KR20070017985A - Method for accessing data, apparatus and recording medium for performing that method - Google Patents

Abstract

An object of the present invention is to guarantee a data transfer rate regardless of the performance of a memory card.

Data is recorded in incremental increments of data size, and a parameter indicating the data transfer efficiency is recorded in advance on the recording medium 101 whose data transfer efficiency varies with the data size. Next, the data access device 105 issues a parameter acquisition command to the recording medium 101. The recording medium 101 which received the parameter acquisition command transmits the said parameter. The data access device 105 selects an optimal data size by matching the received parameter with the data transfer efficiency required for data to be written and read. The data access device 105 then records and reads data from and to the recording medium 101 at the selected optimal data size.

Description

TECHNICAL FOR ACCESSING DATA, APPARATUS AND RECORDING MEDIUM FOR PERFORMING THAT METHOD}

The present invention relates to a technique for ensuring access performance to a memory card type recording medium.

Memory card type recording media (hereinafter referred to as memory cards) using nonvolatile memory have standardized physical shapes and interfaces such as SD card (registered trademark), compact flash (registered trademark), and memory stick (registered trademark), respectively. It is widely used in many devices including recording media of digital cameras and digital cameras.

BACKGROUND OF THE INVENTION As high speed and large capacity memory cards are put into practical use, recently, continuous snapshots of still images and portable devices for recording moving images and audio onto memory cards have also been commercialized (see Patent Document 1, for example). There are several principles of operation in nonvolatile memory. Here, a description will be given of a recording / reproducing technique of a memory card, taking the current mainstream semiconductor flash memory as an example.

First, in terms of write access, a semiconductor flash memory cannot be overwritten while erasing data to an address that has already been written, unlike a magnetic recording medium such as a hard disk. In order to realize an apparent overwriting, it is necessary to erase data already recorded once and then record the data again. However, whenever a part of recorded data is randomly rewritten, it is inefficient to erase the entire area of the storage area and rewrite the data in the entire area again. Therefore, a memory card having a structure in which the memory area of the memory card can be divided into a plurality of erase blocks and erase and write can be performed in units of erase blocks can be commercialized. In this memory card, it is possible to divide write data of arbitrary size into the size of an erase block and to fragment it, and to record the fragment data for each erase block.

When fragment data smaller than the erase block size is written to the semiconductor flash memory,

Temporarily read the data of the erase block containing the address to be written from the buffer.

After that, the erase block is erased.

Temporarily overwrite fragment data that should be written to the buffer.

Temporarily rewrite the data on the buffer into the erase block.

In other words, a so-called Read Modify Write operation is required.

Therefore, even if the fragment data is smaller than the erase block size, a write delay time equal to or greater than that of recording the data for the erase block size occurs. The write delay time indicates the time taken from generating a write / read processing command to ending the processing.

Fig. 7A schematically shows a relationship between the size of recording data for a memory card and the time taken for recording (write delay time). In Fig. 7A, the horizontal axis represents the write data size, and E represents the erase block size. The vertical axis represents the write delay time.

As is apparent from this figure, when the data recording and reading operation on the memory card is observed with the interface of the memory card as the cut surface, one write command is given to the memory card at a certain data size, and the data for the data size is given. The write delay time (i.e., the write processing time) until all of them are written is proportional to the number of erased blocks E that have written in addition to the overhead of the command processing. Therefore, the write delay time with respect to the increase in the size of the write data has a physical property of increasing substantially stepwise, as shown in Fig. 7A.

On the other hand, the read access is not limited by physical characteristics such as an erase block in the semiconductor flash memory like the write access. 7B schematically shows a relationship between the size of read data for a memory card and the time taken to read (read delay time). The horizontal axis | shaft and vertical axis | shaft of FIG. 7B are the same as that of FIG. 7A.

When the writing and reading operations of the data on the memory card are observed with the interface of the memory card as the cut surface, a read command is given to the memory card at a certain data size until the data for all the data sizes is read. The read delay time is the sum of the overhead of command processing and the transfer time in proportion to the read data size.

As apparent from Fig. 7B, when the data size to be read by one command is small, the overhead of the command processing cannot be ignored, so that the influence in the application of the memory card that requires a certain or higher speed for read access is required. Comes out.

Fig. 8 schematically shows the relationship between the overhead of command processing and the access data size of write or read. The overhead of the command processing does not depend on the access data size and requires almost constant processing time. Therefore, the smaller the access data size, the larger the overhead of command processing is.

In a memory card having such a recording / reproducing characteristic, it is designed to record or read at a data rate in consideration of sufficient margin to satisfy the required access performance. Therefore, in the current memory card read / write mechanism, the performance of the memory card cannot be used up to the limit.

<Patent Document 1> Japanese Unexamined Patent Publication No. 2003-32629

Problems to be Solved by the Invention

Today, with the improvement of image technology and the miniaturization of video devices, there is an increasing demand for recording and reproducing moving images on a memory card in a higher quality state. In order to meet these demands, the recording / reproducing speed of data on the memory card tends to increase. However, the erase block size varies depending on the memory card (semiconductor flash memory), and there is no unified standard.

The external specifications of the memory card are standardized in detailed specifications of physical shapes and interfaces such as an SD card (trademark), a compact flash (trademark), and a memory stick (trademark). However, in the internal specification of the memory card, the erase block size is not specified. As a result, it is not possible for each memory card to know what kind of internal data is written to the memory card through any internal operation for any record data size, and it is unknown from the data access device.

This often causes problems in high quality moving picture recording requiring high speed recording, and even in the case of memory cards of the same standard, cards capable of high speed recording and impossible cards are struggling in the market.

This causes, for example, the following problem. In digital still cameras, high-speed recording is required to improve high-speed continuous snapshot performance. In a digital still camera having such a characteristic, a temporary buffer memory capable of high-speed processing and having a memory capacity corresponding to the maximum number of continuous snapshots is provided in the camera. When shooting continuous snapshots, data is stored in a temporary buffer and then copied to a memory card to ensure high speed continuous snapshot performance. However, in this structure, since data is copied to the memory card after the shooting operation is completed, the memory card cannot be removed for a predetermined time after the shooting operation is completed. If the memory card is taken out of the digital still camera after a certain time has elapsed after the shooting operation is completed, the data is damaged during transfer (copying).

This problem when removing the memory card can be solved by writing directly to the memory card without using the temporary buffer memory. However, it is difficult to guarantee the lowest access performance in the current standard of the memory card. In order to guarantee the lowest access performance in the current standard, the performance of the memory card regarding the writing and reading speed may be increased. However, the minimum access performance required varies depending on the application. This leads to an increase in the cost of the memory card due to overspec.

In order to realize the recording / reproducing data rate required by the application and guaranteeing the access performance to the memory card without incurring an increase in the cost of the memory card due to overspecification, it is based on the internal specification information of the memory card. It is necessary to optimally control the size of data accessed for each memory card.

However, even in this way, even if the data size is optimally controlled, there is no guarantee that a data access device designed for today's memory card can be optimally written to a future memory card whose performance improvement is expected. Therefore, when the internal specifications of the memory card change, processing such as upgrading the software on the data access device side is required.

As described above, no corresponding technology is currently established for applications that require high-speed recording that maximizes the performance of the memory card.

Means for solving the problem

In order to solve the above problems, according to the present invention, a data access apparatus stores data in a recording medium whose data transfer efficiency varies depending on the data size when data is recorded and data is recorded in incremental increments. A data access device or method for recording and reading the data is configured as follows.

That is, in the present invention,

In the recording medium, parameters representing the data transfer efficiency are recorded before data is recorded in each of the data sizes on the recording medium. Then, in recording and reading data, the data access device first sends a parameter acquisition command to the recording medium. Subsequently, the recording medium which has received the parameter acquisition command transmits the parameter to the data access device. Furthermore, by setting the optimum data size at the time of data recording, by matching the parameter with the data transfer efficiency required for the data to be written and read by the data access device receiving the parameter do. Then, the data access device writes and reads data between the recording medium and the optimal data size.

Effect of the Invention

According to the present invention, it becomes possible to realize the optimum recording / reproducing access performance in accordance with the characteristics of the individual recording media. Furthermore, the recording / reproducing access performance can be guaranteed for future recording media without the need for software version upgrade on the device side.

1 is a configuration diagram of a memory card and a data access device according to the first embodiment.

2 is a diagram of a user area and a system area in a memory card.

3 is a correspondence table of the recording data size and the delay time recorded in the system area.

4 is a process flow of the memory card and the data access device according to the first embodiment.

5 is a configuration diagram of a memory card and a data access device according to the second embodiment.

6 is a process flow of the memory card and the data access device according to the second embodiment.

7A is a schematic diagram showing the relationship between the recording data size and the recording delay time.

7B is a schematic diagram showing the relationship between the recording data size and the recording delay time.

Fig. 8 is a diagram showing the relationship between the overhead of command processing and the access data size.

<Explanation of symbols for the main parts of the drawings>

101: memory card

102: command interpreting means

103: delay parameter

104: delay parameter reading means

105: data access device

106: delay parameter read command issuing means

107: data reproduction means

108: data recording means

109: means for selecting the optimal data size

202: storage area

203: user area

204 system area

601 memory card

602 command interpreting means

603: delay parameter

604: delay parameter reading means

605: means for selecting the optimal data size

607: means for issuing an optimum data size read command

608: data reproduction means

609: data recording means

(Embodiment 1)

A first embodiment of the present invention will be described with reference to FIGS. 1 to 5 as an example of a system configuration for real-time recording of DV system digital video data. Fig. 1 shows a relationship between a memory card type recording medium (hereinafter referred to as a memory card) and a data access device. The memory card 101, which is a recording medium, is a small size in which the data access device 105 is detachably mounted. As a card-type recording medium, it has a command analyzing means 102, a delay parameter 103 and a delay parameter reading means 104. Each means 102, 103, 104 is composed of software preinstalled on the memory card 101. In this embodiment, a means for reading a parameter from the delay parameter reading means 104 and transmitting it to the data access device 105 is configured.

The data access device 105 includes delay parameter read command issuing means 106, data reproducing means 107 by the designated data size, data recording means 108 by the designated data size, and an optimum data size selecting means 109. Has The delay parameter read command issuing means 106 constitutes " means for issuing parameter acquisition commands ", and the optimum data size selecting means 109 constitutes " means for selecting a data size at the time of data writing " The data reproducing means 107 and the data recording means 108 constitute " means for recording and reading data ". These means are constituted, for example, by software preinstalled in the data access device 105, and at least part of the data reproducing means 107 or the data recording means 108 is constituted by hardware.

The storage area 202 of the memory card 101 has a user area 203 and a system area 204 as shown in FIG. The system area 204 is an area for recording initial data at the time of manufacture of the memory card 201, and is an area in which the user cannot rewrite data. The delay parameter 103 is stored in advance in the system area 204. In the present embodiment, the storage area for parameters is configured in the system area 204.

3 is an example of a table (corresponding table) showing the relationship between the write data size and the write delay time for a memory card (specifically, a semiconductor flash memory mounted therein). When data is recorded from each of the data sizes from this table, a parameter representing the data transfer efficiency (in this embodiment, referred to as delay parameter 103) is configured. In Fig. 3, the average data rate is described, but the average data rate is not included in the table. 3 shows that the average data rate is determined uniformly by this parameter. The average data rate is information indicating how much data can be transferred (MByte / sec) every second, and is an example of information indicating data transmission efficiency.

As described above, the write delay time indicates a time taken from generating a write / read processing command and ending the processing. As shown in Fig. 3, the write delay time varies depending on the data size. The larger the data size, the longer the latency. Information relating to the time taken to record and read data from this recording delay time is configured.

The recording data size recorded as the delay parameter 103 is an integer multiple of the erase block size E of the memory card 101 (semiconductor flash memory), as is apparent from the characteristics shown in Figs. 7A and 7B. The memory card 101 is prepared with a delay parameter read command for reading the delay parameter 103.

Hereinafter, the operation and data access method of Embodiment 1 will be described with reference to the flowchart of FIG. 4. First, the delay parameter 103 is stored in advance in the memory card 101. After the above preprocessing, the memory card 101 is loaded into the data access device 105.

The DV method is a compressed recording method employed in most home digital movies, and data is transmitted at a data rate of 25 Mbit / sec = 3.125 MByte / sec. In order to record this data in real time on the memory card 101 without missing a coma, transfer efficiency for recording data without interruption at a rate of 3.125 MBytes for one second is required. The data access device 105 for recording the DV system digital video data in real time issues a delay parameter read command to the memory card 101 in time before the time point at which real-time data recording is required (S401). In the memory card 101, the command analyzing means 102 extracts a delay parameter read command, reads the delay parameter 103 from the system area 204 in accordance with the extracted command, and transmits it to the data access device 105. (S402). In the data access device 105, in the optimum data size selecting means 109, a recording data size that can achieve 3.125 MBytes / sec is selected from the received delay parameter 103. For example, assuming the value of the delay parameter 103 as shown in FIG. 3, the data access device 105 may record in 128 KB of data size (block) to guarantee the DV data recording data rate. Judgment is made, and the data size is selected as the optimal data size (S403).

Specifically, the optimum data size selecting means 109 calculates an average data rate value by dividing the recording data size constituting the delay parameter by the recording delay time (average data rate value = recording data size / recording delay time). ). Further, the optimum data size selecting means 109 selects as the optimal data size the minimum recorded data size that can achieve the desired average data rate defined in the data system to be transmitted or the like. In the above example where the desired average data rate is 3.125 MBytes / sec, the optimal data size selecting means 109 exceeds the average data rate but the recorded data size becomes the minimum average data rate (3.61 MBytes / sec in this case). 128 KB is selected as the optimal data size.

Based on this data size selection process, the data access device 105 (specifically, the optimum data size selection means 109) issues a write command to access the data recording means 108 at 128 KB. (S404). The data recording means 108 which has received the recording command executes the data recording processing on the recording data size 128 KB to the memory card 101 (S405). Accordingly, the DV system digital video data is always recorded in the memory card 101 with a recording data size of 128 KB.

As described above, in the first embodiment, even in the memory card 101 having different internal detailed specifications, it is possible to optimally select the size of the recording data that satisfies the required performance, thereby ensuring the recording access performance.

On the other hand, in the first embodiment, the recording of the DV system digital video data has been described as an example, but the present invention is not limited to the recording of the DV system digital video data. Regarding reading, the same is true to the point where the optimum data size is selected, and only the portions which access the reproduction by setting the optimum data size selected by the data reproducing means 107 are different.

(Embodiment 2)

5 and 6, Embodiment 2 of the present invention will be described. In addition, since the basic structure of Embodiment 2 is the same as that of Embodiment 1 shown in FIGS. 1-4, description regarding these structures is abbreviate | omitted.

5 shows a relationship between a memory card and a data access device. The memory card 601 has a command interpreting means 602, a delay parameter 603, a delay parameter reading means 604, and an optimum data size selecting means 605. Each of the means 602, 604, and 605 is made up of software pre-installed on the memory card 601. The data access device 606 has an optimum data size read command issuing means 607, data reproducing means 608 by the designated data size, and data recording means 609 by the designated data size. These means 606 to 609 are constituted of, for example, software that is preinstalled in the data access device 606. At least part of the data reproducing means 608 or the data recording means 609 is made of hardware.

The optimum data size read command issuing means 607 constitutes "means for transmitting to the recording medium information indicating the required data transfer efficiency required for data to be recorded and read in the data access apparatus". The data reproducing means 608 and the data recording means 609 are " data size at the time of data recording on the basis of information indicating the optimal data size transmitted by the recording medium which has received the information indicating the required data transmission efficiency. And means for performing data recording and reading to and from the recording medium at the data size thereof. In addition, the optimum data size read command constitutes "information indicating required data transfer efficiency".

The delay parameter reading means 104 includes " means for selecting an optimal data size at the time of data recording by receiving information indicating the required data transfer efficiency transmitted by the data access device and matching the parameter stored in the storage unit " &Quot; means for transmitting information indicating the selected optimal data size to the data access device ".

In the second embodiment, instead of the delay parameter read command in the first embodiment, an optimal data size read command having a desired delay time is created and stored in advance in the memory card 601. An optimal data size selecting means 605, which is a means for selecting a, is provided in the memory card 601, and differs from the first embodiment in these respects.

Hereinafter, an operation and a data access method of Embodiment 2 will be described with reference to the flowchart of FIG. 6. First, the delay parameter 103 is stored in advance in the memory card 601. After the above preprocessing, the memory card 601 is loaded into the data access device 606.

Subsequently, the data access device 606 for recording the DV system digital video data in real time issues an optimal data size read command taking the desired average data rate as a factor to the memory card 601 (S601). The optimal data size read command constitutes information indicating required data transfer efficiency, as described above. This command specifically shows the data transfer efficiency required in the data system to be transferred between the memory card 601. The optimum data size read command issuing means 607 generates and issues an optimal data size read command indicating the data size that is optimal for the data transfer from information such as a data system transferred between the memory card 601 and the like. .

In the memory card 601, an optimal data size read command is read based on the command interpretation of the command analyzing means 602. The delay parameter reading means 604 reads the delay parameter 603 recorded in the system area 204 in accordance with the read command that has been read (S602). The optimum data size selection means 605 calculates an average data rate value based on the read delay parameter 603. As in the first embodiment, the delay parameter 603 is constituted of, for example, a table (target table) indicating the relationship between the settable record data sizes and the delay time in each of these record data sizes.

The optimum data size selecting means 605 calculates the average data rate value by dividing the recording data size by the delay time (average data rate value = recording data size / delay time). In addition, the optimum data size selection means 605 selects as the optimal data size the minimum write data size that can achieve the desired average data rate specified by the argument in the optimum data size read command (S603). For example, if the desired average data rate specified by the argument is 3.125 MBytes / sec, the optimal data size selecting means 605 will exceed this average data rate but the minimum average data rate (in this case 3.61 MBytes / sec) 128 KB of recording data size is selected as the optimal data size.

The optimum data size selection means 605 transmits information indicating the selected optimal data size to the data access device 606. The data access device 606 is a return value of the optimum data size read command issued by the optimum data size read command issuing means 607, and records data size that guarantees recording at a desired data rate (in the example described above). , 128 KB) is received from the memory card 601 and obtained. Accordingly, the data access device 606 generates a recording command for accessing the data recording means 609 or the data reproducing means 608 at 128 KB (S604), and the data recording means 609 for receiving the recording command. ) Always accesses the DV system digital video data to the memory card 601 with a recording data size of 128 KB (S605).

As described above, according to the present invention, even in a memory card having different internal detailed specifications, it is possible to optimally select the recording data size that satisfies the required performance, thereby ensuring the recording access performance.

On the other hand, in the second embodiment, recording of DV video digital video data is taken as an example, but the present invention is not limited to recording DV video digital video data. Regarding reading, the same applies to the selection of the optimum data size, and only the part which accesses reproduction by setting the optimal data size selected by the data reproducing means 608 by the designated data size is different.

According to the present invention, a memory card having a non-volatile memory mounted therein as a recording medium can be used in applications where the access performance of recording / reproducing is required.

Claims (18)

When data is recorded in incremental incremental data size units, the data transfer efficiency varies with the data size when data is recorded, and when the data is recorded with each of the data sizes, a parameter representing the data transfer efficiency is recorded. A data access apparatus for recording and reading data on a recording medium, Means for issuing a parameter acquisition command to the recording medium; By matching the parameter transmitted by the recording medium which has received the parameter acquisition command with the data transfer efficiency required for data to be recorded and read by the data access device, an optimal data size is obtained during data recording. Means for selecting; Means for recording and reading data from and to the recording medium at a selected optimal data size Data access device comprising a. A recording medium in which data is recorded and read in units of data sizes that can be incrementally increased or decreased by the data access apparatus according to claim 1, A storage unit in which the parameter is recorded; Means for receiving the parameter acquisition command sent by the data access device, reading the parameter stored in the storage unit, and transmitting it to the data access device. Recording medium comprising a. The data access apparatus according to claim 1, wherein the parameter is a table in which the data size and the data size correspond to each other information on the time taken to write and read data to and from the recording medium. The recording medium of claim 1, wherein the recording medium is a semiconductor memory, And the data size is an integer multiple of the erase block size of the recording medium. The data access apparatus according to claim 1, wherein the recording medium is a card-type recording medium detachably attached to the data access apparatus. When data is recorded in incremental increments of data size and at the same time data is recorded, the data transfer efficiency varies according to the data size, and when data is recorded in each of the data sizes, a parameter indicating the data transfer efficiency is recorded. A data access apparatus for recording and reading data on a recorded recording medium, Means for transmitting to the recording medium information indicative of necessary data transmission efficiency required for data to be recorded and read in the data access apparatus; The data size at the time of data recording is set on the basis of the information indicating the optimal data size transmitted by the recording medium which has received the information indicating the required data transfer efficiency, and the data size is used as the data size. Means for writing and reading data Data access device comprising a. A recording medium in which data is recorded and read in units of data sizes that can be incrementally increased or decreased by the data access device according to claim 6, A storage unit in which the parameter is recorded; The optimum data size is selected at the time of data recording by receiving the information indicating the necessary data transmission efficiency transmitted by the data access device and matching the information indicating the necessary data transmission efficiency with the parameter stored in the storage unit. Means for doing so; Means for transmitting to the data access device information indicative of the selected optimal data size. Recording medium comprising a. The data access apparatus according to claim 6, wherein the parameter is a table in which the data size and the data size correspond to each other information on the time taken to write and read data to and from the recording medium. The recording medium of claim 6, wherein the recording medium is a semiconductor memory; And the data size is an integer multiple of the erase block size of the recording medium. 7. The data access apparatus according to claim 6, wherein the recording medium is a card-type recording medium detachably attached to the data access apparatus. A data access method in which a data access device writes and reads data on a recording medium whose data transfer efficiency varies in accordance with the data size when data is recorded at the same time as data is recorded in incremental increments. Recording a parameter indicative of data transfer efficiency in advance when data is recorded in each of the data sizes on the recording medium; Transmitting, by the data access apparatus, a parameter acquisition command to the recording medium in recording and reading data; The recording medium receiving the parameter acquisition command sending the parameter to the data access device; Setting the optimum data size at the time of data recording by matching the parameter to the data transfer efficiency required for the data to be written and read by the data access device receiving the parameter; ; The data access device performing recording and reading of data between the recording medium and the optimal data size set; Data access method comprising a. 12. The data access method according to claim 11, wherein the parameter is a table in which the data size and the data size correspond to each other information on the time taken to record and read data to and from the recording medium. 12. The apparatus of claim 11, wherein the recording medium is a semiconductor memory, And the data size is an integer multiple of the erase block size of the recording medium. 12. The data access method according to claim 11, wherein the recording medium is a card-type recording medium detachably attached to the data access device. A data access method in which a data access device writes and reads data on a recording medium whose data transfer efficiency varies in accordance with the data size when data is recorded at the same time as data is recorded in incremental increments. Recording a parameter indicative of data transfer efficiency in advance when data is recorded in each of the data sizes on the recording medium; Transmitting, by the data access apparatus, information indicating necessary data transfer efficiency required for data to be recorded and read in the data access apparatus, to the recording medium in performing data recording and reading; Selecting, by the recording medium which has received the information indicating the required data transmission efficiency, an optimal data size during data recording by matching the information indicating the required data transmission efficiency with the parameter; Transmitting information indicating the optimal data size selected by the recording medium to the data access device; The data access device, having received the information indicating the optimal data size, sets the data size at the time of data recording based on the information indicating the optimal data size, and records the data with the recording medium. Step of reading Data access method comprising a. 16. The data access method according to claim 15, wherein the parameter is a table in which the data size and the data size correspond to information on the time taken to write and read data to and from the recording medium. 16. The recording medium according to claim 15, wherein the recording medium is a semiconductor memory, And the data size is an integer multiple of the erase block size of the recording medium. 16. The data access method according to claim 15, wherein the recording medium is a card-type recording medium detachably attached to the data access device.

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