JP5939120B2 - Flash memory data processing method and program for data processing - Google Patents

Description

  The present invention relates to a data processing method of a flash memory having a limit on the number of times of erasure of stored data, and a program for this data processing.

A flash memory is widely used as a storage device for storing various data generated during the operation of an automobile.
As is well known, this flash memory has a limit on the number of times that stored data can be erased. Therefore, if past data is erased every time data is rewritten, the limit number of times is reached in a short period of time, and operation cannot be guaranteed. End up.

  Therefore, when using a flash memory as a storage device, the storage area is divided into a plurality of blocks, the blocks to be stored are divided according to the type of data, and when new data is generated, the past data is not erased and the corresponding block is deleted. It was memorized cumulatively.

When the storage capacity of the block reaches a certain amount, all data in the block is erased collectively.
In this way, the number of times of erasing data stored in the flash memory can be greatly reduced, so that the operation guarantee period of the flash memory can be greatly extended (Patent Document 1).

JP 2000-243093 A

By the way, when data is stored cumulatively in a block as described above, necessary data and unnecessary data are mixedly stored in the data.
Therefore, in the invention according to Patent Document 1 described above, when each data is stored in the block, a confirmation flag indicating whether the data is necessary is attached to each data, and when the data in the block is erased collectively, Only data required by the confirmation flag is erased after being saved in the RAM.

  Then, after erasing the data in the block, the data saved in the RAM is returned to the original block, and the data saved in the RAM is prevented from being mixed with other saved data. To erase.

  However, when a RAM is used as a data saving destination, if a momentary interruption occurs during saving (the power supplied to the RAM is temporarily turned off), the data saved in the RAM is erased. There was a problem.

As a method for solving this problem, a method of providing a save block for saving in the flash memory and changing the destination for saving data from the RAM to the save block can be considered.
However, there are multiple normal blocks for storing data in the flash memory, and if the process for saving data from each block is performed on one save block, the data saved in the save block is erased. The number of times becomes the total number of normal block erasures.

  Therefore, even if the normal number of erasures of each block does not reach the limit number at which the operation of the flash memory cannot be guaranteed, the entire flash memory cannot be assured of operation at an early stage. was there.

  Accordingly, the present invention provides data for a flash memory that can prevent the entire flash memory from being in a state where the operation cannot be guaranteed at an early stage by exceeding the limit number that the operation cannot be guaranteed only for the number of erasures of the save block. It is an object to provide a processing method and a program for processing this data.

  The data processing method according to claim 1, which is an invention made to achieve the above object, includes a plurality of blocks for storing data, and a save block for saving data stored in the block Is a data processing method of a flash memory having a storage area in which is set.

In the present invention, at the time of saving, saving processing (S38, S50) is performed in which tail information indicating the end of the data group is added to the end of the data group consisting of a plurality of data saved from one block. Is done.

Furthermore, in the present invention, after the evacuation by the evacuation process, the first erasure process (S52) for erasing the data stored in one block of the evacuation source at a time is executed. A recovery process (S54) is performed to return the data group delimited by the tail information to one block of the save source.

  In this way, in the save block, the data group saved from each block can be distinguished by the tail information. A plurality of data groups can be stored cumulatively without erasing them one by one.

  If these multiple data groups are erased at once, the number of times of erasure for the evacuation block can be reduced compared with the case where the data group evacuated to the evacuation block is returned to the evacuation source block and then the data group is erased one by one. Can be reduced.

  Therefore, if this data processing method is used, it is possible to prevent the entire flash memory from being in a state where the operation cannot be guaranteed at an early stage because the number of erasures of the save block exceeds the limit number that the operation cannot be guaranteed.

  The second erasing process according to claim 2, that is, the timing of erasing the data consisting of a plurality of data groups stored in the save block and delimited by the end information at a time is that the storage capacity of the save block is full. However, the present invention is not limited to this.

  Further, whether or not to save the data of any block among the plurality of blocks to the save block may be executed for a block whose storage capacity is full, for example. It is not limited to.

Further , when data is stored as in the data processing method of the flash memory according to claim 3, a save confirmation flag for identifying whether to save is associated with the data, and the data is stored in any of the blocks When the storage process (S10 to S22) to be performed and the process of storing data by the storage process are executed, if the same type of data has been stored in the past, the saving of the same type of data stored in the past is performed. You may make it perform the flag change process (S18) which changes a confirmation flag into what shows what was memorize | stored in the past.
In this case, in the save process, a process of saving the data in which the save confirmation flag is held in the flag change process among the data stored in one of the blocks to the save block may be executed. Good.

In this way, for the same type of data, only the latest data is saved when the save process is performed.
If the program described in claim 4 is installed in a device using a flash memory as a storage device, the same effect as described above can be obtained in the device.

  Incidentally, the reference numerals in parentheses for each of the above means are examples showing the correspondence with the specific means described in the embodiments described later, and the present invention is indicated by the reference numerals in the parentheses of the above respective means. It is not limited to specific means.

It is a block diagram of ECU of this embodiment. In the explanatory view of the flash memory of this embodiment, (a) the storage area is divided into a plurality of blocks, (b) each block is divided into a plurality of records, (c) the configuration of each record FIG. It is a flowchart of a storage process. It is a 1st flowchart of a save process. It is a 2nd flowchart of an evacuation process. It is explanatory drawing which showed notably the mode that data moves. It is explanatory drawing which showed notably the mode that data moves.

Embodiments that implement the data processing method of the present invention will be described below with reference to the drawings.
1. Overall Configuration As shown in FIG. 1, the ECU 1 of the present embodiment is a control device that includes a CPU 10, a RAM 11, a ROM 12, a flash memory 2, and an interface unit 13, each of which is communicably connected via a bus 14.

The CPU 10 is a main control unit that executes various processes described later.
The RAM 11 is a volatile memory that stores data that needs to be temporarily stored, and is a memory that can store and read data.

The ROM 12 is a memory in which data such as various processing programs is stored in advance, and is a memory that can only read data.
The flash memory 2 is a non-volatile memory that stores data that needs to be retained even when the power is shut off, and is a memory that can store and read data.

The interface unit 13 is a device that performs necessary conversion on an input / output signal to the ECU 1 in order to communicate with various sensors provided in the vehicle and various devices to be controlled.
In the ECU 1, the CPU 10 executes various processes based on the program read from the ROM 12, and the data generated in this process, the data converted from the input signal of the interface unit 13, and other data are stored in the RAM 11 and Processing for storing, reading and erasing the flash memory 2 is executed.

2. Flash memory 2
Next, the flash memory 2 will be described in detail with reference to FIG.
In the following description, for ease of explanation, only three blocks 20a to 20c are mentioned as general blocks, but the number of general blocks is not limited to three.

  As shown in FIG. 2A, the flash memory 2 has a storage area divided into a plurality of blocks 20 a to 20 c and 21, one of which is used as the save block 21.

  In the present embodiment, the blocks 20a to 20c where data should be stored are determined in advance according to the type of data so that the data storage frequency does not deviate between the blocks 20a to 20c. Each data is stored in each of the blocks 20a to 20c in accordance with the predetermined place.

Next, the structure of each block 20a-20c is demonstrated.
Each block 20a-20c is comprised by the some record 200, as shown in FIG.2 (b). This record 200 is a minimum unit of storage / reading of the flash memory 2.

Each record 200 includes a recording area for flag 1, flag 2, type data, data, and check data, as shown in FIG.
The flag 1 (stored confirmation flag) is set to “0” when data is stored in the unstored record 200 (stored state), and remains “1” when the data is not stored (unstored state). It is a flag that is maintained.

  The flag 2 (save confirmation flag) is set to “0” for a record in which past data is stored when the same type of data is newly stored in the same block 20a to 20c, and a record in which new data is stored. Is a flag which is maintained as “1”.

  That is, in the present embodiment, when a plurality of the same type of data is stored in each of the blocks 20a to 20c, the flag 2 of the record in which the latest data is stored for the same type of data is set to “1”. The flag 2 of the record storing past data other than is changed to “0”.

The type data is information indicating the type of stored data.
The data corresponds to data generated by processing executed by the CPU, data obtained by converting the input signal of the interface unit 13, and other data, and is data that represents information to be stored. Flag 1 and flag 2, type data, and check data are redundant data for this data.

The check data is checksum data, CRC data, or the like.
By the way, the flash memory cannot overwrite data. For this reason, in the flash memory, if old data is to be rewritten to new data, the old data must be erased once and then new data must be stored thereon.

However, when simply rewriting from “1” to “0”, it is not necessary to erase the old data, and it is possible to rewrite from “1” to “0” as it is.
Therefore, the flags 1 and 2 are set to “1” and “1” respectively in the initial state.

The flag 1 is set to “0” when data is stored in each record.
On the other hand, when the same type of data is newly stored, the flag 2 is set to “0” for a record corresponding to a record of past data, and for a flag corresponding to a record where data is newly stored. “1” is maintained.

3. Storage Process Next, the storage process shown in the flowchart in FIG. 3 will be described among various processes executed in the ECU 1 including the flash memory 2 described above.

  The storage process executed by the ECU 1 of the present embodiment is a process of storing data in any of the blocks 20a to 20c determined in advance according to the types of the data handled in the ECU 1.

This storage process is always executed while the ECU 1 of the present embodiment is operating.
In the present embodiment, as described above, the blocks 20a to 20c to be stored are determined in advance according to the type of data so that the storage frequency in each of the blocks 20a to 20c is not biased.

  Therefore, when this storage process is started, in S10, first, a block in which data is to be stored (hereinafter, a case where data is stored in the block 20a will be described for simplicity) is determined, and an address variable (ADD) included in the CPU 10 is determined. ) Stores the address of the first record of the block 20a.

  It should be noted that the process for determining a block in which data is to be stored may be performed using this type data when the type data is associated with the data as redundant data in advance, or may be determined by another method.

  Next, in S12, it is determined whether or not the flag 1 of the record at the address position indicated by ADD is “0”, that is, whether or not data has been stored in the record at the address position indicated by ADD. In the case of “1” (S12: NO), the process proceeds to step S22, and the process of storing data in the record at the address position indicated by the ADD is executed.

  In S22, the flag 1 of the record at the address position indicated by the ADD is set to “0”, that is, stored, and the flag 2 is held as “1”. Further, in S22, type data, data, and check data are stored.

On the other hand, if the flag 1 of the record at the address position indicated by ADD is “0” in S12, that is, if it has been stored (S12: YES), the process proceeds to S14.
In S14, it is determined whether or not the flag 2 of the record at the address position indicated by the ADD is “1”, that is, whether or not the data stored in the record is the latest data. If the flag 2 is “0”, (S14: NO), it is identified as past data, and the process proceeds to S20. If the flag 2 is “1” (S14: YES), it is identified as the latest data, and the process proceeds to S16.

  In S16, it is determined using the type data whether or not the type of data to be stored matches the type of data stored in the record at the address position indicated by the ADD, and if they do not match (S16: NO) The process proceeds to S20, and if they match (S16: YES), the process proceeds to S18.

  In S18, since the data stored in the record at the address position indicated by the ADD is past data among the same type of data, the flag 2 of the record is rewritten to “0”, and the process proceeds to S20.

In S20, a process of adding 1 to the ADD in the CPU 10 is executed, and the address of the next top record of the block 20a is stored.
Thereafter, the data that triggered the start of the storage process is finally stored in S22 in the record at the address located next to the last address in the record in which data is already stored in the block 20a. Until then, the processing of S12 to S20 is repeated.

4). Next, a save process for saving the data stored in each of the blocks 20a to 20c to the save block 21 will be described with reference to FIGS.

This evacuation process is always executed while the ECU 1 of the present embodiment is operating.
In this saving process, first, in S30, a process for determining whether there is a block 20a to 20c that satisfies a saving condition for saving data is executed.

  This saving condition can be set in various ways. For example, (1) whether the storage capacity of each of the blocks 20a to 20c has reached a predetermined full amount (for example, 90%) of the total storage capacity of each of the blocks 20a to 20c. However, it can be set variously, for example, (2) whether or not the timing determined to be saved in advance has been reached, and (3) when the user gives an instruction to execute the saving process.

This save condition is preferably executed at least before it is predicted that data cannot be newly stored in each of the blocks 20a to 20c.
In S30, if it is determined that any of the blocks 20a to 20c satisfies the retreat condition (S30: YES), the processing from S32 onward is started for the blocks 20a to 20c. If the evacuation condition is not satisfied (S30: NO), a standby process is executed.

  Next, in S32, the address variable (ADD) in the CPU 10 is stored with the address of the first record of the block to be saved (in the following description, the data in the block 20a will be saved for the sake of simplicity). Is done.

  Next, in S34, it is determined whether or not the flag 1 of the record at the address position indicated by the ADD is “0” indicating that it has been stored. If “1” (S34: NO), the process proceeds to S50 and the save block 21 is reached. The process of storing tail information described later is performed.

On the other hand, if the flag 1 of the record at the address position indicated by ADD is “0” indicating that it has been stored (S34: YES), the process proceeds to S36.
In S36, it is determined whether or not the flag 2 of the record at the address position indicated by ADD is “1” indicating that it is the latest data. If flag 2 is “1” indicating the latest data, then S38 is executed. Then, the process of moving the data of the record to the save block 21 is executed, and the process of S40 is executed.

  On the other hand, if the flag 2 is “0” indicating that it is not the latest data in S36, S40 is executed without performing the process of S38, that is, without saving the data.

In S40, 1 is added to the ADD held in the CPU 10, and the address of the next top record in the block 20a is stored.
Thereafter, the processes of S34 to S40 are repeatedly executed, and the flag 1 and the flag 2 of all records in which data is stored among the records in the block 20a are checked.

As a result, all the data stored in the record in which the flag 2 is “1” among the records in the block 20 a are saved in the save block 21.
On the other hand, when the process of saving the data is completed, the process proceeds to S50 (S34: NO).

  In S50, among the records constituting the save block 21, the end of the record at the last address where the data saved from the block 20a to the save block 21 by the processing of S34 to S40 is stored, that is, this last address. The tail information is recorded in the record of the next address with respect to this record.

When S50 ends, S52 is executed next, as shown in FIG.
In S52, a process of collectively erasing the saved data in the block 20a, which is the save source block, is executed. When this processing is executed, all the records in the block 20a are initialized. For example, all the flags 1 and 2 of each record are set to “1”.

  In subsequent S54, a process is executed in which the data saved in the save block 21 from the block 20a in the process of S34 to S40 previously performed is returned to the block 20a that is the save source block changed in S52.

  This processing is performed by deleting the information stored in the record between the record in which the end information is stored by the save processing performed this time and the record in which the end information is stored by the previous save processing after erasing the original data. Processing to return to block 20a is executed.

  If there is no record in which the end information is stored by the previous save process, the information stored in the record at the address before the record in which the end information is stored by the save process performed this time is stored in the save source block 20a. Processing to return is executed.

When the process of S54 is completed, it is determined whether the storage capacity of the save block 21 has reached a predetermined amount and the free capacity is reduced (S56).
If it is determined in S56 that the storage capacity of the save block 21 has not reached the predetermined amount (S56: NO), this process is terminated, and it is determined that the storage capacity of the save block 21 has reached the predetermined amount. Then (S56: YES), all the data in the save block 21 is erased, this processing is terminated, and the processing from S30 is executed again.

5. Conceptual diagram How data is recorded / saved / erased in each of the blocks 20a to 20c and 21 when the storage process and the saving process described above are executed will be briefly described with reference to FIGS.

In FIGS. 6 to 7, each square that divides each of the records 20a to 20c into a plurality means a record.
In the initial state, no data is stored in the records constituting the blocks 20a to 20c and the save block 21.

When the engine of the vehicle is started and the ECU 1 starts operation, data storage is started in each of the blocks 20a to 20c, as shown in FIG.
As for the block 20a, a record in which three types of data are stored is indicated by diagonal lines, vertical stripe lines, and stitch lines.

  Then, for example, as shown in FIG. 6B, when the storage condition of the block 20a is nearly expired (S30: YES in FIG. 4), only the latest data is stored in the block 20a. Move to the retreat block 21 (S38).

  There are a plurality of records indicated by diagonal lines, vertical stripe lines, and stitch lines in the block 20a shown in FIG. 6B, but there is only one record in the evacuation block 21. This is because only the latest data is saved among the same type of data recorded in the record indicated by the line of sight.

Further, at the time of saving, tail information α is added to the end of the data group composed of a plurality of data saved in the save block 21.
Thereafter, as shown in FIG. 6C, the inside of the block 20a is initialized. At this time, all the latest data and past data are erased collectively from the data in the block 20a (S52).

When this initialization is completed, as shown in FIG. 7A, the data saved in the save block 21 is returned to the block 20a (S54).
Thereafter, when data is similarly saved in the other blocks 20b to 20c, a plurality of data groups are stored by being divided into tail information α as shown in FIG. 7B.

  When the amount of data stored in the save block 21 exceeds a predetermined amount (S56: YES), all the data in the save block 21 are also erased collectively as shown in FIG. 7C. (S58).

  In this embodiment, by doing so, it is possible to prevent the number of times of erasure of the save block 21 from being extremely increased compared to the other blocks 20a to 20c, and the operation of the entire flash memory 20 cannot be guaranteed. It is preventing.

6). Characteristic operational effects of the present embodiment In the present embodiment, when the data stored in each of the blocks 20a to 20c is saved in the save block 21, the data group is placed at the end of the data group consisting of a plurality of saved data. Is appended with tail information α indicating that it is the tail.

  In this way, in the save block 21, the data group saved from each of the blocks 20 a to 20 c can be distinguished by the tail information α, and therefore the data group saved in the save block 21 is stored in the save source block. After returning to 20a to 20c, a plurality of data groups can be stored cumulatively without deleting the data groups one by one.

  If the plurality of data groups are erased collectively, the data block saved in the save block 21 is returned to the save source blocks 20a to 20c, and then the data block is erased one by one. The number of erasures for 21 can be reduced.

Therefore, according to the present embodiment, it is possible to prevent the entire flash memory 2 from being in a state where the operation cannot be guaranteed at an early stage because the number of times of erasure of the save block 21 exceeds the limit number where the operation cannot be guaranteed. In this embodiment, the case of saving the latest data has been described. However, the type of data to be saved is not limited to the latest data.

7). Correspondence Relationship The process of S18 corresponds to the flag change process of the present invention, and the processes of S34 and S36 correspond to the save determination process of the present invention.

The process of S52 corresponds to the first erase process of the present invention, the process of S54 corresponds to the recovery process, and the process of S58 corresponds to the second erase process.
The program stored in the ROM 12 that executes the storage process of FIG. 3 and the save process of FIGS. 4 and 5 corresponds to the data processing program of the present invention.

(Other embodiments)
The present invention is not limited to the above-described embodiment as long as it matches the gist of the invention described in the claims.

DESCRIPTION OF SYMBOLS 1 ... ECU 2 ... Flash memory 10 ... CPU 11 ... RAM 12 ... ROM 13 ... Interface part 14 ... Bus 20a-20c ... Block 21 ... Retraction block 200 ... Record

Claims (4)

A data processing method for a flash memory having a plurality of blocks for storing data, and a storage area in which a save block for saving data stored in the block is set,
Save processing (S38, S50) for adding tail information indicating the end of the data group to the end of the data group consisting of a plurality of data saved from one block;
A first erasing process (S52) for collectively erasing data stored in one block of the saving source after saving by the saving process;
After the erasure by the first erasure process, a recovery process (S54) for returning the data group delimited by the end information to one block of the save source;
A data processing method for a flash memory, comprising: The flash memory data processing method according to claim 1,
Second erasure process (S58) for collectively erasing data composed of a plurality of data groups stored in the save block and separated by the tail information
A data processing method for a flash memory, comprising: In the data processing method of any one of Claims 1-2,
In the case of storing data, a storage process (S10 to S22) that associates a save confirmation flag for identifying whether the data is to be saved with the data and stores the data in any of the blocks;
When the process of storing data is executed by the storage process, if the same type of data has been stored in the past, the save confirmation flag of the same type of data stored in the past is stored in the past. A flag change process (S18) for changing to a flag indicating that there is,
Run
In the evacuation process,
A data processing method for a flash memory, comprising: executing a process of saving the data in which the save confirmation flag is held in the flag change process among the data stored in one block to the save block .   A program for data processing of a flash memory, which executes the data processing method for a flash memory according to any one of claims 1 to 3.

Images