JP2002304320A - Data storage method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a data storage method into a nonvolatile memory capable of immediately executing data writing processing without executing erasure processing just before the writing processing. SOLUTION: This method includes a process for retrieving a data non-storage record in the nonvolatile memory having plural record blocks capable of storing data that are erasure units, such as a flash memory 4, by use of a retrieval means facilitating retrieval of the presence of storage of data such as a flag, FFh or a pointer; a process for writing the data into the retrieved data non- storage record; and a process for calculating size of the data non-storage record after the writing process, and erasing stored data of a data storage block different from the data storage block of the record wherein the data are written in the writing process when the calculated size is small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for storing data in a semiconductor memory, and more particularly to a nonvolatile memory such as a flash memory which requires erasure of stored data before data writing and has a limited number of erasures. This is related to a method of storing data in a.

[0002]

2. Description of the Related Art A flash memory or the like is known as a non-volatile memory capable of writing and reading data and further electrically erasing data. When writing to the flash memory, the flash memory needs to be in the initial state, and when rewriting the already written data, that is, the stored data to another data, the stored data is temporarily erased. There is a need. However, erasure of stored data in a flash memory is performed in chip units or
This is performed in units of blocks of about 0 kilobytes, and the time required for the data erasure is large, which is much larger than the data write and read times.

If erasure of stored data is performed every time a write request is issued, not only does the efficiency of the write process deteriorate by the time required for the erasure, but also the number of erasures in the flash memory is limited. There is also a problem that leads to shortening of service life.

In order to solve the above problems, when writing data to a flash memory, an erasing process is not performed every time a write request is generated, but a unit area (hereinafter referred to as a record) to be written is used. There has been proposed a method in which after erasing a plurality of areas of multiple sizes at once, desired data is written in order from the first record of the erased record group.

For example, in the method disclosed in Japanese Patent Application Laid-Open No. 9-259046, a flag for confirming the presence or absence of storage is added to each record. A search for storage is performed, and if a record that does not store data is found, writing of data starts in order from the first record that does not store data.If there is no record that does not store data, a new record is created. The write processing is executed after first erasing the already-written data having a size several times larger than the size of the data to be written and securing a newly writable record group. Therefore, this method avoids the problem of executing the erasing process every time the writing process occurs.

However, in the above-described conventional method, when a write request is issued, an erasure process is performed immediately before a write process in order to secure a writable record group in a case where no data-unstored record exists. Has to be performed, and in that case, there is a problem that the efficiency of the writing process is deteriorated.

Further, when a write request such as an error log occurs, the writing is completed instantaneously, and when it is necessary to retain the stored data even when the power is turned off, erasing and writing are performed after the write request is generated. However, there is a problem that important data is lost because the time required for erasure is long if the above process is performed.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problem in the prior art and to write data to a nonvolatile memory which can be written immediately without performing an erasing process immediately before a data writing process. It is to provide a storage method.

[0009]

The data storage method according to the present invention comprises: (1) a procedure for retrieving the address of a data non-stored record in a nonvolatile memory having a plurality of record blocks capable of storing data as an erasing unit; Procedure B for writing data to the record of the retrieved address, calculating the size of the data-unstored record remaining after the procedure B. If the calculated size is small, the data was written in the procedure B This includes a procedure C for erasing stored data in a record block different from the record block to which the record belongs. (2) In the above (1), in the above procedure a, a search means for facilitating a search for an address of a record not storing data is used. (3) In the above (2), the search means is a flag added to the stored data to indicate whether data is stored. (4) In the above (2), the search means is a pointer indicating the address of a record added to the stored data and storing the next data.

[0010] The data storage method of the present invention further comprises (5) R
When a write pointer indicating the address of a record for storing data next is valid on the RAM using a data storage device having a built-in AM, a plurality of data serving as an erase unit can be stored according to the write pointer. And d) calculating the size of the data non-stored record remaining after the above procedure d. If the calculated size is small, the procedure d. And a procedure for erasing stored data in a record block different from the record block to which the record to which the data is written belongs. (6) The data storage method according to (1) or (5), wherein in (5), the nonvolatile memory is a flash memory. (7) In the above (6), the search means in the above (2) utilizes that the initial state and the erase state of the stored data are FFh.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 1 to 3 illustrate a first embodiment of a data storage method according to the present invention. FIG. 1 illustrates a data storage method to which a data storage method is applied to a flash memory as an example of the nonvolatile memory. FIG. 2 is a schematic structural diagram of a flash memory, and FIG. 3 is a flowchart showing an operation flow of a method of storing data in the flash memory.

In FIG. 1, 1 is a CPU for controlling each part of the data storage device, 2 is a ROM, 3 is a RAM,
Is a flash memory. The ROM 2 stores various programs for the CPU 1 to control, in particular, a program describing a method for the CPU 1 to store data in the flash memory 4. The RAM 3 is used as a temporary storage for general-purpose data. The memory 4 functions to store various types of data that is a main object of the present invention.

As a flash memory usable in the present invention, a flash memory generally having two or more record blocks serving as erase units is used. In the first embodiment, for example, two flash units serving as erase units are used. A flash memory 4 having record blocks A and B is used. FIG. 2 is a diagram in which the address space of the flash memory 4 as viewed from the CPU 1 is allocated, and a partial area of the flash memory 4 is divided into two record blocks, ie, two record blocks.
This indicates that record blocks A and B are allocated. The record block A has a block management area A0 for managing the use state of the block and records A1, A2,..., An. Similarly, the record block B has a block management area for managing the use state of the block. B0 and records B1, B2,.
Bn.

Next, a method of storing data in the flash memory 4 will be described with reference to FIGS. In the record blocks A and B, in the initial state, all records of A1 to Bn are in a data non-stored state, and whether or not data can be stored in both record blocks A and B is managed in each block management area A0, B0. Data to be written include records A1, A2,..., An, B1, B2,
.. And Bn are stored in this order. For the sake of explanation, records A1 to Am and records B1 to B
It is assumed that n has already been stored and only records Am + 1 to An in record block A have no data stored, in other words, new data can be stored.

When a write request is issued from the CPU 1, the address of a record having no data stored therein is searched from the record blocks A and B in the above procedure A, and it is known that only the records Am + 1 to An have no data stored therein ( Step 100). Then, in the above procedure B, data writing is started in order from the record Am + 1 to the data-unstored record thus found (step 101). Thereafter, in procedure C, the size of the remaining data-unstored record is calculated, and it is determined whether the calculated size is equal to or larger than a certain specified value (step 102). As a result of this determination, if the size of unstored data is equal to or larger than the specified value, there is a sufficient amount of unstored records even when a data write request is issued next. finish. On the other hand, as a result of the above calculation, when it is found that the size of the data non-stored record is smaller than the specified value, the data of the next record block (in this case, record block B) is erased and the data for writing the data is written. After securing the record (step 103), the procedure c is completed.

As described above, according to the first embodiment, when a data write request to the flash memory 4 is issued, the operation of erasing the already written data is not performed after a new data write request is issued as in the related art. New data write processing can be immediately executed in response to a write request from the CPU 1. The size of the specified value is appropriately determined in consideration of the type of the data storage device, the operating environment, or other data storage requests.

Embodiment 2 FIG. 4 and 5 illustrate a data storage method according to a second embodiment of the present invention. FIG. 4 is a partial schematic structural diagram of a flash memory, and each structure of records A1 to Bn in FIG. And that a flag indicating that data has been stored is added to the stored data in the record in which the data is stored. FIG. 5 is a flowchart showing an operation flow of a method of storing data in a flash memory.

Next, the operation of the second embodiment when the flag is added will be described with reference to FIGS. In the second embodiment, in the procedure (a) for searching for a data-unstored record, a flag is used as a search means for facilitating the search in accordance with a detailed method described below.

That is, in step 100 (see FIG. 3) of the procedure A in the first embodiment, the write address is set to the address of the first record (step 1).
10) For the record at that address, it is determined whether or not the record has no data stored by the flag (step 111). If the data has not been stored, the data is written to the record at the searched address (step 111). Step 101). On the other hand, if the record at a certain address has already stored the data, the write address is incremented to the next address (step 112), and it is determined again by the flag whether or not the data is not stored. The processes of steps 111 and 112 are repeated until an unstored address is searched. With the above method, the address of the record in which no data is stored is searched to execute data writing (step 101). Subsequent processing is the same as in the first embodiment.

For example, the data storage state is the state shown in the first embodiment, that is, the record Am in the record block A
Assuming that only +1 to An are in a state where no data is stored, a flag indicating a state with data storage is “0”, and a state without data storage is “1”, data is stored in records A1 to Bn. A flag “0” is added to each stored data in the record, and remains “1” in the records Am + 1 to An. Therefore, a search for a flag is started from the record A1, and a record Am + 1 that does not have the flag “0” and is not stored until the record Am + 1 is detected, and data is newly written in order from the record.

As described above, in the second embodiment, when a data write request to the flash memory 4 is issued, the flag added to each record is searched, and the flag in the first embodiment without the flag is added. This has the effect that the address of a record in which data is not stored can be determined more efficiently.

Embodiment 3 FIG. FIG. 6 illustrates Embodiment 3 in the data storage method of the present invention.
5 is a flowchart illustrating an operation flow of a method of storing data in a flash memory. The operation in the third embodiment will be described below with reference to FIGS. In the third embodiment, FFh is used as search means for facilitating the search in the procedure A for searching for a record that does not store data.

That is, the first embodiment of the present invention utilizes the fact that the initial state of the flash memory, ie, the data erase state, is FFh (state of only 1 in hexadecimal notation).
In step 100 (see FIG. 3), the write address is set to the last address of the record (step 1).
20) In the record of the address, it is determined whether or not the data is not stored according to whether or not it is FFh (step 121). If the data is not FFh and the data is stored, the address is incremented. Write data to the address record (steps 123, 10
1). On the other hand, if it is FFh and the data is not stored,
The address is decremented in the direction of the head address (step 122), and it is again determined whether or not the data is not stored according to whether or not the data is FFh. Repeat the process. With the above method, a write address is searched, and data writing (step 101) is executed. Subsequent processing is the same as in the first embodiment.

For example, assuming that the data storage state is the state shown in the first embodiment, records An to An-
By performing the search in the order of 1, An-2,..., It is found that up to the record Am + 1 is FFh and the data is not stored, and that the record Am is reached to the data stored state. Data is written from the record Am + 1 following Am.

As described above, in the third embodiment, there is no need to add a search means such as a flag to each record.
When a data write request to the flash memory 4 is issued, it is possible to determine whether or not each record is FFh, thereby determining the address of an unstored record.

Embodiment 4 7 and 8 illustrate a data storage method according to a fourth embodiment of the present invention. FIG. 7 is a partial schematic structural diagram of a flash memory. Indicates that a pointer indicating the address of the record storing the is added. FIG. 8 is a flowchart showing an operation flow of a method of storing data in a flash memory.

Next, the operation of the fourth embodiment will be described with reference to FIGS. In the fourth embodiment, in the procedure A for searching for a record that does not store data, the above-mentioned pointer is used as search means for facilitating the search. That is, in step 100 (see FIG. 3) in the first embodiment, the write address is set to the head address of the record (step 10).
0), it is determined whether or not the data is not stored based on whether or not the pointer at the address is FFh (step 130). The data is written to the record at the address (step 101). On the other hand, if the pointer is F
If it is not Fh, that is, if the data has been stored, the write address is set to the next address (step 131), and it is determined again whether or not it is unstored based on whether or not it is FFh by the pointer again. Steps 130 and 13 until the address where no data is stored is searched.
Step 1 is repeated. With the above method, a write address is searched, and data writing (step 101) is executed. Subsequent processing is the same as in the first embodiment.

As described above, in the fourth embodiment, when a data write request to the flash memory 4 occurs, the address of an unstored record can be determined by sequentially searching the pointer.

Embodiment 5 9 and 10 illustrate a fifth embodiment of the data storage method of the present invention. FIG. 9 is a schematic structural view of the flash memory 4, which differs from FIG. 2 in that a write pointer 31 indicating the address of a record for storing data next on the RAM 3 is added. FIG. 10 is a flowchart showing an operation flow of a method of storing data in the flash memory 4.

Next, the operation of the fifth embodiment will be described with reference to FIGS. In the fifth embodiment, when a write request is issued, it is first determined whether or not the write pointer on the RAM 3 is valid (step 140). The reason is that the pointer 31 on the RAM 3 may not be valid for some reason in the initial state after the power is turned on. In such a case, the methods of the first to fourth embodiments are adopted. On the other hand, when the write pointer 31 on the RAM 3 is valid, the procedure A executed in the first to fourth embodiments, that is, the search for the data non-stored record becomes unnecessary.
The data write address of the flash memory 4 can be determined without searching for the write address.
After writing the data (procedure d), as in the first embodiment, the remaining records not storing the data are calculated, and the data of the next record block is erased (procedure E) as necessary. The write pointer 31 to the memory 4 is incremented, and the data write processing ends.

As described above, in the fifth embodiment, when a data write request to the flash memory 4 is issued, the write address can be determined without searching for the address of an unstored record. By checking the size of the remaining records that have not been stored, always keep the records in the data non-stored state, and immediately execute the write process without repeating the erase and write procedures after a data write request occurs And the time required to search for a write address is reduced, so that the efficiency of data writing can be further increased.

[0032]

According to the data storage method of the present invention, as described above, (1) non-data storage in a nonvolatile memory having a plurality of record blocks capable of storing data as an erasing unit, for example, (6) a flash memory A procedure for searching for the address of the record, a procedure for writing data to the record at the searched address, b, calculating the size of the data non-stored record remaining after the procedure b,
If the calculated size is small, the method includes a procedure C for erasing stored data in a record block different from the record block to which the record to which the data is written in the procedure B belongs. This eliminates the need for a long-term data erasing process immediately before storing data in the volatile memory, enables efficient writing of data to the retrieved data non-storage records, and eliminates the loss of important data. Can be prevented.

(2) In the above (1), in the above procedure a, a search means for facilitating the search for an address of a record not storing data is used. (3) In the above (2), the above search is performed. The means is a flag added to the stored data to indicate the presence or absence of data storage. (4) In the above (2), the search means is an address of a record added to the stored data and storing the next data. With this pointer, the search for the presence or absence of data storage can be achieved with high efficiency, and as a result, the data storage process becomes even more efficient.

As described above, the data storage method of the present invention uses (5) a data storage device having a built-in RAM, and the write pointer indicating the address of the next record for storing data on the RAM is effective. In the case of, the procedure d for writing data to a non-data-stored record in a non-volatile memory having a plurality of record blocks capable of storing data as an erasing unit, for example, (6) a flash memory in accordance with the write pointer. Calculate the size of the data-unrecorded record remaining after d,
If the calculated size is small, the procedure for erasing the stored data of a record block different from the record block to which the record to which the data was written in the procedure d belongs, and the procedure for searching the write address are included. Since it becomes unnecessary, there is an effect that the efficiency of data writing can be improved.

(7) In the above (6), the search means in the above (2) utilizes the fact that the initial state and the erased state of the stored data are FFh. As in the case of (4), the search for the presence or absence of data storage can be achieved with high efficiency, and the data storage processing becomes more efficient.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a main part of a data storage device used in a first embodiment in a data storage method of the present invention.

FIG. 2 is a schematic structural diagram of a flash memory according to the first embodiment;

FIG. 3 is a flowchart showing an operation of storing data in a flash memory according to the first embodiment;

FIG. 4 is a partial schematic structural diagram of a flash memory according to a second embodiment in the data storage method of the present invention.

FIG. 5 is a flowchart showing an operation of storing data in a flash memory according to the second embodiment;

FIG. 6 is a flowchart showing an operation of storing data in a flash memory according to the third embodiment.

FIG. 7 is a partial schematic structural diagram of a flash memory according to a fourth embodiment of the data storage method of the present invention.

FIG. 8 is a flowchart showing an operation of storing data in a flash memory according to the fourth embodiment.

FIG. 9 is a schematic structural diagram of a flash memory according to a fifth embodiment of the data storage method of the present invention.

FIG. 10 is a flowchart showing an operation of storing data in a flash memory according to the fifth embodiment.

[Explanation of symbols]

1 CPU, 2 ROM, 3 RAM, 31 write pointer, 4 flash memory, A record block, B record block.

Claims (7)

[Claims] 1. A procedure for searching for an address of a non-data-stored record in a nonvolatile memory having a plurality of record blocks capable of storing data as an erasing unit, a procedure for writing data to a record at the searched address, b. Calculate the size of the data non-stored record remaining after step b, and if the calculated size is small, store the data stored in a record block other than the record block to which the record to which the data was written in step b belongs. A data storage method characterized by including an erasing procedure (c). 2. The data storage method according to claim 1, wherein in the step (a), a search means for facilitating a search for an address of a record not storing data is used. 3. The data storage method according to claim 2, wherein said search means is a flag added to the stored data to indicate that data has been stored. 4. The data storage method according to claim 2, wherein said search means is a pointer indicating an address of a record added to the stored data and storing the next data. 5. When a data storage device having a built-in RAM is used, and a write pointer indicating an address of a record for storing data next in the RAM is valid, an erase unit is set according to the write pointer. Procedure d for writing data to a data non-stored record in a nonvolatile memory having a plurality of record blocks capable of storing data, calculating the size of the data non-stored record remaining after the above procedure d, and when the calculated size is small And c. Erasing data stored in a record block other than the record block to which the record to which the data was written in step d above belongs. 6. The data storage method according to claim 1, wherein the nonvolatile memory is a flash memory. 7. The data storage method according to claim 6, wherein the retrieval means in the second aspect utilizes that the initial state and the erase state of the stored data are FFh.