JP2006048585A - Flash memory access method - Google Patents

Abstract

When data stored in a flash memory is updated, an "old" flag is written in a block storing old data. However, it is difficult to write to a flag in a multi-level memory, and another method for determining whether it is new or old is required.
When updating data stored in association with a logical address in a memory card using a flash memory, the physical address of the block in which the data before the update is stored starts in the ascending order. The latest data is stored in the first unused block that can be traced. Then, when obtaining the block in which the latest data of a certain logical address is stored, the maximum value of the physical address in the usable and unused blocks of the flash memory is obtained, and the logical address obtained in the descending order is obtained. It is determined that the data is stored in the first block of the stored block.
[Selection] Figure 1

Description

  The present invention relates to an access method for updating data in a file storage device such as a memory card using a flash memory and determining whether the updated data is new or old.

  A non-volatile memory such as a NAND flash memory occupies a small volume, has low power consumption, and can hold data without supplying power. Taking advantage of this characteristic, it is widely used for file storage devices that store electronic data in a portable form such as a memory card.

  A flash memory stores information by injecting charges such as electrons into a floating gate of a transistor serving as a memory cell and holding it. Data is written by selecting a memory cell corresponding to a specified address and injecting charges. However, in the flash memory, the write operation of the reverse value to remove the injected charge is not performed for each individual memory cell, but is performed collectively for the memory cells in a predetermined block that partitions the cell array region. Is called batch erasure. For this reason, when trying to update the contents of a block in which data has already been written, it is necessary to select an unused block in which all the memory cells are in the erased state and write the corrected data. When data is updated, a value indicating the old is written in a memory cell of a specific bit called a new / old flag to indicate that the old data is stored in the block in which the data before the update is stored. A way to distinguish is taken.

  This new / old flag is assigned a specific bit in the block, and is set in an unwritten state when data is first written. When data is updated and the latest data is written in another block, additional writing is performed on the bits assigned as the old / new flag of the old block.

  When data is written to or read from a memory card using an electronic device such as a personal computer as the host, the address defined by the host device and the address handled by the flash memory are different, and the address handled by the host for data processing Is called a logical address. The flash memory is assigned an address according to a device-specific structure such as a NAND type or a NOR type, and this is called a physical address.

  FIG. 8 shows the data structure when data is written to the flash memory. The storage area of the flash memory 800 is composed of a plurality of blocks 801, each of which is given a physical address 802. The data area 803 is divided into a main area 804 and a spare area 805, and data sent from the host is stored in the main area 804. The spare area 805 stores other information 808 such as a logical address 806, an old / new flag 807, and error correction information. The data of the logical address “579” is stored in the physical addresses “7901” and “7908” blocks, but the old / new flag 807 of the block of the physical address “7901” is flagged as “1”. It shows that it is data of.

As can be seen from the above, in the main area 804 and the spare area 805, the logical address 806 and others 808 are simultaneously written as data when data is first written in this block. However, when the data associated with an arbitrary logical address is updated and written in an unused block, the old / new flag 807 is written with an old value in the old / new flag 807 of the block holding the old data. (See Patent Document 1)
As described above, in the conventional flash memory, if a bit corresponding to the new and old flags is prepared in an unwritten state even for a block in which data has been written once, the corresponding block at the time when the old data is obtained. The corresponding bits of the old and new flags can be selected and written. Therefore, the data update is repeated, so that even if there are a plurality of pieces of data having the same logical address, it is possible to easily identify a block in which the latest data is always written.

  Further, since this information is held in the flash memory which is a non-volatile memory, it is also held after the memory card is turned off.

  In recent years, multivalue technology has been developed and used as means for improving the storage density of flash memory. In the multi-value technique, information of only one bit of “0” and “1” is not stored in one memory cell as in the past, but the amount of injected charge is added as information. This is a technique for storing information of bits or more. The storage principle of the multilevel flash memory cell will be described with reference to FIG. When the charge of one memory cell is injected, the threshold voltage Vth of the cell changes. FIG. 9 shows an example in which the Vth level is divided into four stages together with the erased state that is not injected, and 2-bit information is stored. The vertical axis indicates the threshold voltage Vth of the memory cell, and V1, V2, and V3 indicate voltages for determining the memory state of the memory cell. The horizontal axis shows the distribution of each state of the memory cell. Of the two numbers between “”, the left side indicates the value of the upper bit and the right side indicates the value of the lower bit.

  In the erased state, that is, when Vth <V1, the 2-bit value is “11”, V1 <Vth <V2 is “10”, V2 <Vth <V3 is “01”, and V3 <Vth is “00”. Can be defined as Thus, it can be seen that 2-bit information can be stored by finely dividing the threshold level of the memory cell.

  However, it takes time to write a specific bit value in a block in which data has already been written. For example, when the value of the lower bit is rewritten from “1” to “0”, when the value of the upper bit is “1”, the target threshold value Vth is V1 <Vth <V2, and the value of the upper bit is In the case of “0”, the target threshold value Vth <V3. Thus, in order to write to a specific bit, the write level must be designated after reading the value of the other bit sharing the memory cell. Therefore, rewriting a 1-bit value independently is a laborious operation.

  Moreover, it is possible to select a combination of V01 <Vth <V2 values of “01”, but generally, in a commercially available flash memory, the relationship between the state of such a memory cell and the value of each bit is not disclosed. In general, multi-level flash memory is designed so that the specifications viewed from the external terminal are the same as the conventional single-level memory. Therefore, this bit is combined with the memory user who designs the memory card. It is more difficult because you cannot know the relationship.

In this way, when using a flash card using a multi-level flash memory, the old data is updated, and data “0” is written to a specific bit indicating the new / old flag of the block in which the old data is written. Becomes difficult.
US Pat. No. 5,479,638

  Regarding the management method of new and old data of file storage devices such as memory cards using flash memory, when updating data, the flash memory is erased and new data is written to unused blocks. The new and old data are identified by writing the value of the new and old bits provided in the spare area from the unwritten state “1” to the value “0”.

  However, when a multi-level flash memory is used as a storage medium, since a 2-bit address is assigned to one memory cell, a specific bit in a block in which data has already been written as has been done conventionally. It is not easy to write data in When writing a value representing the old flag to a new and old flag to which a specific bit in a block in which old data is written is assigned as in the past, the value of the other bit in the pair is obtained and obtained as a combination thereof. It is necessary to write with the target Vth value.

  Accordingly, there is a need for a method of finding the newest data from the new and old data that has been updated without performing additional writing to the block in which the data has been written.

In the present invention, when the data already written in one of the blocks of the flash memory is updated, the physical address of the newly written new data is always higher than the physical address where the old data is written. The problem is solved by managing writing so that there is no unused block that is always available between the physical addresses where the old and new data are written in the ascending order.
That is, the update of the flash memory that stores the logical address and the data associated with the logical address in the block associated with the physical address is stored in the block that stores the data. A physical address is obtained, a physical address is generated by sequentially increasing the value of the physical address in the ascending order, and it is sequentially determined whether or not the block associated with the generated physical address is usable and unused. Verification is performed by storing the logical address and the new data in the block when the verification result is a usable and unused block.

  The data updated in this way is used to determine the oldest and newest data stored in association with a predetermined logical address, obtain the maximum value among the physical addresses of usable and unused blocks, and sequentially from the maximum value, Decrease in the descending direction to generate a physical address, sequentially verify the logical address stored in the block of the generated physical address, and when the verified logical address matches the predetermined logical address, it is stored in the block Data is determined to be the latest data.

  By accessing the flash memory in this way, it is possible to make a new / old determination without writing a new / old flag in the block of the flash memory.

  Further, in the data update, when the generated physical address increases in the ascending order exceeds the maximum value of the physical address, the generated physical address is replaced with 0, and in the old and new judgment, the descending direction When the generated physical address becomes a negative value, the generated physical address is replaced with the maximum value of the physical address, so that the block holding the latest data can be used and unused. It can also be found when the physical address is larger than the maximum physical address of the block. That is, by setting the value next to the maximum value to 0 in the ascending order of the physical address, the physical address starting in the procedure of generating the physical address value in the ascending order at the time of data update and the descending order at the time of new / old judgment All physical addresses can be generated regardless of the address value. Therefore, it is possible to detect all blocks.

  In addition, the new and old judgment of the data stored in association with the logical address stored in the block is started, the flash memory is started, the information stored in the flash memory is transferred to the management table created in the volatile memory, The management table information is determined using a determination table created in a volatile memory to determine a physical address for storing the latest data, and the determination result is newly displayed on the management table. During normal operation, it is possible to quickly find a block that holds the latest data by referring to the management table.

  Further, according to the new display in the management table, the old display is performed on the other physical address that holds the logical address on the management table, so that the data before the update is stored The old display can be made on all physical addresses. In addition, the number of usable and unused blocks is reduced by repeatedly updating the data in the flash memory. When the number of unused blocks decreases, the memory cells of the blocks holding the old data are erased and unused. It is necessary to make it. At this time, the erase operation of the flash memory selects all the blocks in which old values are written on the management table, and erases all the selected blocks. After such batch erasure, there is no block that holds old data before being updated. Therefore, even if a new usable and unused block is generated by erasing, all of the old blocks are lost, so the usable and unused blocks between the new and old blocks described above can be used. It is possible to maintain the condition that no exists.

  According to the present invention, when a multi-level flash memory is used for a memory card, it is possible to make a new / old determination without writing an old flag in an updated block.

  The old and new judgment is made by transferring the information held in the spare area of the flash memory at the time of starting the card to the management table generated in the volatile memory and making the judgment on this management table, so that no extra waiting time is required. .

In addition, since the latest data when data is updated or read can be determined on the management table, high-speed operation is possible.

  The following shows the configuration of a memory card for discriminating between old and new data of a flash memory card in the present invention, a method of storing data in the flash memory when updating data, and data stored in the flash memory A setting method, a block erasing method, and a reading method for determining the latest data at start-up will be described.

  FIG. 1 shows a memory card system in which a memory card using flash memory is connected to a host.

  The memory card system 100 includes a memory card 101 and a host 151. The host 151 includes a host I / F 152, and transmits and receives logical addresses and data to and from the memory card via the data bus 153.

  The memory card 101 includes a flash memory 102 and a controller 103, and transmits and receives physical addresses and data between the flash memory 102 and the controller 103 via a data bus 104. The controller 103 includes a memory card I / F 110 that exchanges data with the host 151, an address register 111, a data register 112, a management table 113, an old / old determination table 114, an empty block counter 115, and a CPU 116 that controls the controller. ing.

  When writing data to the memory card 101, the logical address and data sent from the host 151 are stored in the address register 111 and the data register 112, respectively. The CPU 116 refers to the logical address stored in the address register 111 in the management table 113 and determines the physical address of the flash memory to be stored. The data stored in the data register 112 is written to the block of the determined physical address in the flash memory via the data bus 153.

  The management table 113 is composed of a volatile memory, and holds management information such as the correspondence between the logical address and the physical address of data written to the flash memory 102 and the old and new displays when the data is updated. The old / new determination table 114 is composed of a volatile memory.

  The flash memory 102 uses multi-valued cells. For this reason, after data is once written in the block as described above, an operation of writing data into a specific bit corresponding to the new / old flag is not performed again in the same block. For this reason, no symbol representing the new or old data is written anywhere in the spare area of the flash memory. The old and new judgment will be explained in detail below.

  The management table 113 is created based on information stored in the flash memory 102 when the memory card 101 is started, and the contents are corrected according to data write / erase operations. The new / old judgment of the data updated at the time of starting is performed using the old / new judgment table.

  The NAND flash memory 102 is composed of a plurality of blocks, and each block is composed of a plurality of pages. Read and write operations are performed in units of pages, and erase operations are performed in batches in units of blocks. Each block is given a physical address, and data and spare information such as a logical address are stored in the data area of each block.

FIG. 2 shows the data structure of the multi-level flash memory 102.
Each block 121 is given a physical address 122. The data area 123 is divided into a main area 124 and a spare area 125, and data sent from the host is stored in the main area 124. The spare area 125 stores 127 information such as a logical address 126 and error correction information. The basic structure is the same as the data structure shown in FIG. 8, but there is no area corresponding to the new and old flags, and the memory area that constitutes each block is updated once the value is written Will not be written again.

  The physical addresses “0” and “1” are reserved blocks whose use has been reserved in advance, and the address of the defective block is written in the main area of the block of the physical address “0”. Further, boot data is written in the main area of the block having the physical address “1”, and is automatically read when the memory card is started.

  The physical address “2” and later are generally used blocks, and numbers are assigned in the ascending order. In the example of FIG. 2, the physical address “9999” is the maximum value and is defined as the final address. A block written as (unused) in the main area represents a usable and unused block that has no defect and is not reserved.

  Blocks with physical addresses “2” and “3” are examples of usable and unused blocks that are randomly generated by being erased after being used once. The physical address “7903” cannot be used in a defective block. In the blocks of physical addresses “7900 to 7906”, except for defective blocks, the values of logical addresses “578” to “583” are written in the logical address area 126, and the data related to each is written in the main area 124. ing.

  In the physical address “7907”, data of the logical address “810” written thereafter is written. The logical address of the data of the block with the physical address “7908” is also “579”, which is the same value as the block with the physical address “7901”. According to the determination method of the present invention described below, it can be seen that the data at the physical address “7908” is the latest data.

  As shown in FIG. 2, there are a plurality of blocks in which data of the same logical address is written, but the flash memory itself does not have information indicating in which block the latest data is written.

  Next, the configuration of the management table 113 is shown in FIG. The management table 113 is created based on information held in the flash memory 102 when the memory card is started, holds the relationship between logical addresses and physical addresses, and the flash memory 102 at the time of reading, writing, and erasing data during operation. Is managing address information. There are rows corresponding to the physical address 131 from “0” to the final address “9999”, and the values of the logical address 132, the new / old flag 133, the defect flag 134, and the reservation flag 135 are held in each row. In FIG. 3, displayed in correspondence with FIG. 2, “old” is displayed in the new / old flag 133 of the physical address “7901”, and “new” is displayed in the physical address “7908”. . This display method will be described later.

  The following shows how to write to the flash memory when data is updated. When multiple updated logical addresses are stored in different physical address blocks, the latest updated data is stored in which block. The method for determining whether or not it is done will be described in order.

  <Updating data> First, when the memory card is started and in a normal operation state, the host 151 makes a request to update the data to which the logical address already written in the flash memory 102 is assigned. Will be described. The logical address and write data of data to be updated from the host 151 are sent to the memory card 101 via the host I / F 152 and the data bus 153, and to the address register 111 and the data register 112 via the memory card I / F 110. Saved.

  In order to write new data to be updated in the flash memory 102, the physical address of the block in which the latest data is written is obtained from the management table 113 before the update. Then, the physical address is traced in the ascending order, and new data is written in the first usable and unused block found. At the same time, the value in the management table is rewritten to the latest state, and the data update is completed. In the example of FIGS. 2 and 3, the physical address “7901” stores the latest data before the logical address “579” is updated, and the new / old flag 133 of the physical address “7901” indicates “new”. The display is made. At this stage, the block with the physical address “7908” is unused, and the latest updated data with the logical address “579” is written therein.

  The procedure for updating the data will be described with reference to the flowchart of FIG. First, a logical address value to be updated is found from the logical address 132 on the management table 113. If there are a plurality of physical addresses corresponding to the logical address, the physical address 131 of the row in which the old / new flag 133 is “new” is found out, and the value of N is set as the physical address (S111). Further, the value of the new / old flag 133 is changed from “new” to “old” (S112).

  Next, the value of N is replaced with N = N + 1 in the ascending order (S113). The replaced N value is compared with the final block value (S114). When the value of N becomes larger than the value of the last block, the value of N is replaced with N = 0 (S115). This step is because “0” is defined next to the last block when the physical address is sequentially increased in the ascending order.

  Next, it is verified on the management table 113 whether the block with the physical address N is usable and unused (S116). If not, the process returns again to step S113, and this is repeated until an unused block that can use the physical address in the ascending order is found.

  When it corresponds to a usable and unused block in step S116, new data to be updated is written in this block. That is, the logical address held in the address register 111 is written into the logical address 126 of the block having the physical address N of the flash memory 102, and the data held in the data register 112 is written into the main area 124 (S117).

  Subsequently, the logical address held in the address register 111 is written to the logical address 132 of the row where the physical address of the management table 113 is N, and the new / old flag 133 is changed to “new” (S118).

  Next, the value M of the empty block counter 115 is decremented by 1 and replaced with M = M−1 (S119). If the replaced M value is greater than or equal to the designated minimum value Mmin (S120), the process proceeds to step S123 to complete the data update.

  When the value of M becomes smaller than the minimum value Mmin in step S120, all blocks of physical addresses having “old” displayed in the new / old flag 133 of the management table 113 are deleted (S121). Next, the data of the logical address 132 and the new / old flag 133 in the row corresponding to the erased block on the management table are deleted (S122). Thus, the data update is completed (S123).

  When data is continuously read while the memory card 101 is connected to the host 151, the latest updated data can be correctly identified because “new” is displayed in the new / old flag 133 on the management table 113. However, once the power of the memory card 101 is turned off, the data in the management table 113 composed of volatile memory disappears. Therefore, it is necessary to create the management table 113 based on information stored in the flash memory 102 at the time of startup. A method for setting management information in the management table at startup will be described below.

  <Setting at Startup> When the memory card 101 is connected to the host 151, the controller 103 is activated, reads the boot data from the reserved block of the flash memory 102, and gives the CPU 116 a memory card management program. Next, the information in the spare area 125 of each block of the flash memory 102 is sequentially read and transferred to the management table 113.

  The procedure for sequentially reading out the data written in the main area 124 of the reserved block of the flash memory and the spare area 125 of each block and transferring it to the controller to create a management table will be described with reference to the flowchart shown in FIG.

First, the defect address information written in the block of the physical address “0” of the flash memory is read, and the defect indication is written in the column of the defect flag 134 in the row of the corresponding physical address in the management table 113. Subsequently, the reservation is displayed in the reservation flag 134 of the reservation block. (S131)
Next, the value of N designating the physical address is set to N = 0 (S132), and then the value M of the free block counter 115 is set to the number of blocks in the flash memory 102 (S133). Next, it is determined whether or not the block whose physical address is N is a usable block (S134). Here, the usable block is a block which has no defect and is not reserved. If it is a usable block, it is determined whether the block is already used (S135). If already used, the value of the assigned logical address 126 is stored in the logical address 132 of the management table 113 (S136). In this case, since the number of empty blocks is decreased by 1, the value of M is replaced with M = M−1 (S137).

  Next, it is determined whether the value of N is equal to the value of the final address (S138). If they are not equal, the value of N is replaced with N = N−1 (S139), the process returns to step S134, and the same determination is repeated again. If the block of the physical address N is not usable in step S134, the process jumps to step S137, and the number M of free blocks is reduced by one.

  If the block at the physical address N is unused in step S135, the process jumps to step S138 to determine whether the value of N does not match the final address.

  If the value of N matches the final address in step S138, the investigation for all physical addresses is completed, and the creation of the management table 113 for transferring management information from the flash memory 102 at the start is completed (S140).

  Next, when there are a plurality of blocks to which the same logical address is specified, it is necessary to determine which block data is the latest data. Hereinafter, a procedure for setting a flag in the column of the new and old flags 133 using the information read in the management table 113 will be described with reference to the flowchart of FIG.

  In this flow, an old / new determination table 114 provided on a volatile memory is used. As shown in FIG. 7, the new / old determination table 114 includes a logical address 141, the latest physical block 142, and the latest block found flag 143, and is created using the management table 113 created according to the flowchart of FIG. Then, the logical addresses 141 are arranged in the ascending order. When there are a plurality of the same logical addresses, the physical addresses 142 are arranged in the ascending order, and in the initial state, all the latest block found flags 143 are left uninput.

  First, in the first step S151 in FIG. 6, the value of N is set to N = final address. In a normal case, the process is performed subsequent to the management table creation procedure of FIG. 5, and thus N is completed with the final address set. Next, referring to the management table 113, it is determined whether or not the block whose physical address value is N is usable and unused (S152). If none of these apply, the value of N is replaced with N = N−1 (S153), and the determination in step S152 is repeated again. In this way, the value N of the physical address is set and inspected while decreasing by 1 in the descending order from the maximum value, and a block corresponding to the usable and unused condition is found first.

  When the corresponding block is found in step S152, the value of N is set to Nstart (S154). The Nstart thus determined is the largest physical address among usable and unused blocks and can be uniquely determined. The latest data is stored in accordance with the following procedure starting from this physical address. Judge the block that was made.

  At the start of use of the memory card, this Nstart coincides with the final address. However, by repeating the data update and the block erasing, the Naddress is used up to the final address, and the physical address value of the unused block becomes small. Although a situation arises, it can be dealt with by obtaining the above procedure.

  Subsequent to step S154, the value of N is replaced in the descending order by N = N−1 (S155). Then, it is determined whether or not the replaced N value is negative (S156). If it is not negative, the N value is continuously compared with Nstart (S157). If not, the physical address is N in step S159. Determine if the block is usable and has a logical address written to it. If the determination condition is not met, the process returns to step S155. If the logical address is usable and there is a logical address, the logical address 141 and the new / old block found flag 143 in the new / old determination table 114 are referred to and it is determined whether a physical block of the corresponding logical address has already been found (S160). If the logical address has not been found, the process proceeds to step S162, where “new” is displayed in the new / old flag 133 of the management table 113, and “done” is displayed in the latest block found flag 143 of the new / old determination table 114. And it returns to step S155 again.

  If the corresponding logical address has been found in step S160, the new / old flag 133 of the corresponding block in the management table 113 is changed to “old” and the latest block found flag in the new / old determination table 114 is displayed as “completed”.

  In the case of the new / old determination table 114 shown in FIG. 7, in the new / old determination of the physical address corresponding to the logical address “579”, the physical address is traced in the descending order, and the logical address “579” is first discovered with the physical address “7908”. Therefore, “new” is displayed in the new / old flag 133 of the management table 113. At the same time, “completed” is displayed in the latest block found flag in the new / old determination table 114. Accordingly, when the value of the physical address is further decreased in the descending direction and becomes “7901”, since the corresponding logical address “579” has already been discovered, the old / old flag 133 of the management table 113 indicates “old” “Is displayed.

  If the operation of decreasing the value of N by 1 in the descending order is repeated in step S155, finally a negative value of N is generated. In this case, the determination in step S156 proceeds to step S158, where the value of N is replaced with the value of the final address. Then, the process proceeds to step S157 and the procedure according to the flow is repeated.

  When the value of N becomes N = Nstart, it is determined in step S157 that all physical addresses have been verified, and writing to the new / old flag 133 in the management table 113 is completed (S163).

  When N becomes a negative value in step S156, the physical address can be sequentially replaced in the descending order by replacing the value of N with the value of the final address. When it is determined in step S157 that N = Nstart, it is understood that all physical addresses have been verified in the descending order.

  As explained in the section on data update, if there are multiple blocks holding data of the same logical address, the physical address of the latest updated data is always in ascending order from the physical address before the update. It is written to the first available and unused block in the block to follow. Therefore, even when data is updated several times, there is no usable and unused block between the block holding the oldest data and the block holding the latest data. I understand that.

  Since the old and new data are held in this order, the latest data of the logical address held in multiple locations was first discovered by tracing the physical address in descending order from the available and unused block. It can be seen that it is held in the block. Furthermore, there exists a state in which many usable and unused blocks are distributed. In such a case, it is possible to uniquely find a block having a maximum physical address among usable and unused blocks as a starting point.

  Next, block erase will be described.

  <Block Erase> When the value of the empty block counter 115 becomes smaller than the specified value as shown in step S122, the block in which the old data is stored is erased. In the erase operation, all the physical addresses having the old display are designated in the new and old flags 133 of the management table 113, and the block erase function provided in the flash memory 102 is used for batch erase. Since the erasing operation takes more time than data reading or writing, the erasing operation is not necessarily performed at the time of step S122, and may be performed using the time when the memory card is in a waiting state.

  What should be noted in this erasing operation is that all blocks with “old” displayed in the new / old flag 133 on the management table 113 must be erased. Because there is no record corresponding to the old and new flags in the spare area of the flash memory, the order of the physical addresses of the blocks holding the data is strictly limited when there are multiple physical addresses with the same logical address indication. Because.

  That is, as described in the data update, when there are a plurality of blocks storing data of the same logical address, the block in which the latest data is written and the block in which the old data before the update is written are written. The basic condition is that there are no usable and unused blocks. If a part of the old block remains unerased during the erase operation, another block that holds the old data between the physical block that holds the old data and the block that holds the new data is erased and used This is because the block becomes possible and unused, and the above preconditions cannot be satisfied.

  <Reading Data> Next, the procedure for reading data from the memory card will be described. The memory card 101 receives the logical address of data to be read from the host 151 via the interface 152 and holds it in the address register 111. The physical address 131 of the block that matches the logical address stored in the management table 113 and has a new display in the new / old flag 133 is found. Then, the corresponding block data is read from the flash memory 102 and held in the data register 112. Subsequently, the read data is sent to the host 151 via the interface 110.

  As described above, the present invention is characterized in that the update of the data in the flash memory is written from the block holding the old data to the first usable and unused block in the ascending order of the physical address. Therefore, the latest data can be used and the block with the largest physical address in the unused block is traced in the descending order, and the block that holds the target logical address first holds the latest data. Recognize.

  It is obvious that there is no problem even if the ascending order and descending direction are replaced in the practice of the present invention.

  In a file system such as a memory card using a flash memory, the use of a multi-value flash memory is expanding. However, it is difficult for a multi-level flash memory to add data to a specific bit of a block in which data has been written once. According to the present invention, by repeatedly updating data, it is possible to easily determine whether a plurality of blocks having the same logical address are new or old without adding the old and new blocks to the old block as in the prior art. be able to. Since the old and new information is judged by the order of the physical addresses of the data recorded on the memory card, it can be held without power supply, and the old and new judgment can be made from the order of the physical addresses. Done automatically.

It is a figure explaining the memory card system used as the Example of this invention. It is a figure which shows the structure of the data written in a multi-value flash memory. It is a figure which shows a management table. It is a flowchart which shows the procedure which updates data. It is a flowchart which shows the procedure which produces a management table. It is a flowchart which shows the procedure which produces a new and old flag. It is a figure which shows an old and new determination table. It is a figure which shows the conventional data structure written in flash memory. It is a figure explaining the relationship between Vth of a multi-value memory, and a 2-bit value.

Explanation of symbols

100 Memory Card System 101 Memory Card 102 Flash Memory 103 Controller 104 Data Bus 110 Memory Card I / F
111 Address register 113 management table 112 data register 113 management table 114 old / new determination table 115 free block counter 116 CPU
151 Host 153 Data bus

Claims (5)

Update of a flash memory that stores a logical address and data associated with the logical address in a block associated with a physical address, and stores the data instead of the new data.
Find the physical address of the block that stores the data,
Generate the physical address by sequentially increasing the value of the physical address in the ascending order direction,
Sequentially, verify whether the block associated with the generated physical address is a usable and unused block,
When the verification result is a usable and unused block, the logical address and the new data are stored in the block,
The old and new data stored in association with a given logical address
Find the maximum physical address of available and unused blocks,
A physical address is generated by sequentially subtracting from the maximum value in the descending order direction,
Sequentially, the logical address stored in the generated block of physical addresses is verified,
An access method for a flash memory, characterized in that, when a verified logical address matches the predetermined logical address, the data stored in the block is determined to be the latest data.   2. The flash memory access according to claim 1, wherein when the physical address generated by increasing in the ascending order exceeds the maximum value of the physical address, the generated physical address is replaced with zero. Method.   2. The flash memory according to claim 1, wherein when the physical address generated by decreasing in the descending order becomes a negative value, the generated physical address is replaced with the maximum value of the physical address. how to access. New or old judgment of data stored in association with the logical address stored in the block,
Starting the flash memory;
Transfer the information stored in the flash memory to a management table created in volatile memory,
Determine the physical address for storing the latest data using the determination table created in the volatile memory for the information in the management table,
4. The flash memory access method according to claim 1, wherein the determination result is newly displayed in the management table. According to the new display in the management table,
Perform the old display on the other physical address holding the logical address on the management table,
The erase operation of the flash memory selects all blocks in which old values are written on the management table,
5. The flash memory access method according to claim 1, wherein all the selected blocks are erased.

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