Flash memories using minimum push up, multi-cell and multi-permutation schemes for data storage
Rank modulation has been recently proposed as a scheme for storing information in flash memories. Three improved aspects are disclosed. In one aspect the minimum push-up scheme, for storing data in flash memories is provided. It aims at minimizing the cost of changing the state of the memory. In another aspect, multi-cells, used for storing data in flash memories is provided. Each transistor is replaced with a multi-cell of mm transistors connected in parallel. In yet another aspect, multi-permutations, are provided. The paradigm of representing information with permutations is generalized to the case where the number of cells in each level is a constant greater than one.
1. A method of operating a data device, the method comprising:
receiving a data value v=[v 1 , v 2 , . . . , v n ]∈S n wherein v is an element of S, and S is a set of symbols in a rank modulation coding scheme and n is a number of ranks in v to be stored in a group of n rank locations in data storage of the data device containing current values U=[u 1 , u 2 , . . . , u n ]∈S n ;
programming the group of n rank locations according to the rank modulation coding scheme and the value v such that for i=n−1, n−2, . . . , 1 the programmed value of a rank location v i is increased until it is greater than the value of a rank location v i+1 by a minimum cell differentiation amount.
2. A method as in claim 1 wherein each of the n rank locations comprises a cell of the device data storage.
3. A method as in claim 1 wherein each rank location comprises a plurality of cells of the device data storage.
4. A method as in claim 3 , wherein each rank location comprises an equal number of cells of the device data storage.
5. A method as in claim 3 , wherein programming comprises increasing the value of all cells in the rank location v i until the value in each of the cells v i is greater than the value in each of the cells in the rank location v i+1 .
6. A method as in claim 1 wherein the current values of u=[u 1 , u 2 , . . . , u n ]∈S n are read from the device data storage before the programming of the group of n rank locations with v.
7. A memory controller comprising:
an interface that receives a new data set for a rank of a plurality of ranks to be stored in a memory comprising a plurality of cells;
a processor configured to perform operations of:
receiving a data value v=[v 1 , v 2 , . . . , v n ]∈S n wherein v is an element of S, and S is a set of symbols in a rank modulation coding scheme and n is a number of ranks in v to be stored in a group of n rank locations in data storage of the data device containing current values u=[u 1 , u 2 , . . . , u n ]∈S n ;
programming the group of n rank locations according to the rank modulation coding scheme and the value v such that for i=n−1, n−2, . . . , 1 the programmed value of a rank location v i is increased until it is greater than the value of a rank location v i+1 by a minimum cell differentiation amount.
8. A memory controller as in claim 7 , wherein each of the n rank locations comprises a cell of the device data storage.
9. A memory controller as in claim 7 , wherein each rank location comprises a plurality of cells of the device data storage.
10. A memory controller as in claim 9 , wherein each rank location comprises an equal number of cells of the device data storage.
11. A memory controller as in claim 9 , wherein programming comprises increasing the value of all cells in the rank location v i until the value in each of the cells v i is greater than the value in each of the cells in the rank location v i+1 .
12. A memory controller as in claim 7 , wherein the current values of u=[u 1 , u 2 , . . . , u n ]∈S n are read from the device data storage before the programming of the group of n rank locations with v.
13. A data device comprising:
a memory configured to store data values:
a memory controller that is configured to store the data values in the memory by performing operations comprising:
receiving a data value v=[v 1 , v 2 , . . . , V n ]∈S n wherein v is an element of S, and S is a set of symbols in a rank modulation coding scheme and n is a number of ranks in v to be stored in a group of n rank locations in data storage of the data device containing current values u=[u 1 , u 2 , . . . , u n ]∈S n ;
programming the group of n rank locations according to the rank modulation coding scheme and the value v such that for i=n−1, n−2, . . . , 1 the programmed value of a rank location v i is increased until it is greater than the value of a rank location v i+1 by a minimum cell differentiation amount.
14. A data device as in claim 13 , wherein each of the n rank locations comprises a cell of the device data storage.
15. A data device as in claim 13 , wherein each rank location comprises a plurality of cells of the device data storage.
16. A data device as in claim 15 , wherein each rank location comprises an equal number of cells of the device data storage.
17. A data device as in claim 15 , wherein programming comprises increasing the value of all cells in the rank location v i until the value in each of the cells v i is greater than the value in each of the cells in the rank location v i+1 .
18. A data device as in claim 13 , wherein the current values of u=[u 1 , u 2 , . . . , u n ]∈S n are read from the device data storage before the programming of the group of n rank locations with v.