Method for storing and reading data in a multilevel nonvolatile memory

• US 6,646,913 B2
• Filed: 10/11/2001
• Issued: 11/11/2003
• Est. Priority Date: 10/13/2000
• Status: Expired due to Term

• Current Assignee: Micron Technology, Inc.
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Micheloni, Rino, Campardo, Giovanni
• Primary Examiner(s): PHUNG, ANH K
• Application Number:
  US09/976,473
• Publication Number:
  US 20020054505A1
• Time in Patent Office: 761 Days
• Field of Search: 365/185.03, 365/185.11, 365/185.12, 365/185.14, 365/185.19, 365/185.13
• US Class Current: 365/185.03
• CPC Class Codes: G11C 11/56 using storage elements with more than two stable states represented by steps, e.g. of voltage, current, phase, frequency
• CPC Class Codes: G11C 11/5621 using charge storage in a floating gate
• CPC Class Codes: G11C 11/5642 Sensing or reading circuits; Data output circuits
• CPC Class Codes: G11C 8/00 Arrangements for selecting an address in a digital store for stores using transistors G11C11/407, G11C11/413

Abstract

The data management method applies to a multilevel nonvolatile memory device having a memory array formed by a plurality of memory cells. Each of the memory cells stores a number of bits that is not an integer power of two, for example three. In this way, one data byte is stored in a non-integer number of memory cells. The managing method includes storing, in a same clock cycle, a data word formed by a plurality of bytes, by programming a preset number of adjacent memory cells. Reading is performed by reading, in a same clock cycle, the stored data word.

Claims

1. A data managing method in a multilevel nonvolatile memory device having a memory array including a plurality of memory cells, the method comprising:

storing in each of said memory cells a stored number of bits that is not an integer power of two; and

storing a data byte in a non-integer number of the memory cells.

2. A data management method according to claim 1 wherein said stored number of bits is three.

3. A data managing method in a multilevel nonvolatile memory device having a memory array including a plurality of memory cells, the method comprising:

storing in each of said memory cells a stored number of bits that is not an integer power of two; and

storing in the memory array, during a first clock cycle, a data word comprising a plurality of bytes.

4. A data management method according to claim 3, comprising:

reading, in a second clock cycle, said data word comprising said plurality of bytes.

5. A data management method according to claim 4, comprising:

selecting one byte from among said plurality of bytes according to an external address.

6. A data management method according to claim 3, wherein said storing step comprises programming a preset number of adjacent memory cells.

7. A data management method according to claim 6, comprising:

reading, in a second clock cycle, a number of bits equal to the product of said preset number of adjacent memory cells and said stored number of bits, and discarding excess bits.

8. A data management method according to claim 7, in which one byte comprises a preset number of bits, wherein said step of discarding comprises eliminating a number of bits equal to the difference between said number of read bits and a number of stored bits equal to the product of the number of bytes in said plurality of bytes and said preset number of bits.

9. A data management method according to claim 3, wherein said step of storing comprises simultaneously storing said data word and additional information;

said additional information being at least partially stored in memory cells containing bits of said data word.

10. A data management method according to claim 9, wherein said step of storing said data word comprises storing a number of bits equal to the product of said stored number of bits and a number of bytes comprised in said plurality of bytes.

11. A data management method according to claim 9, wherein said step of storing additional information comprises storing a number of bits equal to the difference between a number of available bits and a number of word bits;

said number of available bits being equal to the product of a preset number of the memory cells and said preset number of bits, and said number of word bits being equal to the product of the number of bytes in said plurality of bytes and said preset number of bits.

12. A data managing method in a multilevel nonvolatile memory device having a memory array including a plurality of memory cells, the method comprising:

storing in each of said memory cells a stored number of bits that is not an integer power of tow;

in which a bytes comprises a preset number of bits, the storing step comprising storing in said memory cells a number of bits equal to a non-integer multiple of said preset number of bits.

13. A data management method according to claim 12, comprising:

reading a plurality of bits belonging to adjacent bytes;

storing some bits of said plurality of read bits;

acquiring a byte to be stored; and

programming a plurality of cells based on said byte to be stored and said some bits of said plurality of read bits.

14. A nonvolatile memory device comprising:

a memory array having a plurality of memory cells, wherein each of said memory cells stores a number of bits that is not an integer power of two, wherein said memory array comprises a preset number of adjacent memory cells storing a data word formed by a plurality of bytes;

a preset number of sense amplifiers equal to said preset number of adjacent memory cells, each of said sense amplifiers having an output;

a selector having a plurality of data inputs, a control input and output, said data inputs of said selector being each connected to a respective output of said sense amplifiers; and

a binary column decoder connected to said control input of said selector for connecting a selected data input among said data inputs to said output of said selector.

15. A device according to claim 14, wherein said number of bits is three.

16. A method for storing data in a nonvolatile memory, comprising:

storing in a first memory cell a bit of a first byte; and

storing in the first memory cell a first bit of a second byte while simultaneously storing in the first memory cell the first bit of the first byte.

17. The method of claim 16, further comprising:

storing in a second memory cell a second bit of the second byte; and

storing in the second memory cell a bit of a third byte while simultaneously storing in the second memory cell the second bit of the second byte.

18. The method according to claim 16, further comprising:

storing first and second portions of the first byte in the first memory cell and a second memory cell, respectively, the first portion including the bit of the first byte;

storing first and second portions of the second byte in the first memory cell and a third memory cell, respectively, the first portion of the second byte including the first bit of the second byte.

19. The method of claim 18 wherein if the second byte is to be programmed to a programming value and the first byte is not to be programmed, then the method comprises:

reading the first and second bytes;

storing the first portions of the first and second bytes in temporary storage locations;

programming the third memory cell according to the programming value; and

programming the first memory cell according to the programming value and the stored first portion of the first byte.

20. The method according to claim 18, further comprising storing first and second portions of a third byte in the third memory cell and a fourth memory cell, respectively, wherein if the second byte is to be programmed to a programming value and the first and third bytes are not to be programmed, then the method comprises:

reading the first, second, and third bytes;

storing the first portions of the first, second, and third bytes and the second portion of the second byte in temporary storage locations;

programming the third memory cell according to the programming value and the stored first portion of the third byte; and

programming the first memory cell according to the programming value and the stored first portion of the first byte.

21. The method according to claim 18 wherein if the first and second bytes are requested to be programmed to first and second programming values, the method includes programming the first, second and third memory cells in parallel.