Nonvolatile memory with modulated error correction coding
Data is stored in a nonvolatile memory so that different pages of data stored in the same memory cells are encoded according to different encoding schemes. A first page is decoded according to its encoding scheme and an output is provided based on the decoding of the first page that is subsequently used in decoding a second page.
1. A nonvolatile semiconductor memory system comprising:
a memory array that includes a plurality of memory cells;
an ECC encoder for encoding data of a first page according to a first encoding scheme to obtain a first plurality of encoded data bits and not encoding data that includes a second plurality of bits of a second page according to the first encoding scheme and for storing the first and second plurality of bits in the plurality of cells, wherein each of the plurality of memory cells contains at least one of the first plurality of encoded bits and at least one of the second plurality of bits.
2. The nonvolatile semiconductor memory system of claim 1 wherein the ECC encoder is further configured to encode data of the second page according to a second encoding scheme.
3. The nonvolatile semiconductor memory system of claim 2 wherein the first encoding scheme uses more redundant bits than the second encoding scheme.
4. The nonvolatile semiconductor memory system of claim 1 further comprising:
a reading circuit for reading data from the plurality of memory cells; and
an ECC decoder for decoding the read data.
5. The nonvolatile semiconductor memory system of claim 4 wherein the ECC decoder is further configured to receive the read data as soft-input, decode data of the first page first and use an output of the decoding of the first page, with the read data, to decode data of the second page.
6. The nonvolatile semiconductor memory system of claim 1 wherein the first page includes data of a sector and the second page includes data of the sector.
7. A nonvolatile semiconductor memory system, comprising:
a memory array that includes a plurality of memory cells that individually hold a first bit of data of a first page and a second bit of data of a second page; and
an ECC encoder that encodes data of the first page according to a first encoding scheme prior to storage in the plurality of cells and does not encode data of the second page according to the first encoding scheme prior to storage in the plurality of cells,
wherein the first encoding scheme is a Low Density Parity Check (LDPC) scheme.
8. A nonvolatile semiconductor memory system comprising:
a flash memory array for storing data in a plurality of cells, an individual cell storing at least a first data bit of a first page of data and a second data bit of a second page of data; and
an ECC decoding system for first decoding the first page of data according to a first decoding scheme and subsequently using results of the decoding of the first page of data to decode the second page of data according to a second decoding scheme.
9. The flash memory system of claim 8 wherein the ECC decoding system includes a soft-input soft-output decoder which uses the results of the decoding of the first page along with data read from the plurality of cells as a soft-input.
10. The flash memory of claim 8 wherein data stored in the first page is encoded according to a first encoding scheme and data stored in the second page is not encoded according to the first encoding scheme.
11. The flash memory of claim 10 wherein the data stored in the second page is encoded according to a second encoding scheme.
12. The flash memory of claim 8 further comprising a reading circuit that reads the plurality of cells to provide probability values that are sent to the ECC decoding system.
13. A flash memory system comprising:
a flash memory array that stores at least a first page of data and a second page of data in a plurality of cells, each of the plurality of cells containing a first bit of the first page and a second bit of the second page;
an encoder that encodes data of the first page according to a first encoding scheme and encodes data of the second page according to a second encoding scheme;
a reading circuit that reads the plurality of cells and that provides probability values individually associated with bits stored in the plurality of cells; and
a soft-input soft-output ECC decoder that receives probability values from the reading circuit to decode the first page of data, and uses the results of the decoding of the first page of data to decode the second page of data.
14. The flash memory system of claim 13 wherein the first encoding scheme is a Low Density Parity Check (LDPC) scheme.
15. The flash memory system of claim 13 wherein the second encoding scheme uses fewer redundant bits than the first encoding scheme.
16. The flash memory system of claim 13 wherein the plurality of cells contain at least a third page.
17. The flash memory system of claim 13 wherein a single host-addressable sector extends over the first and second page.
18. The flash memory of claim 13 wherein the encoder encodes the data of the first page according to the second encoding scheme prior to encoding the data of the first page according to the first encoding scheme.
19. The flash memory of claim 18 wherein the decoder decodes the second page of data and the first page of data together using the second encoding scheme.
20. The flash memory system of claim 13 wherein the soft-input soft-output ECC decoder uses the results of the decoding of the second page of data to decode the first page of data.