KR20080100750A - Apparatus for reading data and method using the same - Google Patents

Abstract

A data read apparatus and the method is provided to read data programmed in a memory cell by using two boundary voltages and decodes the read data, and then determines data in the memory cell. A data read apparatus and the method is comprised of steps: comparing the threshold voltage with the first boundary voltage of the memory cell(S610); comparing second boundary voltage having the voltage level higher than the threshold voltage with the first boundary voltage; determining data of the memory cell based on the comparison result of the threshold voltage and the first boundary voltage and threshold voltage and the second boundary voltage(S620); determining data of the memory cell; determining data of the memory cell as disable value if the threshold voltage is voltage between the second boundary voltage and the first boundary voltage(S630).

Description

Data reading device and its method {APPARATUS FOR READING DATA AND METHOD USING THE SAME}

The present invention relates to data reading, and more particularly, to a data reading apparatus and method for determining data of a memory cell by reading and decoding data programmed in a memory cell using two boundary voltages.

When programming data, the flash memory cell adjusts the threshold voltage of the flash memory cell to fit the data to be programmed. That is, the threshold voltage of the flash memory cell refers to data programmed into the flash memory cell.

To read data programmed in the flash memory cell, the data of the flash memory cell is read by comparing a threshold voltage of the flash memory cell with one or more preset reference voltages, that is, a read level. For example, assuming that a flash memory cell operates in a single level cell (SLC) scheme and that the reference voltage is A, if the threshold voltage of the read flash memory cell is less than the reference voltage A, the data programmed in the flash memory cell is set to 1. When the threshold voltage of the read and read flash memory cell is greater than the reference voltage A, the data programmed into the flash memory cell is read as zero.

However, the threshold voltage of a flash memory cell in which data is programmed is changed to a threshold voltage of a different level by various factors such as charge loss and floating poly coupling. If the voltage is changed to near this reference voltage, the reliability of the data of the read flash memory cell is lowered.

In other words, a memory flash cell having a threshold voltage near a reference voltage may have a programmed data of 1 but a read data of 0, and a programmed data of 0 but a read data of 1 may occur. An error will occur.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art as described above, and sets an unreliable voltage region between states representing data of a flash memory cell, and the threshold voltage of the flash memory cell is less reliable. An object of the present invention is to provide a data reading method for outputting an undetermined value when located in an area.

In addition, an object of the present invention is to increase the reliability of the data of the read memory cells by decoding the data of the flash memory cells read through the data reading method and determining the data of the memory cells including the undeterminable value.

In addition, an object of the present invention is to determine the high reliability data through the decoding process even if the threshold voltage of the flash memory cell is changed to output an undeterminable value.

In order to achieve the above object and solve the problems of the prior art, the data reading method according to an embodiment of the present invention comprises the steps of comparing the threshold voltage and the first threshold voltage of the memory cell, the threshold voltage and the first boundary Comparing the second threshold voltage having a voltage level higher than the voltage; and comparing the threshold voltage with the first threshold voltage, and comparing the threshold voltage with the second threshold voltage. Determining.

In this case, the determining of the data of the memory cell may determine the data of the memory cell as a predetermined non-determinable value if the threshold voltage is a voltage between the first and second threshold voltages.

In this case, the memory cell may be a multi-level cell (MLC) type memory cell or a single level cell (SLC) type memory cell.

In this case, the first boundary voltage and the second boundary voltage may be two predetermined voltages between boundary regions separating data programmed in the memory cell.

In this case, the data reading method may further include decoding data of the determined plurality of memory cells and determining data programmed in the memory cells through the decoding.

In this case, the decoding may be a distance decoding using the data of the memory cells.

In this case, the decoding may include calculating a syndrome using data of the memory cells and decoding using the calculated syndrome.

According to an embodiment of the present invention, a data reading apparatus compares a memory cell, a threshold voltage of the memory cell with a first threshold voltage, and a second threshold voltage having a voltage level higher than the first threshold voltage, A voltage comparator for generating a result value and a data read part for determining data of the memory cell based on the result value input from the voltage comparator.

In this case, the data reading device receives a decoding unit for receiving and decoding data of a plurality of memory cells determined by the data reading unit, and receives data of the memory cells decoded by the decoding unit, and receives the decoded memory. The apparatus may further include a data determiner configured to determine data programmed into the memory cells through data of cells.

According to an embodiment of the present invention, a data reading device and method thereof may be configured to set an unreliable voltage region between states representing data of a flash memory cell, and to set a threshold voltage of a flash memory cell in an unreliable voltage region. In this case, a data reading method for outputting an undetermined value can be provided.

In addition, the present invention can increase the reliability of the data of the read memory cells by decoding the data of the flash memory cells read through the data reading method and determining the data of the memory cells including the undeterminable value.

In addition, according to the present invention, even when the threshold voltage of the flash memory cell is changed and an undeterminable value is output, the data may be determined to have high reliability through the decoding process.

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

1 is a block diagram illustrating a data reading apparatus according to an embodiment of the present invention.

Referring to FIG. 1, a data reading apparatus includes a voltage comparator 120 and a data reading unit 130.

The voltage comparator 120 compares the threshold voltage of the memory cell 110 with a second threshold voltage having a voltage level higher than the first threshold voltage and the first threshold voltage to generate a result value.

In this case, the first boundary voltage and the second boundary voltage may be two predetermined voltages included in a boundary region that divides the programmed data between states representing data (0 or 1) programmed in the memory cell. Here, the boundary area for dividing the programmed data is an untrusted area for reading the data, and the boundary area for dividing the programmed data is at least one. In other words, when the memory cell operates in a single level cell (SLC) scheme, there is one boundary area that separates the programmed data, and when the memory cell operates in a multi level cell (MLC) scheme, the programmed data is divided. There is more than one boundary area.

Here, the first boundary voltage and the second boundary voltage become minimum and maximum voltages of the boundary region in which the read data is unreliable when reading data from the memory cell.

In this case, the boundary region may vary depending on the situation, but may be set in consideration of the influence due to the charge loss and the floating poly coupling.

In this case, the memory cell 110 may be a flash memory cell and may be a NAND flash memory cell or a NOR flash memory cell.

In this case, the memory cell 110 may be a multi-level cell (MLC) type memory cell or a single level cell (SLC) type memory cell.

The data reading unit 130 receives a result value generated from the voltage comparator 120 and determines data of the memory cell based on the input result value. That is, the data reading unit 130 reads data of the memory cell based on the result value.

In this case, if the threshold voltage of the memory cell 110 is a voltage between the first and second threshold voltages, the data read unit 130 may determine the data of the memory cell as an undeterminable value. That is, if the result value input from the voltage comparator 120 is a result value indicating that the threshold voltage of the memory cell is the voltage between the first and second threshold voltages, the data of the memory cell is 0. Because we can't be convinced or we can be convinced of 1, we decide with a certain value that is not 0 or 1.

Here, when the data of the memory cell read by the data reading unit 130 is read as an undeterminable value, the undeterminable value is determined to be correct data through a decoding process according to the present invention.

2 is an exemplary view for explaining a data reading apparatus according to the present invention.

2 shows LSB data of most significant bit (MSB) data and least significant bit (LSB) data of a memory cell operating at four levels.

Referring to FIG. 2, the LSB data of the memory cell is read using two boundary voltages between the boundary regions separating the LSB data 0 and 1 of the memory cell.

That is, the first boundary voltage VSEN_1A and the second boundary voltage VSEN_1B between data 1 and 0 of the memory cell between data 11 and 10 of the memory cell, and the LSB of the memory cell between data 00 and 01 of the memory cell. The LSB data of the memory cell is read using the first threshold voltage VSEN_3A and the second threshold voltage VSEN_3B between data 0 and 1.

For example, when the threshold voltage of a memory cell for reading LSB data is less than VSEN_1A or greater than VSEN_3B, the LBS data is read as 1, and when the threshold voltage of the memory cell is a voltage between VSEN_1B and VSEN_3A, the LSB data is 0. Read with

On the other hand, when the threshold voltage of the memory cell is a voltage between VSEN_1A and VSEN_1B or a voltage between VSEN_3A and VSEN_3B, the LSB data is read as a specific value other than 0 or 1.

That is, according to the present invention, when the threshold voltage programmed in the memory cell is changed due to charge loss or floating polycoupling, and the data of the memory cell cannot be read accurately as 0 or 1, the present invention reads as an undeterminable value and cannot determine the value. Is determined to be 0 or 1 using the decoding process.

3 is a block diagram illustrating a data reading apparatus according to another embodiment of the present invention.

Referring to FIG. 3, the data reader includes a voltage comparator 320, a data reader 330, a decoder 340, and a data determiner 350.

The voltage comparator 320 compares the threshold voltages of each of the memory cells constituting the memory 310 with a first threshold voltage and a second threshold voltage having a voltage level higher than the first threshold voltage to generate a result value.

In this case, the first boundary voltage and the second boundary voltage may be two predetermined voltages between boundary regions that divide each of the data programmed in each of the memory cells.

Here, the first boundary voltage and the second boundary voltage become minimum and maximum voltages of the boundary region in which the read data is unreliable when reading data from the memory cell.

In this case, the memory cells may be flash memory cells, and may be NAND flash memory cells or NOR flash memory cells.

In this case, the memory cells may be multi-level cell (MLC) type memory cells or single cell (SLC) type memory cells.

The data reader 330 receives a result value generated from the voltage comparator 320 and determines data of the memory cells based on the input result value.

In this case, the data read unit 330 may determine the data of the memory cell as an undeterminable value if the result value corresponds to a result value corresponding to a voltage between the first and second threshold voltages of the memory cell. That is, the data reading unit 330 determines that the data of the unreliable memory cell is a specific value other than 0 or 1.

The decoding unit 340 decodes data of memory cells determined by the data reading unit 330.

In this case, the decoding unit 340 may perform distance decoding using data other than data of an undeterminable value among data of memory cells determined by the data reading unit 330.

In this case, the decoding unit 340 may decode by using syndrome calculation considering each case of data of the undeterminable value among the data of the memory cells determined by the data reading unit 330.

The data determiner 350 determines the data programmed in the memory cells by using the decoding result of the decoder 340.

In this case, the data determiner 350 may determine the data programmed in the memory cells based on the distance calculated by the distance decoding when the decoding unit 340 performs the decoding through the distance decoding.

An example of a data determination process using distance decoding will be described with reference to FIG. 4.

4 shows the distance between a possible program code word and a read code word when a Hamming code is used as the code word programmed into the memory cells and the code word read from the memory cells is "1010XX1".

Here, X means an undeterminable value.

Referring to FIG. 4, the decoding unit 340 performs distance calculation between the possible program code words for the Hamming code and the read code word "1010XX1", excluding the data at a position corresponding to an undeterminable value.

That is, the distance between the read code word and the possible program code words is calculated through distance calculation using only the data of the remaining positions except the data of the position corresponding to the undeterminable value in the read code word. For example, calculating the distance between the second possible program code word 410 " 1010001 " and the read code word " 1010XX1, " Because they are the same, the distance is zero. In addition, if the distance between the third possible program code word "1110010" and the read code word "1010XX1" is calculated, the left second bit and the right first bit of the remaining data except the undeterminable value in the read code word are the third possible. The distance is two because it is different from the program code word data.

When distances between the code word read through the distance calculation process and possible program code words are calculated, the data determination unit 350 detects the code word having the smallest value among the calculated distances, and the detected code word. Is determined as the program code word. That is, the code word "1010001" whose distance calculated in FIG. 4 is 0 is determined as the program code word. In this case, all of the undeterminable values of the read code word become 0, and the data stored in the memory cells are determined as "1010001".

In this case, the data determiner 350 may determine the data programmed in the memory cells based on the calculated syndrome when the decoding unit 340 performs decoding using the syndrome calculation.

An example of a data determination process through decoding by syndrome calculation will be described with reference to FIG. 5.

FIG. 5 shows a syndrome when a Hamming code is used as the code word programmed into the memory cells and the code word read from the memory cells is "1010X1X21".

Here, X1 and X2 mean undeterminable values.

Referring to FIG. 5, the decoding unit 340 performs syndrome calculation on the read code word “1010X1X21”. Here, the syndrome calculation process for the read code word is obvious to those skilled in the art and will not be described.

The syndrome s by the syndrome calculation becomes "X1 [0 1 1] + X2 [1 1 1]".

The syndrome s calculated by the decoding unit 340 is the syndromes for the possible values 00, 01, 10 and 11 of the undeterminable values X1 and X2, respectively, 000, 111, 011 and 100.

The data determiner 350 checks the error patterns e based on the syndromes calculated by the decoder 340, and determines the code word programmed in the memory cells based on the read code word and the error patterns. That is, the data determination unit 350 calculates possible program code words cp based on the read code words and error patterns corresponding to each of the undeterminable values, and the frequency of the calculated possible program code words is the most. A high possible program code word "1010001" is determined as the program code word to determine the data stored in the memory cells as "1010001".

6 is an operation flowchart for a data reading method according to an embodiment of the present invention.

Referring to FIG. 6, the data read method compares a threshold voltage of a memory cell with a second boundary voltage having a voltage level higher than the first boundary voltage and the first boundary voltage (S610).

In this case, the first boundary voltage and the second boundary voltage may be two predetermined voltages between boundary regions for dividing 0 or 1 which are data that can be programmed in the memory cell.

Here, the number of boundary regions that divide the programmed data may vary according to an operation method of the memory cell. For example, when the memory cell operates in a single level cell (SLC) scheme, there is one boundary area for dividing the programmed data. When the memory cell operates in a multi level cell (MLC) scheme, the boundary region that divides the programmed data is divided. There is more than one boundary area.

Here, the first boundary voltage and the second boundary voltage are the minimum of the boundary region in which the read data is unreliable when reading data between the region in which the data programmed into the memory cell is determined to be 0 and the region in which the programmed data is determined to be 1. Voltage and maximum voltage.

In this case, the boundary region may vary depending on the situation, but may be set in consideration of the influence due to the charge loss and the floating poly coupling.

In this case, the memory cell may be a flash memory cell, and preferably, may be a NAND flash memory cell or a NOR flash memory cell.

In this case, the memory cell may be a multi level cell (MLC) type memory cell or a single level cell (SLC) type memory cell.

It is determined whether the threshold voltage of the memory cell is located between the first threshold voltage and the second threshold voltage (S620). If the threshold voltage is between the first threshold voltage and the second threshold voltage, the data of the memory cell is determined. Read as an impossible value (S630).

On the other hand, if the threshold voltage is not located between the first and second threshold voltages as a result of determining in step S620, the data of the memory cell is read as data set to the voltage region in which the threshold voltage is located (S640). For example, referring to FIG. 2, when the threshold voltage is smaller than VSEN_1A or larger than VSEN_3B, the LSB data of the memory cell is read as one.

7 is a flowchart illustrating a data reading method according to another embodiment of the present invention.

Referring to FIG. 7, in the data reading method, threshold voltages of each of the memory cells constituting a memory are compared with a first boundary voltage and a second boundary voltage having a voltage level higher than the first boundary voltage (S710).

In this case, the first boundary voltage and the second boundary voltage may be two predetermined voltages between boundary regions that divide each of the data programmed in each of the memory cells.

Here, the first boundary voltage and the second boundary voltage are the minimum of the boundary region in which the read data is unreliable when reading data between the region in which the data programmed into the memory cell is determined to be 0 and the region in which the programmed data is determined to be 1. Voltage and maximum voltage.

In this case, the memory cells may be flash memory cells, and may preferably be NAND flash memory cells or NOR flash memory cells.

In this case, the memory cells may be MLC type memory cells or SLC type memory cells.

It is determined whether the threshold voltages of the memory cells are located between the first boundary voltage and the second boundary voltage (S720), and as a result of the determination of each of the memory cells, the threshold voltage of the memory cells is between the first boundary voltage and the second boundary voltage. If it is located at, the data of the corresponding memory cell is read as an undeterminable value (S730).

On the other hand, if the threshold voltage of the memory cell is not located between the first and second threshold voltages as a result of the determination of step S720 for each of the memory cells, the data of the memory cell is set to a voltage region in which the threshold voltage of the memory cell is located. Read in (S740).

The data of the read memory cells are decoded and the data of the memory cells including the undeterminable value are determined through the decoding process (S750).

At this time, the data of the read memory cells may perform distance decoding using data other than data of an undeterminable value among the read data of the memory cells.

In this case, the data of the read memory cells may be decoded by using a syndrome calculation considering each case of undeterminable data among the read data of the memory cells.

FIG. 8 is a flowchart illustrating an embodiment of operation S750 shown in FIG. 7.

Referring to FIG. 8, in the determining of the data of the memory cells, the distances of the code word from which the data of the memory cells are read and the predetermined possible program code words are calculated (S810).

In this case, the possible program code words may vary depending on the code used to program the data in the memory cells.

Here, the calculating of the distances (S810) is performed using data except for the undeterminable value included in the read code word. That is, when the read code word is 7 bits and the undeterminable value is 2 bits, the distance from the possible program code words is calculated using 5 bits of data.

A possible program code word having the smallest value among the calculated distances is detected (S820). That is, the most probable code word among the possible program code words is detected.

The detected possible program code word is determined as the program code word stored in the memory cells to determine the data of the memory cells (S830).

9 is a flowchart illustrating another operation of step S750 illustrated in FIG. 7.

Referring to FIG. 9, the determining of the data of the memory cells calculates a syndrome for the read code word that is the data of the memory cells (S910).

The syndromes for each case of the undeterminable value included in the calculated syndrome are detected (S920). For example, four syndromes are detected when two undeterminable values are included in a received code word.

Based on the detected syndromes, error patterns corresponding to each of the syndromes are checked (S930).

Possible program code words are calculated based on the error patterns and the read code word (S940). For example, when data are programmed into memory cells using a Hamming code, a program code word is calculated by adding a read code word to which 0 or 1 is applied to each of the undetermined values and an error operation of the corresponding error pattern.

The program code word having the highest frequency among the calculated possible code words is determined as the program code word stored in the memory cells to determine the data of the memory cells (S950).

FIG. 10 is a diagram further defining a soft decision value according to another embodiment of the present invention when compared with FIG. 2. Hereinafter, another embodiment of a data reading apparatus according to the present invention will be described with reference to FIG. 10 (see FIGS. 1 and 2).

1 and 2, as an embodiment of the present invention, the data reader 130 receives a result value generated from the voltage comparator 120, and based on the input result value, the memory cell. The data of the memory cell can be determined as an undeterminable value if the threshold voltage of the memory cell 110 is a voltage between the first and second threshold voltages.

However, as another embodiment of the present invention, a soft decision value is generated according to reliability, and an additional reading operation is performed for an unreliable section as needed, thereby making more accurate soft decision. It is possible to generate a value. Therefore, even before the decoding of the data, by performing the process of increasing the accuracy of the data read in the unreliable interval, there is an advantage that the data of the memory cell can be finally determined more accurately.

For example, since the threshold voltage of the memory cell may be a voltage between the (first boundary voltage) and the (second boundary voltage), in order to determine a more accurate position of the threshold voltage, as shown in FIG. In addition, when the threshold voltage is close to the first threshold voltage, the data read unit 130 may include information indicating that the threshold voltage is closer to the first threshold voltage than the second threshold voltage. Determine the data as a specific soft decision value.

On the other hand, if the threshold voltage is approximated to the second threshold voltage by additionally performing the reading operation, the data reading unit 130 includes information indicating that the threshold voltage is closer to the second threshold voltage than the first threshold voltage. Determines the data of the memory cell as a specific soft decision value.

More specifically, for example, as shown in FIG. 10, the soft decision value when the LSB data of any memory cell is 1 is designed to 11 and the soft decision value when the LSB data is 0 is set to '00'. In the design, when the threshold voltage of the memory cell is closer to the first boundary voltage than the second boundary voltage, the data reading unit 130 reads '10' as a soft decision value for the data of the memory cell. On the other hand, when the threshold voltage of the memory cell is closer to the second boundary voltage than the first boundary voltage, the data reading unit 130 reads '01' as a soft decision value for the data of the memory cell.

Therefore, even when the threshold voltage is present between the first and second threshold voltages, i.e., when the threshold voltage is present in an unreliable section, the information on which threshold voltage is close to the threshold voltage is read and decoded, thereby providing data. There is a unique advantage of the present invention that can further improve the accuracy of.

Meanwhile, the same descriptions described above also apply to the other first threshold voltage V _{SEN _3A} and the second threshold voltage V _{SEN _3B} , and even if the description is omitted, those skilled in the art will fully understand the present invention through the above description. As can be appreciated, duplicate descriptions will be omitted.

FIG. 11 is another diagram further defining a soft decision value according to another embodiment of the present invention when compared with FIG. 2. Hereinafter, another embodiment of a data reading apparatus according to the present invention will be described with reference to FIG. 11 (see FIGS. 1, 2, and 10). For reference, when comparing FIG. 11 and FIG. 10, FIG. 10 defines a soft determination value as 2 bits, and FIG. 11 defines a soft determination value as 3 bits, and detailed description thereof will be omitted. Those skilled in the art can easily understand the present invention through the description.

More specifically, for example, as shown in FIG. 11, the soft determination value when the LSB data of any memory cell is 1 is designed as '111' and the soft determination value when the LSB data is 0 is '000'. When the threshold voltage of the memory cell belongs to a specific range that is closer to the first threshold voltage than the second threshold voltage, the data reading unit 130 may be configured as a soft decision value for the data of the memory cell. Read 110 ' On the other hand, when the threshold voltage of the memory cell falls within a specific range that is closer to the second boundary voltage than the first boundary voltage, the data read unit 130 sets '100' as a soft decision value for the data of the memory cell. Read. On the other hand, when the threshold voltage of the memory cell is within a specific range of the same degree as the first threshold voltage and the second threshold voltage, the data reading unit 130 is a soft decision value for the data of the memory cell ' Read 101 '.

The soft decision values of two bits and three bits have been described so far, but the scope of the present invention is not limited thereto, and it is also possible to design soft decision values of bits having other numerical values.

The data reading method according to the present invention can be implemented in the form of program instructions that can be executed by various computer means and recorded in a computer readable medium. The computer readable medium may include program instructions, data files, data structures, etc. alone or in combination. Program instructions recorded on the media may be those specially designed and constructed for the purposes of the present invention, or they may be of the kind well-known and available to those having skill in the computer software arts. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tape, optical media such as CD-ROMs, DVDs, and magnetic disks, such as floppy disks. Magneto-optical media, and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. The medium may be a transmission medium such as an optical or metal wire, a waveguide, or the like including a carrier wave for transmitting a signal specifying a program command, a data structure, or the like. Examples of program instructions include not only machine code generated by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like. The hardware device described above may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

As described above, although the present invention has been described with reference to limited embodiments and drawings, the present invention is not limited to the above embodiments, and those skilled in the art to which the present invention pertains various modifications and variations from such descriptions. This is possible.

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the claims below but also by the equivalents of the claims.

1 is a block diagram illustrating a data reading apparatus according to an embodiment of the present invention.

2 is an exemplary view for explaining a data reading apparatus according to the present invention.

3 is a block diagram illustrating a data reading apparatus according to another embodiment of the present invention.

4 shows the distance between a possible program code word and a read code word when a Hamming code is used as the code word programmed into the memory cells and the code word read from the memory cells is "1010XX1".

FIG. 5 shows a syndrome when a Hamming code is used as the code word programmed into the memory cells and the code word read from the memory cells is "1010X1X21".

6 is an operation flowchart for a data reading method according to an embodiment of the present invention.

7 is a flowchart illustrating a data reading method according to another embodiment of the present invention.

FIG. 8 is a flowchart illustrating an embodiment of operation S750 shown in FIG. 7.

9 is a flowchart illustrating another operation of step S750 illustrated in FIG. 7.

FIG. 10 is a diagram further defining a soft decision value according to another embodiment of the present invention when compared with FIG. 2.

FIG. 11 is another diagram further defining a soft decision value according to another embodiment of the present invention when compared with FIG. 2.

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

120, 320: voltage comparator

130, 330: data reading section

340: decoding unit

350: data determination unit

Claims (27)

Comparing the threshold voltage of the memory cell with the first boundary voltage; Comparing the threshold voltage with a second threshold voltage having a voltage level higher than the first threshold voltage; And Determining data of the memory cell based on a result of comparing the threshold voltage with the first threshold voltage and a result of comparing the threshold voltage with the second threshold voltage; Data reading method comprising a. The method of claim 1, Determining data of the memory cell And when the threshold voltage is a voltage between the first threshold voltage and the second threshold voltage, determining the data of the memory cell as a predetermined undeterminable value. The method of claim 1, The memory cell is A method of reading data, characterized in that it is a flash memory cell. The method of claim 3, The memory cell is A method of reading data of a memory cell, characterized in that it is a MLC (multi level cell) memory cell. The method of claim 3, The memory cell is A data reading method, characterized in that the memory cell of the SLC (single level cell) method. The method of claim 1, The first boundary voltage and the second boundary voltage are And two predetermined voltages between boundary regions separating data programmed into the memory cell. The method of claim 1, The data reading method is Decoding the data of the determined plurality of memory cells; And Determining data programmed into the memory cells through the decoding Data reading method further comprising a. The method of claim 7, wherein The decoding step And performing distance decoding using the data of the memory cells. The method of claim 7, wherein The decoding step And calculating a syndrome using the data of the memory cells and decoding using the calculated syndrome. A computer-readable recording medium having recorded thereon a program for executing the method of any one of claims 1 to 9. Memory cells; A voltage comparison unit comparing the threshold voltage of the memory cell with a first threshold voltage and a second threshold voltage having a voltage level higher than the first threshold voltage, and generating a result value according to a comparison result; And A data reading unit determining data of the memory cell based on the result value input from the voltage comparing unit Data reading device comprising a. The method of claim 11, The data reading unit The data of the memory cell is determined to be a non-determinable value if the result value input from the voltage comparator is a result value indicating that the threshold voltage is a voltage between the first and second threshold voltages. Data read device. The method of claim 11, The memory cell is A data reading device, characterized in that it is a flash memory cell. The method of claim 13, The memory cell is An apparatus for reading data of a memory cell, characterized in that the memory cell is a multi-level cell (MLC) method. The method of claim 13, The memory cell is A data reading device, characterized in that the memory cell of the SLC (single level cell) method. The method of claim 11, A decoding unit which receives and decodes data of a plurality of memory cells determined by the data reading unit; And A data determination unit which receives data of the memory cells decoded by the decoding unit and determines data programmed in the memory cells through the data of the decoded memory cells Data reading apparatus further comprises a. The method of claim 16, The decoding unit And performing distance decoding using the data of the memory cells. The method of claim 16, The decoding unit And calculating a syndrome using data of the memory cells and decoding using the calculated syndrome. Comparing the threshold voltage of the memory cell with the first boundary voltage; Comparing the threshold voltage with a second threshold voltage having a voltage level higher than the first threshold voltage; And Determining the data of the memory cell as a specific soft decision value according to the extent to which the threshold voltage is close to the first boundary voltage or the second boundary voltage. Data reading method characterized in that is made, including. The method of claim 19, The determining step, When the threshold voltage is closer to the first boundary voltage than the second boundary voltage, the data of the memory cell is determined to have a specific softness determination value to include information indicating that the threshold voltage is closer to the first boundary voltage than the second boundary voltage. The data reading method, characterized in that the determination. The method of claim 19, The determining step, If the threshold voltage is closer to the second boundary voltage than the first boundary voltage, the data of the memory cell is determined to be specific softened to include information indicating that the threshold voltage is closer to the second boundary voltage than the first boundary voltage. A data reading method, characterized in that determined by the value. The method of claim 19, The data reading method, Decoding the data of the determined plurality of memory cells; And Determining data programmed into the memory cells through the decoding Data reading method characterized in that it further comprises. A computer-readable recording medium having recorded thereon a program for executing the method of any one of claims 19 to 22. A voltage comparison unit comparing a threshold voltage of a predetermined memory cell with a first threshold voltage and a second threshold voltage having a voltage level higher than the first threshold voltage, and generating a result value according to a comparison result; And A data reading unit determining data of the memory cell as a specific soft decision value according to a degree in which the threshold voltage approximates a first boundary voltage or the second boundary voltage. Data reading device, characterized in that comprises a. The method of claim 24, The data reading unit, When the threshold voltage is closer to the first boundary voltage than the second boundary voltage, the data of the memory cell is determined to have a specific softness determination value to include information indicating that the threshold voltage is closer to the first boundary voltage than the second boundary voltage. The data reading device, characterized in that the determination. The method of claim 24, The data reading unit, When the threshold voltage is closer to the second boundary voltage than the first boundary voltage, the data of the memory cell is determined to have a specific softness determination value to include information indicating that the threshold voltage is closer to the second boundary voltage than the first boundary voltage. The data reading device, characterized in that the determination. The method of claim 24, A decoding unit which receives and decodes data of a plurality of memory cells determined by the data reading unit; And A data determination unit which receives data of the memory cells decoded by the decoding unit and determines data programmed in the memory cells through the data of the decoded memory cells Data reading device, characterized in that further comprises a.

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