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Multi-state Flash EEprom system on a card that includes defective cell substitution

  • US 5,877,986 A
  • Filed: 12/29/1997
  • Issued: 03/02/1999
  • Est. Priority Date: 04/13/1989
  • Status: Expired due to Term
First Claim
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1. A memory card connectable to a computer system, comprising:

  • an array of Electrically Erasable and Programmable Read Only Memory ("EEPROM") cells partitioned into a plurality of flash sectors, the cells of the array being individually programmable into more than two states in order to store more than one bit of data per cell;

    each flash sector being a group of cells that are erasable together as a unit, and having a portion thereof reserved as redundant cells; and

    a memory controller for controlling operations of the EEPROM cells;

    error detection means within said memory controller for detecting any defective cells within the array;

    defect pointers, each generated by said memory controller for linking a detected defective cell'"'"'s address to that of a corresponding redundant cell substituting for the defective cell, said defect pointers being stored within the array; and

    defective cell substituting means within said memory controller and responsive to said defect pointers for substituting said detected defective cell with said corresponding redundant cells.

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