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States encoding in multi-bit flash cells

  • US 7,310,347 B2
  • Filed: 01/18/2005
  • Issued: 12/18/2007
  • Est. Priority Date: 03/14/2004
  • Status: Active Grant
First Claim
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1. A method of storing N bits of data, comprising the steps of:

  • (a) providing ┌

    N/M┐

    cells; and

    (b) programming each cell with up to M of the bits according to a valid, nonserial bit ordering that satisfies a criterion selected from the group consisting of;

    (i) a number of threshold voltage comparisons for sequentially and statically reading said M bits exceeds a minimum said number of threshold voltage comparisons by at most 1,(ii) a maximum number of threshold voltage comparisons for statically reading any one of said M bits is minimized,(iii) a minimum number of threshold voltage comparisons for statically reading any one of said M bits is minimized,(iv) a maximum number of threshold voltage comparisons for statically reading any one of said M bits exceeds a minimum number of threshold voltage comparisons for statically reading any one of said M bits by at most 1,(v) a number of threshold voltage comparisons for sequentially and dynamically reading said M bits exceeds a minimum said number of threshold voltage comparisons by at most 1,(vi) a maximum number of threshold voltage comparisons for dynamically reading any one of said M bits is minimized,(vii) a minimum number of threshold voltage comparisons for dynamically reading any one of said M bits is minimized, and(viii) a maximum number of threshold voltage comparisons for dynamically reading any one of said M bits exceeds a minimum number of threshold voltage comparisons for dynamically reading any one of said M bits by at most 1;

    wherein M is at least 3.

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