JP2007219793A - Writing method of flash memory - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure the number of writing guarantees necessary when user adjustment data are stored in a flash memory used for a program memory. <P>SOLUTION: Use efficiency of the memory is improved in recording of the user adjustment data so that a variable length record organized by a plurality of memory blocks smaller than a delete unit of the flash memory 5 is used. Further, an effective data management function is provided for the records scattered around a plurality of delete blocks so that the number uniquely identifying a record is assigned. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to management of data for a non-volatile memory in a control device such as a display display device or a digital still camera in which a microprocessor is incorporated for control.

  In a control device in which a conventional microprocessor is incorporated for control, as disclosed in Patent Document 1, as data held using a nonvolatile memory capable of holding data even when power is not turned on, (1) Data that is written only once in the manufacturing process of the program main body, etc. (2) Process adjustment data that is written by adjusting only in the manufacturing process, (3) User adjustment data that changes frequently due to user operations, etc. There are three types. In particular, a portable device based on battery driving cannot always secure a stable power supply, and thus a mechanism for saving the state regardless of whether or not power is supplied is indispensable for improving operability.

  Conventionally, as a nonvolatile memory that holds the setting state of the apparatus, an EEPROM that can be electrically written and read and that holds the written data even during the power-off period has been used. The number of times data is rewritten in the EEPROM or flash memory for storing user adjustment data needs to be guaranteed that no error occurs even if data is rewritten, for example, 1 million times during the design lifetime of the apparatus.

Therefore, in Patent Document 1, when data is managed by a fixed-length record different from the erase block of the flash memory, and the size of the fixed-length record is smaller than the size of the erase block, the number of erases of the flash memory is reduced. The write life of flash memory has been extended for small data recording that is frequently rewritten.
JP 2002-7221 A

  However, in the method for increasing the guaranteed number of write operations of the flash memory described in Patent Document 1, since the data is managed by dividing it into fixed-length records, the memory utilization efficiency is low, and user adjustment data is collectively collected. The moment when all the effective data is lost when trying to control the number of erases per erase block by allocating multiple erase blocks to the storage area for user adjustment data for deletion and distributing writing and erasing. When a block that is in use is determined by a specific empty determination area, the area itself falls into a state where it cannot be rewritten due to the rewrite life of the flash or the like (bit clear cannot be performed, etc.) There are problems such as the entire block becoming unavailable.

  The present invention is equivalent to the case where a separate EEPROM is prepared for storing conventional user data when storing the control program and frequently-adjusted user adjustment data in the same flash memory. This is to ensure the number of write guarantees described above.

  The method of the present invention is a flash memory writing method in a control device including a flash memory in which a data storage area is divided into sectors, the data can be erased in the sectors, and the data can be written in storage blocks smaller than the sectors. Then, the user adjustment data that changes according to the user's operation is divided into one or more variable numbers of the storage blocks, and each time the user adjustment data is updated, a unique identifiable number is assigned to the variable number of storage blocks. In addition, the user adjustment data is sequentially recorded in the unwritten area.

  Further, when a plurality of sectors are allocated to the area for storing the user adjustment data and there is no unwritten area in the sector, the sector storing the user adjustment data recorded last is stored. The next sector may be erased and the user adjustment data may be written again.

  In addition, when the uniquely identifiable number reaches the limit of the range that can be expressed, it is possible to reuse the duplicated number by clearing the bits of the number part of all the other recorded storage blocks. You may make it do.

  Since the present invention writes to a variable number of storage blocks, the erasing frequency can be reduced as compared with the case of writing with a conventional fixed-length record. In addition, while the number of guaranteed writes is higher than when writing and erasing to a single sector, the user adjustment data area is exhausted and all valid data is temporarily lost when erasing all at once. The problem that has occurred can also be solved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of a control device for realizing a flash memory writing method according to an embodiment of the present invention. This control device performs processing by a central processing unit (hereinafter referred to as CPU) 1 that performs various operations and processing, a flash memory 5 that is a non-volatile memory that mainly stores programs and data executed by the CPU 1, and is mainly processed by the CPU 1. The RAM 4 is a readable / writable volatile memory for storing data, the peripheral device 3 mainly provides an I / O function, and the bus 2 that connects them. In general, the flash memory 5 and the RAM 4 are collectively referred to as a main memory, a main memory, or a system memory.

  FIG. 2 is a conceptual diagram showing a memory arrangement on the flash memory 5 in the first embodiment. In the area of the flash memory 5, program code 8 executed by the CPU 1, constant data 9 similarly referred to when executing the program, factory adjustment data 10 set during the manufacturing process and referred to when executing the program, user User adjustment data 11 that changes based on the operation is placed. Of these, data other than the user adjustment data 11 is written once by factory shipment and rarely rewritten, so it is arranged in the fixed data area 6 where the fixed data is arranged, and the user The adjustment data 11 is arranged in the variable data area 7. The fixed data area 6 and the variable data area 7 are merely determined conceptually on the flash memory 5, and the characteristics of the flash memory 5 are the same. Accordingly, the fixed data area 6 is treated as an area where rewriting is not performed (an area like a write-once memory), and the variable data area 7 is treated as an area where rewriting is performed (an erasable / writable area). Each of the flash memory 5 includes a plurality of continuous sectors.

  Here, the data recording area of the flash memory 5 is divided into sector units, and the sectors serve as erase units. Writing is performed in units (recording blocks) smaller than sectors. Further, when the user adjustment data 11 is written in the variable data area 7, it is recorded in a variable-length record comprising a number of recording blocks that are variable in accordance with the data capacity. A variable-length record is given a record number that can be uniquely identified.

  FIG. 3 is a flowchart showing a recording process for recording the user adjustment data 11 in the first embodiment. FIG. 4 is a flowchart showing processing in the record number initialization processing (step 101) in FIG.

  The operation will be described below with reference to FIGS.

  Normally, the recording process of the user adjustment data 11 occurs by a menu operation by the user or a power-off process. At that time, the user adjustment data 11 is written in the form of a record. Each record starts with a 16-bit (2 byte) record number, followed by the record length, the record data body, and finally the data validation. Ends with checksum data. When the recording process of the user adjustment data 11 occurs, the system activation and the user interface part are already in operation and are necessary for the operation of these systems. Therefore, the latest (last) user adjustment data 11 is stored. Information such as the record to be shown, the record number, and the sector position is known. The latest (last) user-adjusted data that can be found by a simple linear search among the records whose validity is confirmed by the checksum and having the largest record number among the record numbers 1 to 65534 All are obvious from the record that indicates.

  First, a number obtained by adding 1 to the latest record number is set as the number of the next record, and it is determined whether or not the next record number indicates an unused area (step S100). Next, when the next record number is a number indicating an unused area, a record number initialization process (step S101) shown in FIG. 4 is performed. In other cases, it is determined whether or not the remaining amount of the unused area on the sector where the latest record exists is larger than the record to be added (step S102). The next sector assigned to the adjustment data storage area is erased, and the recording position of the next record is set to the head (step S103). If the unused area is not insufficient, the recording position of the next record is naturally the head of the unused area. A new record is written in the format of “record number (2 bytes), record length (1 byte), record data (variable length), checksum (1 byte)” (step S104), and the record additional recording process ends.

  Among these, the record number initialization process (step S101) determines whether the initialization process has been completed in order from the first sector of the user adjustment data recording area as shown in FIG. 5 (step S105). It is determined whether the record is an unused area (number is 0 to 65534) in order from the first record (step S106). If it is a used (valid) record, the record number is rewritten to 0 (step S108), and the next record (Step S109). If an unused record is found in the unused area determination step in step S106, the process proceeds to the next sector (step S107), and is repeated until there are no more unprocessed sectors.

  As described above, according to the present embodiment, since writing is performed on a variable number of storage blocks, writing can be performed more efficiently and erasing frequency can be reduced as compared with the case of writing with a conventional fixed-length record. I can do it. In addition, while the number of guaranteed writes is higher than when writing and erasing to a single sector, the user adjustment data area is exhausted and all valid data is temporarily lost when erasing all at once. The problem that has occurred can also be solved.

  In addition, when assigning numbers to new records simply in ascending order, when the record number reaches the limit of the representable range that exists in the data structure, it becomes impossible to identify the latest number by cycling through the number, In order to avoid this, if all bits are “1”, the numbers are assigned as unused areas, other areas are assigned as used areas, and when all bits are “0”, invalid record numbers are assigned. The number can be reassigned by rewriting all the valid record numbers to invalid record numbers. That is, when a new record number cannot be generated, the record numbers of all existing valid records can be rewritten so that the record numbers can be reused.

  In addition, when multiple sectors are allocated for recording user adjustment data, the size of the next record is compared with the unwritten area in the sector where the last record exists for each additional recording of the variable-length record. If the unwritten area is insufficient, the next sector (however, if it is the last sector column) is erased, and the record is written to the next sector.

  As described above, according to the flash memory writing method of the present invention, the number of erasures per sector can be greatly reduced and the number of write guarantees can be substantially increased as compared with the prior art. Can be provided.

  The flash memory writing method according to the present invention has an advantage that the utilization efficiency and fault tolerance of the flash memory can be improved at the same time without dropping new costs, and is useful for a control device using a nonvolatile memory.

The block diagram which shows the structure of the control apparatus which implement | achieves the writing method of the flash memory by Embodiment 1 of this invention Conceptual diagram showing memory layout in the same control device Flow chart showing recording process of user adjustment data in the control device Flowchart showing record number initialization processing in the same control device

Explanation of symbols

1 CPU
2 Bus 3 Peripheral device 4 RAM
5 Flash memory 6 Fixed data area 7 Variable data area 8 Program code 9 Constant data 10 Factory adjustment data 11 User adjustment data

Claims (3)

A method of writing a flash memory in a control device comprising a flash memory in which a data storage area is divided into sectors, erasable in units of sectors, and writable in units of storage blocks smaller than the units of sectors,
Dividing user adjustment data that changes according to user operations into one or more variable number of the storage blocks,
A flash memory writing method in which each time the user adjustment data is updated, a uniquely identifiable number is assigned to the variable number of storage blocks, and the user adjustment data is sequentially recorded in an unwritten area. When a plurality of sectors are allocated to the area for storing the user adjustment data, and an unwritten area does not exist in the sector, the sector that stores the user adjustment data recorded last is stored. 2. The flash memory writing method according to claim 1, wherein a sector is erased and the user adjustment data is written again. When the uniquely identifiable number reaches the limit of the range that can be expressed, the duplicated number can be reused by clearing the bit of the number part of all the other storage blocks already recorded. Item 2. A flash memory writing method according to Item 1.

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