Method for using a multi-bit cell flash device in a system not designed for the device
AssigneeSanDisk IL Ltd.
InventorsMenahem LASSER, Avraham MEIR
Life of this patent
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Abstract
A computerized system is booted from a flash memory device configured to always operate one or more of its blocks only in a M-bit-per-cell mode and the rest of its blocks in a N>M-bit-per-cell mode. When the system is powered up, an initialization program is retrieved from the M-bit-per-cell block(s), corrected for errors using a first error correction method, and executed. Data accessed subsequently from the N-bit-per-cell blocks are corrected using an error correction method that corrects more errors per block than the first error correction method.
Claims12
A method for booting a computerized system, the method comprising:
- (a) providing a flash memory device that includes a plurality of memory cells grouped into a plurality of blocks, said device being configured so that at least one of said blocks is always operated only in a mode in which M bits are stored per cell and never in a mode in which more than M bits are stored per cell, and so that a remainder of said blocks is always operated only in a mode in which N>M bits are stored per cell and never in a mode in which only M bits are stored per cell, where M and N are integral numbers;
- (b) upon powering up the computerized system:
- (i) retrieving an initialization program for the booting from at least one said block storing M bits per cell,
- (ii) correcting at least one error in said initialization program, using a first error correction method, and
- (iii) executing said initialization program;
- and
- (c) upon completing said executing:
- (i) accessing at least one remaining said block storing N bits per cell, and
- (ii) correcting data accessed in said at least one remaining block, using a second error correction method that corrects more errors per block than said first error correction method.
A flash memory device comprising a plurality of memory cells grouped into a plurality of blocks, the device being configured so that
- (a) at least one said block always is operated only in a mode in which M bits are stored per cell and never in a mode in which more than M bits are stored per cell, an initialization program for booting a computer system being stored in at least one of said at least one block, and so that
- (b) a remainder of said blocks always is operated only in a mode in which N>M bits are stored per cell, and never in a mode in which only M bits are stored per cell, wherein N and M are integral numbers.
A method of operating a computerized system, the method comprising:
- (a) providing a flash memory device that includes a plurality of memory cells grouped into a plurality of blocks, said device being configured so that at least one of said blocks is always operated only in a mode in which M bits are stored per cell and never in a mode in which more than M bits are stored per cell, and so that a remainder of said blocks is always operated only in a mode in which N>M bits are stored per cell and never in a mode in which only M bits are stored per cell, where M and N are integral numbers;
- (b) storing, in said at least one block, an initialization program for booting the computerized system;
- (c) upon powering up the system, retrieving said initialization program from said at least one block and executing said initialization program;
- and
- (d) upon completing said executing, accessing at least one other block from among said remainder of the blocks.
Dependencies are inferred from the claim text.