JP2007109148A - External storage - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an external storage provided with high secrecy of information or fast operation. <P>SOLUTION: Inside a USB memory 10 to which a power supply unit 11 is connected, for example, are provided with a controller 102, a dynamic random access memory (DRAM) 103 as a storage medium, a timer battery 104, a timer 105, and a remaining time display LED 106. The controller 102 is provided with a function for performing normal refresh operation following the timer 105 with respect to the DRAM 103 and a function so as to stop the refresh operation when a time of the timer 105 has reached a preset time. Thus, even when the USB memory 10 is stolen or lost while being carried, for example, internal storage data are automatically deleted. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an external storage device, and more particularly to a technique effective when applied to a portable external storage device such as a USB memory.

  According to a study by the present inventor, the following can be considered as the technology of the external storage device.

  For example, portable external storage devices represented by USB memories and memory cards are widely known. Such an external storage device includes a nonvolatile memory such as a flash memory. For example, a USB memory is used by being inserted into a USB port of a personal computer (PC) or the like, and power is supplied from the PC via the USB port. And in actual use, when you want to use the data stored in one PC with another PC, download the data stored in one PC to the USB memory, carry the USB memory, and insert it into the USB port of another PC. Such work is performed.

  By the way, as a result of the study of the technique of the external storage device as described above, the following has been clarified.

  For example, the external storage device as described above may be lost or stolen while being carried. In recent years, all information has been converted into electronic data, and there are cases where, for example, in-house confidential information is included. However, once an external storage device is obtained by another person, the internal information is easily leaked.

  Further, since the external storage device as described above uses a flash memory or the like, its operation speed (especially erase / write speed) is as slow as about 5 MB / s, for example, when writing a large amount of data. Is required. In some cases, the limitation of the number of times of writing may be a problem.

  Therefore, an object of the present invention is to provide an external storage device having high information confidentiality. Another object of the present invention is to provide a high-speed external storage device.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

  An external storage device according to the present invention is used by being connected to an information processing device such as a PC and can be carried. A power supply means, a controller that operates by supplying power from the power supply means, a storage A medium and a timer are included. The controller has a function of erasing data stored in the storage medium when the timer reaches a preset time.

  As a result, for example, even if the external storage device is stolen or lost while the data is being carried between two PCs using the external storage device, the stored data can be automatically deleted. Become. This makes it possible to protect the confidentiality of the stored data.

  Furthermore, a password protection function may be provided for reading or writing access to stored data. Then, even if the external storage device is placed in a state where it can be read by others before it is erased, it is more likely to reach the time it is erased while breaking the password, thus protecting confidentiality. Can be improved.

  By the way, as a storage medium of such an external storage device, for example, a volatile DRAM may be used. In this case, the stored data can be erased by stopping the refresh operation when the timer reaches the set time. In addition, if the power supply capability from the power supply means is reduced or stopped with the passage of time, the erase operation itself is impossible in a flash memory or the like, whereas in the DRAM the data naturally disappears, so the stored data Can be protected. Furthermore, the use of a DRAM makes it possible to increase the speed of the external storage device.

  The DRAM is preferably composed of a plurality of DRAM chips, and data can be stored by designating individual DRAM chips from the PC. Furthermore, in this case, it is desirable that the controller can set a time for stopping the refresh operation for each DRAM chip. As a result, for example, data including confidential matters that are desired to be deleted when time elapses can be stored separately from general data that is not, and flexibility in practical use is increased. Further, in this case, it is not necessary to perform a refresh operation on the DRAM chip having no stored data, thereby realizing reduction in power consumption.

  If the effect obtained by the representative one of the inventions disclosed in the present application is briefly described, it is possible to improve the confidentiality of data stored in the external storage device. In addition, the speed of the external storage device can be realized.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

  FIG. 1 is a block diagram showing an example of the configuration of an external storage device according to an embodiment of the present invention. The external storage device shown in FIG. The external shape of the USB memory 10 is provided with an input / output connector 100 and a power connector 101. The USB memory 10 includes, for example, a controller 102, a dynamic random access memory (DRAM) 103, a timer battery (power supply means) 104, a timer 105, a remaining time display LED 106, and the like. Yes.

  The input / output connector 100 has, for example, a host connector shape in a USB connector, and can be connected to a USB port of an information processing apparatus represented by a PC. The power connector 101 is, for example, a convex connector, and a power supply device (power supply means) 11 comprising a battery or a rechargeable battery provided with a concave power connector 110 can be connected to this connector. .

  The power supply device 11 includes a convex power connector 111 in addition to the concave power connector 110. The power connector 111 can be connected to, for example, a large-capacity power supply device 12 having a concave power connector 120 as necessary. Note that the large-capacity power supply device 12 can be directly connected to the power supply connector 101 of the USB memory 10 via the power supply connector 120. In addition, a convex power connector 121 is also provided here for the large-capacity power supply device 12.

  As described above, the power supply apparatuses 11 and 12 can be added to or replaced with the power supply connector 101 of the USB memory 10 as necessary. The power supply devices 11 and 12 may be rechargeable or not, but the rechargeable is preferable from the viewpoint of convenience. In the case of a rechargeable power supply device, a typical example is a lithium ion type. In this case, it is desirable to have a function for preventing overdischarge and overcharge inside.

  Here, a main feature of the external storage device of FIG. 1 is that a DRAM 103 is used as a storage medium instead of a flash memory or the like. In addition, when the USB memory 10 is carried, the power supply devices 11 and 12 are provided or can be connected to hold the storage data of the volatile DRAM 103. And since such a power supply device is necessary, the volatility characteristic that is considered to be inherently undesirable for a portable memory is actively used to improve the confidentiality of data. It is done. Hereinafter, description will be made including details of these features.

  The USB memory 10 operates by receiving power supply from the power supply devices 11 and 12 when carried, and operates by receiving power supply from the USB port of the PC when connected to a PC or the like. When the rechargeable power supply devices 11 and 12 are used, it is preferable that the power supply devices 11 and 12 can be charged via the USB port when connected to a PC or the like. The controller 102 includes, for example, a small-capacity nonvolatile memory 102a such as an EEPROM in the same chip. The controller 102 has a function of controlling data transfer based on the USB protocol between the input / output connector 100 and the DRAM 103, and further controlling the refresh operation of the DRAM 103 using information of the timer 105.

  The function of this refresh operation is roughly divided into two types. One of the functions is to perform a normal refresh operation for holding stored data in the DRAM 103 such as distributed refresh using the timer 105. The other function is a characteristic function. For example, when the user sets a time in advance in the nonvolatile memory 102a or the like and the controller 102 reaches the set time while referring to the timer 105, the refresh operation is stopped. To do. That is, when a predetermined time is reached, the data stored in the DRAM is erased.

  As a result, even if the USB memory 10 is lost or stolen while being carried, if the stored data is erased, it will not leak at all, and confidentiality can be maintained. However, a leakage problem occurs before the set value of the timer 105 is reached, but this problem is solved to some extent by using a setting function such as a password for the controller 102 as will be described later with reference to FIGS. Is possible. And such a setting is preserve | saved at the non-volatile memory 102a in the controller 102, for example.

  The remaining time display LED 106 is controlled by the controller 102 and displays, for example, the remaining time until data stored in the DRAM 103 as described above is erased. Here, instead of the LED 106, notification may be made by, for example, an audio reproduction function. The timer battery 104 is provided to always supply power to the timer 105. Thus, it is possible to prevent a malfunction of the timer when the voltages of the power supply devices 11 and 12 are lowered, and it is not necessary to reset the timer time even if the power supply devices 11 and 12 are cut off.

  The DRAM 103 is composed of, for example, a plurality of chips (A, B, C, D). The plurality of chips are managed by the controller 102 as folders. Therefore, for example, when data is stored only in the chip A, the refresh operation for the chips B to D for holding the stored data becomes unnecessary, and the power consumption can be reduced. Of course, the DRAM includes a synchronous DRAM and the like.

  As described above, for example, the following effects can be obtained by using the external storage device as shown in FIG.

  (1) First, a small and lightweight external storage device that is convenient to carry can be realized. Since a volatile memory such as a DRAM is used as the storage medium, high speed operation (for example, 60 MB / s) is possible for both writing and reading. Furthermore, it is possible to increase the confidentiality of data by using this volatile characteristic as described above. Note that it is possible to easily increase the capacity of the external storage device by using a highly integrated DRAM.

  (2) Since the power supply device can be removed, replaced, and added to the external storage device, for example, when carrying it for a short time, a small power supply device is attached to increase the convenience, Then, it is possible to use a large-capacity power supply device or add a power supply device. This makes it possible to flexibly cope with any actual operational situation. For example, even if the power supply is likely to be cut off, if additional power supplies are added, power can be continuously supplied to the external storage device, so the stored data is lost unintentionally due to the interruption of power supply. Can be prevented.

  In this example, the USB memory is used as an example of the external storage device, but the present invention is also applicable to a PC card, a memory card, and the like. In this case, the input / output connector 100 is, for example, a terminal for a CF (CompactFlash) card or a terminal for an MMC (MultiMediaCard (registered trademark)) card, and the controller 102 performs data input / output processing according to each standard. Will do. The input / output connector 100 is also advantageously a fire wire, for example, in order to make use of the high-speed operability of the DRAM.

  FIG. 2 is a block diagram showing another example of the configuration of the external storage device according to the embodiment of the present invention. In the external storage device shown in FIG. 2, the USB memory 20 includes an input / output connector 200 and a power connector, and the power devices 21 and 22 can be connected to the power connector, as in the configuration of FIG. FIG. 2 shows a state where the power supply device 21 is connected to the power connector. The USB memory 20 also includes a controller 202, a DRAM 203, a timer battery 204, a timer 205, and a remaining time display LED 206 as in the configuration of FIG. It is the composition provided with. The flash memory 207 is also composed of a plurality of chips (E, F, G, H), and is managed as a folder, like the DRAM 203.

  As described above, a volatile DRAM and a non-volatile flash memory are provided as storage media, and data that is not to be erased even when the power is turned off can be stored by selectively using which one to store. Further, for example, it is also possible to use such that data that does not particularly require confidentiality management is stored in the flash memory 207 and data that requires confidentiality management is stored in the DRAM 203. In the case of a configuration including the flash memory 207, the controller 202 may be configured not to include the nonvolatile memory 202a. As a result, the controller 202 can be simplified and downsized.

  Next, an example of the setting function provided in the controller described in FIG. 1 will be described. FIG. 3 is a process flow diagram showing an example of a setting procedure performed for the controller in the external storage device of FIGS. 1 and 2. This process flow diagram shows, for example, software processing that the PC performs on the USB memory in a state where the USB memory is inserted into the PC. The software program is, for example, a CD-ROM attached to the USB memory. It is installed on the PC from The controller has functions necessary for various settings performed in the processing flow. Hereinafter, the processing flow of FIG. 3 will be described assuming that the USB memory 10 of FIG. 1 is used, but the same applies to the case of using a memory card or the like.

  First, when the USB memory 10 is inserted into the PC (S301), it is recognized and an icon indicating the USB memory 10 is displayed on the PC screen (S302). Here, when the icon of the USB memory 10 is clicked, a screen for inputting a password (PW) is displayed (S303). On the other hand, when the icon of the USB memory 10 is right-clicked, a pop-up menu is displayed, and there is a PW change in the menu (S304). When this is selected, the PW change screen appears and the PW can be changed (S305). When the PW is changed, the PW is stored in, for example, the nonvolatile memory 102a in the controller 102.

  Next, when the PW input screen is displayed in S303, if the PW is input, the determination is performed. If the PW collation is obtained, the user is regarded as a user and the folders A, B, C, and D are displayed. An icon indicating each is displayed (S306). This PW determination is performed by the PC reading the PW from the nonvolatile memory 102a in the controller 102, for example, and comparing it with the inputted PW. On the other hand, if the PW verification is not obtained, it is recognized as a guest (S307), and processing as described later in FIG. 4 is performed. Note that the icons of the folders A to D correspond to the chips A to D of the DRAM 103 as described in FIG.

  Here, when one of the displayed folders A, B, C, and D is right-clicked, a pop-up menu is displayed, which includes “file management setting display / edit” (S308). When this is selected, items that can be set in various ways are displayed (S309). That is, the displayed items can be set for each folder. The settable items in S309 include, for example, the following items.

  [1] Erase reservation Y / N: In this item, it is possible to select whether or not to erase the data in the folder when the reservation time comes.

  [2] Erase time: In this item, the time to execute erasure is input when [1] erase reservation is YES. Alternatively, the setting may be “after, how many days / hours / minutes”. That is, for example, before carrying, a deletion is reserved a little after the scheduled reaccess time. Even if it is stolen or lost during the travel process, data will be lost after the scheduled time, and there is little risk of data leakage. Since it takes time to break the PW and the encryption, the scheduled deletion time is set so that the data is erased before that.

  When such erasure setting is performed, the controller 102 monitors the time of the timer 105 (for example, every second) and controls the remaining time display LED 106. Until the scheduled time is reached, for example, the self-refresh state in the folder (= the chip) of the DRAM 103 is held. On the other hand, when the time of the timer 105 exceeds the scheduled time, the self-refresh of the chip is stopped. As a result, a part of the data in the chip is volatilized within a few seconds and becomes unusable.

  [3] Read permission Y / N: In this item, it is possible to set whether or not the icon of the file in the folder is displayed for the guest and can be read. If NO, no icon is displayed. Therefore, if the read permission is set to NO, a person other than himself who does not know the PW cannot see the file as a guest, so the confidentiality of the file can be protected. Here, even if an attempt is made to break the PW, substantial protection can be achieved by using the erase function [1] so that the PW is erased before that. On the other hand, the user always has READ permission YES.

  [4] Read permission inversion Y / N: In this item, it is possible to select whether or not to reverse the read permission setting for the guest at the scheduled time. Here, two types of setting are possible: reversal from permission to non-permission and reversal from non-permission to permission. The reversal from permission to non-permission is set so that, for example, when a guest is carried and viewed, it changes from permission to non-permission slightly after the guest's scheduled access time. As a result, even if theft or loss during carrying, it can be protected by PW over time. However, in this case, it will be seen that the PW is broken before time passes. On the other hand, the reversal from non-permission to permission can be used for, for example, a problem paper for school tests. That is, the test is returned from the disapproval to the permit at the test start time so that the student can see the problem. At test end time, the test is reversed from permit to disallow and the test is forcibly terminated.

  [5] Read permission reversal time (1) (2): First, in the item (1), when [4] is YES, the time for reversing the read permission setting is input. Alternatively, the setting may be “after, how many days / hours / minutes”. In the item (2), it is possible to input a time to reverse (that is, return) again after (1). If it is blank, no return will occur. In addition, when the dates of (1) and (2) are blank and only the time is reached, they are reversed and returned every day. Furthermore, it is possible to specify the day of the week to cause inversion and return, and to invert and return to the same day every week.

  As an example of this use, for example, it is assumed that daily work is performed on a file with Read permission YES on the guest screen. Every day, if you set the READ permission to reverse from YES to NO near the time of return and set the READ permission to return from NO to YES near the time of coming to work, others will remove the memory from the PC and see the contents after returning home You can reduce fear. In addition, by setting the read permission to return from NO to YES only on Monday through Friday, it is possible to reduce the risk that another person will remove the memory from the PC and view the contents on the weekend.

  [6] Write permission Y / N: In this item, it is possible to set whether to overwrite or newly write a file in the folder. If it is not allowed, the user can not write in addition to the guest. That is, it is possible to prevent erroneous overwriting by disabling the user.

  [7] Write permission inversion Y / N: In this item, it is possible to select whether or not to reverse the write permission setting at the scheduled time.

  [8] Write permission inversion time (1) (2): In this item, when [7] is YES, the time of inversion and reinversion of Write permission is set as in [5]. This function can be used for, for example, a school test answer sheet. When the test start time is reached, the permission is returned from the write disapproval to the permission. When the test end time is reached, the permission is reversed to the disapproval, and the test is forcibly ended.

  The setting conditions as described above are stored in, for example, the nonvolatile memory 102a in the controller 102. However, depending on circumstances, it is also possible to store such setting conditions and PW in a register in the DRAM 103 or the controller 102. In this case, the non-volatile memory 102a in the controller 102 is not necessary. However, when the data stored in the DRAM 103 is erased by the above-described erasure reservation, it is necessary to set the PW and each folder each time. Therefore, from the viewpoint of convenience, it is desirable to store both the PW and each setting condition in the nonvolatile memory 102a. After such setting conditions are stored, the controller 102 controls access to the DRAM 103 based on the above-described YES / NO setting conditions and referring to the time by the timer 105 depending on the setting conditions. .

  Next, in the state where the above-described settings have been made, when the icons of the folders A to D displayed in S306 are clicked, a window is opened and the file icons and directory icons contained therein are displayed (S310). ). After clicking the file icon, since the user knows the PW here, the file can be opened and edited (S311). When a save operation is performed after editing, if the above-mentioned [6] Write permission is YES, the file can be overwritten (S312). At the time of overwriting, the erasure schedule presence / time of the folder to which the file belongs, the read permission / permission reversal schedule / the time, the write permission / permission reversal schedule / the time stored in the nonvolatile memory 102a are displayed, and OK is displayed. When clicked, overwriting is executed (S313). On the other hand, if the write permission is NO, a message is output and the process returns (S312).

  Further, in the state where the icons of the folders A to D are displayed in S306, by dragging a file or directory on the PC to any folder, the folder (that is, any one of the chips A to D of the DRAM 103). It is possible to store new data. This case is also handled in the same manner as the file saving described above. If the write permission of the folder is Yes (S314), the file storage setting information such as the set deletion schedule is displayed, and then the data is stored. It becomes possible (S315). On the other hand, if the write permission is NO (S314), a message that cannot be written is displayed and the screen returns to the original S306.

  As another function, the controller 102 has a function of controlling the presence or absence of the refresh operation for each chip A to D based on the presence or absence of the storage data for each chip A to D of the DRAM 103 during storage data holding. Prepare. The presence / absence of stored data for each of the chips A to D can be determined by, for example, the controller 102 monitoring whether or not the erasure or write command is generated for each of the chips A to D. As a result, it is not necessary to perform a refresh operation on a chip having no stored data.

  In FIG. 3, the processing flow for a user who knows the password has been described. However, for a guest who does not know the password (that is, in the case of S307), for example, the processing flow is as shown in FIG. . FIG. 4 is a process flow diagram showing an example of a process when passwords do not match in the process flow of FIG. As described below, the guest is given access authority based on the conditions set by the user in step S309 in FIG.

  4, first, after inserting the USB memory 10 into the PC as in FIG. 3 (S401), an icon indicating it is displayed on the PC (S402). At this time, if the icon is right-clicked, a password (PW) change screen can be selected from the pop-up menu. However, since it cannot be changed unless the previous PW is known, the PW cannot be changed by the guest (S404, S405). On the other hand, when the icon indicating the USB memory 10 is clicked, a password input screen is displayed (S403). In this case, since the passwords do not match, the guest screen is displayed (S406).

  The guest screen in S406 is a screen on which an icon for each folder is displayed as in S306 of FIG. 3 described above. However, even if right-clicking is performed on this screen, since it is a guest, various setting screens such as S309 in FIG. 3 cannot be displayed. When any of folders A to D is clicked on the guest screen in S406, read permission is determined (S407). That is, when the read permission of the folder set in [3] of S309 in FIG. 3 is YES, a file icon and a directory icon stored in the folder are displayed (S408). On the other hand, when the read permission of the folder is NO in S407, such an icon is not displayed.

  When the file icon or directory icon displayed in S408 is clicked, the file can be opened or edited (S409). When a save operation is performed after editing, a write permission determination is made (S410). That is, if the write permission of the folder set in [6] of S309 in FIG. 3 is YES, the file can be overwritten. At this time, the erasure schedule presence / time of the folder to which the file belongs, the read permission / permission reversal schedule / time, the write permission / permission reversal schedule / the time are displayed, and overwriting is executed when OK is clicked (S411). . On the other hand, if the write permission is NO in S410, a message is issued and the process returns.

  In addition, by dragging a file or directory on the PC to any folder with the icons of the folders A to D displayed in S406, new data can be stored in the folder. . This case is also handled in the same manner as in the case of saving the file described above. If the write permission of the folder is Yes (S412), the file storage setting information such as the set deletion schedule is displayed, and then the data is stored. It becomes possible (S413). On the other hand, if the write permission is NO (S412), a message that cannot be written is displayed and the screen returns to the original screen of S406.

  As described above, the function of the controller 102 described with reference to FIGS. 3 and 4 can protect the confidentiality of the stored data for each folder with a password, and can impose a time constraint by erasure reservation even when the password is broken. Therefore, it is possible to provide high confidentiality. Further, the power consumption can be reduced by controlling the refresh operation for each folder. Furthermore, based on the time set in the timer 105, the permission or non-permission of reading or writing can be switched, and this function can be used effectively for various purposes.

  FIG. 5 is a block diagram showing still another example of the configuration of the external storage device according to the embodiment of the present invention. In the external storage device shown in FIG. 5, the USB memory 50 includes an input / output connector 500 and a power connector, and power devices 51 and 52 can be connected to the power connector, as in the configuration of FIG. FIG. 5 shows a state where the power supply device 51 is connected to the power connector. The USB memory 50 also includes a controller 502 and a nonvolatile memory 502a, a timer battery 504, a timer 505, and a remaining time display LED 506 as in the configuration of FIG. In this configuration, the flash memory 507 is provided.

  The flash memory 507 is composed of a plurality of chips (E, F, G, H), and each is managed like a folder. The controller 502 has a setting function similar to that described in FIGS. However, the controller 502 of FIG. 5 differs from FIG. 3 and FIG. 4 in the processing contents at the time of erasure reservation.

  That is, since the controller 502 includes only the non-volatile flash memory 507, when the set time for erasure reservation is reached, an erasure command is generated for the flash memory chip corresponding to the folder. Then, the erase operation associated with this erase command is performed using the power of the power supply device 51. This also ensures the same level of confidentiality as described in FIGS. However, since it is a flash memory, the operation speed is slower than the DRAM of FIG. In addition, since the flash memory is non-volatile, the stored data may be read by removing the chip itself in some cases. From this viewpoint, the level of confidentiality is inferior to that of DRAM.

  FIG. 6 is a block diagram showing still another example of the configuration of the external storage device according to the embodiment of the present invention. In the external storage device shown in FIG. 6, the USB memory 60 includes an input / output connector 600 and a power connector, and the power device 61 is connected to the power connector, as in the configuration of FIG. The USB memory 60 also includes a controller 602 and a nonvolatile memory 602a, a DRAM 603, a timer battery 604, a timer 605, and a remaining time display LED 606, as in the configuration of FIG.

  However, unlike the USB memory 10 of FIG. 1, the USB memory 60 of FIG. 6 has a configuration in which a power switch 608 is provided for each chip A to D of the DRAM 603. That is, in this configuration, the DRAM erasing method in the controller 602 is different, and the stored data is erased by shutting off the power switch 608 for each chip instead of erasing by stopping the refresh operation described in FIG. I do. Even in this configuration, the same level of confidentiality as that described with reference to FIGS. In addition, power consumption can be reduced by cutting off the power switch of a chip that does not have stored data. However, since the configuration of FIG. 6 requires a power switch, the mounting area slightly increases.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  For example, as an application example other than those described in the above description, the external storage device has a function to add time restrictions to the processing of stored data, so it is effective as a storage medium for video or music to be rented. Can be used for Further, for example, in FIG. 1 and the like, an example in which one power connector 101 is provided in the USB memory 10 is shown, but it is also beneficial to provide a plurality of these. Then, for example, when the USB memory 10 is carried, even if the power of the power supply device 11 connected to a certain power connector 101 is reduced, a new power supply device 11 is connected to another power connector 101 to reduce the power. The device 11 can be removed. In other words, it is possible to easily replace the power supply device 11 while maintaining the power supply.

  The external storage device of the present invention is a particularly useful technique when applied to a portable memory product represented by a USB memory and a memory card.

1 is a block diagram illustrating an example of the configuration of an external storage device according to an embodiment of the present invention. FIG. 10 is a block diagram showing another example of the configuration of the external storage device according to the embodiment of the present invention. FIG. 3 is a processing flowchart showing an example of a setting procedure performed for the controller in the external storage device of FIGS. 1 and 2. FIG. 4 is a process flow diagram illustrating an example of a process when passwords do not match in the process flow of FIG. 3. FIG. 12 is a block diagram showing still another example of the configuration of the external storage device according to the embodiment of the present invention. FIG. 12 is a block diagram showing still another example of the configuration of the external storage device according to the embodiment of the present invention.

Explanation of symbols

10, 20, 50, 60 USB memory 11, 12, 21, 22, 51, 52, 61 Power supply device 100, 200, 500, 600 Input / output connector 101, 110, 111, 120, 121 Power supply connector 102, 202, 502 , 602 Controller 103, 203, 603 DRAM
104, 204, 504, 604 Timer battery 105, 205, 505, 605 Timer 106, 206, 506, 606 Remaining time display LED
102a, 202a, 502a, 602a Nonvolatile memory 207, 507 Flash memory 608 Power switch

Claims (5)

An external storage device that can be used by connecting to an information processing device.
Power supply means;
A controller, a storage medium, and a timer that operate by supplying power from the power supply means;
The controller has a function of erasing data stored in the storage medium when the time of the timer reaches a preset time. The external storage device according to claim 1,
The storage medium is a DRAM;
The external storage device, wherein the controller erases the stored data by stopping a refresh operation of the DRAM when the time of the timer reaches a preset time. The external storage device according to claim 2,
The DRAM is composed of a plurality of DRAM chips,
The information processing apparatus can store data by designating any of the plurality of DRAM chips,
The external storage device, wherein the controller can set different times for stopping the refresh operation for each of the plurality of DRAM chips. The external storage device according to claim 2,
The controller further has a function of protecting whether or not read / write access to the DRAM is possible with a password. The external storage device according to claim 3.
The external storage device, wherein the controller is capable of individually controlling execution or non-execution of a refresh operation for each of the plurality of DRAM chips based on the presence or absence of storage data for each of the plurality of DRAM chips.

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