Selecting erase method based on type of power supply for flash EEPROM

• US 5,933,847 A
• Filed: 09/24/1996
• Issued: 08/03/1999
• Est. Priority Date: 09/28/1995
• Status: Expired due to Fees

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Ogawa, Takeshi
• Primary Examiner(s): Bragdon, Reginald G.
• Application Number:
  US08/710,946
• Time in Patent Office: 1,043 Days
• Field of Search: 711/103, 711/156, 711/202, 711/203, 711/104, 711/165, 353/909.1
• US Class Current: 711/103
• CPC Class Codes: G06F 12/023 Free address space management
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory

Abstract

A flash ROM has a plurality of blocks each consisting a data area and a management area. A first erasing method extracts a valid block from the flash ROM, moves the contents of the block, and erases the block. A second erasing method extracts valid storage blocks, moves the contents of the blocks to a random access memory, and erases the blocks. The first or second erasing method is selected based on the type of power supply of the apparatus into which the flash ROM is incorporated.

Claims

1. A flash ROM management apparatus comprising:

managing means for forming a plurality of storage blocks each consisting of a data area and a management area corresponding to the data area in a flash ROM, storing state information indicating a storage state of the data area of each storage block in the management area of the storage block, and managing access to said flash ROM on the basis of the state information;

first erasing means for extracting, from one erase block of said flash ROM, on the basis of the state information, a storage block in which valid data exists in the data area, moving contents of the extracted storage block, and erasing the erase block;

second erasing means for extracting, from a plurality of erase blocks, on the basis of the state information, storage blocks in which valid data exists in the data area, moving contents of the extracted storage blocks to a storage area including a random access memory, and erasing the erase blocks; and

executing means for selecting one of said first erasing means and said second erasing means and executing an erase operation on the basis of the type of power supply of an apparatus into which said flash ROM is incorporated.

2. The apparatus according to claim 1, wherein said first erasing means has an additional erase block of said flash ROM and a random access memory as a moving destination to which the contents of the storage block containing valid data in one erase block are moved, and preferentially selects the additional erase block of said flash ROM.

3. The apparatus according to claim 1, wherein said executing means uses said first erasing means when said power supply is a battery and uses said second erasing means when said power supply is an AC adaptor.

4. A flash ROM management method comprising:

a managing step of forming a plurality of storage blocks each consisting of a data area and a management area corresponding to the data area in a flash ROM, storing state information indicating a storage state of the data area of each storage block in the management area of the storage block, and managing access to said flash ROM on the basis of the state information;

a first erasing step of extracting, from one erase block of said flash ROM, on the basis of the state information, a storage block in which valid data exists in the data area, moving contents of the extracted storage block, and erasing the erase block;

a second erasing step of extracting, from a plurality of erase blocks, on the basis of the state information, storage blocks in which valid data exists in the data area, moving contents of the extracted storage blocks to a storage area including a random access memory, and erasing the erase blocks; and

an executing step of selecting one of said first erasing step and said second erasing step and executing an erase operation on the basis of the type of power supply of an apparatus into which said flash ROM is incorporated.

5. The method according to claim 4, wherein the first erasing step comprises having an additional erase block of said flash ROM and a random access memory as a destination to which the contents of the storage block containing valid data in one erase block are moved, and preferentially selecting the additional erase block of said flash ROM.

6. The method according to claim 4, wherein the executing step comprises using the first erasing step when said power supply is a battery and using the second erasing step when said power supply is an AC adaptor.

7. A computer control apparatus for controlling a computer by reading out a predetermined program from a memory medium, wherein said memory medium comprises:

code for managing forming a plurality of storage blocks each consisting of a data area and a management area corresponding to the data area in a flash ROM, storing state information indicating a storage state of the data area of each storage block in the management area of the storage block, and ranging access to said flash ROM on the basis of the state information;

first erasing code for extracting, from one erase block of said flash ROM, on the basis of the state information, a storage block in which valid data exists in the data area, moving contents of the extracted storage block, and erasing the erase block;

second erasing code for extracting, from a plurality of erase blocks, on the basis of the state information, storage blocks in which valid data exists in the data area, moving contents of the extracted storage blocks to a storage area including a random access memory, and erasing the erase blocks; and

code for selecting one of said first erasing code and said second erasing code and executing an erase operation on the basis of the type of power supply of an apparatus into which said flash ROM is incorporated.