Method for page- and block based scrambling in non-volatile memory
A method and system for programming and reading data with reduced read errors in a memory device. In one approach, date to be written to the memory device is scrambled using a first pseudo random number which is generated based on a page of the memory device to which the data is to be written, to provide first scrambled data, which is scrambled using a second pseudo random number which is generated based on a block of the memory device to which the data is to be written. This avoids bit line-to-bit line and block-to-block redundancies which can result in read errors. The data may also be scrambled using a third pseudo random number that depends on a section within a page. Scrambling may also be based on one or more previous pages which were written.
1. A method of writing data into a page of a flash memory device, where the pages of the flash memory device are grouped into blocks that are each erasable as a single unit, the method comprising:
receiving data to be stored in the page;
scrambling the data to generate first scrambled data, where the scrambling depends on a number of the page within a block containing the page;
calculating second scrambled data that is a function of the first scrambled data and another number, wherein the another number depends on a block number of the block containing the page; and
writing the second scrambled data into the page.
2. The method of claim 1 wherein the first scrambled data is an XOR of the received data and a number which is a function of the number of the page within the block containing the page.
3. The method of claim 1 wherein the second scrambled data is an XOR of the first scrambled data and the number of the page within the block containing the page.
4. The method of claim 1 wherein the another number does not depend on the number of the page within the block containing the page.
5. The method of claim 1 wherein the scrambling depends nonlinearly on the number of the page within the block containing the page.
6. The method of claim 5 wherein the nonlinear dependency comprises at least one of a modulo operation and a multiplication over a finite field.
7. The method of claim 1 wherein the page comprises multiple sections, and the scrambling also depends on a number of a section within the page.
8. The method of claim 7 wherein the scrambling depends nonlinearly on the number of the section within the page.
9. The method of claim 1 wherein the number of the page within the block containing the page is a pseudo random number.
10. The method of claim 1 wherein the number of the page within the block containing the page is a random number.
11. A method of writing data into a page of a flash memory device, where the pages of the flash memory device are grouped into blocks that are each erasable as a single unit, the method comprising:
receiving data to be stored in the page;
scrambling the data to generate first scrambled data, where the scrambling depends on a number and wherein the number depends on a block number of the block containing the page;
calculating second scrambled data that is a function of the first scrambled data and a number of the page within the block containing the page; and
writing the second scrambled data into the page.
12. The method of claim 11 wherein the number on which the scrambling depends does not depend on the number of the page within the block.
13. The method of claim 11 wherein the second scrambled data is a non-linear function of the number of the page within the block containing the page.
14. The method of claim 11 wherein the page comprises multiple sections, and the second scrambled data depends on a number of a section within the page.
15. The method of claim 14 wherein the second scrambled data depends nonlinearly on the number of the section within the page.
16. The method of claim 11 wherein the number on which the scrambing depends is a pseudo random number.
17. A method of descrambling first data from a page of a flash memory device, where the pages of the flash memory device are grouped into blocks that are each erasable as a single unit, the method comprising:
reading the first data from the page;
calculating a number, wherein the number depends on a block number of a block containing the page;
descrambling the first data using the number to provide second data; and
descrambling the second data based on a number of the page within the block containing the page to provide third data.
18. The method of claim 17 wherein the third data is an XOR of the second data and a number which is a function of the number of the page within the block containing the page.
19. The method of claim 17 wherein the number which depends on the block number of the block containing the page, does not depend on the page number within the block.
20. The method of claim 17 wherein the page comprises multiple sections, and at least one of the descrambling of the first data and the descrambling of the second data, depends on a number of a section within the page.
21. The method of claim 17 wherein the number which depends on the block number of the block containing the page, is a pseudo random number.