KR100697792B1 - Storage medium reproducing apparatus, storage medium reproducing method, and computer readable medium for reading information from storage medium - Google Patents

Abstract

A storage medium reproducing device, a storage medium reproducing method, and a computer readable medium for reading information from a storage medium are provided to store contents of error correction in correction record storage units only when an error corrected by using an ECC(Error Correction Code) is considered as an error caused by discharge, thereby limiting an unnecessary correcting operation. A storage unit is composed of plural information storage units(M1-Mn) for storing information, depending on whether an amount of electric charges is larger than a predetermined amount of electric charge threshold values, and correction code storage units(EC1-ECn) for storing ECCs for the stored information. Correction record storage units(EL1-ELn) store correction records which include contents of the correction and ID information for identifying the information storage units(M1-Mn). A correction record execution unit(102) corrects the information according to the contents of the correction when the information is read from the information storage units(M1-Mn) identified by the ID information. A correction unit(103) conducts a correcting operation by using the ECCs for the corrected information, and registers the contents of the correction and the correction records which include the ID information in the correction record storage units(EL1-ELn).

Description

A storage medium reproducing apparatus, a storage medium reproducing method, and a computer readable medium for reading information from the storage medium.

1 is a block diagram showing the configuration of a storage medium reproducing apparatus according to the first embodiment of the present invention.

2 shows an example of an equivalent circuit of a memory unit formed of four-value memory elements.

3 shows the discharge of the memory elements.

4 shows an example of the charge distribution of the memory elements.

5 shows an exemplary data structure of the correction history storage unit.

6 is a flowchart of a storage medium reproducing operation according to the first embodiment.

7 is a flowchart of a storage medium reproducing operation according to the second embodiment of the present invention.

Fig. 8 is a block diagram showing the construction of a storage medium reproducing apparatus according to the third embodiment of the present invention.

9 shows an exemplary data structure of the correction history storage unit.

10 is a flowchart of a storage medium reproducing operation according to the third embodiment.

11 is a block diagram showing the structure of a storage medium reproducing apparatus according to a fourth embodiment of the present invention.

Fig. 11 is a block diagram showing the structure of the storage medium reproducing apparatus according to the fourth embodiment of the present invention.

12 is a flowchart of a storage medium reproducing operation according to the fourth embodiment.

The present invention relates to a storage medium reproducing apparatus, a storage medium reproducing method, and a computer readable medium for reading information from a storage medium.

Recently, semiconductor memories such as flash memories for storing information in accordance with the amount of charge have been widely used. In addition, in order to store a plurality of bits of information, a multi-value memory technology has been developed in which a plurality of threshold values are set for the amount of charge.

In such semiconductor memories, charge is released over time. Therefore, if the amount of discharged charges exceeds a threshold, an error occurs in reading information. In particular, in multi-value memories with thresholds at narrow intervals, the probability of error occurrence is high.

On the other hand, in order to maintain the reliability of the stored information, an error correction code is assigned to the memory cell groups, each memory cell group includes a certain number of memory elements, and errors in the information are, for example, Japanese Patent Application Laid-Open No. H11. Correction using error correction codes according to the method disclosed in -154394.

However, memory elements having a charge amount exceeding a threshold value due to discharge consistently generate an error upon reading. Therefore, according to the conventional error correction method, the same error correction operation must be performed each time reading is performed, so that a large amount of calculation is generated in each correction operation.

In addition to a memory device in which an error occurs constantly due to discharge, there may be a memory device that newly generates an error. In order to correct errors of such a plurality of memory elements, a plurality of correction codes are required. This causes even more computation in each correction operation.

According to one aspect of the present invention, the storage medium reproducing apparatus includes a storage unit, a correction history storage unit, a correction history execution unit, and a correction unit. The storage unit includes a plurality of information storage units for storing information depending on whether the charge amount is greater than a preset charge amount threshold value, and a correction code storage unit for storing error correction codes for information stored in the plurality of information storage units. It includes. The correction history storage unit stores identification information for identifying an information storage unit in which a correction operation using an error correction code is performed between the information storage units, and a correction history including the contents of the correction. The correction history execution unit corrects the information according to the contents of the correction stored in the correction history storage unit when the information is read out from the information storage unit identified by the identification information. The correction unit performs a correction operation using the error correction code on the corrected information, and registers a correction history including the contents of the correction of the information storage unit corrected using the error correction code and identification information in the correction history storage unit. do.

According to another aspect of the present invention, a storage medium reproducing method comprises: an information storage unit corrected using an error correction code among a plurality of information storage units, each of which stores information depending on whether the amount of charge is greater than a predetermined charge amount threshold; Correcting the information read from the information storage unit identified by the identification information according to the correction contents stored in the correction history storage unit which stores the correction history including the identification information and the correction contents identifying the identification information; And performing a correction operation on the corrected information by using an error correction code, and registering a correction history including identification information and correction contents of the information storage unit corrected by using error correction in the correction history storage unit. do.

A computer readable medium according to another aspect of the present invention allows a computer to perform the storage medium reproducing method according to the present invention.

Exemplary embodiments of a storage medium reproducing apparatus, a storage medium reproducing method, and a computer readable medium according to the present invention are described in detail below with reference to the accompanying drawings.

The storage medium reproducing apparatus according to the first embodiment stores a correction history in the storage unit using past error correction codes, and performs a correction operation with reference to the correction history when reading information. The storage medium reproducing apparatus also performs a correction operation by using an error correction code in the correction result performed by referring to the history.

1 is a block diagram showing the configuration of the storage medium reproducing apparatus 100 according to the first embodiment. As shown in Fig. 1, the storage medium reproducing apparatus 100 includes storage units M1 to Mn, correction history storage units EL1 to ELn, control unit 101, correction history execution unit 102, And a correction unit 103.

The memory units M1 to Mn are memory elements that store information, and use a difference in the amount of charge with respect to a threshold value predetermined for the amount of charge. The storage units M1 to Mn may be formed of a commonly used semiconductor memory, such as flash memory or DRAM (Dynamic Random Access Memories). The memory units M1 to Mn may also be formed of binary memory elements which maintain one threshold and store binary information consisting of zeros and ones. Alternatively, the memory units M1 to Mn may be formed of multi-value memory elements that hold different threshold values. Next, a configuration in which the memory units M1 to Mn are formed of four-value memory elements will be described.

The memory units M1 to Mn include memory cell groups MC1 to MCn and correction code memory units EC1 to ECn, respectively. The memory cell groups MC1 to MCn are memory units, each of which includes memory cells that are four-value memory elements. Information to be stored in the storage units M1 to Mn is actually stored in the memory cell groups MC1 to MCn.

The correction code storage units EC1 to ECn are storage units, and each of the storage units includes memory cells that are four-value memory elements, such as the memory cell groups MC1 to MCn. Instead of the information to be stored, the correction code storage units EC1 to ECn store error correction codes corresponding to the information to be stored. The number of memory cells constituting each of the correction code storage units EC1 to ECn is not limited to 1, but may reach the maximum number of corrections.

2 shows an example of an equivalent circuit of a storage unit including four-value memory elements. The equivalent circuit shown in FIG. 2 is a storage unit (hereinafter, referred to as a storage unit Mn) of the storage units M1 to Mn.

As shown in Fig. 2, the memory unit Mn includes memory elements (cells 0 to cell i) and is designed to accumulate charge in each of the memory elements. The accumulated charge is compared with the three thresholds by a comparator, so that 2-bit information of bits B0 and B1 can be output. Thus, 4-value information (01, 00, 10, 11) can be stored.

Some of the memory elements (cells 0 to cell i) constitute the memory cell groups MCn shown in Fig. 11, and the rest of the memory elements constitute the correction code memory units ECn.

3 shows discharges from the memory elements. In the graph shown in Fig. 3, the starting point of recording is represented by 0, the horizontal axis represents elapsed time, and the vertical axis represents output voltage. A semiconductor memory such as a flash memory or a DRAM can retain the stored contents even when power supply is cut off. However, as shown in Fig. 3, the charges accumulated in the memory elements are discharged after a long period of time, so that the output voltage decreases.

4 shows an example of the charge distribution in the memory elements. The left side of Fig. 4 shows the charge distribution observed immediately after the write operation. 4 shows the distribution of charges observed after a certain period of time. Thresholds for the amount of charge are represented by Eth0 to Eth2.

As shown in Fig. 4, the charges accumulated in the memory elements are discharged over time, and the charge distribution approaches a threshold. As a result, the probability of an error to be caused when reading information becomes higher.

The correction history storage units EL1 to ELn are storage units that store a history of the content corrected by the correction unit 103 using the error correction code. The correction history storage units EL1 to ELn are formed of memory elements that do not require a refresh operation, such as Ferroelectric Random Access Memories (FeRAM) or Static Random Access Memories (SRAM).

The correction history storage unit ELn is referred to when the correction history execution unit 102 corrects the information with reference to the correction history. In the first embodiment, the storage units M1 to Mn include the correction history storage units EL1 to ELn, respectively.

5 shows an exemplary data structure of the correction storage units EL1 to ELn. The data structure shown in Fig. 5 is the data structure of the correction history storage units (hereinafter referred to as the correction history storage unit ELn) of the correction history storage units EL1 to ELn.

As shown in FIG. 5, the correction history storage unit ELn stores a cell ID of a memory cell corrected by an error correction code among memory cells included in the memory cell group MCn. The cell ID is stored in association with the content of the correction. For example, when "11" is corrected to "10", information of "11-> 10" is stored.

The correction histories stored in the correction history storage units EL1 to ELn are erased each time new information is recorded in the corresponding storage units M1 to Mn. This is because sufficient charge is accumulated in the memory cell groups MC1 to MCn when new information is written.

The control unit 101 receives a command such as an information read command for the storage units M1 to Mn. In accordance with the command, the control unit 101 selects a storage unit to which information is read, and controls the correction operation.

The correction history execution unit 102 refers to the correction history stored in the corresponding correction history storage units EL1 to ELn with respect to the information read out from the storage units M1 to Mn. Next, the correction history execution unit 102 performs the same correction operation as the correction contents included in the correction history.

For example, when the information of the storage unit Mn is read out and the correction history of "Cell ID = 1" and "Calibration contents = 11-> 10" is stored in the correction history storage unit ELn, the information "11" to "" is stored. The change operation to 10 " is performed on the cell having the cell ID " 1 " in the storage unit Mn.

The correction unit 103 performs a correction operation using an error correction code on the information corrected by the correction history execution unit 102 in accordance with the correction contents of the correction history. Correction operations using error correction codes are performed by conventional error correction techniques that enable immediate decoding, such as Bose-Chaudhuri-Hocquenghem (BCH) code decoding or Reed-Solomon (RS) code decoding.

The correction unit 103 also stores the contents of the error correction operation in the correction history storage units EL1 to ELn. More specifically, the cell ID of the memory cell having an error is stored in the correction history storage units EL1 to ELn in association with the correction contents including information before and after correction.

Next, a recording medium reproducing operation to be performed by the recording medium reproducing apparatus 100 having the above structure according to the first embodiment will be described. 6 is a flowchart of an entire storage medium reproducing operation according to the present invention.

First, the control unit 101 reads out information from the storage unit that stores the information designated to be reproduced (step S601). Here, the information is read from the memory unit Mk (k is an integer).

The correction history execution unit 102 includes the contents of past corrections from the correction history storage unit ELk corresponding to the storage unit Mk, and performs a correction operation on the information read in accordance with the obtained contents of the correction (step S602).

The correction history shown in FIG. 5 is stored in, for example, the correction history storage unit ELk, and information “11” is “1” among the memory cells included in the memory cell group MCk of the memory storage unit Mk in step S601. Is read from a memory cell having a cell ID of " In this case, the correction history corresponding to the cell ID of "1" exists in the correction history storage unit ELk, and the correction content indicates a change from information "11" to "10". Therefore, the information "11" changes to "10" according to the correction.

This calculation is not essential to the method of the first embodiment, although a calculation for identifying the cell which caused the error and identifying the value to be corrected is required in the conventional error correction operation using the error correction code. Therefore, the work load in each correction operation can be reduced.

Next, the correction unit 103 determines whether an error exists in the information corrected by the correction history execution unit 102 (step S603). If an error exists (“YES” in step S603), the correction unit 103 determines whether or not the error can be formed using an error correction code (step S604). Using the correction technique, whether correction can be made or not depends on whether the number of error bits exceeds the correctable number of bits.

If it is determined that correction can be made (YES in step S604), the correction unit 103 calculates an error position and an error vector and corrects the information (step S605). Information indicating the memory cells to be included is the same as the cell ID of the correction history storage unit ELk The error vector is information indicating how to convert the error information into the correction information, and the correction stored in the correction history storage unit ELk. Same as the content.

Next, the correction unit 103 registers the calculated cell ID and the correction contents as the correction history in the correction history storage unit ELk (step S606). The correction history calculated in step S605 is a correction history of an error newly generated in the current information reading operation. In this way, only the correction history of the newly generated error is additionally registered in the correction history storage unit ELk, so that the correction history can be referred to in the subsequent read operation.

After the correction history is registered in the correction history storage unit ELk (step S606) or after it is determined that an error does not exist in the information corrected by the correction history execution unit 102 ("NO" in step S603) The correction unit 103 outputs the corrected information or executes the read information after the normal reading (step S607), where the storage medium reproduction operation is terminated.

If it is determined that the correction using the error correction code has not been performed ("NO" in step S604), the control unit 101 forms an output to the effect that an error has been generated (step S608). The playback operation ends.

As described above, in the storage medium reproducing apparatus according to the first embodiment, error correction can be performed with reference to the history of error correction using the error correction code stored in the storage unit. Thus, the calculation load can be reduced in each correction operation. Also, when the correction using the error correction code is performed only on newly generated errors, the number of correction codes required for the correction can be reduced.

In the first embodiment, errors generated due to factors other than discharge, such as an error caused by noise, are also stored as the correction history. Therefore, even if noise is removed and reading is appropriately performed, correction is performed by the correction history execution method. As a result, unintended correction may be made.

The storage medium reproducing apparatus according to the second embodiment eliminates this problem by storing the contents of the error correction in the storage unit only when the error to be corrected using the error correction code is considered to have been caused by the discharge.

The second embodiment is different from the first embodiment in the operation to be performed by the correction unit 103. Other aspects of configuration and function are the same as those of the storage medium reproducing apparatus 100 of the first embodiment shown in the block diagram of FIG. 1, and the description thereof will not be repeated here.

Next, a storage medium reproducing operation to be performed by the recording medium reproducing apparatus according to the second embodiment will be described. 7 is a flowchart of a storage medium reproducing operation according to the second embodiment.

Since the information reading processing and the information correcting processing of steps S701 to S705 are the same as the processing of steps S601 to S605 to be performed in the storage medium reproducing apparatus 100 according to the first embodiment, the description thereof will not be repeated here.

After correcting the information using the error correction code (step S705), the correction unit 103 determines whether or not the corrected error is caused over time (step S706). "Error caused by time" is an error generated by the discharge of the memory elements as shown in FIG.

More specifically, the correction unit 103 determines whether the error in the information exceeds the thresholds Eth0 to Eth2 due to the discharge as shown in FIG. 4. For example, the information "01" is erroneously read as "00" and may be regarded as an error exceeding the threshold value Eth2 shown in Fig. 4 due to the discharge. Thus, the correction unit 103 determines that the error is caused over time.

Errors that can be triggered over time include "01-> 00", "00-> 10" and "10-> 11". If a long period has elapsed, the error may exceed two thresholds, and thus may include “01-> 10”, “01-> 11” and “00-> 11”.

If it is determined that the error was not caused by time (“NO” in step S706), the correction history is not registered in the correction history storage units EL1 to ELn, but the corrected information is output (step S708).

If it is determined that the error has been caused by time ("YES" in step S706), the correction history is registered in the correction history storage units EL1 to ELn (step S707), and the corrected information is output (step S708).

As in the first embodiment, if it is determined that correction is impossible in step S704, an error message is output (step S709).

As described above, in the storage medium reproducing apparatus according to the second embodiment, the contents of the error correction are written to the correction history storage unit only when the error corrected using the error correction code can be regarded as an error caused by the discharge. The contents of the error correction can be referred to later correction operation. Thus, unnecessary correction operations can be limited to the minimum possible number of times.

The storage medium reproducing apparatus according to the third embodiment of the present invention stores correction histories of a plurality of storage units in a single storage unit.

8 is a block diagram showing the structure of the storage medium reproducing apparatus 800 according to the third embodiment. As shown in Fig. 8, the storage medium reproducing apparatus 800 includes the storage units M1 to Mn, the correction history storage unit EL, the control unit 101, the correction history execution unit 802, and the correction unit. 803.

The third embodiment differs from the first embodiment in the operation to be performed by the correction history execution unit 802 and the correction unit 803 in only one correction history storage unit EL. Other aspects of the configuration and function of the third embodiment are the same as those of the storage medium reproducing apparatus 100 of the first embodiment shown in the block diagram of FIG. 1, and the description thereof will not be repeated here.

Like the correction history storage units EL1 to ELn in the first embodiment, the correction history storage unit EL stores a history of the content corrected by the correction unit 803 using the error correction code. The correction history storage unit EL is formed of storage elements that do not require a refresh operation, such as FeRAM and SRAM.

Although correction history units EL1 to ELn are provided for the storage units M1 to Mn in the first embodiment, only one correction history storage unit EL is used to store the storage units M1 to Mn in the third embodiment. Mn).

9 shows an example of the data structure of the correction history storage unit EL. As shown in Fig. 9, the correction history storage unit EL includes a storage unit ID for identifying a subject storage unit among the storage units M1 to Mn, and a memory in the storage unit identified by the storage unit ID. Among the memory cells included in the cell group MCn, a cell ID for identifying a memory cell corrected by an error correction code and the correction contents are stored. Here, the storage unit ID, the cell ID, and the correction contents are associated with each other.

If the storage units M1 to Mn are involved, the allocation of a large storage area to each storage unit may lead to a large unused area in the storage area, because the number of storage units that frequently generate errors is limited. In the third embodiment, the storage units M1 to Mn share the correction history storage unit EL, thereby improving the use efficiency of the storage area.

The number of correction history storage units is not limited to one, but a plurality of correction history storage units may be employed. In this case, the storage units M1 to Mn are divided into groups, and one correction history storage unit EL is provided for each of the groups, so that the correction history storage unit EL is stored in each group. Can be shared between them.

The correction history execution unit 802 retrieves the correction history storage unit EL for the correction history corresponding to the storage unit ID of the storage unit (one of the storage units M1 to Mn) from which the information was read. If a correction history is found, a correction operation is performed in accordance with the contents of the correction history.

In the third embodiment, correction histories of all the storage units M1 to Mn are stored in the single correction history storage unit EL, unlike in the case of the first embodiment. Therefore, the correction history associated with the storage unit ID of the storage unit from which the information was read is retrieved. If a correction history is found, a correction operation is performed according to the correction contents included in the obtained correction history.

Like the correction unit 103 of the first embodiment, the correction unit 803 performs a correction operation using an error correction code on the information corrected by the correction history execution unit 802 according to the correction contents of the correction history. The correction unit 803 of the third embodiment differs from the correction unit 103 of the first embodiment in that the correction history storage unit EL stores the contents of the error correction operation in all the storage units M1 to Mn. Different.

Next, a storage medium reproducing operation to be performed by the storage medium reproducing apparatus 800 according to the third embodiment will be described. 10 is a flowchart of a storage medium reproducing operation according to the third embodiment.

The information reading operation in step S1001 is the same as that of step S601 to be performed in the storage medium reproducing apparatus 100 of the first embodiment, and therefore the description of step S1001 is not repeated.

After the information reading operation (step S1001), the correction history execution unit 802 acquires the contents of the past correction of the storage unit Mk from which the information has been read, from the correction history storage unit EL, and then the contents of the past correction. Then, a correction operation is performed (step S1002). More specifically, the correction history corresponding to the storage unit ID of the storage unit Mk from which the information was read is retrieved from the correction history storage unit EL. If a correction history is found, a correction operation is performed according to the correction contents of the retrieved correction history.

The correction operation using the error correction code and the information output operation of steps S1003 to S1008 are the same as those of steps S603 to S608 to be performed in the storage medium reproducing apparatus 100 of the first embodiment, and thus the description thereof will not be repeated here. .

As described above, in the storage medium reproducing apparatus according to the third embodiment, correction histories of a plurality of storage units are stored in a single correction history storage unit. Thus, the number of memory elements required for storing the correction histories can be reduced, so that the use efficiency of the storage area can be increased.

The storage medium reproducing apparatus according to the fourth embodiment performs a refresh operation on the storage elements if the error amount exceeds a predetermined threshold.

11 is a block diagram showing the configuration of the storage medium reproducing apparatus 1100 according to the fourth embodiment. As shown in FIG. 11, the storage medium reproducing apparatus 1100 includes the storage units M1 to Mn, the correction history storage units EL1 to ELn, the control unit 101, and the correction history execution unit 102. ), A correction unit 103, and a refresh control unit 1104.

The fourth embodiment is different from the first embodiment in that the refresh control unit 1104 is added. Other aspects of the configuration and function of the fourth embodiment are the same as those of the storage medium reproducing apparatus 100 of the first embodiment shown in the block diagram of FIG. 1, and the description thereof will not be repeated here.

When the error generation amount indicating the degree of error generation exceeds the predetermined threshold value, the refresh control unit 1104 performs a refresh operation to maintain the charge amount of the memory elements at a normal value. For example, if the error generation amount is the number of correction histories recorded in the correction history storage units EL1 to ELn, the refresh operation is performed when the number of correction histories exceeds a predetermined threshold.

If the discharge of the memory elements of the memory cell groups MC1 to MCn proceeds at substantially the same rate, the memory cell group having a plurality of correction histories has a long period elapsed since the last write operation, and the charge amount exceeds the threshold value. There is a tendency to include many memory elements which generate errors in the information read operation (Eth1 to Eth2 shown in Fig. 4). Therefore, when the number of stored correction histories exceeds a predetermined value, the refresh operation is performed.

The timing of the write information in the memory elements of the memory cell groups MC1 to MCn does not vary greatly in terms of the nature of the operation of writing the information and adding the error correction codes corresponding to the information. Therefore, the write operation in the memory elements of the memory cell groups MC1 to MCn can be considered to be performed at the same time. Thus, the number of correction histories can be used as a criterion for the error generation amount, as described above.

The criterion for the error generation amount is not limited to the number of correction histories, but may be in any form of information as long as the degree of error generation is indicated.

For example, the number of memory elements newly corrected by the error correction code may be used as a reference for the error generation amount. In the memory cell groups MC1 to MCn having many errors newly discovered through a correction operation using a correction code, a long time has passed since the last write operation. If the discharge of the memory elements in the memory cell groups MC1 to MCn proceeds at substantially the same speed, there is a high probability of exceeding the threshold for the amount of charge and including many memory elements that generate an error in a read operation.

Alternatively, the number of memory elements exceeding a predetermined number of thresholds for the amount of charge may be used as a reference for the amount of error generation. For example, in the case of four-value memory elements, a refresh operation may be performed on the memory cell groups MC1 to MCn in which the number of memory elements exceeding a plurality of thresholds for the charge amount is larger than a predetermined threshold value.

Exceeding the plurality of thresholds for the charge amount rarely occurs. However, these memory cell groups MC1 to MCn have a long period after the last write operation. If the discharge of the memory elements in the memory cell groups MC1 to MCn proceeds at substantially the same rate, there is a high probability of including many memory elements that exceed the threshold for the amount of charge and generate an error in a read operation.

Alternatively, the capacity of the information storage of the correction history storage units EL1 to ELn may be used as a reference for the error generation amount. In particular, in the case where the correction history storage unit EL is shared between the storage units M1 to Mn in the third embodiment, the correction history storage unit EL is found in the memory cell groups MC1 to MCn. Even if the number of errors is small, the storage capacity may be exceeded.

In this case, the memory cell groups MC1 to MCn to be refreshed may be arbitrarily selected from the memory cell groups sharing the correction history storage units EL. However, the refresh operation may be performed on the memory cell group having the maximum number of stored error correction histories, and the corresponding correction history is erased. Therefore, the reliability of the information stored in the memory cell groups having many errors can be maintained, and the storage area of the correction history storage units EL can be increased appropriately.

Next, a storage medium reproducing operation to be performed by the storage medium reproducing apparatus 1100 according to the fourth embodiment will be described. 12 is a flowchart of a storage medium reproducing operation according to the fourth embodiment.

Since the information reading processing and the information correcting processing of steps S1201 to 1205 are the same as those of steps S601 to S605 to be performed in the storage medium reproducing apparatus 100 according to the first embodiment, the description thereof will not be repeated here.

After the correction unit 103 corrects the information using the error correction code (step S1205), the refresh control unit 1104 sets a threshold at which the number of correction histories recorded in the correction history storage units EL1 to ELn is predetermined. It is determined whether it is larger than the value (step S1206).

If the number of correction histories is larger than the predetermined threshold value (YES in step S1206), the refresh control unit 1104 performs a refresh operation on the memory cell group from which the information has been read, and the correction history storage units EL1 to ELn. The correction histories are erased (step S1208).

If the number of correction histories is not larger than the predetermined threshold value (“NO” in step S1206), the correction unit 103 registers the cell ID and correction contents as the correction history in the correction history storage unit ELk (step S1207).

The information output processing of steps S1209 and S1210 is the same as that of steps S607 and S608 to be performed in the storage medium reproducing apparatus 100 of the first embodiment, and therefore description thereof will not be repeated.

Although the number of correction histories is used as the error generation amount in FIG. 12, the number of memory elements newly corrected using the error correction code, the number of memory elements exceeding a predetermined number of charge amount thresholds, or the correction history memory units EL1. It is also possible to determine whether or not the refresh operation is necessary in accordance with the error generation amount indicated by the information storage capacity of ELn).

As described above, in the storage medium reproducing apparatus according to the fourth embodiment, when the amount of error generation exceeds a predetermined threshold, a refresh operation is performed on the storage elements. This refresh operation can reduce error generation, and the amount of calculation required for the correction operation can be reduced accordingly.

The storage medium reproduction program to be performed in the storage medium reproducing apparatuses of the first to fourth embodiments is previously incorporated into a memory such as a ROM (Read Only Memory).

The storage medium reproducing program to be executed in the storage medium reproducing apparatuses of the first to fourth embodiments is a compact disk read only memory (CD-ROM), a flexible disk (FD), a compact disk recordable (CD-R), or a digital versatile Or an executable file recorded on a computer-readable recording medium such as a disk.

The storage medium reproduction program to be performed in the storage medium reproduction apparatuses of the first to fourth embodiments may be stored in a computer connected to a network such as the Internet, or may be downloaded via a network. The storage medium reproduction program to be executed in the storage medium reproduction apparatuses of the first to fourth embodiments may also be provided or distributed through a network such as the Internet.

The storage medium reproduction program to be executed in the storage medium reproduction apparatuses of the first to fourth embodiments has a module configuration including the above-described components (control unit, correction history execution unit, correction unit, and refresh unit). In real hardware, the CPU (Central Processing Unit) reads the storage medium reproduction program from the ROM and executes the storage medium reproduction program. Thus, the above-described components are mounted on the main memory device and created.

Additional advantages and modifications will be readily made to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

According to the storage medium reproducing apparatus according to the present invention, the contents of the error correction are stored in the correction history storage unit only when the error corrected using the error correction code can be regarded as an error caused by the discharge. The contents can be referred to later correction operations, so that unnecessary correction operations can be limited to the minimum possible number of times.

Further, in the storage medium reproducing apparatus according to the present invention, since the correction histories of the plurality of storage units are stored in a single correction history storage unit, the number of storage elements required for storing the correction histories is reduced, thereby increasing the use efficiency of the storage area. do.

Further, in the storage medium reproducing apparatus according to the present invention, when the amount of error generation exceeds a predetermined threshold, a refresh operation is performed on the storage elements so that the refresh operation can reduce error generation and the amount of calculation required for the correction operation. This can be reduced.

Claims (10)

A plurality of information storage units for storing information depending on whether the charge amount is greater than a predetermined charge amount threshold; And A correction code storage unit for storing error correction codes for the information stored in the plurality of information storage units A storage unit comprising a; A correction history storage unit for storing identification information for identifying said information storage unit, wherein a correction operation using an error correction code is performed between said information storage units, and a correction history including contents of said correction; A correction history execution unit that corrects the information in accordance with the contents of the correction stored in the correction history storage unit when the information is read out from the information storage unit identified by the identification information; And Performing a correction operation by using an error correction code to the corrected information, and storing the correction history including the contents of the correction and the identification information of the information storage unit corrected using the error correction code; Correction unit to register to the unit A storage medium reproducing apparatus comprising a. The correction history according to claim 1, wherein the correction unit corrects the correction contents and the identification information of the corrected information storage unit when the information error generated due to the release of charge accumulated in the information storage unit is corrected. The storage medium reproducing apparatus which stores in a storage unit. 2. The storage medium reproducing apparatus as claimed in claim 1, wherein the correction histories of all the information storage units included in the storage units are stored in the correction history storage unit. The apparatus according to claim 1, further comprising a refresh control unit for determining whether an error generation amount indicating an error generation degree exceeds a first predetermined threshold value, and if the error generation amount exceeds the first threshold value, And a refresh operation so that a refresh control unit keeps the amount of charge in the information storage unit at a normal value. 5. The refresh control unit according to claim 4, wherein the refresh control unit determines whether a plurality of correction histories stored in the correction history storage unit exceeds a second predetermined threshold value, and the number of correction histories sets the second threshold value. If exceeded, the refresh control unit performs a refresh operation. 5. The refresh control unit according to claim 4, wherein the refresh control unit uses error correction codes to determine whether a plurality of information storage units corrected by the correction unit exceed a predetermined third threshold value, and the information storage unit And the refresh control unit performs a refresh operation when the number of pieces exceeds the third threshold. 5. The refresh control unit according to claim 4, wherein the refresh control unit determines whether a plurality of information storage units having an amount of charge exceeding a predetermined number of thresholds exceeds a predetermined fourth threshold, and the number of information storage units is determined. And if the fourth threshold value is exceeded, the refresh control unit performs a refresh operation. 5. The refresh control unit according to claim 4, wherein the refresh control unit determines whether or not the information storage capacity of the correction history storage unit exceeds a predetermined fifth threshold value, and if the information storage capacity exceeds the fifth threshold value. And the refresh control unit performs a refresh operation. Correction history including the correction information and the identification information identifying the information storage unit corrected using the error correction code among the plurality of information storage units which respectively store the information according to whether the charge amount is larger than the predetermined charge amount threshold or not; Correcting information read from the information storage unit identified by the identification information according to the correction contents stored in the correction history storage unit to be stored; And A correction operation is performed on the corrected information using an error correction code to register a correction history including the identification information and the correction contents of the information storage unit corrected using the error correction code to the correction history storage unit. Steps to The storage medium playback method comprising a. A computer readable medium comprising programmed instructions for reproducing data on a storage medium, wherein when the instructions are executed by a computer, the computer may: Correction history including the correction information and the identification information identifying the information storage unit corrected using the error correction code among the plurality of information storage units which respectively store the information according to whether the charge amount is larger than the predetermined charge amount threshold or not; Correcting information read from the information storage unit identified by the identification information according to the correction contents stored in the correction history storage unit to be stored; And A correction operation is performed on the corrected information using an error correction code to register a correction history including the identification information and the correction contents of the information storage unit corrected using the error correction code to the correction history storage unit. Steps to Computer readable medium.

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