JP2000243093A - Data storing method for flash memory and data reading out method from flash memory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a data storing method for a flash memory by which the efficiency of processing of writing data in a flash memory can be improved and a long life can be achieved. SOLUTION: When new data (record) is stored in a sector in a state in which data is stored halfway in a sector to be processed in a flash memory 4, data is stored at a position of which a flag 1 is in a state being not yet stored. Also, when new data (record) is stored in a sector in a state in which data is stored all in a sector to be processed, record in which a flag 2 is effective data is stored temporarily in a RAM 3, a sector to be processed is all erased, effective record stored temporarily in the RAM 3 is stored again from the leading of the sector to be processed, and new data (record) is stored at a position of which the successive flag 1 is in a state being not yet stored.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of storing data in a memory made of a semiconductor or the like, and more particularly, to a memory such as a flash memory which requires erasing before writing data and has a limit on the number of erasing. And a data reading method.

[0002]

2. Description of the Related Art A flash memory or the like is a memory capable of freely writing and reading data, electrically erasing contents, and storing data even when the power is turned off.

In writing data to the flash memory, usually, for each minimum unit of data to be written, an area having the same size as the data of the minimum unit is secured, and the secured storage area is erased. Thereafter, the new minimum unit of data is written, and thereafter, erasure and writing are repeated for each minimum unit of data in the same manner to write all desired data.

[0004]

In the above-mentioned prior art, erasing is performed immediately before writing for each minimum unit of data. Therefore, the efficiency of the writing process is low by the time required for erasing, and data is to be written. There has been a problem that the overall processing efficiency is reduced with an increase in the number of data.

Further, in the case of a flash memory, the number of times of erasing is limited, so that the number of times of writing increases with an increase in the number of data, which causes a problem of shortening the life.

The present invention has been made in view of the above problems, and provides a method of storing data in a flash memory, which requires a small number of erasing processes before data writing. It is another object of the present invention to provide a method of storing data in a flash memory, which can improve the efficiency of a write process and extend the life of the flash memory.

[0007]

According to the present invention, claim 1 is provided.
When writing desired data, a stored confirmation flag for confirming the presence or absence of storage in a memory, a valid data confirmation flag indicating validity or invalidity of the data, and type data indicating type information of the data And record data in which the data is added to the data.

According to a second aspect of the present invention, when writing to the memory, the address of the unstored data is sequentially detected from the top of the memory area based on the stored confirmation flag, and the address of the unstored data is detected. The record data is written to the detected unstored address.

According to a third aspect of the present invention, upon writing to the memory, the address of the unstored data is sequentially detected from the head of the memory area based on the stored confirmation flag, and the address of the unstored data cannot be detected. In this case, the valid record data is temporarily stored based on the valid data confirmation flag, the data is erased in sector units, and then the temporarily stored valid record data is sequentially rewritten from the beginning of the memory area.

According to a fourth aspect of the present invention, upon writing to the memory, the address of the unstored data is sequentially detected from the beginning of the memory area based on the stored confirmation flag, and the address of the unstored data cannot be detected. In the case, based on the valid data confirmation flag and the type information, the valid record data is temporarily stored, and after erasing the data in sector units,
The temporarily stored valid record data is sequentially rewritten from the beginning of the memory area.

According to a fifth aspect of the present invention, the temporarily stored valid record data is sequentially rewritten from the beginning of a memory area, and then record data having desired data is written to an address immediately after the rewrite. .

According to a sixth aspect of the present invention, there is provided a method of reading data written by the method of storing data in a flash memory according to any one of the second to fifth aspects, wherein the data is sequentially stored from the beginning of the memory area. It is characterized by detecting a confirmation flag, a valid data confirmation flag, and type information, and reading out data when desired type information is detected.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS.

First, FIG. 1 shows an example of the configuration of an apparatus using a method of storing data in a flash memory according to an embodiment of the present invention. The data is stored in the flash memory for some control or the like. It is composed. It should be noted that FIG. 1 shows only the main parts directly related to the execution of the data storage method in the flash memory. FIG. 2 is a schematic diagram showing a state in which a flash memory area is allocated in all the memory areas. FIG. 3 is a flowchart illustrating a method of storing data in a flash memory and a method of erasing data according to the present invention. FIG. 4 is a flowchart illustrating a reading method for reading data from a flash memory according to the present invention. FIG. 5 is a schematic diagram showing a state when the present invention is used.

In FIG. 1, 1 is a CPU, 2 is a CPU 1
ROM storing a program to be executed by
Is a RAM for temporarily storing programs and data, 4 is a flash memory for storing various data,
1, the ROM 2, the RAM 3, and the flash memory 4 are connected by a bus 5.

In this configuration, a method for storing data in the flash memory will be described. Flash memory 4
It is assumed that a flash memory area is allocated to a position as shown in FIG.

The flash memory area is composed of a plurality of areas (referred to as sectors) as shown in FIG. 2A, and in the present invention, data is erased using this sector as a minimum unit. Each sector is composed of a plurality of records as shown in FIG. Further, as shown in FIG. 2C, each record is composed of a stored confirmation flag (flag 1), a valid data confirmation flag (flag 2), a data type, a data size, data, and CRC check data. .

The stored confirmation flag of a record is set to “0” when the record is written to the flash memory (stored state), and is set to “1” when the record is not written (unstored state). Is done. The valid data confirmation flag of the record is set to “1” when the data of the record is valid, and is set to “0” when the data of the record is invalid. When the flash memory is in the initial state, the stored confirmation flag and the valid data confirmation flag of each record are “1” and “1”. The data type of the record is information indicating the type of data to be stored. For example, type information indicating that the information stored in the data portion is a file name, billing data, time data, or the like is stored. The CRC check data is a known CR
It is assumed that the C check method is used. In addition, CRC
In addition to checking, checksum data may be used. In this data storage method, data is written in record units sequentially from the head of the flash memory area.

Next, based on the flowchart of FIG.
A storage processing method for the flash memory based on the control of U1 will be described.

When a write process from the CPU 1 to the flash memory 4 occurs, at step S301, C
The start address of the flash memory area is stored in an address variable (ADD) included in PU1, and step S3 is executed.
Go to 02. Initially, the start position address of record 0 of sector 0 is stored in the address variable (ADD).

In step S302, it is determined whether or not the stored information "0" is stored in the flag 1 of the record indicated by the address variable (ADD). Proceeding to S312, a process of writing desired data to be written is performed. In the writing process in step S312, the address variable (AD
D) stores the stored information “0” in the flag 1 of the record at the address position indicated by D), stores “1” indicating that the data is valid data in the flag 2, and stores the desired data to be written in the data type. The type information is stored, the size of the data to be written and the actual data are stored, and the CRC check data is stored, that is, the data for one record is stored.
If the stored information “0” is stored in the flag 1 in step S302, the process proceeds to step S303.

In step S303, it is determined whether or not "1" indicating valid data is stored in the flag 2, and if it is not valid data "1", that is, the data is stored but invalid. If data “0” is stored, the process proceeds to step S307, and if valid data is stored, the process proceeds to step S304.

In step S304, it is determined whether or not the desired data to be written matches the stored data type.
The process proceeds to step 306, and if they match, the process proceeds to step S305.

In step S305, since the desired data to be written and the stored data are the same type of data, the currently stored data is determined to be old information, and The valid data “1” of the flag 2 of the record that has been set is rewritten to invalid data “0” as invalid data, and step S3
Proceed to 07. Normally, in order to rewrite the information in the already written state, it is necessary to erase the already written data and write the rewritten data again.
When rewriting from “1” to “0”, there is no need to erase, and it is possible to rewrite from “1” to “0” as it is.

In step S306, step S3
If it is determined in step 04 that the desired data to be written does not match the type of the stored data, the record in which the valid data is stored, that is, the record indicated by the address variable (ADD) is stored. All the data is temporarily stored in the RAM 3 via the bus 5, and step S307
Proceed to.

In step S307, it is determined whether or not data to be written (data for one record) can be written to the flash memory, that is, whether or not the area of the sector to be written in the flash memory area has ended. If the end is determined, the process proceeds to step S309. If not, the process proceeds to step S308. The address at which the next record is located is stored in an address variable (ADD) in the CPU 1, and the process proceeds to step S302.
The processing of step S302 and subsequent steps are sequentially repeated for the next record.

In step S309, since data is stored in the entire flash memory area, all data in the current sector to be written is erased, and the flow advances to step S310. It should be noted that when erasing, all of the sectors are set to "1".

In step S310, the head address of the sector erased in step S309 is stored in an address variable (ADD) provided in the CPU 1, and the address position stored in the address variable (ADD) is sequentially determined.
In step S306, the record data temporarily stored in the RAM 3 is re-written via the bus 5 while updating the address variable (ADD). When all the record data temporarily stored in the RAM 3 is written to the flash memory 4, the process proceeds to step S306. Proceed to S311. That is, step S
In steps 309 to S310, a writable area can be secured by erasing invalid data and rewriting only valid data.

In step S311, the address at which the next record is located is stored in the address variable (ADD) of the CPU 1, and the flow advances to step S312. That is, in step S311, the address of the unstored state record position after the valid data rewritten in step S310 is stored.

In step S312, the stored information "0" is stored in the flag 1 of the record at the address position indicated by the address variable (ADD) in the CPU 1, and the flag 2 is set to "1" indicating valid data. Is stored, the type information of the data to be written is stored in the data type, the size and actual data of the desired data to be written are stored, and the CRC check data is stored, that is, the data for one record is stored. .

Next, based on the flowchart of FIG.
A method for processing reading from the flash memory based on the control of U1 will be described.

When a read process from the flash memory 4 occurs from the CPU 1, in step S401,
The start position address of the sector to be read in the flash memory area is stored in the address variable (ADD) of the CPU 1, and the process proceeds to step S402.

In step S402, it is determined whether or not the stored information "0" is stored in the flag 1 of the record indicated by the address variable (ADD). Proceeds to S406 and proceeds to flag 1
If the stored information “0” is stored in step S403, the process proceeds to step S403.

In step S403, it is determined whether or not "1" indicating valid data is stored in the flag 2. If not, the valid data is not "1", that is, the data is stored but invalid. If data "0" is stored, the process proceeds to step S407, and if valid data is stored, the process proceeds to step S404.

In step S404, it is determined whether the desired read data matches the stored data type. If not, the flow advances to step S407.
If they match, the flow advances to step S405 to read one record of data indicated by the address variable (ADD) via the bus 5.

In step S406, it is determined whether or not the start position address of the sector to be currently read is stored in the address variable (ADD). S
Proceeding to 407, if the start address of the sector is stored, proceeding to step S409, the process ends as there is no corresponding data.

In step S407, it is determined whether or not the address variable (ADD) is the end of the area of the sector to be read in the flash memory. If it is, the process proceeds to step S409. Proceeding to step S408, the address at which the next record is located is stored in the address variable (ADD) of the CPU 1, and the process proceeds to step S402, where the processing of step S402 and subsequent steps is sequentially repeated for the next record.

FIG. 5 schematically shows the state of the data storage method and the data read method as described above. FIG. 5 shows a state in which a sector to be processed in the flash memory 4 is partially stored. When new data (record) is to be stored in the sector, the flag 1 is stored at a position where the data is not stored (see FIG. 5A). In the case where new data (record) is stored in a sector while being stored in all the sectors to be processed (FIG. 5B)
Record), the record in which the flag 2 is valid data is temporarily stored in the RAM 3, all the sectors to be processed are erased, and the valid record temporarily stored from the RAM 3 is stored again from the beginning of the sector to be processed. The new data (record) to be stored is stored at a position where the flag 1 following the flag is not stored (see FIG. 5C).

As described above, writing n records conventionally required n erasures. However, the use of the method of the present invention makes it possible to greatly reduce the number of erasures. And the life can be prolonged as the number of erases decreases.

Furthermore, since valid data before erasure is also stored continuously, repeated writing processing can be reduced, and further efficiency can be achieved.

Further, even if there are a plurality of valid data, desired data can be efficiently read out based on the stored confirmation flag, the valid data confirmation flag, and the type information.

[0042]

According to the present invention, the number of erasures can be greatly reduced, the efficiency of the writing process can be improved, and the life can be prolonged with the decrease in the number of erasures. Furthermore, since valid data before erasure is also stored continuously, repeated writing processing can be reduced, and further efficiency can be achieved. In addition, even if there are a plurality of valid data, desired data can be efficiently read based on the stored confirmation flag, the valid data confirmation flag, and the type information.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an apparatus using a method of storing data in a flash memory according to the present invention.

FIG. 2 is a schematic diagram showing an embodiment in which a flash memory area in all memory areas is allocated.

FIG. 3 is a flowchart illustrating an embodiment of a method of storing data in a flash memory and a method of erasing data according to the present invention.

FIG. 4 is a flowchart illustrating an embodiment of a reading method for reading data from a flash memory according to the present invention.

FIG. 5 is a schematic diagram showing an embodiment of a state in a flash memory when the present invention is used.

[Explanation of symbols]

 1 CPU 2 ROM 3 RAM 4 Flash memory 5 Bus

Claims (6)

[Claims] When writing desired data, a stored confirmation flag for confirming whether or not data is stored in a memory, a valid data confirmation flag indicating validity or invalidity of the data, and type information of the data, Type data shown,
And writing record data in which the data is added to the data. 2. When writing to a memory, an address of unstored data is sequentially detected from the beginning of a memory area based on the stored confirmation flag, and when an address of unstored data is detected, the detected unstored data is detected. 2. The method of storing data in a flash memory according to claim 1, wherein the record data is written to an address of the flash memory. 3. When writing to a memory, an address of unstored data is sequentially detected from the beginning of the memory area based on the stored confirmation flag. 2. The flash according to claim 1, wherein the valid record data is temporarily stored based on the confirmation flag, the data is erased in sector units, and then the temporarily stored valid record data is sequentially rewritten from the beginning of a memory area. A method of storing data in memory. 4. When writing to a memory, an address of unstored data is sequentially detected from the beginning of a memory area based on the stored confirmation flag. 2. The method according to claim 1, wherein the effective record data is temporarily stored based on a confirmation flag and the type information, the data is erased in sector units, and then the temporarily stored effective record data is sequentially rewritten from a head of a memory area. 3. A method for storing data in a flash memory according to item 1. 5. The method according to claim 3, wherein the temporarily stored valid record data is rewritten sequentially from the beginning of a memory area, and then record data having desired data is written to an address immediately after the rewrite. Item 5. The method for storing data in a flash memory according to Item 4. 6. A method for reading data written by the method for storing data in a flash memory according to claim 2, wherein the storage confirmation flag and the valid data are sequentially stored from the top of the memory area. A method for reading data from a flash memory, comprising detecting a confirmation flag and type information, and reading data when desired type information is detected.