Partial block data programming and reading operations in a non-volatile memory

• US 6,763,424 B2
• Filed: 01/19/2001
• Issued: 07/13/2004
• Est. Priority Date: 01/19/2001
• Status: Expired due to Term

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Corporation (Western Digital Corporation)
• Inventors: Conley, Kevin M.
• Primary Examiner(s): Sparks, Donald
• Assistant Examiner(s): Dinh, Ngoc V
• Application Number:
  US09/766,436
• Publication Number:
  US 20020099904A1
• Time in Patent Office: 1,271 Days
• Field of Search: 711/103, 711/113, 711/115, 365/185.11, 365/185.33, 365/218
• US Class Current: 711/103
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/1016 Performance improvement
• CPC Class Codes: G06F 2212/1032 Reliability improvement, data loss prevention, degraded operation etc
• CPC Class Codes: G06F 2212/7202 Allocation control and policies
• CPC Class Codes: G06F 2212/7208 Multiple device management, e.g. distributing data over multiple flash devices
• CPC Class Codes: G06F 2212/7209 Validity control, e.g. using flags, time stamps or sequence numbers
• CPC Class Codes: G11C 16/102 External programming circuits, e.g. EPROM programmers; In-circuit programming or reprogramming; EPROM emulators
• CPC Class Codes: G11C 16/105 Circuits or methods for updating contents of nonvolatile memory, especially with 'security' features to ensure reliable replacement, i.e. preventing that old data is lost before new data is reliably written
• CPC Class Codes: G11C 2216/16 Flash programming of all the cells in an array, sector or block simultaneously

Abstract

Data in less than all of the pages of a non-volatile memory block are updated by programming the new data in unused pages of either the same or another block. In order to prevent having to copy unchanged pages of data into the new block, or to program flags into superceded pages of data, the pages of new data are identified by the same logical address as the pages of data which they superceded and a time stamp is added to note when each page was written. When reading the data, the most recent pages of data are used and the older superceded pages of data are ignored. This technique is also applied to metablocks that include one block from each of several different units of a memory array, by directing all page updates to a single unused block in one of the units.

Claims

1. In a non-volatile memory system having a plurality of blocks of memory storage elements that are individually erasable as a unit and which are individually organized into a plurality of pages of memory storage elements that are individually programmable together, a method of substituting new data for superceded data within at least one page of one of the plurality of blocks while data in at least another page of said one block is not replaced, comprising:

programming the new data into at least one page of said one or another of the plurality of blocks,

identifying the at least one page of superceded data and the at least one page of new data by a common logical address,

recording a relative time of programming the at least one page of new data and the at least one page of superceded data; and

wherein the at least one page of superceded data is less than all the data contained in said one block.

2. The method of claim 1, wherein the relative time of programming is recorded for the individual pages in which the new and superceded data are programmed, whereby the at least one page of new data is distinguishable from the at least one page of superceded data by their recorded relative times of programming.

4. The method of claim 1, wherein nothing is written into the at least one page of superceded data as part of substituting the new data for the superceded data.

5. The method of claim 1, wherein recording a relative time of programming the new and superceded data includes storing a value of a clock at each of the times that the new and superceded data are programmed.

6. The method of claim 1, wherein recording a relative time of programming the new and superceded data includes storing a different value of a sequence of numbers at each of the times that the new and superceded data are programmed.

7. The method of either of claim 5 or 6, wherein storing the value indicating a relative time of programming the new and superceded data includes storing the individual values within the same pages as the new and superceded data to which the values relate.

8. The method of claim 1, wherein programming the new data into at least one page of another said one or another of the plurality of blocks includes programming the new data into the first available unused pages within said one or another block in a predefined order.

9. The method of claim 1, wherein identifying the at least one page of superceded data and the at least one page of new data by a common logical address includes recording at least part of the common logical address in the individual pages as overhead data.

10. The method of claim 9, including building a table in volatile memory including multiple physical block addresses for the common logical address.

11. A method of reading data that has been updated according to claim 2, comprising:

reading pages of data from said one block and, if new data has been programmed thereinto, said another block,

identifying any multiple pages of data that have the same logical address,

utilizing the recorded relative time of programming the new and superceded data to identify the most current of any pages having the same logical address, and

assembling data in the most current of any pages having the same logical address along with pages in said at least another page of said one block that have not been updated.

13. The method of either one of claim 11 or 12, additionally comprising operating the individual memory storage elements with more than two storage states, thereby storing more than one bit of data in each storage element, and reading pages of data includes reading the more than two storage states from the individual memory storage elements.

14. The method of any one of claims 1, 2 and 3-6, additionally comprising operating storage elements of the individual memory cells with more than two storage states, thereby storing more than one bit of data in each storage element.

15. The method of claim 14, wherein the storage elements include individual floating gates.

16. The method of any one of claims 1, 2 and 3-6, wherein the non-volatile memory system is formed within an enclosed card having an electrical connector along one edge thereof that operably connects with a host system.

3. In a non-volatile memory system having a plurality of blocks of memory storage elements that are individually erasable as a unit and which are individually organized into a plurality of pages of memory storage elements that are individually programmable together, a method of substituting new data for superceded data within at least one page of one of the plurality of blocks while data in at least another page of said one block is not replaced, comprising:

programming the new data into at least one page of said one or another of the plurality of blocks,

identifying the at least one page of superceded data and the at least one page of new data by a common logical address,

recording a relative time of programming the at least one page of new data and the at least one page of superceded data; and

wherein the data in at least another page of said one block that is not replaced are not copied into said one or another block as part of substituting the new data for the superceded data.

12. In a non-volatile memory system having a plurality of blocks of memory storage elements that are individually erasable as a unit and which are individually organized into a plurality of pages of memory storage elements that are individually programmable together, a method of substituting new data for superceded data within at least one page of one of the plurality of blocks while data in at least another page of said one block is not replaced, comprising:

programming the new data into at least one page of said one or another of the plurality of blocks, wherein pages within the individual blocks are programmed in a designated order,

identifying the at least one page of superceded data and the at least one page of new data by a common logical address,

reading pages of data within said one and, if new data has been programmed thereinto, another block in a reverse order from which they were programmed,

passing over any pages of data so read which have the same logical page address as a page whose data has already been read; and

wherein the at least one page of superceded data is less than all the data contained in said one block.

31. The method of claim 12 wherein the data in at least another page of said one block that is not replaced are not copied into said one or another block as part of substituting the new data for the superceded data.

17. A method of operating a non-volatile memory system having an array of memory storage elements organized into at least two sub-arrays, wherein the individual sub-arrays are divided into a plurality of non-overlapping blocks of storage elements wherein a block contains the smallest group of memory storage elements that are erasable together, and the individual blocks are divided into a plurality of pages of storage elements wherein a page is the smallest group of memory storage elements that are programmable together, comprising:

linking at least one block from individual ones of said at least two sub-arrays to form a metablock wherein its component blocks are erased together as a unit, and

updating pages of original data within any of the metablock component blocks less than all the pages within the block by programming replacement data into pages within another at least one block in only a designated one of the sub-arrays regardless of which sub-array the data being updated is stored.

18. The method of claim 17, wherein storing the original and replacement data includes:

identifying the original and replacement data by the same logical address to the memory system, and

distinguishing the replacement data from the original data by keeping track of the relative times that the original and replacement data have been programmed their respective pages of the memory.

19. In a re-programmable non-volatile memory system having a plurality of blocks of memory storage elements that are erasable together as a unit, the plurality of blocks individually being divided into a plurality of a given number of pages of memory storage elements that are programmable together, a method of operating the memory system, comprising:

programming individual ones of a first plurality of pages with original data, a logical page address associated with the original data and an indication of a relative time of programming the original data,

thereafter programming individual ones of a second plurality of a total number of pages less than said given number with updated data, a logical page address associated with the updated data and an indication of a relative time of programming the updated data, wherein at least some of the logical page addresses associated with the updated data are the same as those associated with the original data programmed into the first plurality of pages, and

thereafter reading and assembling data from the first and second plurality of pages including, for pages having the same logical addresses, comparing the relative time indications programmed therein and selecting the updated data from the pages having the more recent time indication and omitting use of the original data from the pages having the older time indication.

20. In a re-programmable non-volatile memory system having a plurality of blocks of memory storage elements that are erasable together as a unit, the plurality of blocks individually being divided into a plurality of a given number of pages of memory storage elements that are programmable together, a method of operating the memory system, comprising:

programming individual ones of a first plurality of said given number of pages in each of at least a first block with original data and a logical page address associated with the original data,

thereafter programming individual ones of a second plurality of a total number of pages less than said given number in a second block with updated data and a logical page address associated with the updated data, wherein the logical page addresses associated with the updated data programmed into the second plurality of pages are the same as those associated with the original data programmed into the first plurality of pages, and

thereafter reading and assembling data from the first and second plurality of pages including, for pages having the same logical addresses, selecting the updated data from the pages most recently programmed and omitting use of the original data from the pages earlier programmed.

21. The method of claim 20, wherein

programming the first plurality of pages with original data and programming the second plurality of pages with updated data additionally includes programming the individual pages with an indication of a relative time of programming, and

reading and assembling data from the first and second plurality of pages includes, for pages having the same logical addresses, selecting the updated data from the pages having the more recent time indication and omitting use of the original data from the pages having the older time indication.

22. The method of claim 20, wherein reading and assembling data from the first and second plurality of pages includes reading the first and second plurality of pages in an order that is reverse to an order in which they were programmed, and ignoring data read from pages having logical addresses that are the same as logical addresses of other pages from which data has previously been read.

23. The method of claim 20, wherein programming the second plurality of pages in a second block includes causing the updated data to be programmable in pages of the second block having the same offset positions therein than the offset positions of pages within the first block containing the original data associated with the same logical page addresses.

24. The method of claim 20, wherein programming the second plurality of pages in a second block includes causing the updated data to be programmable in pages of the second block having different offset positions therein than the offset positions of pages within the first block containing the original data associated with the same logical page addresses.

25. The method of either of claim 21 or 22, wherein programming the second plurality of pages in a second block includes causing the updated data to be programmable in pages of the second block having the same offset positions therein than the offset positions of pages within the first block containing the original data associated with the same logical page addresses.

26. The method of either of claim 21 or 22, wherein programming the second plurality of pages in a second block includes causing the updated data to be programmable in pages of the second block having different offset positions therein than the offset positions of pages within the first block containing the original data associated with the same logical page addresses.

27. The method of claim 20, wherein reading and assembling data includes reading and using original data stored in the first plurality of pages that has not been updated.

28. The method of claim 20, additionally comprising operating the individual memory storage elements with more than two storage states, thereby storing more than one bit of data in each storage element, wherein programming the pages includes programming the individual memory storage elements into more than two storage states and reading the pages includes reading the more than two storage states from the individual memory storage elements.

29. The method of claim 28, wherein the storage elements include individual floating gates.

30. The method of any one of claims 20-24, wherein the non-volatile memory system is formed within an enclosed card having an electrical connector along one edge thereof that operably connects with a host system.