KR20110015288A - A method for recovering erase-information of a flash memory - Google Patents

Abstract

PURPOSE: A method for recovering erasure information of a flash memory is provided to prevent the deterioration of access speed by recovering the recorded erasure information when the power is supplied to a storage device. CONSTITUTION: The final erasure frequency table is seared(S310). The erasure frequency table is recovered by referring to the MAP block(S320). It is checked whether the MAP change information exists in the spare area of the MAP block(S330). A physical block number recorded in the spare area is checked. The recovery completion of the erasure frequency table is checked(S350).

Description

A method for recovering erase-information of a flash memory

The present invention relates to a flash memory, and more particularly, to a method for restoring information about the erase count of each block in a flash memory.

Flash memory is a nonvolatile memory capable of electrically writing or erasing data, and can be rewritten within a limited number of times. Flash memory does not erase stored information even when the power is turned off.It is widely used as a storage device for portable electronic devices such as digital cameras, PDAs, MP3 players and mobile phones due to its low power consumption, fast operation speed, and excellent durability. Recently, it is used in various fields such as solid state disk (SSD) and turbo memory.

The flash memory is divided into a plurality of blocks, and one block is divided into a plurality of pages. One page is again divided into sectors and spares. Data is stored in the sector area, information about the stored data is recorded in the spare area, and information about data stored in the corresponding sector area can be obtained by referring to the spare area.

In flash memory, write operations are performed in units of pages, and erase operations are performed in units of blocks. In flash memory, an overwrite operation cannot be performed. An erase before write operation must be performed to overwrite new data that has already been used, that is, a block in which data is written.

The number of times a flash memory can be erased is limited to about 100,000 times in a single level cell (SLC) and about 10,000 times in a multi-level cell (MLC). In order to prevent a specific block from being used repeatedly and intensively, compared to other blocks, the controller of the flash memory stores and manages information on the erase count of each block on a random access memory (RAM). Information about the erase count of each block is simultaneously stored in RAM and flash memory. When the erase count of a block is recorded only in the RAM, when the power is turned off before the block is used, it is impossible to restore the record of the number of times the block is used.

Therefore, information on the erase count and use of each block is stored together in the flash memory, and when the power is turned off, the information in the SRAM is restored using the information stored in the flash memory.

According to the conventional erase count writing method, whenever a block erase occurs in the flash memory, the erase count table in which the erase count of each block is recorded is updated. Since RAM can be overwritten, the erase count table of the designated area can be continuously updated.However, since the flash memory cannot be overwritten, the erase count table of the changed contents is empty. It should be recorded on the page. In other words, it consumes a new page.

As the storage capacity of the flash memory increases, the space occupied by the erase count table increases, and block erase occurs more frequently. As a result, page consumption is increased due to the update of the erase count table, and the erase of the blocks in which the erase count table is written occurs more frequently, thereby shortening the lifespan of the blocks.

An object of the present invention is to efficiently erase the erase information of each block in the flash memory and quickly restore the erased information when the storage device is powered on, thereby preventing waste of pages and deterioration of the access speed and writing the erase count. It is to provide an erase count recording method for preventing a block from being quickly worn out.

Another object of the present invention is to provide a method for recording the erase count of a block for managing the block life of a flash memory and a method that is not affected by the speed of data input and output by updating block erase information which will occur frequently.

According to an aspect of the present invention, a method of restoring erase information for each block in the flash memory by the controller of a storage device including a flash memory and a controller, wherein the MAP is changed in the flash memory. An erase information restoration method is provided, wherein the erase count of each block is calculated using the information.

Here, the MAP change information is a physical block number of erased blocks, and the MAP change information is recorded in a spare area of a block in which a MAP table is recorded.

Here, setting the erase count of each block in the last erase count table as a base value; And increasing the base value for each block by the number of times the physical block number for each block is recorded in the spare area.

According to another aspect of the invention, a flash memory in which MAP change information is recorded; A controller configured to calculate an erase count of each block by using the MAP change information; And a random access memory (RAM) in which an erase count table in which the erase count is recorded is stored.

Here, the MAP change information is a physical block number of erased blocks, and the MAP change information is recorded in a spare area of a block in which a MAP table of a flash memory is recorded.

The controller may set the erase counts included in the last erase count table in the flash memory as a base value of each block, and the base counts the number of times the physical block number of each block is written in the spare area. Increase the value.

The erase information restoration method according to the present invention has an effect of preventing a page from being wasted due to frequent writing and a block from which the erase count is recorded to be quickly worn out.

In addition, the erase information restoration method according to the present invention has an effect of improving the speed of access to the flash memory from the user terminal by minimizing the write and erase operations due to the erase count recording.

In addition, the erase information restoration method according to the present invention has an effect that the speed of data input / output is not affected by the method of writing the erase count of the block for managing the block life of the flash memory and the update of the block erase information which will occur frequently. .

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all transformations, equivalents, and substitutes included in the spirit and scope of the present invention. In the following description of the present invention, if it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a view showing the configuration of a flash memory storage device according to the present invention.

Referring to FIG. 1, the flash memory storage device 100 includes an interface 110, a controller 120, and a flash memory 130. Here, the flash memory storage device 100 includes both a case where the flash memory storage device 100 is embedded in portable devices such as a digital camera or an MP3 player as well as an independent device for data storage such as an SSD or a USB memory.

The flash memory storage device 100 is electrically connected to a host such as a PC or a notebook through the interface 110, and the controller 120 drives the interface 110 and the flash memory 130 to store data. Read, write, erase During the write operation, the controller 120 determines a location where data input through the interface is stored and writes the data at the determined location.

In order to allocate a physical block in the flash memory 130 to which a data block input from the host is to be written, the controller 120 may determine a logical block number (LBN) and a physical block number (PBN). Refer to the mapping table (hereinafter, referred to as 'MAP table') in which information is recorded. In general, the logical block number is a number assigned by the host for each data block, and the physical block number is a number sequentially assigned to each physical block in the flash memory 430.

The MAP table operates in a random access memory (RAM) 440 in the controller 420 for quick access. The RAM 440 can be overwritten at any time and mainly uses a fast static RAM (SRAM). Since the RAM 440 is volatile memory and all the data stored in the memory are erased when the power is not supplied, the controller 420 restores the MAP table to the RAM 440 to restore the MAP table to the RAM 440 when the power is turned off. ) And flash memory 430 at the same time. The MAP table is stored in one or a plurality of blocks in the flash memory 430. The block in which the MAP table is stored is called a MAP block.

2 is a diagram illustrating a MAP table and MAP change information recorded in a MAP block in a flash memory according to the present invention.

According to the present invention, the controller 120 records the MAP table and the MAP change information together in the MAP block. The MAP change information is information on a block in which a change occurs in the MAP table. For example, the MAP change information may be a physical block number of a block in which an erase operation occurs.

Referring to FIG. 2, a MAP table is recorded in a sector area of a MAP block, and MAP change information is recorded in a spare area. Since the MAP table is recorded in page units, each page is a single MAP table. One page is divided into a total of 2048 regions, and each divided region corresponds to 2048 logical blocks. In FIG. 2, logical block numbers 0 to 2048 are sequentially mapped from right to left of the page. In each divided area, a physical block number corresponding to the logical block number of the corresponding area is recorded.

If a change occurs in any block in the flash memory 130, the MAP table is updated, and the updated MAP table is written to the MAP block. The circled portion of each page is the block where the change occurred, in this case, the blocks to which the block has been reallocated. The reassignment of a block means that the physical block number corresponding to one logical block is reassigned to another physical block number, which means that the block corresponding to the physical block number before the reallocation is erased.

To the right of the sector area there is a respective spare area corresponding to each page of the sector area. MAP change information is recorded in the spare area. In FIG. 2, the physical block number of the erased block is recorded in the spare area. The fact that physical blocks are reassigned to logical blocks means that existing physical blocks have been erased, so that the physical block number before reallocation is recorded in the spare area. For example, comparing <page 0> and <page 1>, physical block number 32 was assigned to logical block number 2 on <page 0> and physical block number 112 was reassigned on <page 1>. . This means that the physical block is erased before the reallocation of the physical block number 32, and therefore, the erased physical block number 32 is recorded in the spare area of <page 1>.

Here, the number of times each physical block number is recorded in the spare area of one MAP block represents the number of times the physical block corresponding to the corresponding physical block number has been erased. Therefore, when the number of physical block numbers recorded in the spare area is accumulated, the number of times each block in the flash memory 130 is erased may be calculated.

The cumulative calculation of the erase count is repeatedly performed at regular intervals. In particular, when the MAP block is erased, all pages in the corresponding MAP block are consumed due to, for example, writing of the MAP table, and a new block must be allocated to the MAP block. In this case, the number of times each physical block number is recorded in the spare area in the MAP block is cumulatively calculated to generate an erase count table in which the number of erases of each physical block is recorded. The erase count table thus generated is written on the flash memory. The block in which the erase count table is written is called an erase information block.

According to the present invention, unlike the prior art in which the erase count table must be written every time a block erase occurs, the erase count table is written to the erase information block only when the MAP block is erased. The consumption can be minimized.

In general, one block in the flash memory 130 includes 128 pages. According to the present invention, it is not necessary to write the erase count table until the block is erased 128 times in the flash memory 130, thereby preventing the page from being frequently consumed.

This not only reduces the page consumption in the erase information block but also reduces the number of times of access to the flash memory according to the writing of the erase count table or the erase of the erase information block, thereby minimizing the resources consumed for managing the flash memory. By investing more resources in your work, you can contribute to the performance of flash memory.

3 is a flowchart illustrating a method of restoring an erase count table using MAP change information recorded in a MAP block according to the present invention.

As described above, the erase count table of the flash memory 130 operates on the RAM 140, and the erase count table written to the flash memory 130 is used to restore the erase count table on the RAM 140. . According to the present invention, when power is supplied to the flash memory storage device 100, the controller 120 may read the erase count table stored in the erase information block of the flash memory 130 and the MAP change information recorded in the spare area of the MAP block. It is possible to simply restore the erase count table on the RAM 140 by using.

Referring to FIG. 3, in step S310, the controller 120 searches for an erase count table (hereinafter, referred to as a “last erase count table”) last recorded in an erase information block. Here, the last erase count table includes the latest erase count for each block. The erase count of each block included in the last erase count table is set as a base value for restoring the erase count table, and in step S320, the controller 120 starts to restore the erase count table with reference to the MAP block. First, in order to restore the erase count table, the controller 120 must accumulate the erase count of each block that has occurred since the last erase count table was generated in the erase count of each block included in the last erase count table. When the erase count table is generated and written only when the MAP block is erased, the last erase count table is calculated because the last erase count table recorded in the erase information block refers only to the MAP block before the current MAP block is allocated. The erase count of each subsequent block is calculated by referring to the MAP change information recorded in the spare area of the current MAP block. In this case, the controller 120 stores the last erase count table found in step S310 as a base value of the erase count table on the RAM 140, and bases the block as many times as the number of physical blocks written in the spare area of the MAP block. Restore the erase count table by increasing the value. Of course, when the controller 120 first generates the erase count table, since there is no erase count table recorded in the erase information block, the controller 120 only needs to calculate the number of times the physical block number is recorded in the spare area of the MAP block. In this case, the base value of each block is set to 0 in the erase count table on the RAM 140. In step S330, the controller 120 checks whether MAP change information exists in the spare area of the MAP block. If the MAP change information does not exist in the spare area, it is immediately checked whether the restoration of the erase count table is completed. If the MAP change information exists in the spare area in step S330, the controller 120 checks the physical block number recorded in the spare area in step S340 and records the erase count of the corresponding physical block number in the erase count table on the RAM 140. 1 increases. In step S350, it is checked whether the restoration of the erase count table is completed. If the erase count table is restored, the restore operation of the erase count table ends. If the restoration of the erase count table is not completed, in step S360, the controller 120 reads the next spare area and returns to step S330 to perform an iterative operation.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. It will be understood that the invention may be varied and varied without departing from the scope of the invention.

1 is a view showing the configuration of a flash memory storage device according to the present invention

2 is a diagram illustrating a MAP table and MAP change information recorded in a MAP block in a flash memory according to the present invention.

3 is a flowchart illustrating a method of restoring an erase count table using MAP change information recorded in a MAP block according to the present invention.

<Description of the symbols for the main parts of the drawings>

100: flash memory storage device

120: controller

130: flash memory

Claims (8)

A method of recovering erase information for each block in the flash memory by the controller of a storage device including a flash memory and a controller, the method comprising: And erasing number of each block is calculated using MAP change information recorded in the flash memory. The method of claim 1, And the MAP change information is a physical block number of erased blocks. The method of claim 2, And the MAP change information is recorded in a spare area of a block in which a MAP table is recorded. The method of claim 3, wherein Setting the erase count of each block in the last erase count table as a base value; And And increasing the base value for each block by the number of times the physical block number for each block is recorded in the spare area. A flash memory in which MAP change information is recorded; A controller configured to calculate an erase count of each block by using the MAP change information; And And a random access memory (RAM) in which the erase count table in which the erase count is recorded is stored. The method of claim 5, The MAP change information is a physical block number of erased blocks. The method of claim 6, The MAP change information is recorded in a spare area of a block in which a MAP table of a flash memory is recorded. The method of claim 7, wherein The controller comprising: Sets the erase count included in the last erase count table in the flash memory as a base value of each block, And increasing the base value by the number of times the physical block number for each block is written in the spare area.

Images