Assignee: Fujitsu Fanuc Ltd (Fanuc Corporation)
• Inventors: Inoue, Michiya, Imazeki, Ryoji
• Primary Examiner(s): Fears, Terrell W.
• Application Number:
  US06/564,208
• Time in Patent Office: 509 Days
• Field of Search: 365/200, 365/222, 371/8, 371/10, 371/13
• US Class Current: 365/222
• CPC Class Codes: G06F 11/1435 using file system or storage system metadata
• CPC Class Codes: G11C 14/00 Digital stores characterised by arrangements of cells having volatile and non-volatile storage properties for back-up when the power is down
• CPC Class Codes: G11C 19/0875 Organisation of a plurality of magnetic shift registers

Abstract

A method and system for rewriting data in a non-volatile memory in which the rewriting of one access unit of stored data is executed by erase and write cycles, the stored data being protected in the event of an interruption in electric power. In rewriting into second data the first data which is stored in a data storage area of the non-volatile memory, either the first or the second data is stored in a save area of the non-volatile memory, after which the first data in the data storage area is erased, followed by the writing of the second data in the data storage region to complete the rewrite operation.

Claims

1. A method of rewriting data in a non-volatile memory including a data storage area, having a plurality of portions, and a save area, by storing first data in the data storage area of the non-volatile memory and rewriting the first data, the method comprising the steps of:

(a) storing the first data in the save area of the non-volatile memory;

(b) erasing the first data stored in the data storage area, generating a predetermined pattern in the area in which the first data was stored;

(c) writing second data into the data storage area;

(d) detecting an interruption in the power supply;

(e) successively retrieving data from each of the plurality of portions of the data storage area of the nonvolatile memory upon return of the power supply;

(f) testing each successive portion of the plurality of portions of the data storage area for the predetermined pattern; and

(g) writing the first data stored in the save area into the portion of the data storage area that has the predetermined pattern.

2. A method according to claim 1, wherein said step (a) comprises the substeps of:

(i) reading the first data from the data storage area of the non-volatile memory;

(ii) storing, in a volatile memory, the first data read from the non-volatile memory; and

(iii) storing the first data stored in the volatile memory in the save area of the non-volatile memory.

3. A method according to claim 2, wherein said testing step (f) comprises comparing the pattern stored in the nonvolatile memory after said erasing step (b) with each successive portion of the plurality of portions of the data storage area.

6. A method according to claim 1, wherein said writing step (c) comprises the substeps of:

(i) storing data in the data storage area which is divided into a plurality of page areas, each page area having a different page address and a storage capacity;

(ii) editing the second data and dividing the second data into a plurality of data groups equivalent to the storage capacity of the page.

7. A method according to claim 6, wherein the non-volatile memory has a blank page storage area having blank page information, wherein said step (e) comprises retrieving one of the plurality of page areas in which no data is written due to reading of blank page information from the blank page storage area, and wherein said step (g) comprises writing a plurality of data groups having the first data into the plurality of page areas including the page area in which no data is written.

8. A method according to claim 2, further comprising the substeps of:

(aa) receiving external modification data; and

(bb) forming the second data from the first data stored in the volatile memory and the external modification data.

4. A method of rewriting data in a non-volatile memory including a data storage area, having a plurality of portions, and a save area, by storing first data in the data storage area of the non-volatile memory and rewriting the first data as second data, the method comprising the steps of:

(a) storing the second data in the save area of the non-volatile memory;

(b) erasing the first data in the data storage area;

(c) writing the second data into the data storage area;

(d) detecting an interruption in the power supply;

(e) successively retrieving data from each of the plurality of portions of the data storage area of the non-volatile memory upon return of the power supply;

(f) testing each successive portion of the plurality of portions of the data storage area for a predetermined pattern; and

(g) writing the second data stored in the save area into the portion of the data storage area having the predetermined pattern.

5. A method according to claim 4, wherein said testing step (f) comprises comparing the pattern stored in the non-volatile memory after said erasing step (b) with each successive portion of the plurality of portions of the data storage area.

9. A method of rewriting data in a magnetic bubble memory, said method comprising the steps of:

(a) storing old data, or new data, in a save area of the bubble memory, without destroying the old data;

(b) erasing the old data from the bubble memory so as to obtain a forbidden pattern of all "zero" bits in its place in the bubble memory;

(c) writing new data, when an interruption of the power supply does not occur, into the area of the bubble memory in which the old data was erased;

(d) discriminating whether or not the forbidden pattern is present in the bubble memory when an interruption of the power supply occurs;

(e) writing the data stored in the save area, upon restoration of the power supply, into the area of the bubble memory having the forbidden pattern.

10. A method according to claim 9, in which said storing step (a) comprises the substeps of:

(i) nondestructively reading the old data from the bubble memory;

(ii) storing in an additional memory, the old data read from the bubble memory; and

(iii) writing the old data, stored in the additional memory, into the save area of the bubble memory.

11. A method according to claim 10, further comprising the substep of forming new data from the old data stored in the additional memory and from modification data entered by an external means.

12. A method according to claim 10, in which said steps (i) and (ii) are performed by transferring data between the bubble memory and the additional memory under the control of a direct memory access controller operable in response to instructions from a processor.

13. A method according to claim 10, further comprising the substeps of:

(aa) receiving external modification data;

(bb) forming new data in dependence upon the old data stored in the additional memory and the external modification data.