(12) United States Patent
`Friedman et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 7,000,063 B2
`Feb. 14, 2006
`
`USOO7000063B2
`
`(54)
`
`(75)
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`(73)
`
`(*)
`
`(21)
`(22)
`(65)
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`(51)
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`(52)
`(58)
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`(56)
`
`WRITE-MANY MEMORY DEVICE AND
`METHOD FOR LIMITING ANUMBER OF
`WRITES TO THE WRITE-MANY MEMORY
`DEVICE
`
`Inventors: David R. Friedman, Menlo Park, CA
`(US); J. James Tringali, Los Altos, CA
`(US)
`Assignee: Matrix Semiconductor, Inc., Santa
`Clara, CA (US)
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 342 days.
`Appl. No.: 09/972,787
`
`Notice:
`
`Filed:
`
`Oct. 5, 2001
`
`Prior Publication Data
`US 2003/0070034 A1
`Apr. 10, 2003
`
`Int. Cl.
`(2006.01)
`G06F 12/14
`U.S. Cl. ...................................................... 711/103
`Field of Classification Search ................ 711/103,
`711/154, 163
`See application file for complete Search history.
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`5,153,462 A 10/1992 Agrawal et al.
`5,264,740 A 11/1993 Wright
`5,414.829 A 5/1995 Fandrich et al.
`5,734,816 A * 3/1998 Niijima et al. ......... 395/182.06
`5,737.742 A * 4/1998 Achiwa et al. ............. 711/103
`6,034.882 A 3/2000 Johnson et al.
`6,058,047 A * 5/2000 Kikuchi ................. 365/185.33
`6,134,141. A 10/2000 Wong
`6,151,246 A 11/2000 So et al.
`6,181,603 B1
`1/2001 Jyouno et al.
`6.219.282 B1
`4/2001 Tanaka
`
`Write - Many Memory Device
`With Sideband Fields
`
`
`
`4/2001 Guterman et al.
`6,222,762 B1
`5/2001 Gudesen et al.
`6,236,587 B1
`8/2001 Wong et al.
`6,278,633 B1
`3/2002 Wong
`6,363,008 B1
`4/2002 Corisis
`6,376,282 B1
`4/2002 Gonzalez et al.
`6,376,284 B1
`OTHER PUBLICATIONS
`“64Mx8 Bit NAND Flash Memory,” Samsung Electronics
`(Oct. 27, 2000).
`“How Flash Memory Works,” wysivvyg://8/http://www.
`howStuffWorkS.com/flash-memory.html?printable=1, 5 pages
`(1998).
`“Datalight FlashFXTM 4.06 User's Guide," p. 11 (Aug.
`2000).
`
`(Continued)
`Primary Examiner-Kevin L. Ellis
`(74) Attorney, Agent, or Firm-Brinks Hofer Gilson &
`Lione
`
`(57)
`
`ABSTRACT
`
`The preferred embodiments described herein provide a
`write-many memory device and method for limiting a num
`ber of writes to the write-many memory device. In one
`preferred embodiment, a write-many memory device is
`provided comprising a plurality of blocks of memory, each
`block being limited to N number of writes. Data can be
`stored in a block of memory only if there has been fewer
`than N number of writes to the block. In another preferred
`embodiment, a write-many memory device is provided
`comprising a plurality of blocks of memory, wherein each
`block comprises a first Sideband field Storing data indicating
`whether the block is free and a second sideband field storing
`data indicating how many times the block has been written
`into. The first and second sideband fields are used in a
`method for limiting a number of writes to the write-many
`memory device. Other preferred embodiments are provided,
`and each of the preferred embodiments can be used alone or
`in combination with one another.
`
`45 Claims, 3 Drawing Sheets
`
`Software
`Ard.Or
`Hardware
`
`DataSource
`
`if O
`
`Micron Ex. 1016, p. 1
`Micron v. Vervain
`IPR2021-01549
`
`

`

`US 7,000,063 B2
`Page 2
`
`OTHER PUBLICATIONS
`“How Does TrueFFS(R) manage Wear Leveling?," http://
`www.m-SyS.com/content/information/calcInfo.asp, 2 pages
`(printed Oct. 5, 2001).
`“Intel StrataFlashTM Memory Technology Development and
`Implementation,” Fazio et al., Intel Technology Journal, 13
`pages (Q41997).
`“A 125mm 1Gb NAND Flash Memory with 10MB/s
`Program Throughput,” Nakamura et al., ISSCC 2002/Ses
`Sion 6/SRAM and Non-Volatile Memories/6.4, 2002 IEEE
`International Solid-State Circuits Conference, Digest of
`Technical Papers, pp. 106-107 (2002).
`“On the Go With Sonos,” White et al., Circuits & Devices,
`pp. 22-31 (Jul. 2000).
`“NROM: A Novel Localized Trapping, 2-Bit Nonvolatile
`Memory Cell.” Eitan et al., IEEE Electron Device Letters,
`vol. 21, No. 11, pp. 543-545 (Nov. 2000).
`“A512Mb NROM Flash Data Storage Memory with 8MB/s
`Data Rate,” Maayan et al., ISSCC 2002/Session 6/SRAM
`and Non-Volatile Memories/6.1, 2002 IEEE International
`Solid-State Circuits Conference, Digest of Technical Papers,
`pp. 100-101 (2002).
`
`Unified Memory-A High-Performance
`“Ovonic
`Nonvolatile Memory Technology for Stand-Alone Memory
`and Embedded Applications,” Gill et al., ISSCC 2002/
`Session 12/TD Digital Directions/124, 2002 IEEE
`International Solid-State Circuits Conference, Digest of
`Technical Papers, pp. 202-203 (2002).
`“0.13
`um Metal-Oxide-Nitride-Oxide-Semiconductor
`Single Transistor Memory Cell with Separated Source
`Line.” Fujiwara et al., Jpn. J. Appl. Phys. Vol. 39, pp.
`417-423, Part 1, No. 2A (Feb. 2000).
`“Three-Dimensional Memory Array and Method of Fabrica
`tion,” U.S. Appl. No. 09/560,626, filed Apr. 28, 2000,
`inventor: N. Johan Knall.
`“Digital Memory Method and System for Storing Multiple
`Bit Digital Data.” U.S. Appl. No. 09/932,701, filed Aug. 17,
`2001, inventors: Michael A. Vyvoda and N. Johan Knall.
`“Memory Device and Method for Reliably Reading Multi
`Bit Data from a Write-Many Memory Cell,” U.S. Appl. No.
`10/144,451, filed May 9, 2002, inventor: Bendik Kleveland.
`* cited by examiner
`
`Micron Ex. 1016, p. 2
`Micron v. Vervain
`IPR2021-01549
`
`

`

`U.S. Patent
`
`Feb. 14, 2006
`
`Sheet 1 of 3
`
`US 7,000,063 B2
`
`Write - Many Memory Device
`With Sideband Fields
`
`Software
`And/Or
`Hardware
`
`Data Source
`
`Fig. f
`
`1 O
`
`
`
`Write - Many
`Memory
`Device
`
`Fig. 2
`
`Micron Ex. 1016, p. 3
`Micron v. Vervain
`IPR2021-01549
`
`

`

`U.S. Patent
`
`Feb. 14, 2006
`
`Sheet 2 of 3
`
`US 7,000,063 B2
`
`Insert Memory Device
`into Host Device
`
`
`
`
`
`
`
`HOW
`Much Space
`
`SO5
`
`O
`3OO
`
`Query Loop
`Not Free
`
`Max
`Free
`Not Max
`
`31 O
`
`J& O
`
`
`
`
`
`Cannot
`Erase File
`(or free up space in
`this area)
`
`Create
`Free Space
`
`Choose File
`To Erase
`
`35.
`
`Only On Fields
`otAt Max
`
`File Chosen To Erasels:
`- 375
`Partially On Max
`Partially Not Max
`
`NeW
`Data
`Available
`
`
`
`Store Data in
`Free Blocks And
`Deallocate Space
`
`d
`
`Clear Free Bit
`And Update Count
`d
`Field in Each
`Block Used
`
`r
`
`Set "Free
`Bit in
`Each Block
`Erased
`
`indicator:
`
`Only X Data
`Available By
`Erasino. This
`g
`Location
`
`
`
`
`
`
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`
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`
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`Fig. 3
`
`37O
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`Micron Ex. 1016, p. 4
`Micron v. Vervain
`IPR2021-01549
`
`

`

`U.S. Patent
`
`Feb. 14, 2006
`
`Sheet 3 of 3
`
`US 7,000,063 B2
`
`
`
`Micron Ex. 1016, p. 5
`Micron v. Vervain
`IPR2021-01549
`
`

`

`1
`WRITE-MANY MEMORY DEVICE AND
`METHOD FOR LIMITING ANUMBER OF
`WRITES TO THE WRITE-MANY MEMORY
`DEVICE
`
`BACKGROUND
`
`Users of write-many memory devices can be segmented
`into a variety of categories based on how many times they
`need to re-write the memory device and on what they are
`Willing to spend for the memory device. Currently, there are
`no write-many memory devices that control the number of
`allowable writes (or re-writes) to the memory device.
`Accordingly, it is very difficult to Segment the write-many
`memory device market into those willing to pay for two
`re-writes from those willing to pay for ten re-writes, for
`example.
`Additionally, Some write-many memory devices, Such as
`Flash memory, are reliable only for a limited number of
`writes. Ablock of Flash memory can “wear out” and become
`“stuck' at one logic State after repeated erase operations due
`to the inability to remove all of the charge trapped in the
`oxide under a floating gate of a Storage transistor. To
`equalize the wear (i.e., the number of erase times) of the
`Flash memory, a Flash Translation Layer (FTL) can employ
`a “wear leveling algorithm to use all areas of the Flash
`memory in an equal manner. In operation, when a file Stored
`in a block of memory needs to be updated, the FTL notices
`that the block is non-Virgin and does not erase and overwrite
`the old data. Instead, the FTL writes the updated data to
`unused blocks of memory and directs Subsequent read
`accesses to those blocks. The old data is marked as “old” and
`is not erased until the block has to be reused. Although the
`wear leveling algorithm tends to balance the wear on the
`blocks, a block can Still wear out after repeated erase
`operations.
`There is a need, therefore, for a write-many memory
`device and method for limiting a number of writes to the
`write-many memory device.
`
`SUMMARY
`
`The present invention is defined by the following claims,
`and nothing in this Section should be taken as a limitation on
`those claims.
`By way of introduction, the preferred embodiments
`described below provide a write-many memory device and
`method for limiting a number of writes to the write-many
`memory device. In one preferred embodiment, a write-many
`memory device is provided comprising a plurality of blockS
`of memory, each block being limited to N number of writes.
`Data can be stored in a block of memory only if there has
`been fewer than N number of writes to the block. In another
`preferred embodiment, a write-many memory device is
`provided comprising a plurality of blocks of memory,
`wherein each block comprises a first Sideband field Storing
`data indicating whether the block is free and a Second
`Sideband field Storing data indicating how many times the
`block has been written into. The first and second Sideband
`fields are used in a method for limiting a number of writes
`to the write-many memory device. Other preferred embodi
`ments are provided, and each of the preferred embodiments
`can be used alone or in combination with one another.
`The preferred embodiments will now be described with
`reference to the attached drawings.
`
`US 7,000,063 B2
`
`2
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is an illustration of a write-many memory device
`with sideband fields of a preferred embodiment.
`FIG. 2 is a block diagram of a write-many memory device
`coupled with a host device of a preferred embodiment.
`FIG. 3 is a flow chart of a method of a preferred
`embodiment for limiting a number of writes to a write-many
`memory device.
`FIGS. 4A-4D are illustrations of a method of a preferred
`embodiment for limiting a number of writes to a write-many
`memory device.
`
`DETAILED DESCRIPTION OF THE
`PRESENTLY PREFERRED EMBODIMENTS
`
`15
`
`The preferred embodiments described herein relate to a
`write-many memory device. The terms “memory device”
`and “storage device' will be used interchangeably herein. In
`a write-many memory device, an un-programmed digital
`State of a memory location (e.g., the Logic 0 (or Logic 1)
`State) can be restored after it is Switched to a programmed
`digital State (e.g., the Logic 1 (or Logic 0) state). In this way,
`Stored data can be erased and/or over-written with new data.
`The write-many memory device is preferably field-program
`mable So that the memory locations of the memory device
`can be programmed by a user at a time after the memory
`device has been manufactured. Any Suitable type of write
`many memory device can be used. For example, a write
`many memory device can take the form of a Solid-State
`Storage device (Such as Flash memory) or a magnetic Storage
`device. If a memory device with a memory array is used, the
`memory array can be two-dimensional or three-dimensional
`and be made of any Suitable material (e.g., Semiconductor,
`phase-change, amorphous Solids, MRAM, or organic pas
`sive elements). Preferably, the write-many memory device is
`non-volatile So that it maintains its contents without any
`external Source of power. It is preferred that the write-many
`memory device take the form described in “Dense Arrays
`and Charge Storage Devices, and Methods for Making
`Same,” U.S. patent application Ser. No. 09/927,648, filed
`Aug. 13, 2001, which is hereby incorporated by reference.
`Turning now to the drawings, FIG. 1 is an illustration of
`a write-many memory device 100 of a preferred embodi
`ment. The write-many memory device 100 is in communi
`cation with a data Source 110 and Software and/or hardware
`components 120 that are operative to Store data Supplied by
`the data source 110 in the write-many memory device 100.
`The data Source 110 can be a component that itself generates
`data (e.g., part of a digital camera that generates a digital
`picture) or can be a component that receives data from
`another Source Such as a network (e.g., the Internet) or
`another computer. "Data' can take any Suitable form, Such
`as, but not limited to, digital images, Video, audio, books,
`maps, and numerous other examples that will be readily
`apparent to those skilled in the art.
`The write-many memory device 100, the data source 110,
`and the software and/or hardware components 120 can be
`integrated together in a Single System, Such as a general
`purpose or application-specific computing System. Alterna
`tively, as shown in FIG. 2, the write-many memory device
`100 can be a removable device that couples with a host
`device 200, which contains the data Source 110 and the
`Software and/or hardware components 120. AS used herein,
`“coupled with means directly coupled with or indirectly
`coupled with through one or more named or unnamed
`intervening components. In one embodiment, the write
`
`25
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`60
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`65
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`Micron Ex. 1016, p. 6
`Micron v. Vervain
`IPR2021-01549
`
`

`

`US 7,000,063 B2
`
`15
`
`35
`
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`3
`many memory device 100 takes the form of a compact,
`modular device, Such as a card or a Stick with an exposed
`electrical connector, that is readily inserted into and
`removed from a corresponding port in the host device 200.
`The host device 200 can be a consumer electronic device,
`Such as a digital camera, a digital audio player, a personal
`digital assistant, a cellular telephone, a game player, a digital
`book, or a general-purpose computer. The memory device
`100 can be used to store data generated by the host device
`200 and can also be used to transfer data from the host
`device 200 to another device (e.g., from a PC to a PDA).
`Returning to FIG. 1, the write-many memory device 100
`of this preferred embodiment has a plurality of blocks 102
`of memory, each block comprising two sideband fields 104,
`106. As used herein, a “block” refers to an allocation unit of
`memory. A block can be of any size. For example, a block
`can include one memory unit, more than one memory unit,
`or all of the memory units in the memory device 100. If files
`to be stored in the memory device 100 are of a single size,
`it may be preferred to match the size of a block to the size
`of the file so that a file is stored in a single block. If files to
`be stored in the memory device 100 are of different sizes, it
`may be preferred to design the size of a block to be Smaller
`than the Size of a file. This finer granularity reduces the
`potential for wasted Space. In one preferred embodiment, a
`block contains 512 bytes of memory that can be written into
`by a user of the memory device 100. Each block is associ
`ated with 16 bytes of “reserved” memory that is not user
`accessible. At least some of the 16 bytes are used for the first
`and second sideband fields 104,106. The 512-byte block and
`its associated 16-byte reserved memory is referred to as a
`"page.'
`The first and second Sideband fields 104, 106 are used in
`a method for limiting a number of writes to the write-many
`memory device 100. The first sideband field 104 stores data
`indicating whether its associated block 102 is free. A block
`is free if the block does not contain data that should not be
`overwritten or erased. In one preferred embodiment, the first
`Sideband field 104 Stores a “1” if the block 102 is free and
`stores a “0” if the block 102 is not free. The second Sideband
`field 106 stores data indicating how many times the block
`102 has been written into. For example, the second sideband
`field 106 can store a count of how many times the block 102
`has been written into, and each time the block 102 is written
`into, the count is increased. Alternatively, the Second Side
`band field 106 can Store a count representing the remaining
`number of times that the block 102 can be written into, and
`this count is decremented each time the block 102 is written
`into. In either alternative, the count can represent the number
`of re-writes instead of the number of writes.
`AS will be discussed in greater detail below, the data
`stored in the second sideband fields 106 can be preset by a
`manufacturer of the memory device 100 to limit the number
`of writes to a certain number, N. In this way, data is Stored
`in the block 102 only if there have been fewer than N
`55
`number of writes to the block 102. The memory device 100
`can be preset by the manufacturer So that it writeS as few as
`one time (resulting in the write-many memory device oper
`ating as a WORM) or as many times as desired, preferably
`not more than (i.e., equal to or fewer than) the maximum
`allowable qualified writes (if Such a maximum exists). AS
`used herein, a “manufacturer of a memory device refers to
`any party who handles the memory device before it is Sold
`or distributed to an end user (e.g., a consumer). A "manu
`facturer' can include a party involved in the manufacturing,
`assembly, packaging, Sale, or distribution of the memory
`device.
`
`45
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`50
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`60
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`
`4
`Turning again to the drawings, FIG. 3 is a flow chart of
`a method of a preferred embodiment for limiting a number
`of writes to a write-many memory device. As shown in FIG.
`3, the memory device 100 is first inserted into the host
`device 200 (act 300). The host device 200 then determines
`how much space is free in the memory device 100 (act305).
`To do this, the host device 200 runs a query loop (act 310)
`that determines how many blocks of memory are free (i.e.,
`how many blockS have first Sideband fields containing a
`“1”). Additionally, the query loop determines how many
`blocks have been written into a maximum number of times.
`This data is aggregated into four categories in a run-time
`allocation table: (1) not free; not max, (2) not free, max, (3)
`free; not max, and (4) free; max. Next, the host device 200
`checks the allocation table and determines if there is enough
`free space (i.e., enough blocks with a “1” in the first
`Sideband field) to Store data of an expected size based on
`user specifications (act315). For example, if the host device
`200 is a digital camera, the host device 200 can determine
`if there is enough space available on the memory device 110
`to Store a new picture given the quality Setting and com
`pression ratio Set by the user. This determination is made
`before the user is allowed to take a new picture (i.e., the
`determination is made before run-time). If there is enough
`free space, the host device waits for input (act 320) and
`determines if new data is available (act 325).
`If new data is available, the host device 200 stores the data
`in at least Some of the free blocks and de-allocates that Space
`from the amount indicated in the free, not max and/or free;
`max categories of the run-time allocation table (act 330).
`Then, in each block that was used to Store the data, the free
`bit in the first sideband field is cleared (e.g., set from 1 to 0)
`to indicate that the block is not free, and the data in the
`second sideband field (the “count” field) is updated to
`indicate that the block was used (act 335). An example of
`this process is shown in FIGS. 4A and 4.B. FIG. 4A shows
`a memory device with nine blocks (blocks 1-9). File A is
`stored in blocks 1-3, and File B is stored in blocks 4-7.
`Accordingly, Blocks 1-7 are not free (i.e., the first sideband
`fields contain a 0), and blocks 8 and 9 are free (i.e., the first
`sideband fields contain a 1). As shown in FIG. 4B, when a
`two-block long file (File C) is stored in free blocks 8 and 9,
`the free bit in the first sideband fields of blocks 8 and 9 is
`cleared (Switched from 1 to 0), and the data in the second
`sideband fields of blocks 8 and 9 is updated (from 4 to 5).
`Returning to the flow chart of FIG. 3, after act 335 is
`performed, the host device 200 again determines if there is
`enough free space to store data of an expected size (act315).
`AS described above, in act 330, the host device 200 de
`allocates the Space used to Store the file from the amount
`indicated in the free; not max and/or free, max categories in
`the run-time copy of the allocation table created in act 305.
`Because a run-time copy is used, act 305 does not need to
`be re-performed, thereby Saving time and resources in the
`host device 200. In an alternate embodiment, instead of
`de-allocating Space in a run-time copy of the allocation table
`in act 330, the host device 200 can re-run the query loop
`(acts 305 and 310) after each write operation.
`If the host device 200 determines that there is not enough
`free Space, the user is given the option of creating free Space
`(act 340). If the user does not want to create free space (e.g.,
`the user does not want to delete any of the stored files), the
`memory device 100 will be considered full by the host
`device 200 (act 345). If the user does want to create free
`Space, the user will be asked to choose a file to erase from
`the memory device 100 (act350). The host device 200 then
`determines whether some or all of the blocks storing the
`
`Micron Ex. 1016, p. 7
`Micron v. Vervain
`IPR2021-01549
`
`

`

`US 7,000,063 B2
`
`15
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`40
`
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`Selected file have been written into a maximum number of
`times (in this example, the maximum number is 5). If the
`selected file is stored only in blocks that have been written
`into a maximum number of times (scenario 355), such as
`File C in FIG. 4B, then the host device 200 prevents the user
`from erasing the file (act 360) since erasing the file would
`not create free Space to Store a new file. Of course, the user
`can be given the option to override this protection. If the
`selected file is stored only in blocks that have been written
`into fewer than the maximum number of times (Scenario
`365), the user is given the option to erase the file (act 370).
`If the selected file is stored both in blocks that have been
`written into fewer than the maximum number of times and
`in blocks that have been written into the maximum number
`of times (scenario 375), such as File B in FIG. 4B, the user
`is provided with an indicator alerting him that erasing the file
`will only free Some of the Space occupied by the file (act
`380). The user is then given the option to erase the file (act
`370). The user may choose not to erase the file after knowing
`that the erasure of the file will not create the Space needed
`to Store a new file.
`If the user chooses to erase a file stored only in blocks that
`have been written into fewer than the maximum number of
`times, the free bit is set in the first sideband fields of each of
`the erased blocks. For example, as shown in FIG. 4C, if the
`user Selects to erase File A, which is Stored only in blockS
`that have been written into fewer than the maximum number
`of times, the first Sideband fields of blocks 1-3 are set from
`0 to 1. If the user chooses to erase a file stored both in blocks
`that have been written into fewer than the maximum number
`of times and in blocks that have been written into the
`maximum number of times, the free bit is set in the first
`Sideband fields of each of the erased blocks that have not
`been written into a maximum number of times. Consider, for
`example, the Situation in which a user erases File B. Some
`of the blocks storing File B (blocks 4, 5, and 7) have been
`written into fewer than the maximum number of times, while
`block 6 has been written into the maximum number of times.
`As shown in FIG. 4D, when File C is erased, the free bit is
`set in the first sideband fields of blocks 4, 5, and 7 but not
`in block 6. This prevents block 6 from being written into
`again.
`With Some write-many technologies, old data in a block
`can be overwritten with new data without first returning the
`cells of the block to their un-programmed digital state. With
`these technologies, the erase operation Sets the free bit in the
`first sideband field of the block but does not necessarily
`return the cells of the block to their un-programmed digital
`State. In this way, the erase operation is simply a bookkeep
`ing function (i.e., Setting the free bit in the first Sideband
`field). However, with other write-many technologies, Such
`as Flash memory, the cells of a block must be returned to
`their un-programmed digital State before new data can be
`written into the block. With these technologies, the erase
`operation both sets the free bit in the first sideband field of
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`the block and returns the cells of the block to their un
`programmed digital State.
`There are Several applications that can be used with this
`preferred embodiment. For example, this preferred embodi
`ment can be used by a manufacturer of memory devices to
`provide a consumer with an alternative to conventional
`write-once and write-many memory devices. AS discussed
`above, users of write-many memory devices can be Seg
`mented based on how many times they need to write to the
`memory device and on what they are willing to spend for the
`memory device. With this preferred embodiment, a memory
`device manufacturer can create a variety of write-many
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`memory devices with different maximum number of writes,
`and these memory devices can be priced at different levels
`depending on their maximum number of writes. This Selec
`tion allows a consumer to purchase the memory device with
`the write capability and price that he desires. For example,
`instead of merely deciding between a write-once memory
`device or a write-many memory device, a consumer can
`decide to purchase a “Write-5' memory device or a “Write
`10” memory device. The “Write-5” and “Write-10” memory
`devices can be priced between the write-once and write
`many memory devices, with the “Write-10” memory device
`being more expensive than the “Write-5' memory device.
`In another application, the maximum number of writes is
`used to limit the use of a program Stored in the memory
`device. Consider, for example, an interactive computer game
`Stored on a write-many memory device that Stores data on
`the memory device as the user interacts with the game.
`Limiting the number of writes to the write-many memory
`device effectively limits the user's opportunity to interact
`with the game. When the memory device no longer accepts
`user interaction, a user would be motivated to purchase a
`new game card. There are many additional applications that
`can be created around the functionality of limiting the
`number of writes to the write-many memory device. For
`example, applications can be developed for Smart Cards that
`only allow a user to interact with a record a limited number
`of times before the record is "frozen' on the card.
`In yet another use of this preferred embodiment, the
`maximum number of writes to the memory device is Set to
`assure a quality write to the memory device. AS discussed
`above, Some write-many memory devices are reliable only
`for a limited number of uses. Setting the maximum number
`of writes at or below the maximum allowable qualified
`number of uses will prevent a user from using the memory
`device for more writes than the memory device should be
`expected to handle. The control logic implemented in the
`Software and/or hardware components 120 can be modified
`to accommodate the quality and reliability-related use of this
`preferred embodiment. For example, it may be preferred to
`Switch the order of acts 330 and 335 in the flow chart of FIG.
`3 so that the count field is updated before data is stored in
`the memory device 100. If there is an error writing data to
`a block, the host device 200 may attempt to write the data
`to the block several times. By switching the order of acts 330
`and 335, the usage count of the block is updated each time
`an attempt is made to Store the data in the block. Otherwise,
`the usage count would be updated only once even though the
`block was written into several times. Additionally, if the
`erase operation includes the act of returning the cells of a
`block to their un-programmed digital State, it may be pre
`ferred to update the count field for this operation Since the
`erase operation has the effect of wearing out the block.
`There are several alternatives that can be used with these
`preferred embodiments. For example, instead of using Soft
`ware and/or hardware components 120 in the host device
`200, a controller in the memory device can be used to
`implement control logic responsible for Some or all of the
`functionality described in the flow chart in FIG. 3. In another
`alternative embodiment, a block’s “free” and “count” status
`can be determined without the use of sideband fields (ac
`cordingly, Sideband fields should not be read into the claims
`unless explicitly recited therein). For example, a blocks
`“free” and “count Status can be tracked using file System
`Structures Stored in the memory device. A "file System
`Structure' can take the form of an allocation table, a listing
`of Stored files, a Search tree, a boot block, a partition header,
`a partition footer, and a description of contents of the
`
`Micron Ex. 1016, p. 8
`Micron v. Vervain
`IPR2021-01549
`
`

`

`US 7,000,063 B2
`
`7
`memory device. Of course, other file System Structures in
`addition to those listed above can be used. In operation, the
`host device's file System examines the file System Structures
`to determine the “free” and “count” status of a given block
`from the file System Structures.
`Additionally, with any of the preferred embodiments
`described above, a write-many memory device can comprise
`a plurality of blocks of memory that are limited to a
`maximum number of writes and one or more additional
`blocks that are either limited to a different number of writes
`or that have no limit at all. For example, it may be preferred
`not to restrict the number of writes to the blocks that store
`file System Structures Since these structures are frequently
`updated by the host device's file system.
`It is intended that the foregoing detailed description be
`understood as an illustration of Selected forms that the
`invention can take and not as a definition of the invention.
`It is only the following claims, including all equivalents, that
`are intended to define the Scope of this invention. Finally, it
`should be noted that any aspect of any of the preferred
`embodiments described herein can be used alone or in
`combination with one another.
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`8. A method for limiting a number of writes to a write
`many memory device, the method comprising:
`(a) providing a write-many memory device comprising a
`plurality of blocks of memory, each block comprising
`a first Sideband field Storing data indicating whether the
`block is free and a Second Sideband field Storing data
`indicating how many times the block has been written
`into;
`(b) determining whether there are enough blocks free to
`Store a file; and
`(c) if there are enough blocks free to store the file:
`(c1) Storing the file in at least Some of the blocks free
`to store the file;
`(c2) in the first sideband fields of the blocks storing the
`file, Storing data indicating that the blocks are not
`free, and
`(c3) in the second sideband fields of the blocks storing
`the file, updating the data indicating how many times
`the blocks have been written into; wherein a maxi
`mum number of times a block can be written into is
`fewer than a maximum allowable number of quali
`fied writes to the write-many memory device.
`9. The invention of claim 8, wherein (c1) is performed
`before (c3).
`10. The invention of claim 8, wherein (c3) is performed
`before (c1).
`11. The invention of claim 8 further comprising:
`(d) if there are not enough blocks free to store the file,
`Selecting a previously-Stored file to be erased, the
`previously-Stored file being Stored in a first Set of
`blocks.
`12. The invention of claim 11 further comprising:
`(e) if the second sideband fields of the first set of blocks
`indicate that the first set of blocks has been written into
`fewer than a maximum number of times:
`(e1) in the first sideband fields of the first set of blocks,
`Storing data indicating that the blocks are free; and
`(e2) Storing the file in at least Some of the first set of
`blocks.
`13. The invention of claim 11 further comprising:
`(e) if the second sideband fields of the first set of blocks
`indicate that the first set of blocks has been written into
`a maximum number of t