Nonvolatile memory system, nonvolatile memory device, data read method, and data read program

• US 7,424,648 B2
• Filed: 03/08/2006
• Issued: 09/09/2008
• Est. Priority Date: 03/10/2005
• Status: Active Grant

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Honda, Toshiyuki
• Primary Examiner(s): Iqbal; Nadeem
• Application Number:
  US11/370,233
• Publication Number:
  US 20060206751A1
• Time in Patent Office: 916 Days
• Field of Search: 714/52, 714/54, 714/57, 714/48, 714/42, 714/39, 714/27, 714/30
• US Class Current: 714/52
• CPC Class Codes: G06F 11/1068 in sector programmable memories, e.g. flash disk G06F11/1072 takes precedence

Abstract

A nonvolatile memory device has a controller and flash memory. The flash memory stores user data and an error correcting code for correcting an error in the user data. When there is a read command from the outside, the user data and error correcting code are read from the flash memory. If there is any correctable error in the read user data, error correction is performed and then the data is outputted. If the there is uncorrectable error, the data is outputted directly without any correction.

Claims

1. A nonvolatile memory system comprising a nonvolatile memory device, and an access device that accesses said nonvolatile memory device to read user data in the nonvolatile memory device,

wherein said nonvolatile memory device includes:

a nonvolatile memory including a user data area into which user data are written and a management area which stores an error correcting code for performing error correction on the data written in said user data area; and

a controller including an error correction circuit for correcting an error in user data read from said nonvolatile memory based on the error correcting code stored in said management area, which includes;

an error correction read in which user data is read from said nonvolatile memory and the error correction is performed with the use of said error correction circuit if there is any error while the data is directly read if there is no error; and

a raw data read in which the user data read from said nonvolatile memory is directly outputted without any correction, and

wherein said access device reads user data in combination with said error correction read and said raw data read from the nonvolatile memory device.

2. The nonvolatile memory system according to claim 1,

wherein, to read the user data, said access device uses said error correction read by directing said nonvolatile memory device, and makes switching to the raw data read when said error correction cannot be performed.

3. The nonvolatile memory system according to claim 1,

wherein, in the user data reading with the use of said error correction read, based on that no data is outputted from said nonvolatile memory device, said access device determines that an correctable error by said error correction circuit has occurred.

4. The nonvolatile memory system according to claim 2,

wherein said controller has a flag for identifying whether or not to perform correction with the use of an error correcting code, and based on said flag, makes switching between said error correction read and said raw data read.

5. A nonvolatile memory device comprising:

a nonvolatile memory having a user data area into which user data is written and a management area which stores error correcting code for performing an error correction on data written in said user data area; and

a controller including an error correction circuit for correcting error in user data read from said nonvolatile memory based on said error correcting code,

wherein said controller comprises;

a normal read mode wherein data in the user data area is directly outputted if there is no error, the error in the data in the user data area is corrected and then outputted, if there is any correctable error, and data is not outputted if there is any uncorrectable error; and

a special read mode wherein data in the user data area is outputted directly if there is no error, the error in the data in the user data area is corrected and then outputted, if there is any correctable error, and data in the user data area is directly outputted without any correction if there is any uncorrectable error.

6. The nonvolatile memory device according to claim 5,

wherein said controller has the flag for identifying whether or not to permit data output without use of the error correction, and makes switching between said normal read mode and said special read mode based on a value of said flag.

7. The nonvolatile memory device according to claim 5,

wherein said flag is switched from outside said nonvolatile memory device.

8. A data read method for reading user data from a nonvolatile memory device which comprises:

a nonvolatile memory having a user data area into which the user data is written and a management area which stores error correcting code for performing an error correction on the data written in said user data area; and

a controller including an error correction circuit for correcting error in user data read from said nonvolatile memory based on the error correcting code stored in said management area,

comprising;

reading user data from said nonvolatile memory;

determining presence or absence of the error in the user data read from the nonvolatile memory;

directly outputting data if there is no error in the user data;

outputting data after subjecting the data to the error correction with the use of said error correction circuit if there is any error; and

directly outputting user data read from said nonvolatile memory without any correction if the error cannot be corrected with the use of said error correction circuit.

9. A data read program for reading user data from a nonvolatile memory device which comprises:

a nonvolatile memory having a user data area into which the user data is written and a management area which stores error correcting codes for performing an error correction on the data written in said user data area; and

a controller including an error correction circuit for correcting errors in the user data read from said nonvolatile memory based on the error correcting code stored in said management area,

comprising;

reading user data with the use of a normal read mode in which said controller corrects the error in the user data read from said nonvolatile memory with the use of said error correction circuit and outputs the data to an outside of said nonvolatile memory device, and

reading user data with the use of an ECC-off read in which said controller directly outputs the user data read from said nonvolatile memory to an outside of said nonvolatile memory device without the use of said error correction circuit, when the error which cannot be corrected by said error correction circuit occurs in said nonvolatile memory and it is judged that the reading cannot be achieved by said normal read mode.

10. The data read program according to claim 9,

wherein said normal read and said ECC-off read are used by switching in a sector unit.

11. The data read program according to claim 9,

wherein, in reading with the use of said normal read, when no data from said nonvolatile memory device is outputted, it is judged that the error which cannot be corrected by said error correction circuit occurs in said nonvolatile memory and the data cannot be read by said normal read.

12. A data read program for reading user data from the nonvolatile memory device which comprises:

a nonvolatile memory having a user data area into which the user data is written and a management area which stores error correcting codes for performing an error correction on the data written in said user data area; and

a controller including an error correction circuit for correcting errors in user data read from said nonvolatile memory based on the error correcting code stored in said management area,

comprising;

reading user data from said nonvolatile memory by a special read which outputs;

user data from said nonvolatile memory after correcting the user data when an error in user data is correctable; and

row data read from said nonvolatile memory when the error is not correctable.