JP2001318829A - Device and method for controlling rewriting of flash memory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the rewriting control method of a flash memory for preventing the deterioration of a processing speed due to the data erasing time of a flash memory, and for efficiently using the flash memory. SOLUTION: At the time of writing data in each block 5A-5D of a flash memory 5, a time when the data are written is recorded in time information areas 5a-5d of each block. The data written in the block 5B after a prescribed time has elapsed since the writing time are temporarily read in a saving area 4a of an RAM 4 based on this time information, and the time information at that time is stored in a history information area 4b. The read data are erased from the block 5B. Then, whether or not the data stored in the RAM 4 are referred to not less than the prescribed number of times is judged, and when the data have been referred to not less than the prescribed number of times, the data are written again in the flash memory 5, and otherwise, the data are erased from the RAM 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a flash memory rewrite control device and a flash memory rewrite control method.

[0002]

2. Description of the Related Art Conventionally, flash memories are often used as rewritable memories in embedded control devices. For example, Japanese Utility Model 7-3280
No. 0 discloses a memory control device for notifying the time of replacement of a flash memory or the like. This memory control device can avoid system malfunctions due to memory life.

Generally, a flash memory has a capacity of 64 KB.
It is divided into (kilobyte) or 128 KB blocks, and data can be electrically erased and written in block units. In rewriting a block in which data has already been recorded, it is necessary to first erase all data in the block to be rewritten and then write new data. The erasing step takes less than one second for a relatively expensive flash memory, but takes about 3 to 5 seconds for a relatively inexpensive flash memory. For this reason, an error occurred during a series of operations, and data was sometimes lost. Therefore, there has been proposed a method capable of avoiding data loss even when a data write error occurs.

For example, Japanese Patent Application Laid-Open No. Hei 10-124403 discloses a writing method for a block erase flash memory provided with a data saving block. Also, for example, Japanese Patent Application Laid-Open No. 10-161942 discloses an information storage method, an information storage device, and an information processing device in which a backup block is provided in a flash memory.

[0005]

However, relatively inexpensive flash memories and special structures as described above take a long time to erase in block units. This is CP
This causes a heavy burden on U and causes a decrease in system performance. For this reason, there has been a demand for higher speed and higher efficiency in the rewriting process.

An object of the present invention is to provide a flash memory rewriting control method for preventing a decrease in system performance due to a data erasing time of the flash memory and for more efficiently using the flash memory.

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems, the invention according to claim 1 is directed to a flash memory rewrite control device (1) for controlling rewriting of a flash memory having a plurality of memory blocks. Writing control means (for example, CPU 2 shown in FIG. 1) for writing time information indicating the date and time of writing together with the data when writing data to each of the memory blocks;
Temporary storage means for reading and storing data written in a predetermined memory block based on the time information written by the write control means (for example, step S in FIG. 3)
CPU 2 that performs the processing shown in 3; RAM 4 shown in FIG. 1)
And an erasing unit (for example, a CPU 2 performing the process shown in step S4 of FIG. 3) for erasing from the flash memory the data of the predetermined memory block from which the data is read by the temporary storage unit. And

Here, as the flash memory, for example, a memory having a capacity of 128 KB for each memory block may be mentioned, but it may be 64 KB or another capacity. The time information is, for example, data indicating the year, month, day, hour, minute, and second of the date and time when the data was written to the memory block.

According to the first aspect of the present invention, the data written in the predetermined memory block is read out and stored by the temporary storage means based on the time information written by the write control means. The data in the memory block from which the data has been read by the storage means is erased from the flash memory by the erasing means. Therefore, when writing new data, the data can be written to the empty block from which the data has already been erased, so that it is possible to prevent the performance of the system from deteriorating due to the data erasing time of the flash memory.

According to a second aspect of the present invention, in the flash memory rewrite control device according to the first aspect, the determining means (for example, determining whether or not the data stored in the temporary storage means has been referred to a predetermined number of times or more). Step S7 in FIG.
CPU 2) which performs the processing shown in FIG. 3) and writes again the data determined to have been referred to by the discrimination means a predetermined number of times or more in the flash memory, and deletes the data discriminated by the discrimination means to be not referred to by the predetermined number of times or more. Rewriting control means for erasing from the temporary storage means (for example, a CPU for performing the processing shown in steps S8 and S9 in FIG. 3)
2) is further provided.

Here, the predetermined number can be set arbitrarily according to the nature of the data. In addition, a certain time for determining whether or not a reference has been made a predetermined number of times or more can be arbitrarily set according to the nature of data.

According to the second aspect of the present invention, of the data stored in the temporary storage means, the data referred to a predetermined number of times or more is written into the flash memory again. Is saved. Further, among the data stored in the temporary storage means, data not referred to more than a predetermined number of times is determined to be extremely low in importance and is deleted from the temporary storage means. Can be.

[0013] The invention according to claim 3 is the invention according to claim 1 or 2.
In the flash memory rewrite control device described above, the temporary storage means reads and stores data from a memory block in which time information indicating a date and time earlier than a predetermined time from the present is written out of the respective memory blocks. It is characterized by.

According to the third aspect of the present invention, the data written in the memory block is read out by the temporary storage means when a predetermined time or more has elapsed from the date and time indicated by the time information. For this reason, data that has passed a certain time or more is sequentially stored in the temporary storage means, and is stored or deleted according to the number of times referred to. Therefore, the flash memory can be used more efficiently.

According to a fourth aspect of the present invention, there is provided a flash memory rewrite control method for controlling rewriting of a flash memory including a plurality of memory blocks, wherein when writing data to each of the memory blocks, the data is written together with the data. A step of writing time information indicating the date and time of each memory block into each memory block, and reading out the data written in a predetermined memory block based on the time information written in the first step to read out the storage medium ( For example, a second process (for example, step S3 shown in FIG. 3) to be stored in the RAM 4 shown in FIG.
And a third step (for example, step S4 shown in FIG. 3) of erasing from the flash memory the data of the predetermined memory block from which the data has been read in the second step.

According to the fourth aspect of the present invention, data written in a predetermined memory block is read out and stored in a storage medium based on time information written together with the data,
The data in the memory block from which the data has been read to the storage medium is erased from the flash memory. Therefore, when writing new data, the data can be written to the empty block from which the data has already been erased, so that it is possible to prevent the performance of the system from deteriorating due to the data erasing time of the flash memory.

According to a fifth aspect of the present invention, in the flash memory rewriting control method according to the fourth aspect, it is determined whether or not the data stored in the storage medium in the second step has been referred to a predetermined number of times or more. A fourth step (for example, step S7 shown in FIG. 3), and a fifth step (for example, as shown in FIG. 3) of rewriting the data determined to have been referred to a predetermined number of times or more in the fourth step into the flash memory. Step S8)
And a sixth step (eg, step S9 shown in FIG. 3) of erasing, from the storage medium, data determined to have not been referred to a predetermined number of times in the fourth step.

According to the fifth aspect of the present invention, the data referred to a predetermined number of times or more out of the data stored in the storage medium is written into the flash memory again, so that important data is preserved. Further, among the data stored in the storage medium, data that has not been referred to a predetermined number of times or more is determined to be of low importance and is deleted from the temporary storage means, so that the flash memory can be used efficiently. .

The invention according to claim 6 is the invention according to claim 4 or 5.
The rewriting control method for a flash memory according to the above, wherein in the second step, data is read from a memory block in which time information indicating a date and time a predetermined time or more before the current time is written, among the memory blocks. It is characterized by.

According to the present invention, the data written in the memory block is read out to the storage medium when a predetermined time or more has elapsed from the date and time indicated by the time information. For this reason, data that has passed a certain time or more is sequentially stored in a storage medium and stored or deleted according to the number of times of reference. Therefore, the flash memory can be used more efficiently.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings.

First, the configuration will be described. FIG. 1 is a block diagram showing an internal circuit configuration of a flash memory rewrite control device 1 according to an embodiment of the present invention. Control device 1
Is a control device built in these devices or connected to the outside in order to control various household and industrial electronic devices. As shown in FIG. 1, this control device 1
PU (Central Processing Unit) 2, ROM (Read On
ly Memory) 3, RAM (Random Access Memory) 4,
A flash memory 5 and a control interface 6;
These are connected by a bus 7.

The CPU 2 reads and executes various system programs stored in the ROM 3, and controls the driving of each unit. Specifically, the CPU 2 writes data in the blocks 5A to 5D of the flash memory 5 and records time information indicating the date and time when the data was written in each block in the time information areas 5a to 5d of each block. . here,
The time information is recorded as data indicating, for example, year, month, day, hour, minute, and second.

Further, the CPU 2 checks the time information areas 5a to 5d at predetermined time intervals.
Based on the information recorded in a to 5d, data of a block which has been written for a predetermined time has been read out and RA
The data is stored in the save area 4a of M4, and the data of this block is erased. New data is appropriately written into the block from which data has been erased.

The CPU 2 reads out the data and sends it to the RAM 4
The time information indicating the date and time when the data is stored in the evacuation area 4a is recorded in the history information area 4b, for example, in the form of year, month, day, hour, minute, and second. Is recorded in the history information area 4b.

When the data in the save area 4a is referred to a predetermined number of times or more within a predetermined time, the CPU 2 writes the data in the save area 4a again into a free block of the flash memory 5. Time information indicating the date and time when data was written to the empty block is also recorded in the time information area of the block. If the data in the save area 4a has not been referred to more than a predetermined number of times, the RAM 4
Erase data from. Also, the data is read and RA
For a certain period after being stored in the evacuation area 4a of M4,
If the data is never referred to, the data in the save area 4a is erased from the RAM 4.

The RAM 4 temporarily stores various programs executed by the CPU 2 and data relating to these programs. Further, as shown in FIG.
The AM 4 is provided with a save area 4 a for temporarily saving data from the flash memory 5. Further, the evacuation area 4a is provided with a history information area 4b for recording the number of times data in the evacuation area 4a is referred to. In the history information area 4b, the date and time when the data in the flash memory 5 is read and stored in the evacuation area 4a is recorded as data representing, for example, year, month, day, hour, minute, and second.

The flash memory 5 stores data relating to various programs executed by the CPU 2 and the like. The flash memory 5 includes four data writing memory blocks 5A to 5D, each of which has a capacity of 128 KB. In each of the blocks 5A to 5D, a time information area 5a to record the date and time when data is written in each block, for example, date, hour, minute and second.
5d is provided.

The control interface 6 is for the home use,
This is an interface for connecting the industrial electronic device and the control device 1, and the devices are driven and controlled by data and control signals input and output via the control interface 6.

Next, the operation of this embodiment will be described. FIG. 3 is a flowchart showing the operation of control device 1 in the present embodiment. The CPU 2 has a flash memory 5
The data is written in each of the blocks 5A to 5D, and time information indicating the date and time when the data was written is represented by, for example, year, month, day, hour, minute, and second, and the time information areas 5a to 5d of the blocks 5A to 5D. To record.

Then, at predetermined time intervals, the CPU 2 elapses a predetermined time from the time of writing to each of the blocks 5A to 5D of the flash memory 5 based on the time information recorded in the time information areas 5a to 5d. A search is made for the block that is present (step S1). If there is no corresponding block, the process returns to step S1, and if there is a corresponding block, step S3
Go to (Step S2). Here, a description will be given assuming that processing is performed on the block 5B of the flash memory 5.

The CPU 2 reads out the data of the block 5B for which a certain time has elapsed from the writing time and reads the data from the RAM 5B.
4 in the evacuation area 4a. Further, the CPU 2 records time information indicating the date and time when the data of the block 5B is read and stored in the evacuation area 4a in the history information area 4b of the evacuation area 4a as data representing, for example, year, month, day, hour, minute and second. (Step S3).

Then, the CPU 2 erases the data read and stored in the save area 4a of the RAM 4 from the block 5B of the flash memory 5, and also erases the time information of the data recorded in the time information area 5b (step S4). ). Therefore, the block 5B becomes an empty area, and data can be written as appropriate.

In step S5, the number of times the data stored in the save area 4a of the RAM 4 has been referred to is recorded in the history information area 4b. In addition, time information indicating the date and time when the data is referred to is also recorded in the history information area 4b, for example, expressed as year, month, day and hour, minute, second. And step S
In step 6, based on the time information recorded in the history information area 4b, the process waits until a certain time elapses from the time when the data is stored in the RAM 4, and after the certain time elapses, proceeds to step S7.

In step S7, it is determined whether or not the data stored in the save area 4a of the RAM 4 has been referred to a predetermined number of times or more based on the number of times of reference to the data recorded in the history information area 4b. Here, when it is determined that the data in the evacuation area 4a has been referred to a predetermined number of times or more within a certain time, the process proceeds to step S8.

In step S8, the data in the save area 4a is referred to as important data since it has been referred to more than a predetermined number of times within a predetermined time, and is written again to an empty block of the flash memory. In the corresponding time information area, new time information indicating the date and time when the data was written again is recorded, for example, in terms of year, month, day, hour, minute, and second.

On the other hand, if it is determined in step S7 that the data in the evacuation area 4a has not been referred to more than a predetermined number of times within a predetermined time, the process proceeds to step S9. In step S9, the data in the save area 4a and the time information recorded in the history information area 4b are deleted from the RAM 4.

Here, the predetermined number of times for determining whether to rewrite the data in the save area 4a to the flash memory 5 or to erase the data from the RAM 4 in step S7 may be set according to the nature of the data. In addition, the predetermined time for determining whether or not reference has been made a predetermined number of times or more in step S6 may be set according to the nature of the data.

For example, from the time when the data of the block 5B is read and stored in the save area 4a,
The time until the data in a is referred to for the first time is measured. And 3 times or 5 times this time,
The above-mentioned fixed time is set. In this case, the data in the block 5B is stored or deleted based on the time until the data is first referred to, instead of the uniformly prescribed time. That is, the importance is not determined based on the absolute time, but the importance of the data is determined based on a change in the frequency of referring to the data. For this reason,
Even data that is referenced less frequently than other data and that is important is not accidentally deleted, and is deleted when the frequency of reference is reduced.

Further, for example, the time information recorded in the history information area 4b may be periodically sampled, and the number of times the data in the save area 4a is referred to within a certain time may be predicted. Then, the data in the evacuation area 4a is
When the predicted number of times is referred within a certain period of time, or
When the data is referred to more than the predicted number of times, the data may be recorded again in a free block of the flash memory 5. Further, when the number of times the data in the save area 4a is referred to within a certain time is smaller than the predicted number, the data may be deleted from the RAM 4.

As described above, according to the control device 1 of the embodiment of the present invention, when writing data to the flash memory 5, the data is written in the blocks 5A to 5A.
D is recorded together with the time information written in D, and after a certain time elapses, is temporarily evacuated to the evacuation area 4a of the RAM 4,
The saved data is erased from the flash memory 5.
Therefore, the old data is erased from the flash memory 5 and new data can be written and used in the block from which the data has been erased, so that the performance degradation of the system due to the data erasing time can be prevented, and The flash memory 5 can be used efficiently.

For the data once saved in the save area 4a of the RAM 4, the time information when the data is read out to the RAM 4, the number of times the data is referred, and the time information when the data is referred are stored in the history information area 4b. Data that has been recorded and referenced more than a predetermined number of times is written into the flash memory 5 again. Therefore, important data that is frequently referred to is stored in either the flash memory 5 or the RAM 4, so that erasure of important data can be prevented. On the other hand, data of low importance whose number of times of reference is equal to or less than the predetermined number of times is erased from the RAM 4, so that the flash memory 5 can be used efficiently.

In the above embodiment, the size of each block of the flash memory 5 is 128 KB. However, the present invention is not limited to this, and may be, for example, 64 KB. Of course, it is also possible to set the size. In the above embodiment, the flash memory 5 has four blocks. However, the number of blocks is arbitrary.

In the above embodiment, the RAM
The data saved in the block 4 is assumed to have passed a certain time from the time of writing to each block. However, the present invention is not limited to this. You may make it evacuate.

[0045]

According to the first aspect of the present invention, the data written in the predetermined memory block is read out and stored by the temporary storage means based on the time information written by the write control means, The data in the memory block from which the data has been read by the temporary storage means is erased from the flash memory by the erasing means. Therefore, when writing new data, the data can be written to the empty block from which the data has already been erased, so that it is possible to prevent the performance of the system from deteriorating due to the data erasing time of the flash memory.

According to the second aspect of the present invention, the data which is referred to a predetermined number of times or more out of the data stored in the temporary storage means is written into the flash memory again, so that important data which is frequently referred to is stored. Is saved. Further, among the data stored in the temporary storage means, data not referred to more than a predetermined number of times is determined to be extremely low in importance and is deleted from the temporary storage means. Can be.

According to the third aspect of the present invention, the data written in the memory block is read out by the temporary storage means when a predetermined time or more has elapsed from the date and time indicated by the time information. For this reason, data that has passed a certain time or more is sequentially stored in the temporary storage means, and is stored or deleted according to the number of times referred to. Therefore, the flash memory can be used more efficiently.

According to the fourth aspect of the present invention, data written in a predetermined memory block is read out and stored in a storage medium based on time information written together with the data,
The data in the memory block from which the data has been read to the storage medium is erased from the flash memory. Therefore, when writing new data, the data can be written to the empty block from which the data has already been erased, so that it is possible to prevent the performance of the system from deteriorating due to the data erasing time of the flash memory.

According to the fifth aspect of the present invention, the data referred to a predetermined number of times or more out of the data stored in the storage medium is written into the flash memory again, so that important data is preserved. Further, among the data stored in the storage medium, data that has not been referred to a predetermined number of times or more is determined to be of low importance and is deleted from the temporary storage means, so that the flash memory can be used efficiently. .

According to the invention described in claim 6, the data written in the memory block is read out to the storage medium when a predetermined time or more has elapsed from the date and time indicated by the time information. For this reason, data that has passed a certain time or more is sequentially stored in a storage medium and stored or deleted according to the number of times of reference. Therefore, the flash memory can be used more efficiently.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an internal circuit configuration of a control device 1 including a flash memory according to an embodiment of the present invention.

FIG. 2 is a diagram schematically showing a configuration of a flash memory 5 and a RAM 4 shown in FIG.

FIG. 3 is a flowchart showing a flash memory data rewriting process executed by the control device 1 shown in FIG. 1;

[Explanation of symbols]

 Reference Signs List 1 control device 2 CPU 3 ROM 4 RAM 4a save area 4b history information area 5 flash memory 5A to 5D memory block 5a to 5d time information area 6 control interface

Claims (6)

[Claims] 1. A flash memory rewriting control device for controlling rewriting of a flash memory comprising a plurality of memory blocks, wherein when writing data to each of the memory blocks, time information indicating the date and time of writing together with the data. Write control means for writing data into each memory block, temporary storage means for reading and storing data written in a predetermined memory block based on time information written by the write control means, A flash memory rewriting control device, comprising: an erasing means for erasing, from the flash memory, data of the predetermined memory block from which data has been read by the storage means. A determining means for determining whether or not the data stored in the temporary storage means has been referred to a predetermined number of times or more; 2. The flash memory according to claim 1, further comprising: rewriting control means for rewriting data into the memory, and erasing, from the temporary storage means, data determined as not being referred to by a predetermined number of times or more by the determination means. Rewriting control device. 3. The temporary storage means reads and stores data from a memory block in which time information indicating a date and time that is a predetermined time or more before the present time is written from among the respective memory blocks. Item 3. A flash memory rewrite control device according to item 1 or 2. 4. A flash memory rewriting control method for controlling rewriting of a flash memory including a plurality of memory blocks, wherein when writing data to each of the memory blocks, time information indicating the date and time of writing together with the data. And a second step of reading data written in a predetermined memory block and storing it in a storage medium based on the time information written in the first step. A third step of erasing from the flash memory the data of the predetermined memory block from which the data has been read in the second step;
A method for controlling rewriting of a flash memory, comprising the steps of: 5. A fourth step of determining whether the data stored in the storage medium in the second step has been referred to a predetermined number of times or more, and it is determined in the fourth step that the data stored in the storage medium has been referred to a predetermined number of times or more. A fifth step of rewriting data to the flash memory; and a sixth step of erasing, from the storage medium, data determined to have not been referred to by the predetermined number of times in the fourth step. 5. The flash memory rewriting control method according to claim 4, wherein: 6. The method according to claim 4, wherein in the second step, data is read from a memory block in which time information indicating a date and time a predetermined time or more before the current time is written. Or the rewriting control method of a flash memory according to 5.