Adaptive Operation of Multi Level Cell Memory
First Claim
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1. An adaptable method of operating a plurality of cells of a Multi-Level Cell (MLC) nonvolatile memory array in different binary modes, comprising:
- assigning a first binary state to a first MLC state of three or more MLC states;
assigning a second binary state to a second MLC state of the three or more MLC states in a first mode; and
subsequently reassigning the second binary state from the second MLC state to a third MLC state of the three or more MLC states in a second mode.
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Abstract
A Multi Level Cell (MLC) nonvolatile memory is tested and, if it fails to meet an MLC specification, is reconfigured for operation as an SLC memory by assigning two of the MLC memory cell states as SLC states in a first SLC mode, according to predefined sets of criteria. Subsequently, different MLC memory cell states are assigned as SLC states in a second SLC mode.
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Citations
19 Claims
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1. An adaptable method of operating a plurality of cells of a Multi-Level Cell (MLC) nonvolatile memory array in different binary modes, comprising:
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assigning a first binary state to a first MLC state of three or more MLC states; assigning a second binary state to a second MLC state of the three or more MLC states in a first mode; and subsequently reassigning the second binary state from the second MLC state to a third MLC state of the three or more MLC states in a second mode. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A nonvolatile memory array comprising:
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a plurality of nonvolatile memory cells having three or more threshold voltage ranges individually assigned to represent logic states; and programming circuits that in a first programming mode program the plurality of cells to a first two of the three or more threshold voltage ranges and that in a second programming mode program the plurality of cells to a second two of the three or more threshold voltage ranges, the second two including at least one threshold voltage range that is not included in the first two. - View Dependent Claims (14, 15, 16)
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17. An adaptable method of configuring a plurality of cells of a Multi-Level Cell (MLC) nonvolatile memory array comprising:
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determining if the plurality of cells meet a first set of metrics for operation of MLC nonvolatile memory; if the plurality of cells meet the first set of metrics, then configuring the plurality of cells to store more than one bit per cell using three or more predetermined threshold voltage ranges; if the plurality of cells do not meet the first set of metrics, then configuring the plurality of cells to store one bit per cell using a first two of the three or more predetermined threshold voltage ranges; and subsequently reconfiguring the plurality of cells to store one bit per cell using a second two of the three or more predetermined threshold voltage ranges. - View Dependent Claims (18)
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19. An adaptable method of operating a plurality of cells of an N state per cell Multi-Level Cell (MLC) nonvolatile memory array in different modes that use fewer than N states per cell, comprising:
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configuring the N state per cell MLC nonvolatile memory for operation using fewer than N states by assigning M of the N cell states to represent M logical states, leaving M−
N of the N cell states unassigned, where M is less than N, in a first operating mode; andsubsequently reassigning at least one of the M logical states to one of the previously unassigned M−
N cell states.
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Specification