System and method for multi-bit flash reads using dual dynamic references
First Claim
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1. A multi-bit memory system, comprising:
- a reference component that reads a programmed bit value from a first multi-bit reference cell and an unprogrammed bit value from a second multi-bit reference cell to determine an average dynamic reference value; and
a comparison component that employs the average dynamic reference value to facilitate determination of a program state for a bit of at least one multi-bit data cell.
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Abstract
A system and methodology is provided for proper reading of multi-bit memory cells in a memory device. A first reference cell and a second reference cell is employed to determine an average dynamic reference value. The average dynamic reference value is determined by reading a programmed bit of the first reference cell and reading an unprogrammed or erased bit of a second reference cell to determine an average dynamic reference value. The average dynamic reference value can be utilized to determine whether data cells are in a programmed state or in an unprogrammed state.
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Citations
36 Claims
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1. A multi-bit memory system, comprising:
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a reference component that reads a programmed bit value from a first multi-bit reference cell and an unprogrammed bit value from a second multi-bit reference cell to determine an average dynamic reference value; and
a comparison component that employs the average dynamic reference value to facilitate determination of a program state for a bit of at least one multi-bit data cell. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A system for reading bits in an array of dual bit flash memory cells, the dual bit memory cells having a normal bit and a complimentary bit associated with the normal bit, the system comprising:
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a memory array having a plurality of dual bit data cells;
a reference array having a plurality of dual bit reference cells; and
a controller tat determines an average read value of a programmed bit of a first reference cell and an unprogrammed bit of a second reference cell to determine if a bit in at least one of the dual bit data cells is in one of a programmed state and an unprogrammed state. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. A method for reading bits in an array of multi-bit flash memory cells, the method comprising:
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determining a first read value from a programmed bit of a first reference cell and a second read value from an unprogrammed bit of a second reference cell;
evaluating an average threshold value from the first read value and the second read value;
reading a bit of a data cell to determine a data bit read value;
comparing the data bit read value with the average threshold value; and
determining if the bit is one of a programmed bit and an unprogrammed bit based on the comparison. - View Dependent Claims (27, 28, 29, 30, 31, 32)
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33. A system for reading dual bit flash memory cells, a dual bit memory cell having a normal bit and a complimentary bit associated with the normal bit, the system comprising:
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means for programming bits in a dual bit memory array;
means for programming a first bit in a first reference cell and a second bit in a second reference cell, such that the first reference cell has a programmed bit and an unprogrammed bit and the second reference cell has a programmed bit and an unprogrammed bit;
means for determining an average read value associated with the programmed bit of the first reference cell and an unprogrammed bit of the second reference cell;
means for determining a bit read value of a bit in the dual bit memory array; and
means for comparing the bit read value with the average read value to determine if a bit is in one of a programmed state and an unprogrammed state. - View Dependent Claims (34, 35, 36)
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Specification