JPWO2006038260A1 - USB storage system and USB storage device - Google Patents

Abstract

  For example, a plurality of USB hosts including a USB host [1] 10a and a USB host [2] 10b are connected to an external medium 13 such as a memory card, and the plurality of USB hosts can be connected by USB cables 12a and 12b, respectively. A USB reader/writer 11 is provided, and software or the like in the USB reader/writer 11 is provided with a function of rejecting a write request from the other USB host during writing processing from the one USB host to the external medium 13. The shared access of the external medium 13 by the plurality of USB hosts is realized.

Description

  The present invention relates to a USB (Universal Serial Bus) storage system and a USB storage device, and more particularly to a technique effective when applied to a USB storage system and a USB storage device that are used by being connected to a plurality of hosts.

  According to a study made by the present inventor, the following techniques can be considered as the technique of the USB storage system.

  In recent years, a USB storage device (hereinafter, referred to as a USB reader) that handles an external medium such as a memory card or a floppy disk (registered trademark) as a removable disk due to ease of use by a plug-and-play function or the like and improvement in data transfer rate according to the USB 2.0 standard There are many).

  By the way, as a result of the present inventor's examination of the technology of the USB storage system as described above, the following has become clear.

  With the recent price reduction of PCs (Personal Computers), the number of users who use a plurality of PCs is increasing. Under such circumstances, as a configuration of the USB storage system, a configuration as shown in FIG. 10 is usually cited. FIG. 10 is a schematic diagram showing an example of the configuration of the USB storage system of the technique studied as the premise of the present invention, and (a) to (c) show different configuration examples.

  First, in FIG. 10A, the USB reader/writer 101a connected to the USB host PC 100 by the USB cable 102 can insert one external medium such as an SD (Secure Digital) memory card or a floppy disk. In FIG. 10B, a USB reader/writer 101b connected in the same manner as in FIG. 10A includes a plurality of different types such as a CF (CompactFlash (registered trademark)) card, an SD memory card, and a Memory Stick (registered trademark). External media [1], [2],..., [N] can be inserted. In FIG. 10C, a USB reader/writer 101c connected in the same manner as in FIG. 10A includes a plurality of external media [1] and [2] of the same type including an MMC (MultiMediaCard (registered trademark)) card or the like. ,..., [N] can be inserted.

  However, in any of the configurations, the correspondence relationship between the USB host PC and the external medium is one-to-one or one-to-many. Therefore, for example, when a user who uses a plurality of PCs uses a certain external medium with a plurality of PCs (USB host PCs), for example, the work shown in FIG. 11 is performed.

  FIG. 11 is a diagram for explaining the work contents when a specific external medium is used by a plurality of USB host PCs in the USB storage system of the technique studied as the premise of the present invention. That is, after the external medium is used by the USB host PC[1] 110a, the USB cable 112 connected to the USB host PC[1] 110a is removed (S110), and the USB cable 112 is connected to the USB host PC[2]. The work of (S111) is performed.

  As described above, when using a specific external medium with a plurality of PCs, the user needs to perform a troublesome work such as reconnecting the USB cable. Then, every time the USB cable is reconnected, it is necessary to reconfigure the USB network by plug and play and initialize the external medium such as a memory card, which wastes time and power.

  Therefore, an object of the present invention is to provide a USB storage system and a USB storage device that can be improved in time efficiency when used by a plurality of hosts.

  Another object of the present invention is to provide a USB storage system and a USB storage device that can save power when used by a plurality of hosts.

  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.

  The following is a brief description of the outline of the typical invention disclosed in the present application.

  A USB storage system according to the present invention has a plurality of USB hosts and a USB function including a function as an external storage medium, and performs data transfer based on the USB protocol between the USB function and the plurality of USB hosts. Is. The USB function has a function of enabling a plurality of USB hosts to share access to an external storage medium of the USB function in a state where the plurality of USB hosts are connected to the USB function. ing.

  As a result, when the USB function as an external storage medium is used by a plurality of USB hosts, the work and processing such as reconnecting the USB cable and the initialization associated therewith are not required, which improves time efficiency and saves time. It is also possible to make electricity.

  Here, the function that enables the shared access is, for example, while one USB host of the plurality of USB hosts is executing the writing process to the external storage medium of the USB function, It includes a function of rejecting a write request generated from another USB host of the plurality of USB hosts.

  This makes it possible to prevent the data stored in the USB function as the external storage medium from being destroyed by writing from a plurality of USB hosts.

  In addition, the plurality of USB hosts include a first USB host and a second USB host, and a function that enables the shared access is an external storage medium of a USB function generated by the first USB host. When the second USB host issues a second write request to the external storage medium during the process of handling the first write request to the second USB host, the second USB host rejects the second write request. It includes a function of notifying and continuing the processing corresponding to the first write request.

  The function of the USB function as an external storage medium is realized by, for example, a memory card. As a result, it is possible to reduce the initialization processing of the memory card and the like that are conventionally required every time the USB cable is reconnected, improve time efficiency, and save power.

  Also, the USB storage system according to the present invention has a plurality of USB hosts and a USB function including a function as an external storage medium, and the USB function is a plurality of USB connector terminals to which the plurality of USB hosts are connected. And a function of performing data transfer based on the USB protocol with a plurality of USB hosts, a function of performing data transfer based on a predetermined protocol between the USB function and an external storage medium, a USB protocol and the predetermined protocol. And a function for mutually converting and, while one USB host of the plurality of USB hosts is executing the writing process to the external storage medium of the USB function, the other USB hosts are It has a function of rejecting a write request that has occurred.

  Here, the function of rejecting the write request is realized by a program process by a computer provided with a USB function, and this program process is performed when a write request to the external storage medium from the one USB host is accepted. A step of setting a flag, a step of releasing the operation flag when the processing of the received write request is completed, and a step of writing a request from the other USB host while the operation flag is set. And a step of notifying the other USB host of the refusal of the generated write request. That is, by adding the function of rejecting the write request to the software, it becomes possible to easily realize the sharing of the external storage medium by the plurality of USB hosts. The step of notifying the refusal of the write request can be performed using the data of the request sense command, for example.

  The USB storage device of the present invention includes a plurality of USB connector terminals connected to a plurality of USB hosts and a media connector terminal connected to an external storage medium, and the plurality of USB hosts based on the USB protocol. Between the plurality of USB hosts are connected to the plurality of USB connector terminals, and the plurality of USB hosts are connected to the media connector terminal with an external storage medium. It has a function that enables shared access to an external storage medium.

  A memory card is an example of the external storage medium. The USB storage device may include a plurality of the media connector terminals, and a plurality of memory cards of the same type or different types may be connected to the plurality of media connector terminals. Further, the USB storage device can also be provided with a bridge function that can arbitrarily set a connection between the plurality of USB connector terminals and the plurality of media connector terminals.

  The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows.

  By providing a function that enables shared access of the external storage medium by a plurality of USB hosts in a USB function having a function as an external storage medium, it is possible to use the external storage medium by a plurality of USB hosts. The time efficiency can be improved, and the power consumption can be saved.

1 is a schematic diagram showing an example of a system configuration of a USB storage system according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of a logical configuration of a USB host in the USB storage system of FIG. 1. FIG. 3 is a diagram showing an example of a logical configuration of a USB reader/writer in the USB storage system of FIG. 1. FIG. 2 is a perspective view showing an example of an outer shape of a USB reader/writer in the USB storage system of FIG. 1. It is explanatory drawing which shows an example of the operation|movement outline|summary in the USB reader/writer of FIG. FIG. 4 is a processing flow chart showing an example of processing of interface software in the USB reader/writer of FIG. 3. FIG. 3 is a process flow diagram illustrating an example of the operation in the system configuration of FIG. 1. FIG. 2 is a schematic diagram showing an example of a system configuration obtained by expanding FIG. 1 in the USB storage system according to the embodiment of the present invention. 1 is a schematic diagram showing an example of a configuration in which a plurality of external media can be shared by a plurality of USB hosts in a USB storage system according to an embodiment of the present invention. FIG. 1 is a schematic diagram showing an example of the configuration of a USB storage system of the technique studied as the premise of the present invention, and FIGS. FIG. 6 is a diagram for explaining the work contents when a specific external medium is used by a plurality of USB host PCs in the USB storage system of the technique studied as the premise of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In all the drawings for explaining the embodiments, the same members are denoted by the same reference symbols in principle and their repeated description is omitted.

  FIG. 1 is a schematic diagram showing an example of the system configuration of a USB storage system according to an embodiment of the present invention. The USB storage system shown in FIG. 1 is, for example, a plurality of USB hosts including a USB host [1] 10a and a USB host [2] 10b, and is connected to the plurality of USB hosts by USB cables 12a and 12b, respectively, and becomes a USB function. It is composed of a USB reader/writer 11. A typical example of the USB host is a personal computer.

  The USB reader/writer 11 is a USB storage device having a function as an external storage medium, and can be connected to an external medium (external storage medium) 13 such as a memory card or a floppy disk. In FIG. 1, three or more USB hosts are also applicable, but in the following description, there are two USB hosts for simplification.

  Each of the USB host [1] 10a and the USB host [2] 10b has a configuration shown in FIG. FIG. 2 is a diagram showing an example of a logical configuration of a USB host in the USB storage system of FIG. The USB host shown in FIG. 2 is provided with an application layer, a system software layer, and a hardware layer from the upper layer to the lower layer.

  The application layer includes application software 20. Typical examples of the application software 20 include, for example, an explorer having a function of operating folders and files, an audio player having a music data reproducing function, and the like. When performing USB transfer, the application layer transmits/receives data to/from the system software layer.

  The system software layer manages the hardware layer and performs conversion and the like based on the USB protocol with respect to transmission/reception data with the application layer or the hardware layer. Then, as software for performing such processing, the system software layer includes a USB mass storage class driver 21a and a USB bus driver 21b.

  The USB mass storage class driver 21a manages a command transport, a data transport, a status transport defined by the standard called the USB mass storage class. The USB bus driver 21b performs processing common to each USB class, such as transaction management.

  The hardware layer includes the USB host controller 22. The USB host controller 22 is electrically connected to the USB reader/writer through the USB cable 23, and is a hardware that processes electrical signals of the USB host such as connection detection of the USB reader/writer and packet transmission/reception with the USB reader/writer. It is wear.

  On the other hand, the USB reader/writer 11 has a configuration as shown in FIGS. 3 and 4. FIG. 3 is a diagram showing an example of a logical configuration of a USB reader/writer in the USB storage system of FIG. FIG. 4 is a perspective view showing an example of the outer shape of a USB reader/writer in the USB storage system of FIG.

  The USB reader/writer shown in FIG. 3 is, for example, two USBs including a USB function module [1] (hereinafter, USB module [1]) 30 and a USB function module [2] (hereinafter, USB module [2]) 31. It includes a function module, an external media module 32, interface software (hereinafter, interface software) 33, and the like.

  The USB module [1] 30 includes a USB mass storage class firmware [1] 30a which is software and a USB function controller [1] 30b which is hardware, and is connected to a USB host [1] or the like by a USB cable 12a. To be done. Similarly, the USB module [2] 31 includes the USB mass storage class firmware [2] 31a and the USB function controller [2] 31b, and is connected to the USB host [2] or the like by the USB cable 12b. The external media module 32 includes an external media firmware 32a, which is software, and an external media host controller 32b, which is hardware, and is connected to the external media 13.

  Further, these configurations can be divided into an application layer, a system software layer, and a hardware layer, like the logical configuration of the USB host. When classified by such a logical configuration, the interface layer 33 is included in the application layer. The interface software 33 is software responsible for controlling data transfer between the USB modules [1] 30, [2] 31 and the external media module 32.

  Then, the interface software 33 is further provided with a function of performing a corresponding process when a write request is issued from the other USB module during the response process of the write request from the one USB module to the external medium 13. The interface software 33 is stored in, for example, a ROM or the like included in the USB reader/writer, and the interface software 33 is executed by, for example, a microcomputer and a RAM included in the USB reader/writer. Also, various kinds of software of the system software layer described later are the same.

  The system software layer includes USB mass storage class firmware [1] 30a, [2] 31a and external media firmware 32a. The USB mass storage class firmware [1] 30a (or [2] 31a) controls the USB function controller [1] 30b (or [2] 31b) and performs processing unique to the USB mass storage class. The external media firmware 32a manages transactions of the external media 13 and controls the external media host controller 32b.

  The hardware layer includes USB function controllers [1] 30b and [2] 31b and an external media host controller 32b. The USB function controllers [1] 30b and [2] 31b perform processing of USB function electrical signals such as packet transmission and reception. The external media host controller 32b performs processing of electrical signals such as command transmission to the external medium 13, response reception from the external medium 13, and data transmission/reception with the external medium 13.

  Then, such a USB reader/writer has an outer shape as shown in FIG. 4, for example. In the USB reader/writer shown in FIG. 4, for example, a housing 40 is provided with two USB connectors [1] 41a and [2] 41b and an external media connector (external media slot) 42. The USB connectors [1] 41a and [2] 41b are connector shapes for USB functions, and are connected to the USB hosts [1] and [2] by USB cables 12a and 12b, respectively. An external medium such as a memory card or a floppy disk is inserted and connected to the external medium connector 42.

  In the system configuration as described above, a feature of the present invention is to realize shared access of external media by the USB host [1] and the USB host [2]. In order to realize this, as described with reference to FIG. 3, a plurality of USB modules are provided in the USB reader/writer, and the arbitration function when the processing requests are simultaneously issued from the plurality of USB modules by using the interface software. Has been realized. The details of the arbitration function of this interface software will be described below.

  The request from the USB host to the USB reader/writer includes a request to write data in the memory of the external medium (hereinafter, write request), a request to read data from the memory of the external medium (hereinafter, read request), and a request of the USB reader/writer. There is a request for acquiring the status and information (hereinafter, status acquisition request).

  Even if there are two USB hosts, there will be a particular problem if the requests from the USB host and the response processing by the USB reader/writer for the requests do not overlap in time, or if the contents of the external media memory are not changed even if they overlap. do not do. In other words, for the read request and the status acquisition request, the interface software of the USB reader/writer may perform exclusive control so that mutual requests and data read from the external medium do not overlap, and the stored data in the external medium may be destroyed. No serious problems occur. The problem arises when there are two USB hosts, and the USB reader/writer issues a write request from another USB host during a write request process from a certain USB host. Therefore, for example, the following operation avoids this problem.

  When the USB reader/writer receives a write request from another USB host (referred to as USB host [1]) during the process of responding to the write request from a certain USB host (referred to as USB host [2]). , Rejects the request from the USB host [1], and continues the processing for handling the write request from the USB host [2]. That is, the operation outline is as shown in FIG.

  FIG. 5 is an explanatory diagram showing an example of an operation outline of the USB reader/writer of FIG. In FIG. 5, when the interface software 33 in the USB reader/writer receives the write request [2] from the USB module [2] 31, it returns an acceptance response to the USB module [2] 31 and requests the external media module 32 to write. Send data corresponding to [2]. Then, when a write request is received from the USB module [1] 30 during the write request handling process from the USB module [2] 31, the interface software 33 virtually sends an external medium to the USB module [1] 30. 13 communicates that it is in the operating state, and rejects the request from the USB host [1].

  More specifically, this operation outline is realized by a processing flow as shown in FIG. 6, for example. FIG. 6 is a process flow chart showing an example of the process of the interface software in the USB reader/writer of FIG. First, the interface software 33 is activated after connecting the external medium 13 or after connecting the USB cable 12a (or 12b) (S601), and enters an event waiting state. The events received by the interface software 33 include a read request and a write request from the USB module (USB module [1] 30 or USB module [2] 31) and a read completion notification from the external media module 32 (of the interface software 33). There are a read completion notification corresponding to the read request) and a write completion notification (write completion notification corresponding to the write request of the interface software 33).

  When there is a read request from the USB module [1] 30 (or [2] 31) in the event waiting state (S602), the content of the read request is analyzed and read identification information is created (S603). The read identification information is used to identify the read requests when a plurality of read requests overlap. The read identification information includes a read request ID, a USB module number for identifying the USB module of the request destination, a read address, and a read size. After creating the read identification information, a read request is issued to the external media module 32 (S604). Then, it shifts to the event waiting state.

  When a write request is issued from the USB module [1] 30 (or [2] 31) in the event waiting state (S605), it is determined whether the operation state flag is ON (S606). The operation state flag is a flag indicating that the writing process to the external medium 13 is being performed, and is used for exclusive control so that the writing processes to the external medium 13 do not overlap, and the initial value is OFF.

  If the operation status flag is ON, an operation status notification is created and sent to the corresponding USB module [1] 30 (or [2] 31) to reject the write request (S607). On the other hand, if the operation state flag is OFF, the operation state flag is turned ON (S608). Then, a write request is made to the external media module 32 (S609). Then, it shifts to the event waiting state.

  When a read completion notification is given from the external media module 32 in the event waiting state (S610), the ID and read identification information are analyzed (S611), and the corresponding USB module [1] 30 (or [2] 31) The corresponding read data is transmitted (S612). Then, it shifts to the event waiting state.

  When the external media module 32 gives a write completion notification in the event waiting state (S613), the operation state flag is turned off to cancel the writing process (S614). Then, it shifts to the event waiting state.

  In the event waiting state, the state of the external medium 13 is checked (S615), and if the external medium 13 is removed, the process ends. If not removed, the event waiting state is continued.

  As described above, with the system configuration and the operation thereof described above, a plurality of USB hosts can share and use the external medium. As a result, the following effects (1) and (2) can be obtained.

  (1) When a specific external medium is used by a plurality of USB hosts, the user does not have to perform the troublesome work of successively connecting the USB cables. Further, even if a plurality of USB hosts are connected, a USB reader/writer corresponding to the feature of plug and play such as USB and memory card can be realized.

  (2) Since it is not necessary to successively connect the USB cable, reconfiguration of the USB network and reinitialization of an external medium such as an SD memory card can be omitted. As a result, it is possible to improve time efficiency and save power.

  Next, an example of the operation of the entire system of FIG. 1 will be described with reference to FIG. FIG. 7 is a process flow diagram for explaining an example of the operation in the system configuration of FIG. In FIG. 7, a process when the USB host [1] 10a transmits a data write request to the USB reader/writer 11 while the USB host [2] 10b of FIG. 1 is writing data will be described as an example. In addition, it is assumed here that data transfer is performed according to the generally known USB mass storage standard. In the following, description will be made in correspondence with the process numbers in FIG. 7.

  (1) The USB host [2] 10b issues a write [2] request CBW (Command Block Wrapper) defined in the USB mass storage class to the USB reader/writer 11. The CBW is a packet that is defined by the USB mass storage class and stores a command requested by the USB host to the USB function and the contents related thereto.

  (2) Upon receiving the write [2] request CBW, the USB reader/writer 11 analyzes the write address and the number of data. Also, the write [2] request CBW is converted into a command format unique to the external medium 13. That is, protocol conversion is performed.

  (3) After the conversion is completed, the USB reader/writer 11 issues the write [2] command converted to the unique command format to the external medium 13.

  (4) Upon receiving the write [2] command, the external medium 13 analyzes the write address and the number of data.

  (5) The USB host [2] 10b transmits the write [2] data to the USB reader/writer 11 in the format defined by the USB mass storage class.

  (6) Upon receiving the write [2] data, the USB reader/writer 11 converts the write [2] data into a data format specific to the external medium 13. That is, protocol conversion is performed.

  (7) After the conversion is completed, the USB reader/writer 11 transmits the converted write [2] data to the external medium 13.

  (8) When the external medium 13 receives the converted write [2] data, it writes it in its own memory.

  (1') Here, the USB host [1] 10a issues a write [1] CBW defined in the USB mass storage class to the USB reader/writer 11 in order to write data in the memory of the external medium 13.

  (2′) The USB reader/writer 11 receives the write [1] request CBW, but since the USB host [2] 10b is in the process of responding to the write [2] request, it writes to the USB host [1] 10a. [1] Reject the request. That is, by the processing of the interface software 33 described above, an operation state notification for notifying that the external medium 13 is virtually in the operation state is created.

  Here, as an example of a method of creating the operation status notification, in the data of the request sense (Request Sense) command defined by the SCSI command of the USB mass storage class, 04'h is set to ASC (Additional Sense Code) and ASCQ is set. 07'h is set in (Additional Sense Code Qualifier). The request sense command data is data that is returned to the host when the USB host issues a request sense command to the USB reader/writer.

  (3') After the operation status notification is created, the USB reader/writer 11 sends the operation status notification (here, the data of the request sense command) to the USB host [1] 10a.

  (4') When the USB host [1] 10a receives the operation status notification, it recognizes that data cannot be written in the memory of the external medium 13, and notifies the upper application or the like.

  (9) When the writing of the converted write [2] data is all completed, the external medium 13 notifies the USB reader/writer 11 of the completion.

  (10) Upon receiving the completion notification, the USB reader/writer 11 converts the completion notification into a write [2] completion CSW (Command Status Wrapper). The CSW is a packet defined by the USB mass storage class and used when the USB host acquires the execution result for the CBW from the USB function.

  (11) After the conversion is completed, the USB reader/writer 11 transmits the write [2] completion CSW to the USB host [2] 10b.

  (12) When the USB host [2] 10b receives the write [2] completion CSW, the USB host [2] 10b recognizes that the write operation is completed, and the write operation is completed.

  With the system configuration and operation as described above, the external medium can be shared by a plurality of hosts by data transfer conforming to the USB mass storage standard.

  By the way, in the above description, the case where one external medium is shared by a plurality of USB hosts is taken as an example. It is also possible to do so.

  FIG. 8 is a schematic diagram showing an example of a system configuration obtained by expanding FIG. 1 in the USB storage system according to the embodiment of the present invention. 8, N USB hosts [1] 80a, [2] 80b,..., [N] 80n are connected to the USB reader/writer 82, and the USB reader/writer 82 further includes N external media [[ 1] 83a, [2] 83b,..., [N] 83n are inserted.

  In a normal UBS storage system, it is possible to access N external media of different types or the same type from one USB host as described in FIG. Therefore, when N USB hosts are connected to the USB reader/writer 82, N different types of external media such as CF cards, SD memory cards, and memory sticks can be shared by the N USB hosts. Further, of course, the same applies to N external media of the same type. This makes it possible to increase the efficiency of connection work and initial setting operation N times as compared with a normal UBS storage system.

  Further, as shown in FIG. 9, a plurality of external media can be shared by a plurality of USB hosts by adding a bridge function in the USB reader/writer. FIG. 9 is a schematic diagram showing an example of a configuration in which a plurality of external media can be shared by a plurality of USB hosts in the USB storage system according to the embodiment of the present invention. The USB reader/writer shown in FIG. 9 includes, for example, a plurality of USB connectors [1] 90a, [2] 90b,..., [N] 90n and a plurality of external media connectors [1] 91a, [2] 91b,. [N] 91n, and further, it is possible to arbitrarily set the connection between the plurality of USB connectors [1] 90a to [N] 90n and the plurality of external media connectors [1] 91a to [N] 91n. It has a bridge function 92.

  The bridge function 92 is provided with, for example, a DIP switch for each of the plurality of USB connectors [1] 90a to [N] 90n and each of the plurality of external media connectors [1] 91a to [N] 91n, or the USB function. This can be realized by adding a selection function to the interface software 33 on the reader/writer.

  By using such a configuration, it becomes possible to arbitrarily select the connection between the USB host and the external medium, such as 1:1, 1:N, N:1, or N:N. Further, as another point of view, for example, when one external medium is shared by a plurality of USB hosts, it is possible to replace the USB cable reconnection work, which was required in the past, with a DIP switch ON/OFF work. Becomes

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

  The USB storage system of the present invention is particularly useful when applied to a system in which the USB function is a USB reader/writer compatible with various memory cards such as SD memory cards and memory sticks, and is not limited to this. Instead, it can be widely applied to a system including a USB reader/writer corresponding to a floppy disk or a hard disk.

Claims (11)

A USB storage system having a plurality of USB hosts and a USB function including a function as an external storage medium, and performing data transfer based on a USB protocol between the plurality of USB hosts and the USB function,
The USB function has a function that enables the plurality of USB hosts to perform shared access to the external storage medium of the USB function while the plurality of USB hosts are connected to the USB function. USB storage system characterized in that. The USB storage system according to claim 1,
The function that enables the shared access is performed by the plurality of USB hosts while one USB host among the plurality of USB hosts is executing the writing process to the external storage medium. USB storage system characterized by including a function of rejecting a write request generated from another USB host inside. The USB storage system according to claim 1,
The plurality of USB hosts includes a first USB host and a second USB host,
The function that enables the shared access is performed from the second USB host to the external storage medium during the process of responding to the first write request for the external storage medium generated by the first USB host. When a second write request is generated, a function of notifying the second USB host of the refusal of the second write request and continuing the processing corresponding to the first write request is included. USB storage system. The USB storage system according to any one of claims 1 to 3,
A USB storage system, wherein the function as the external storage medium is realized by a memory card. A USB storage system having a plurality of USB hosts and a USB function including a function as an external storage medium,
The USB function is
A plurality of USB connector terminals to which the plurality of USB hosts are connected;
A function of performing data transfer based on the USB protocol with the plurality of USB hosts;
A function for performing data transfer based on a predetermined protocol with the external storage medium,
Having a function of mutually converting the USB protocol and the predetermined protocol,
Further, while one USB host of the plurality of USB hosts is executing a writing process to the external storage medium, a write request generated from another USB host of the plurality of USB hosts. A USB storage system having a function of rejecting. The USB storage system according to claim 5,
The function of rejecting the write request is realized by program processing by a computer provided with the USB function,
The program processing is
Setting an operation flag when a write request to the external storage medium from the one USB host is accepted;
Canceling the operation flag when the processing of the received write request is completed,
When a write request from the other USB host is generated while the operation flag is set, a step of notifying the other USB host of rejection of the generated write request. USB storage system. The USB storage system according to claim 6,
The USB storage system, wherein the step of notifying the refusal of the write request is performed using data of a request sense command. A USB storage having a plurality of USB connector terminals connected to a plurality of USB hosts and a media connector terminal connected to an external storage medium, and capable of transferring data to and from the plurality of USB hosts based on a USB protocol. A device,
With the plurality of USB hosts connected to the plurality of USB connector terminals and the external storage medium connected to the media connector terminal, the plurality of USB hosts share access to the external storage medium. A USB storage device having a function that enables the above. The USB storage device according to claim 8,
The USB storage device, wherein the external storage medium is a memory card. The USB storage device according to claim 8,
A plurality of the media connector terminals,
A USB storage device, wherein a plurality of memory cards of the same type or different types are connected to the plurality of media connector terminals. The USB storage device according to claim 10,
A USB storage device having a bridging function that allows the connection between the plurality of USB connector terminals and the plurality of media connector terminals to be arbitrarily set.

Images