JP2004220343A - Memory device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a memory device whose life is extended while the reliability of data storage of the device is maintained. <P>SOLUTION: A storage part 50 is provided with a first storage block 51 and a second storage block 52 as an area for storing data of the same kind, and when the data are updated, the data to be stored are written in either the first storage block 51 or the second storage block 52, and when data are newly updated, the data to be stored are written in the other storage block where the previous data are not written. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a memory device in which the same type of data is written to two storage blocks in order to increase the reliability of data storage.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an image forming apparatus or the like is provided with a non-volatile memory device (for example, a flash ROM or the like) such as an EEPROM for storing various data relating to the operation state. This memory device is provided with two storage areas: a normal storage area for storing various data in a normal state, and a backup storage area for data recovery when an abnormality occurs in the data storage state. Sometimes the same data is written to each of the two storage areas.
[0003]
Further, in the prior art document, the data written in the first memory 301 is written at a predetermined timing in the second memory 300 storing the control program, and the data is stored in the second memory 300 as necessary. Also, a memory device has been proposed in which the reliability of data storage is improved by writing data into the first memory 301 (for example, see Patent Document 1).
[0004]
[Patent Document 1]
JP-A-11-31107
[0005]
[Problems to be solved by the invention]
However, in a memory device in which data is written to both the normal storage area and the backup storage area at the time of data update, the number of times of writing data to both of the two areas is large, and the life of both of the two areas is long. As a result, there is a problem that the life of the entire memory device is shortened.
[0006]
Further, the memory device disclosed in Patent Document 1 can easily recover data using the data stored in the second memory 300 when the first memory 301 is destroyed. The first memory 301 composed of a non-volatile memory device such as that described above cannot be used when the limit of the endurance of writing is reached by repeating data writing many times. From the viewpoint of extending the life of the memory, it is preferable to reduce the number of times of data writing. However, the memory device disclosed in Patent Document 1 does not solve such a problem.
[0007]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and has as its object to provide a memory device having an extended life while maintaining the reliability of data storage.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 includes a storage unit having two storage blocks in which the same type of data is stored;
Data write control means for writing data to be stored in one of the storage blocks at the time of data update, and writing data to be stored to a storage block to which data has not been previously written at the time of new data update;
Is a memory device provided with.
[0009]
In this configuration, when updating data, data is written using only one of the two storage blocks, and the same data is not written to both storage blocks as in the conventional case. The number of times of writing to each storage block at the time of updating is reduced to half. As a result, the life of each memory block can be doubled, so that the life of the memory device as a whole can be doubled while maintaining the reliability of data storage. In this configuration, the latest data cannot be recovered if an abnormality occurs on the storage block side where the latest data is stored. However, when data that is frequently updated in a short time is held, the difference is Minor, no adverse effects.
[0010]
According to a second aspect of the present invention, in the memory device according to the first aspect, the data write control unit is configured to perform a predetermined time period when a data update is required for any one of the storage blocks. When a certain period of time elapses and a plurality of data need to be updated within the predetermined time, the updating of the plurality of data to this storage block is executed by one writing.
[0011]
According to this configuration, when it becomes necessary to update a plurality of data within a predetermined time, the updating of the plurality of data to the storage block is performed by writing once, so that the number of times of writing data to the storage block can be reduced. it can.
[0012]
According to a third aspect of the present invention, in the memory device according to the first or second aspect, the area used as the storage unit is a low-frequency area used as a storage unit with a low data update frequency. A rewrite area and a high-frequency rewrite area used as a storage unit with a high data update frequency;
The data writing control means simultaneously writes the storage target data into the two storage blocks in the storage unit at the time of data update for the storage unit in the low-frequency rewrite area, and writes the data to the storage unit in the high-frequency write area. On the other hand, when data is updated, the storage target data is written to any of the storage block areas in the storage unit, and when new data is updated, the storage target data is written to the storage block to which the previous data has not been written.
[0013]
According to this configuration, data is simultaneously written to two storage areas at the time of data update in the storage unit of the low-frequency rewrite area in which a time interval from the previous data writing to the latest data writing is assumed to be long. And the contents of the data stored in both recording blocks are always the same, so even if there is a time interval from the last data write to the latest data write, When an abnormality occurs in one of the storage blocks, the reliability of the data restored using the data stored in the other recording block is improved. In addition, since the number of times of data writing is small in the storage unit in the low-frequency rewrite area, there is no problem that the life of the recording block is shortened. On the other hand, by writing data to only the storage block of the two storage blocks at the time of data update, the number of times of writing to each storage block at the time of data update is updated. Can be reduced by half, and the life of each storage block and memory device can be doubled.
[0014]
According to a fourth aspect of the present invention, there is provided the memory device according to any one of the first to third aspects, further comprising a free area other than an area used as the storage unit,
When the number of times of writing to the storage unit reaches the limit of the number of durable data writes, the data writing control unit replaces the empty area with a new storage unit instead of the area previously used as the storage unit. Is used.
[0015]
According to this configuration, when the number of times of writing to one storage unit reaches the limit of the durable number of times of data writing, the data is stored as a new storage unit with an empty area, so that the usage period of the entire memory device is reduced. Can be stretched.
[0016]
According to a fifth aspect of the present invention, there is provided the memory device according to any one of the first to third aspects, further comprising an empty area other than an area used as the storage unit,
When the number of times of writing to the storage unit has reached 1 / n of the number of durable times of data writing, the data writing control unit replaces the empty region with a new one instead of the area previously used as the storage unit. When used as a storage unit and there is no free space, an area that was previously used as a storage unit and is not currently used as a storage unit is used as a free space as a new storage unit, The same area is repeatedly used as a storage unit up to n times.
[0017]
According to this configuration, when the number of times of writing to the storage unit reaches 1 / n of the number of times of durable data writing, the area used as the storage unit is shifted to another area. The memory device can be used up to the number of times, and the life of the memory device can be further extended.
[0018]
That is, if control is performed so that the storage unit does not move to another area until the number of times of data writing reaches the limit of the number of endurance times, for example, a memory in which the guaranteed number of times of data writing is set to about 100,000 times is When the data write endurance count of the data storage area reaches about 70,000 times, the data write count for the area currently used as the storage unit is reduced to about 70, even though data can be written to other areas. When the number of times reaches 10,000, the memory device reaches the end of its life. However, as in the invention according to the fifth aspect, before the number of times of data writing reaches the limit of the number of endurance times, the area used as the storage unit is successively increased. If the area is moved to another area, the memory device can be used until the number of times of data writing in all the areas reaches about 70,000 times, so that the life of the memory device is further improved. It can be extended to become.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a memory device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a memory device according to the present invention. A memory device 1 according to the present invention includes a control unit (data write control means) 2 for controlling writing and reading of data to and from a flash ROM 5, and a ROM 3 for storing a control program and the like for writing and reading data. A RAM 4 used as a work area of the control unit 2, a flash ROM 5 for storing data that can be repeatedly erased and written for each block and whose contents need to be retained regardless of whether the power is on or off, A timer 6 for counting the passage of time. These are connected by a bus 7 so that data transfer required for data writing and reading and various operation controls can be performed.
[0020]
2A and 2B are diagrams conceptually illustrating an example of data writing to the flash ROM 5, in which FIG. 2A illustrates a state before data writing, FIG. 2B illustrates a state after data writing, and FIG. FIG. 3 is a diagram showing a state in which further data writing is performed, and FIG. 3 is a flowchart showing a first embodiment of the data updating process. The flash ROM 5 includes a storage unit 50 including a first storage block 51 and a second storage block 52. The same data is stored in the first storage block 51 and the second storage block 52, and plays a role of backing up another storage area. A case where two types of data (data 1 and data 2) are written and stored in each of the first storage block 51 and the second storage block 52 will be described.
[0021]
In the initial state of the flash ROM 5 (FIG. 2A), if it is necessary to rewrite the data (YES in S1), the data is written to either the first storage block 51 or the second storage block 52 ( S2). For example, when it is necessary to rewrite the numerical value of data 1 to “2”, data 1 is written to “2” only in the first storage block 51, and data is written to the second storage block 52. Is not performed (FIG. 2B).
[0022]
If it is necessary to further rewrite the data (YES in S3), the data is written to the storage block in which the previous data has not been written (S4). For example, when it becomes necessary to rewrite data 2 to “3”, the process of rewriting data 1 to “2” and data 2 to “3” is performed in the second storage block 52 in which the data has not been previously written. (FIG. 2C). That is, the data that has been written to the first storage block 51 (data 1 = 2) and the data that needs to be rewritten this time (data 2 = 3) is written to the second storage block 52.
[0023]
Thereafter, if it is necessary to further rewrite the data, it is determined whether the number of times of writing data in the storage unit 50 has reached a predetermined value (a numerical value of the limit of the number of times of endurance of writing) (S5). Until the number of data blocks reaches the value, the process of rewriting the storage block in which data has not been written last time to the latest data content is repeated (NO in S5). If the number of times of data writing has reached the predetermined value (YES in S5), the process ends.
[0024]
Next, a description will be given of a second embodiment of the process of updating the data in the flash ROM 5. FIGS. 4A and 4B are diagrams conceptually showing an example of the second embodiment of writing data to the flash ROM 5, in which FIG. 4A shows a state before data writing, and FIGS. FIG. 7D is a diagram showing a state of waiting for data writing, and FIG. 7D is a diagram showing a state of writing data after a predetermined time has elapsed. FIG. 5 is a flowchart showing a second embodiment of the data update process.
[0025]
In this embodiment, data writing to the flash ROM 5 waits until a predetermined time elapses from the time when the necessity of data update occurs, and collects each data that needs to be updated at the time when the predetermined time elapses. Write at once. The first embodiment differs from the first embodiment in that, of the first storage block 51 and the second storage block 52 of the storage unit 50, only the storage area in which data has not been written previously is rewritten to the latest data content. Is the same as
[0026]
For example, assuming that the next storage area in which data is to be written is the first storage area, data 1 is “0” and data 2 is “3” in the first storage block 51 as shown in FIG. If it is necessary to update the data 1 to '1' when the data is stored as' (YES in S11), the timer 6 starts measuring the time from the time when the data needs to be updated (S12). The process of immediately rewriting data 1 to "1" is not performed (FIG. 4B).
[0027]
Then, a predetermined time from the time when the necessity of the update occurs (a time period in which it is assumed that no trouble occurs even if the data is not immediately written, for example, a few seconds when the number of prints in the image forming apparatus is stored). (S13: YES), the data is updated to the latest contents (S14), but if the data needs to be updated separately within this predetermined time (see, for example, FIG. 4). As shown in (c), the data 2 is updated to “8”), the process of rewriting the data 1 to “1” and the process of rewriting the data 2 to “8” are performed by one write (FIG. 4 ( d)). According to the data writing process according to the second embodiment, a plurality of data updating processes occurring within a predetermined time are performed by one writing, so that the number of times of writing data to the storage area can be reduced.
[0028]
Next, a third embodiment of the data update processing of the flash ROM 5 will be described. FIG. 6 is a diagram showing a state in which storage areas of the flash ROM 5 are divided according to rewriting frequency, and FIG. 7 is a flowchart showing a third embodiment of the data update process. The flash ROM 5 is divided into a low-frequency rewrite area 501 in which data is written at a low frequency and a high-frequency rewrite area 502 in which data is written at a high frequency. The storage unit 50 is provided in each of the low-frequency rewrite area 501 and the high-frequency rewrite area 502.
[0029]
For example, the area from the address 0x0000 to the address 0x1000 of the flash ROM 5 is set as the low-frequency rewrite area 501, and the area from the address 0x1001 to the address 0xffff is set as the high-frequency rewrite area 502. Examples of the data that is rewritten infrequently include the serial number of the image forming apparatus provided with the memory device 1 and the setting data of the fixing temperature of the fixing device. Since these data are hardly updated until the life of the image forming apparatus, these data having almost no chance of updating are stored in the low-frequency storage area 501.
[0030]
When the data needs to be updated (YES in S21), it is determined whether the writing of the data that needs to be updated is performed in the storage unit 50 provided in the low-frequency rewrite area 501 or the high-frequency rewrite area 502. It is determined (S22). If it is necessary to update the data in the storage unit 50 in the low-frequency rewriting area 501 (the low-frequency rewriting area in S22), the same data to be saved is stored in the first storage as in the conventional data writing process. Data is simultaneously written to each of the block 51 and the second storage block 52 (S23). If it is necessary to update the data in the storage unit 50 in the high-frequency write area 502 (the high-frequency rewrite area in S22), the data to be saved is one of the first storage block 51 and the second storage block 52. When data is written to only one of them and a new data update needs to be performed, the latest data content is stored in the storage area of the first storage block 51 and the second storage block 52 to which the previous data has not been written. The writing process is performed (S24). That is, a write process similar to the data write process described in the first embodiment is performed.
[0031]
In the flash ROM 5 divided into the low-frequency rewrite area 501 and the high-frequency rewrite area 502 as described above, a predetermined time is set when data need to be updated, similarly to the data write processing described in the second embodiment. After a lapse of time, a plurality of data rewrites may be collectively performed by one write.
[0032]
Next, a fourth embodiment of the data update processing of the flash ROM 5 will be described. FIG. 8 is a diagram showing the area division of the flash ROM 5 used in the fourth embodiment, FIG. 9 is a diagram showing the contents of a management data storage area in the flash ROM 5, and FIG. 10 is a flowchart showing a fourth embodiment of the data update process. It is.
[0033]
The flash ROM 5 according to this embodiment stores a low-frequency rewrite area 501 in which data is written at a low frequency, a high-frequency rewrite area 502 in which data is written at a high frequency, and various types of management data. It is divided into a management data storage area 503. For example, as shown in FIG. 8, addresses 0x0000 to 0x0fff of the storage area of the flash ROM 5 are defined as a low-frequency rewrite area 501, addresses 0x1000 to 0x10ff are defined as a management data storage area 503, and addresses 0x1100 to 0xffff are defined as a high-frequency rewrite area 502. Assign as
[0034]
The high-frequency rewrite area 502 has a free area having a capacity several times as large as a required amount of the storage unit 50. This free area is the number of times that the number of times of data writing to the first storage block 51 or the second storage block 52 of the storage unit 50 is a predetermined number (the number of times that the data writing endurance is 1 / n; When the number of times reaches 1000 times (for example, 1000 times), the area is newly used as the storage unit 50 instead of the area used as the storage unit 50 until then. If the capacity of this free area is determined based on the data write endurance count and the data update count (predicted value), it is possible to set the lifetime of the entire memory device 1 to a desired period.
[0035]
The management data management area 503 includes a start address and an end address of an area used as the high-frequency rewrite area 502 and a new storage unit 50 when the number of times of writing data to the storage unit 50 reaches the predetermined number. And the data of the index address (head address) of the currently used area as the storage unit 50 are stored.
[0036]
For example, as shown in FIG. 9, address 0x1000 to address 0x10ff of the management data storage area 503 is divided into two areas, and addresses 0x1000 to 0x107f are set as a normal storage area where the management data of the storage unit 50 is stored. Address 0x1080 to address 0x10ff is set as a recovery storage area in which management data similar to the normal storage area is stored. In the normal storage area, the top address of the high-frequency rewrite area 502 is stored at addresses 0x1000 to 0x1001, and the last address of the high-frequency rewrite area 502 is stored at addresses 0x1002 to 0x1003. Addresses 0x1004 to 0x1005 store addresses of candidate areas to be used next as new storage units when the number of times of writing data to any of the recording blocks in the storage unit 50 reaches a predetermined number. . The addresses 0x1006 to 0x1007, the addresses 0x1008 to 0x1009, the addresses 0x100a to 0x100b, the addresses 0x100c to 0x100d, and the addresses 0x100e to 0x100f store the addresses of the areas currently used as the storage unit 50, respectively. Note that similar data is also stored in the recovery storage area at addresses 0x1080 to 0x10ff, and the same data writing as in the normal storage area is performed.
[0037]
A specific data write process will be described with reference to FIG. When it is necessary to update certain data, it is determined whether or not the storage unit 50 to which the data is written is the storage unit 50 in the high-frequency rewrite area 502 (S31). If the storage unit 50 is the storage unit 50 in the low-frequency rewrite area 501 (NO in S31), the latest data is written to both the first storage block 51 and the second storage block 52 in the storage unit 50. (S32), the process ends.
[0038]
If the storage unit 50 in which the data to be updated is written is the storage unit 50 in the high-frequency rewrite area 502 (YES in S31), a predetermined time (same as the time described in the second embodiment) elapses. Until then, writing of data to the storage unit 50 is refrained (S33). When the predetermined time has been reached (YES in S33), it is determined whether the number of times of writing data to the first storage block 51 or the second storage block 52 in the storage unit 50 exceeds the predetermined number (S34). If the number of times of data writing to the first storage block 51 or the second storage block 52 of the storage unit 50 does not exceed the predetermined number of times (NO in S34), the storage block to which the previous data has not been written is A plurality of pieces of data that need to be updated within a predetermined time are written together at once (S35).
[0039]
In S34, the number of times of data writing to either the first storage block 51 or the second storage block 52 of the storage unit 50 is equal to the predetermined number (the number of times equal to 1 / n of the number of times of data writing endurance, for example, the number of times of writing endurance). If the number exceeds 100,000 times (eg, 1000 times) (YES in S34), an index address indicating a candidate area to be next used as a new storage unit 50 is read from the management data storage area 503. Then, data to be written is written in the area indicated by the read index address as a new storage unit 50 (S37). In this case, since the first data is written to the new storage unit 50, the data is written to both the first storage block 51 and the second storage block 52 of the new storage unit 50. Then, the index address indicating the area being used as the storage unit 50 that has been stored in the management data storage area 503 until then is rewritten to the index address indicating the area newly set as the storage unit 50 in S37 (S38).
[0040]
Subsequently, an index address indicating a new candidate area to be next used as the storage unit 50 is searched (S39). In other words, in order from the first address to the last address (these addresses are stored in the management data storage area 503) of the high-frequency rewrite area 502, they are not currently used as the storage unit 50 but are used in the past. A search is made for an index address indicating an area that has never been found. Further, if an index address indicating an unused area is not found even when the search is performed up to the last address of the high-frequency rewrite area 502, the control returns to the first address, and the storage unit 50 is stored in the past in order from the first address to the last address. An index address (an area where the number of times of data writing has not reached the endurance number) that indicates an area that is not currently used as the storage unit 50 is searched for, although there is a history of being used. Then, the index address indicating the candidate area to be used as the next storage unit 50 stored in the management data storage area 503 is rewritten to the index address found by the search (S40). Accordingly, when the storage unit 50 in which the number of times of data writing has reached the predetermined number occurs next time, an area to be used as a new storage unit 50 can be specified based on the index address.
[0041]
The search and rewrite processing of the index address of the new candidate area used as the storage unit 50 in S39 and S40 is performed until the number of times of data writing to the storage unit 50 reaches the endurance of data writing. That is, when the storage unit is moved to another area with 1 / n of the durable number of data writing set as the predetermined number of times, the same area is repeatedly used as the storage unit up to n times.
[0042]
Note that the present invention is not limited to the configuration of the above embodiment, and various modifications are possible. For example, in the data writing process shown in FIG. 10 of the above embodiment, the number of times of data writing to the storage unit 50 is set to 1 / n of the durable number of data writing, and the storage unit 50 is moved to another area as the predetermined number of times. However, the storage unit 50 may be moved to another area when the number of times of writing data to the storage unit 50 reaches the limit of the number of times of endurance of writing.
[0043]
Further, in the above embodiment, the data writing to the flash ROM 5 has been described as an example, but the present invention can be applied to a memory other than the flash ROM as long as the memory has a limited number of times of data writing.
[0044]
【The invention's effect】
As described above, according to the first aspect of the present invention, when updating data, data is written using only one of the two storage blocks, and the same data is written to both of the two storage blocks as in the related art. Since data is not written to the storage block, the number of times of writing to each storage block at the time of updating data is reduced to half. As a result, the life of each memory block can be doubled, so that the life of the memory device as a whole can be doubled while maintaining the reliability of data storage.
[0045]
According to the second aspect of the present invention, when a plurality of data needs to be updated within a predetermined time, a plurality of data is updated in the storage block by writing once, so that the data writing to the storage block is performed. The number of times can be reduced.
[0046]
According to the third aspect of the present invention, the storage unit of the low-frequency rewrite area, which is assumed to have a long time interval from the last data write to the latest data write, has two storage areas at the time of data update. Since the data is simultaneously written and held, and the contents of the data stored in both recording blocks are always the same, the time interval from the last data writing to the latest data writing is open. Even in this case, when an abnormality occurs in one of the storage blocks, the reliability of the data recovered using the data stored in the other recording block can be improved. In addition, since the number of times of data writing is small in the storage unit in the low-frequency rewrite area, there is no problem that the life of the recording block is shortened. On the other hand, by writing data to only the storage block of the two storage blocks at the time of data update, the number of times of writing to each storage block at the time of data update is updated. Can be reduced by half, and the life of each storage block and memory device can be doubled.
[0047]
According to the fourth aspect of the present invention, when the number of times of writing to one storage unit reaches the limit of the durable number of times of data writing, data is stored as a new storage unit in an empty area. The use period of the entire apparatus can be extended.
[0048]
According to the fifth aspect of the present invention, when the number of times of writing to the storage unit reaches 1 / n of the durable number of data writing, the area used as the storage unit moves to another area. The memory device can be used until the number of times of data writing reaches the endurance number in the area, and the life of the memory device can be further extended.
[0049]
That is, if control is performed so that the storage unit does not move to another area until the number of times of data writing reaches the limit of the number of endurance times, for example, a memory in which the guaranteed number of times of data writing is set to about 100,000 times is When the data write endurance count of the data storage area reaches about 70,000 times, the data write count for the area currently used as the storage unit is reduced to about 70, even though data can be written to other areas. When the number of times reaches 10,000, the memory device reaches the end of its life. However, as in the invention according to the fifth aspect, before the number of times of data writing reaches the limit of the number of endurance times, the area used as the storage unit is successively increased. If the area is moved to another area, the memory device can be used until the number of times of data writing in all the areas reaches about 70,000 times, so that the life of the memory device is further improved. It can be extended to become.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of a memory device according to the present invention.
2A and 2B are diagrams conceptually illustrating an example of data writing to a flash ROM, where FIG. 2A illustrates a state before data writing, FIG. 2B illustrates a state after data writing, and FIG. FIG. 7 is a diagram showing a state in which further data writing has been performed.
FIG. 3 is a flowchart illustrating a first embodiment of a data update process.
FIGS. 4A and 4B are diagrams conceptually showing an example of a second embodiment of writing data to a flash ROM, where FIG. 4A shows a state before data writing, and FIGS. FIG. 9D is a diagram illustrating a state of waiting for previous data writing, and FIG. 9D is a diagram illustrating a state of performing data writing after a predetermined time has elapsed.
FIG. 5 is a flowchart showing a second embodiment of the data update process.
FIG. 6 is a diagram showing a state where storage areas of a flash ROM are classified according to rewriting frequency.
FIG. 7 is a flowchart illustrating a third embodiment of the data update process.
FIG. 8 is a diagram showing area divisions of a flash ROM used in a fourth embodiment.
FIG. 9 is a diagram showing contents of a management data storage area in a flash ROM.
FIG. 10 is a flowchart showing a fourth embodiment of the data update process.
[Explanation of symbols]
1 Memory device
2 Control unit
50 storage unit
51 1st memory block
52 Second memory block
501 Infrequent storage area
502 High-frequency storage area
503 Management data storage area

Claims (5)

A storage unit having two storage blocks in which the same type of data is stored;
Data write control means for writing data to be stored in one of the storage blocks when updating data, and writing data to be stored in a storage block to which data has not been previously written when updating new data. Memory device. The data writing control unit waits for a predetermined time to elapse when the data update is required for any of the storage blocks, and when it is necessary to update a plurality of data within the predetermined time, 2. The memory device according to claim 1, wherein the updating of the plurality of data in the storage block is performed by one write. The area used as the storage unit includes a low-frequency rewrite area used as a storage unit with a low data update frequency, and a high-frequency rewrite area used as a storage unit with a high data update frequency.
The data writing control means simultaneously writes the storage target data into the two storage blocks in the storage unit at the time of data update for the storage unit in the low-frequency rewrite area, and writes the data to the storage unit in the high-frequency write area. On the other hand, at the time of data update, the storage target data is written to any of the storage block areas in the storage unit, and at the time of new data update, the storage target data is written to the storage block to which the previous data has not been written. The memory device according to claim 1 or 2, wherein An empty area other than the area used as the storage unit is provided,
When the number of times of writing to the storage unit reaches the limit of the number of durable data writes, the data writing control unit replaces the empty area with a new storage unit instead of the area previously used as the storage unit. 4. The memory device according to claim 1, wherein the memory device is used as a memory device. An empty area other than the area used as the storage unit is provided,
When the number of times of writing to the storage unit has reached 1 / n of the number of durable times of data writing, the data writing control unit replaces the empty region with a new one instead of the area previously used as the storage unit. When used as a storage unit and there is no free space, an area that was previously used as a storage unit and is not currently used as a storage unit is used as a free space as a new storage unit, 4. The memory device according to claim 1, wherein the same area is repeatedly used as a storage unit up to n times.

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