Flash solid state disk card with selective use of an address conversion table depending on logical and physical sector numbers

• US 5,742,934 A
• Filed: 03/11/1996
• Issued: 04/21/1998
• Est. Priority Date: 09/13/1995
• Status: Expired due to Term

• Current Assignee: Renesas Electronics Corporation
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Shinohara, Takayuki
• Primary Examiner(s): Gossage, Glenn
• Application Number:
  US08/613,670
• Time in Patent Office: 771 Days
• Field of Search: 395/430, 395/412, 395/419, 395/413, 395/416, 395/417, 395/402, 395/442, 395/421.11
• US Class Current: 711/103
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. 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
• CPC Class Codes: G11C 29/765 in solid state disks

Abstract

A flash solid state disk card comprises a flash memory comprising M block or M blocks and r redundant blocks, and an address conversion table which outputs a physical sector number 1 to N, or 1 to N and (M+1) to (M+r) in correspondence to an input of a logical sector number 1 to N. The number of blocks M is larger than N. If data in a block for a logical sector number (LSN) having a value L, equal to or less than N is updated, another data are erased in a block for a physical sector number (PSN) determined by the address conversion table, the data are written to a free block, and a physical sector number in correspondence to the logical sector number LSN=L in the address conversion table is changed to a number of the block to which the data to be updated are written. If a logical sector number (LSN) having a value L is equal to or less than N, data are read from a block for a physical sector number in correspondence to the logical sector number LSN=L in the table, otherwise data are read from a block for a physical sector number PSN=L. Thus, a flash solid state disk card can be used efficiently for a longer time. Preferably, a substitution table is provided for defective blocks to substitute a block for a defective block.

Claims

1. A flash solid state disk card comprising:

a flash memory having M blocks having physical sector numbers between 1 and M, the M blocks including N blocks for sector management, where N is smaller than M;

a random access memory storing an address conversion table which outputs a physical sector number for one of the N blocks in correspondence to an input of a logical sector number between 1 and N;

data write processing means for writing data to a block for a logical sector number L, said data write processing means including means for, if L satisfies a relationship of 1≦

L≦

N, erasing another data in a block having a physical sector number determined by the address conversion table stored in said random access memory according to the logical sector number L, writing the data to be written to a free block among the N blocks, and changing a physical sector number in correspondence to the logical sector number L in the address conversion table to a physical sector number of the block to which the data are written, and for, if the logical sector number L is larger than N, writing data to be written to a block having a physical sector number equal to the logical sector number L; and

data read processing means for reading data from a block in said flash memory for a physical sector number in correspondence to the logical sector number L in the address conversion table in said random access memory if the logical sector number L is equal to or less than N, and for reading data from a block for a physical sector number L in said flash memory if the logical sector number L is larger than N.

2. The card according to claim 1, wherein each of the N blocks includes a sector data area and a sector management area, each sector management area storing a logical sector number in correspondence to a physical sector number.

3. The card according to claim 2, wherein each sector data area has 512 bytes and each sector management area has 16 bytes.

4. A flash solid state disk card comprising:

a flash memory having (M+r) blocks having physical sector numbers between 1 and (M+r), the (M+r) blocks including N blocks for sector management and r redundant blocks;

a random access memory storing an address conversion table which outputs a physical sector number for one of the N blocks and the r redundant blocks in correspondence to an input of a logical sector number between 1 and N, wherein N is smaller than M;

data write processing means for, if a logical sector number L satisfies a relationship of 1≦

L≦

N, erasing another data in a block having a physical sector number determined according to the logical sector number L by the address conversion table stored in said random access memory, writing the data to be written to a free block among the N blocks and the r redundant blocks, and changing a physical sector number in correspondence to the logical sector number L in the address conversion table to a physical sector number of the block to which the data are written, and for, if the logical sector number L is larger than N, writing data to be written to a block having a physical sector number equal to the logical sector number L; and

data read processing means for reading data from a block in said flash memory for a physical sector number in correspondence to the logical sector number L in the address conversion table in said random access memory if the logical sector number L is equal to or less than N, and for reading data from a block for a physical sector number L in said flash memory if the logical sector number L is larger than N.

5. The card according to claim 4, said random access memory further including a substitution table which stores logical sector numbers and physical sector numbers of substitute blocks for defective blocks determined for the logical sector numbers with the address conversion table, each block in said flash memory including a data area for writing data and a management data area for writing a logical sector number or data indicating a defective block, wherein said data write processing means further writes data indicating a defective block to the management data area for the block for the physical sector number L, writes data to a free block among the r redundant blocks, and writes the logical sector number L and a physical sector number for a block to which the data are written in the substitution table, if the logical sector number N is larger than L and a block for the physical sector number L has a defect, and said data read processing means further reads data of a redundant sector number from the substitution table for the physical sector number L if the logical sector number L is larger than N and data indicating a defective block is written to the management data area for the physical sector number L.

6. The card according to claim 4, wherein each of the N blocks and the r redundant blocks includes a sector data area and a sector management area, each sector management area storing a logical sector number in correspondence to a physical sector number.

7. The card according to claim 6, wherein each sector data area has 512 bytes and each sector management area has 16 bytes.