Memory controller, memory controller control method, and memory system
According to one embodiment, a memory controller includes a compression unit that compresses two or more determination voltage values for threshold voltages of a memory cell to a vector quantity, the memory cell being capable of storing three or more data values. The memory controller further includes a storing unit that stores the vector quantity into a memory region. The memory controller further includes a decompression unit that decompresses the stored vector quantity to provide the determination voltage values.
1. A memory controller, comprising:
a compression unit configured to compress n determination voltage values for threshold voltages of a memory cell to a vector quantity including a total of m vector components, where n and m are integers satisfying the relationship n>m≥2, the memory cell being capable of storing three or more data values therein according to the n determination voltage values;
a storing unit configured to store the vector quantity into a memory region; and
a decompression unit configured to decompress the stored vector quantity to provide the n determination voltage values for reading data values from or writing data values to the memory cell.
2. The memory controller according to claim 1 , wherein the compression unit is configured to compress a shift value for the n determination voltage values from a predetermined voltage to the vector quantity.
3. The memory controller according to claim 1 , wherein the n determination voltage values are set for each block of a memory array.
4. The memory controller according to claim 1 , wherein the n determination voltage values are set for each word line of a memory array.
5. The memory controller according to claim 1 , wherein at least one of the compression unit and the decompression unit is trained based on an error between a determination voltage value before being compressed by the compression unit and a corresponding determination voltage value after being decompressed from the stored vector quantity by the decompression unit.
6. The memory controller according to claim 1 , wherein at least one of the compression unit and the decompression unit is trained based on a fail bit count (FBC) value for data read from a memory array.
7. The memory controller according to claim 6 , wherein the storing unit is configured to store the vector quantity in associated with the FBC value in the memory region.
8. The memory controller according to claim 1 , wherein the compression unit is configured to compress the n determination voltage values to the vector quantity by converting a subset of values selected from the n determination voltage values to the m vector components of the vector quantity.
9. The memory controller according to claim 8 , wherein the decompression unit is configured to decompress the vector quantity to provide the n determination voltage values by estimating each determination voltage value from the vector quantity.
10. The memory controller according to claim 9 , wherein the decompression unit is configured to adjust the estimation of each determination voltage value from the vector quantity to reduce an error between estimated determination voltage value and a corresponding determination voltage value.
11. The memory controller according to claim 1 , wherein the compression unit is configured to compress the n determination voltage values to the vector quantity by a first neural network.
12. The memory controller according to claim 11 , wherein the decompression unit is configured to decompress the vector quantity to provide the n determination voltage values by a second neural network.
13. A memory controller control method, comprising:
compressing n determination voltage values for threshold voltages of a memory cell to a vector quantity including a total of m vector components, where n and m are integers satisfying the relationship n>m≥2, the memory cell being capable of storing three or more data values therein according to the n determination voltage values;
storing the vector quantity into a memory region; and
decompressing the stored vector quantity to provide the n determination voltage values for reading data values from or writing data values to the memory cell.
14. The memory controller control method according to claim 13 , further comprising:
compressing a shift value of the n determination voltage values from a predetermined voltage to the vector quantity.
15. A memory system, comprising:
a memory array including a memory cell capable of storing three or more data values therein according to different threshold values of the memory cell; and
a memory controller including:
a compression unit configured to compress n determination voltage values for the threshold voltages of the memory cell to a vector quantity including a total of m vector components, where n and m are integers satisfying the relationship n>m≥2;
a storing unit configured to store the vector quantity into a memory region of the memory array; and
a decompression unit configured to decompress the stored vector quantity to provide the n determination voltage values.
16. The memory system according to claim 15 , wherein the n determination voltage values are set for each block of the memory array.
17. The memory system according to claim 15 , wherein the n determination voltage values are set for each word line of the memory array.