Abstract:
An information processing system includes a host device transmitting an order according to a USB standard and an information processing terminal responding to the order. The information processing terminal includes a storing unit, a first operation unit, a receiver, an operation-mode switch, a first processor, and a first outputting unit. The host device includes a second operation unit, a transmitter, a second processor, and a second outputting unit.

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to a technique for causing an information processing terminal to operate in plural operation modes. 
     2. Related Art 
     As a user-friendly interface, a USB (Universal Serial Bus) standard is widely spread. Recently, this USB standard is used in, for example, a portable music player that plays music, a digital camera that photographs and displays images, and an electronic book in which a book converted into text data can be viewed as well. A terminal implemented with such a USB standard (hereinafter referred to as USB terminal) is connected to a host device, whereby new data can be added to the USB terminal from the host device and the USB terminal can transfer data stored therein to the host device. Japanese Patent No. 3766429 discloses a technique for restricting access from a host device to a USB terminal to prevent a malicious user from committing manipulation of data and illegal copying when the USB terminal is lost. 
     Incidentally, when such a USB terminal is connected to the host device, the USB terminal transitions to a so-called slave mode and is completely controlled by the host device. Therefore, processing corresponding to operation of a user cannot be executed on the USB terminal side. For example, while the portable music player is connected to the host device, addition and deletion of music data can be performed from the host device but music cannot be played on the portable music player side. Therefore, for example, when new music data is added to the portable music player by using the host device, music based on the music data cannot be played on the portable music player side while the portable music player is kept connected to the host device. 
     In other words, at the time of a reproduction mode when the USB terminal operates alone, the USB terminal manages a file system of a storage device in the USB terminal itself. On the other hand, in the slave mode, the host device at the USB connection destination manages the file system of the storage device in the USB terminal. In order to prevent inconsistency and breakage of data due to conflict, management of the file system of the storage device in the USB terminal can be performed only from one of the USB terminal side and the host device side. The USB terminal in the past performs this switching of the operation modes by judging presence or absence of connection to the host device. Therefore, when the USB terminal is connected to the host device, processing cannot be executed on the USB terminal side. Moreover, in the slave mode, even if the host device and the USB terminal are connected, it is impossible to operate the USB terminal from the host device to cause the USB terminal side to execute processing. This is user-unfriendly and inconvenient. 
     SUMMARY 
     It is an object of the present invention to execute, even in a state in which an information processing terminal such as a USB terminal is connected to a host device, processing corresponding to operation of a user in the information processing terminal. The present invention provides an information processing system including a host device that transmits an order according to a USB (Universal Serial Bus) standard and an information processing terminal that responds to the order, which is transmitted from the host device, according to the USB standard. The information processing system is characterized in that the information processing terminal includes storing unit that stores data, first operation unit that receives operation for instructing processing, receiving unit that receives the order transmitted from the host device according to the USB standard, operation-mode switching unit that switches, when the receiving unit receives an operation mode switching order for ordering the information processing terminal to switch an operation mode of the information processing terminal itself in a state in which the information processing terminal is connected to the host device, the operation mode of the information processing terminal to a first operation mode or a second operation mode according to the operation mode switching order, first processing unit that executes, in the first operation mode, the processing instructed by the operation using the data stored in the storing unit and does not execute, in the second operation mode, the processing instructed by the operation, and first outputting unit that outputs a result of the processing executed by the first processing unit, and the host device includes second operation unit that receives operation for instructing processing, transmitting unit that transmits, when the host device is instructed to switch the operation mode of the information processing terminal by the operation received by the second operation unit, an operation mode switching order for ordering the information processing terminal to switch the operation mode to an instructed operation mode to the information processing terminal according to the USB standard, second processing unit that performs, when processing for the storing unit of the information processing terminal is instructed by the operation received by the second operation unit after the operation mode of the information processing terminal is switched to the second operation mode according to the operation mode switching order transmitted by the transmitting unit, the processing using the data stored in the storing unit, and second outputting unit that outputs a result of the processing executed by the second processing unit. 
     In the present invention, the transmitting unit of the host device may transmit, when the host device is instructed by the operation received by the second operation unit to switch the operation mode of the information processing terminal to a third operation mode, an operation mode switching order for ordering the information processing terminal to switch the operation mode to the third operation mode to the information processing terminal according to the USB standard. The operation-mode switching unit of the information processing terminal may switch, when the receiving unit receives an operation mode switching order for ordering the information processing terminal to switch the operation mode of the information processing terminal itself to the third operation mode in a state in which the information processing terminal is connected to the host device, the operation mode of the information processing terminal to the third operation mode according to the operation mode switching order. The host device may include ordering unit that orders, when processing for the storing unit by the information processing terminal is instructed by the operation received by the second operation unit after the operation mode of the information processing terminal is switched to the third operation mode according to the operation mode switching order transmitted by the transmitting unit, the information processing terminal to execute the processing. The first processing unit of the information processing terminal may execute the processing ordered by the ordering unit using the data stored in the storing unit. 
     In the present invention, the information processing terminal may include first primary storing unit that temporarily stores a result of the processing executed by the first processing unit or a history of the processing before causing the storing unit to store the result or the history. The host device may include second primary storing unit that temporarily stores a result of the processing executed by the second processing unit before causing the storing unit to store the result. The first processing unit may cause, when an operation mode switching order for ordering the information processing terminal to switch the operation mode of the information processing terminal to the second operation mode is received by the receiving unit, the storing unit to store the result of the processing or the history of the processing stored in the first primary storing unit. The operation-mode switching unit may switch, after the result of the processing or the history of the processing is stored in the storing unit by the first processing unit, the operation mode of the information processing terminal to the second operation mode. The second processing unit may reflect, when an operation mode switching order for ordering the information processing terminal to switch the operation mode of the information processing terminal from the second operation mode to another operation mode is transmitted by the transmitting unit, the result of the processing stored in the second primary storing unit on the data stored in the storing unit of the information processing terminal. The operation-mode switching unit may switch the operation mode of the information processing terminal from the second operation mode to the another operation mode after the result of the processing is reflected on the data stored in the storing unit of the information processing terminal by the second processing unit. 
     The present invention provides an information processing terminal that responds to an order, which is transmitted from a host device, according to a USB standard. The information processing terminal is characterized by including storing unit that stores data, operation unit that receives operation for instructing processing, receiving unit that receives the order transmitted from the host device according to the USB standard, operation-mode switching unit that switches, when the receiving unit receives an operation mode switching order for ordering the information processing terminal to switch an operation mode of the information processing terminal itself in a state in which the information processing terminal is connected to the host device, the operation mode of the information processing terminal to a first operation mode or a second operation mode according to the operation mode switching order, processing unit that executes, in the first operation mode, the processing instructed by the operation using the data stored in the storing unit and does not execute, in the second operation mode, the processing instructed by the operation, and outputting unit that outputs a result of the processing executed by the processing unit. 
     The present invention provides a host device that transmits an order according to a USB standard. The host device is characterized by including operation unit that receives operation for instructing processing, transmitting unit that transmits, when the host device is instructed to switch an operation mode of an information processing terminal by the operation received by the operation unit, an operation mode switching order for ordering the information processing terminal to switch the operation mode to an instructed operation mode to the information processing terminal according to the USB standard, processing unit that performs, when processing for storing unit of the information processing terminal is instructed by the operation received by the operation unit after the operation mode of the information processing terminal is switched to a second operation mode for not executing processing instructed by operation in the information processing terminal according to the operation mode switching order transmitted by the transmitting unit, the processing using data stored in the storing unit, and outputting unit that outputs a result of the processing executed by the processing unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram showing a configuration of an information processing system  1 ; 
         FIG. 2  is a block diagram showing the structure of an information processing terminal  10 ; 
         FIG. 3  is a block diagram showing the structure of a host device  20 ; 
         FIG. 4  is a table in which differences among respective operation modes of the information processing terminal  10  are collated; 
         FIG. 5  is a diagram for explaining processing performed in the information processing terminal  10  at the time of an unconnected mode; 
         FIG. 6  is a diagram for explaining processing in the information processing terminal  10  at the time of a connected mode; 
         FIG. 7  is a diagram for explaining processing performed in the information processing terminal  10  at the time of a mass-storage mode; 
         FIG. 8  is a diagram for explaining processing performed in the information processing terminal  10  at the time of an external operation mode; 
         FIG. 9  is a sequence chart showing operations in the connected mode; 
         FIG. 10  is a diagram showing a screen at the time when access to a flash ROM  13  is instructed; 
         FIG. 11  is a sequence chart showing operations in an external operation mode; 
         FIG. 12  is a diagram showing a screen for receiving operation for ordering processing; 
         FIG. 13  is a sequence chart showing operations in the mass-storage mode; 
         FIGS. 14A ,  14 B, and  14 C are diagrams showing transition of a screen in accessing the flash ROM  13 ; and 
         FIG. 15  is a diagram showing a screen displayed during transmission of content data. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     [Embodiment] 
       FIG. 1  is a diagram showing a configuration of an information processing system  1  according to an embodiment of the present invention. As shown in  FIG. 1 , this information processing system  1  includes an information processing terminal  10  and a host device  20 . The host device  20  is, for example, a personal computer and the information processing terminal  10  is, for example, a display device including electronic paper. The information processing terminal  10  has an interface detachably attachable to the host device  20 . This interface is connected to the host device  20 , whereby the information processing terminal  10  and the host device  20  can communicate with each other. The host device  20  functions as a USB host and the information processing terminal  10  functions as a USB device. The USB host is a device that transmits information (including various orders) to the USB device according to a USB standard. On the other hand, the USB device is a device that executes some response processing complying with the USB standard, for example, execute processing on information transmitted from the USB host. Under the USB standard, this USB device performs processing according to an instruction from the USB host. A function of voluntarily transmitting information from the USB device to the USB host is not defined. 
       FIG. 2  is a block diagram showing the structure of the information processing terminal  10 . As shown in  FIG. 2 , this information processing terminal  10  includes a CPU (Central Processing Unit)  11 , a RAM (Random Access Memory)  12 , a flash ROM (Read Only Memory)  13 , a USB (Universal Serial Bus) connector  15 , a USB controller  16 , an operation unit  17 , and a display unit  18 . The CPU  11  performs various kinds of processing by reading out and executing software stored in the flash ROM  13 . The RAM  12  is a work area for the CPU  11 . In this RAM  12 , for example, a result of the processing executed by the CPU  11  is temporarily stored. The flash ROM  13  is a nonvolatile memory such as an EEPROM (Electrically Erasable and Programmable Read Only Memory) or a flash memory. In this flash ROM  13 , software such as an OS (Operating System) for managing the entire information processing terminal  10  and plural content data D are stored. This content data D is data used in the processing by the CPU  11  and is, for example, document data for causing the display unit  18  to display a sentence. 
     The USB connector  15  is an interface detachably attachable to the host device  20 . The USB controller  16  performs transmission and reception of information to and from the host device  20  according to the USB standard under the control by the CPU  11 . Consequently, the information processing terminal  10  and the host device  20  are connected to be capable of communicating with each other according to the USB standard. The operation unit  17  includes operation devices such as a pen device and a joystick. The operation unit  17  receives operation for instructing processing by a user and supplies a signal corresponding to the operation to the CPU  11 . The display unit  18  is displaying unit employing a cholesteric liquid crystal, a microcapsule type electrophoresis element, or the like. The display unit  18  displays various images under the control by the CPU  11 . This display unit  18  has memory properties in that the display unit  18  can continue to display the images even if the supply of electric power is stopped. A processing result of the CPU  11  is outputted by this display unit  18 . 
       FIG. 3  is a block diagram showing the structure of the host device  20 . As shown in  FIG. 3 , this host device  20  includes a CPU  21 , a RAM  22 , a ROM  23 , a storing unit  24 , a USB port  25 , a USB controller  26 , an operation unit  27 , and a display unit  28 . The CPU  21  performs various kinds of processing by reading out and executing software stored in the ROM  23  or the storing unit  24 . The RAM  22  is a work area for the CPU  21 . In this RAM  22 , for example, a result of the processing executed by the CPU  21  is temporarily stored. The ROM  23  is a read-only nonvolatile memory. In this ROM  23 , a program for booting the host device  20  is stored. The storing unit  24  is, for example, a hard disk. In this storing unit  24 , an OS for managing the entire host device  20  and a software group including processing order software for ordering the information processing terminal  10  to perform processing are stored. 
     The USB port  25  is a connection port to which the USB connector  15  of the information processing terminal  10  is connected. The USB controller  26  performs communication with the information processing terminal  10  according to the USB standard under the control by the CPU  21 . The operation unit  27  is, for example, a keyboard and a mouse. The operation unit  27  receives operation by the user for instructing processing and supplies a signal corresponding to the operation to the CPU  21 . The display unit  28  is, for example, a liquid crystal display. The display unit  28  displays various images under the control by the CPU  21 . 
     Here, operation modes of the information processing terminal  10  are explained. 
     The information processing terminal  10  operates in any one of three kinds of operation modes, namely, a connected mode (a first operation mode), a mass-storage mode (a second operation mode), and an external operation mode (a third operation mode) in a state in which the information processing terminal  10  is connected to the host device  20 . The connected mode is an operation mode for not accepting processing for the flash ROM  13  from the host device  20 . The mass-storage mode is an operation mode for accepting processing for the flash ROM  13  from the host device  20 . The external operation mode is an operation mode for accepting a processing order for the flash ROM  13  from the host device  20 . More specifically, the operation modes are as described below. 
     The connected mode is an operation mode for not accepting processing for the flash ROM  13  from the host device  20  and, on the other hand, executing processing that the user instructs using the operation unit  17  of the information processing terminal  10 . However, even in this connected mode, when a command (order) for instructing switching to another operation mode is transmitted from the host device  20 , the information processing terminal  10  accepts the command and executes operation mode switching processing as instructed by the command. In other words, the information processing terminal  10  in the connected mode executes operation mode switching processing according to the command for instructing switching to another operation mode transmitted from the host device  20  in a state in which the information processing terminal  10  is connected to the host device  20  via a USB cable. However, in the processing other than the operation mode switching processing, the information processing terminal  10  performs processing equivalent to processing performed when the information processing terminal  10  operates alone. 
     Next, the mass-storage mode is an operation mode in which the host device  20  directly accesses the flash ROM  13  of the information processing terminal  10  and executes processing. In this mass-storage mode, since the information processing terminal  10  is controlled by the host device  20 , even if the operation unit  17  of the information processing terminal  10  is operated by the user, processing instructed by the operation is not executed. In this way, the information processing terminal  10  in the mass-storage mode applies processing of a mass storage, which is the same as that of a normal storage medium such as a removable disk drive, to the host device  20 . However, in the mass-storage mode, when a command for instructing switching to another operation mode is transmitted from the host device  20 , the information processing terminal  10  performs operation mode switching processing according to the command. 
     The external operation mode is an operation mode in which the information processing terminal  10  executes processing instructed by user operation in the host device  20  (i.e., an external device for the information processing terminal  20 ). In this external operation mode, in order to prevent conflict between operation on the information processing terminal  10  side and operation on the host device  20  side, even if the operation unit  17  of the information processing terminal  10  is operated by the user, processing instructed by the operation is not executed. In other words, the operation on the host device  20  side is given priority. This external operation mode is different from the mass-storage mode in that, whereas, in the external operation mode, when the host device  20  orders the information processing terminal  10  to perform processing, the information processing terminal  10  executes the processing using resources (the RAM  12 , etc.) of the information processing terminal  10  itself according to the order and provides the host device  20  with a result of the processing or performs display on the display unit  18  thereof, in the mass-storage, the host device  20  itself accesses the flash ROM  13  and executes processing using resources (the RAM  22 , etc.) of the host device  20 . 
       FIG. 4  is a table in which differences among operations of the information processing terminal  10  in the respective operation modes are collated. “USB connector connection” in the figure is an item indicating whether the USB connector  15  of the information processing terminal  10  and the USB port  25  of the host device  20  are connected. “O” indicates that the USB connector  15  and the USB port  25  are connected. “X” indicates that the USB connector  15  and the USB port  25  are not connected. “Operation mode switching order” is an item indicating whether operation mode switching processing is executed by the information processing terminal  10  according to a command for instructing switching to another operation mode transmitted from the host device  20 . “O” indicates that the operation mode switching processing is executed and “X” indicates that the operation mode switching processing is not executed. “File system external management” is an item indicating whether an operation for accepting a processing order to the flash ROM  13  by the host device  20 , i.e., an operation in a mass-storage class is performed. “O” indicates that the operation in the mass-storage class is performed and “X” indicates that the operation in the mass-storage class is not performed. “File system internal management” is an item indicating whether the CPU  11  of the information processing terminal  10  performs management of a file system of the flash ROM  13 . “O” indicates that the CPU  11  performs the management of the file system and “X” indicates that the CPU  11  does not perform the management of the file system. “Main body operation” is an item indicating whether the information processing terminal  10  executes processing according to operation received by the operation unit  17  of the information processing terminal  10  itself. “O” indicates that the information processing terminal  10  executes the processing and “X” indicates that the information processing terminal  10  does not execute the processing. “Processing order by external operation” is an item indicating whether the information processing terminal  10  executes processing according to a processing order instructed by operation received by the operation unit  27  of the host device  20 . “O” indicates that the information processing terminal  10  executes the processing and “X” indicates that the information processing terminal  10  does not execute the processing. 
     When the USB connector  15  is not connected to the USB port  25  of the host device  20 , the information processing terminal  10  operates in the “unconnected mode”. As shown in the figure, in the “unconnected mode”, “USB connector connection” is “X”, “operation mode switching order” is “X”, “file system external management” is “X”, “file system internal management” is “O”, “main body operation” is “O”, and “processing order by external operation” is “X”. In other words, the behavior of the information processing terminal  10  in the “unconnected mode”, is as described below. First, in the unconnected mode, the USB connector  15  of the information processing terminal  10  and the USB port  25  of the host device  20  are not connected. Therefore, in the information processing terminal  10  at the time of the unconnected mode, all of the operation mode switching processing complying with the command for instructing switching to another operation mode transmitted from the host device  20 , the operation in the mass-storage class, and the processing complying with the processing order instructed by the operation of the operation unit  27  of the host device  20  are not performed. In the information processing terminal  10  at the time of this unconnected mode, the file system of the flash ROM  13  is managed by the CPU  11  that operates according to the OS and processing instructed by the operation of the operation unit  17  is executed. In short, the information processing terminal  10  operates standalone. 
       FIG. 5  is a diagram for explaining processing executed in the information processing terminal  10  at the time of the unconnected mode. Respective kinds of processing shown in the figure are realized by the CPU  11  of the information processing terminal  10  reading out a software group, which should be executed in the unconnected mode, from the flash ROM  13  and executing the software group. Hatched portions in the figure indicate processing that is not executed at the time of the unconnected mode. 
     As described above, in the unconnected mode, the information processing terminal  10  operates standalone. However, if the USB connector  15  of the information processing terminal  10  and the USB port  25  of the host device  20  are connected in this mode, the CPU  11  detects an electric connection state thereof, whereby the unconnected mode is switched to another operation mode. In this unconnected mode, management of the file system of the flash ROM  13  is performed by the CPU  11  and external management of the file system, i.e., the operation in the mass-storage class is not performed. In the unconnected mode, processing instructed by the operation of the operation unit  17  is executed. Consequently, for example, processing for causing the display unit  18  to display an image is performed. 
     Subsequently, as shown in  FIG. 4 , in the “connected mode”, “USB connector connection” is “O”, “operation mode switching order” is “O”, “file system external management” is “X”, “file system internal management” is “O”, “main body operation” is “O” and “processing order by external operation” is “X”. In other words, the behavior of the information processing terminal  10  in the “connected mode” is as described below. First, in the connected mode, the USB connector  15  of the information processing terminal  10  and the USB port  25  of the host device  20  are connected. In the information processing terminal  10  at the time of the connected mode, operation mode switching processing is executed according to a command for instructing switching to another operation mode transmitted from the host device  20 . In the information processing terminal  10  at the time of the connected mode, as in the case of the unconnected mode described above, the operation in the mass-storage class is not performed. The file system of the flash ROM  13  is managed by the CPU  11  that operates according to the OS. In this information processing terminal  10 , processing instructed by the operation of the operation unit  17  is executed but processing ordered by the operation of the operation unit  27  of the host device  20  is not executed. 
       FIG. 6  is a diagram for explaining processing executed in the information processing terminal  10  at the time of the connected mode. The respective kinds of processing shown in the figure are realized by the CPU  11  of the information processing terminal  10  reading out a software group, which is executed in the connected mode, from the flash ROM  13  and executing the software group. Hatched portions in the figure indicate processing that is not executed at the time of the connected mode. 
     As shown in the figure, in the connected mode, operation mode switching processing is executed according to an operation mode switching order, which is a command for instructing switching to another operation mode, transmitted from the host device  20 . In this connected mode, the CPU  11  of the information processing terminal  10  performs the management of the file system of the flash ROM  13  and the external management of the file system and the operation in the mass-storage class are not performed. This “external management of the file system is not performed” specifically unit that the information processing terminal  10  replies to an inquiry from the host device  20  that a device type of the information processing terminal  10  itself is a removable disk and further notifies the host device  20  that a storage medium such as a medium is not present in the removable disk. Consequently, it is possible to pretend that a storage medium is not present in the removable disk connected to the host device  20 . The host device  20  does not access the removable disk in which a storage medium is not present. Therefore, the information processing terminal  10  can prevent the processing order to the flash ROM  13  by the host device  20  from being received. In this connected mode, as in the case of the unconnected mode, processing instructed by the operation of the operation unit  17  is executed. Consequently, for example, processing for causing the display unit  18  to display an image is performed. 
     Subsequently, as shown in  FIG. 4 , in the “mass-storage mode”, “USB connector connection” is “O”, “operation mode switching order” is “O”, “file system external management” is “O”, “file system internal management” is “X”, “main body operation” is “X”, and “processing order by external operation” is “X”. In other words, the behavior of the information processing terminal  10  in the “mass-storage mode” is as described below. First, in the mass-storage mode, as in the case of the of the connected mode described above, the USB connector  15  of the information processing terminal  10  and the USB port  25  of the host device  20  are connected. In the information processing terminal  10  at the time of the mass-storage mode, the operation mode switching processing is executed according to a command for instructing switching to another operation mode transmitted from the host device  20 . In this mass-storage mode, the external management of the file system, i.e., the operation in the mass-storage class is received. The management of the file system of the flash ROM  13  by the CPU  11  is not performed. Moreover, in the mass-storage mode, the processing complying with the operation of the operation unit  17  and the processing ordered by the operation of the operation unit  27  of the host device  20  are not executed. 
       FIG. 7  is a diagram showing processing executed in the information processing terminal  10  at the time of the mass-storage mode. Respective kinds of processing shown in the figure is realized by the CPU  11  of the information processing terminal  10  reading out a software group, which should be executed in the mass-storage mode, from the flash ROM  13  and executing the software group. Hatched portions in the figure indicate processing that is not executed at the time of the mass-storage mode. 
     As shown in the figure, in the mass-storage mode, as in the case of the connected mode described above, the operation mode switching processing is executed according to the operation mode switching order. In the mass-storage mode, the external management of the file system, i.e., the operation in the mass-storage class is performed and the management of the file system of the flash ROM  13  by the CPU  11  is not performed. In the mass-storage mode, the processing instructed by the operation of the operation unit  17  and the processing ordered by the operation of the operation unit  27  of the host device  20  are not executed. For example, even if processing for displaying a certain image on the display unit  18  is instructed by operation received by the operation unit  17 , the CPU  11  does not execute the processing. 
     Subsequently, as shown in  FIG. 4 , in the “external operation mode”, “USB connector connection” is “O”, “operation mode switching order” is “O”, “file system external management” is “X”, “file system internal management” is “O”, “main body operation” is “X”, and “processing order by external operation” is “O”. In other words, the behavior of the information processing terminal  10  in the “external operation mode” is as described below. In the external operation mode, as in the case of the connected mode described above, the USB connector  15  of the information processing terminal  10  and the USB port  25  of the host device  20  are connected. In the information processing terminal  10  at the time of the external operation mode, the operation mode switching processing complying with the command for instructing switching to another operation mode from the host device  20  is executed. In the information processing terminal  10  at the time of the external operation mode, as in the case of the connected mode described above, the external management of the file system, i.e., the operation in the mass-storage class is not performed. The CPU  11  that operates according to the OS manages the file system of the flash ROM  13 . The processing up to here is the same as the operation in the case of the connected mode. However, in this external operation mode, the processing instructed by the operation received by the operation unit  17  is not executed and the processing ordered by the operation received by the operation unit  27  of the host device  20  is executed. 
       FIG. 8  is a diagram showing processing executed in the information processing terminal  10  at the time of the external operation mode. Respective kinds of processing shown in the figure is realized by the CPU  11  of the information processing terminal  10  reading out a software group, which should be executed in the external operation mode, from the flash ROM  13  and executing the software group. Hatched portions in the figure indicate processing that is not executed at the time of the external operation mode. 
     As shown in the figure, in the external operation mode, as in the case of the connected mode described above, the operation mode switching processing is executed according to the operation mode switching order transmitted from the host device  20 . In this external operation mode, as in the case of the connected mode described above, the CPU  11  of the information processing terminal  10  performs management of the file system of the flash ROM  13  and the external management of the file system, i.e., the operation in the mass-storage class is not performed. In other word, the operation mode switching processing and the management of the file system are performed as in the connected mode described above. However, in this external operation mode, the processing instructed by the operation received by the operation unit  17  is not executed and the processing complying with the processing order ordered by the operation received by the operation unit  27  of the host device  20  is performed. The CPU  21  of the host device  20  orders the information processing terminal  10  to perform the processing instructed by the operation received by the operation unit  27  according to the processing order software stored in the storing unit  24 . For example, the host device  20  causes the display unit  18  of the information processing terminal  10  to display the file stored in the flash ROM  13  or orders processing for turning over pages of contents displayed on the display unit  18 . In this external operation mode, the host device  20  cannot directly access the flash ROM  13  of the information processing terminal  10 . Therefore, the host device  20  requests the information processing terminal  10  to transmit a list of files stored in the flash ROM  13  and the information processing terminal  10  transmits the list of the files to the host device  20  in response to the request, whereby an order for processing from the host device  20  is performed. 
     The connected mode, the mass-storage mode, and the external operation mode can be mutually switched according to operation by the user. However, to prevent inconvenience from occurring in processing, transition among the operation modes may be limited. 
     Next, operations according to this embodiment are explained. 
     First, operations in the connected mode are explained with reference to a sequence chart shown in  FIG. 9 . When the USB connector  15  of the information processing terminal  10  is connected to the USB port  25  of the host device  20 , the CPU  11  of the information processing terminal  10  detects a voltage supplied from the USB port  25  by the connection. The CPU  11  recognizes, by detecting this voltage, that the information processing terminal  10  is connected to the host device  20  (step SA 110 ) and switches an operation mode of the information processing terminal  10  to the connected mode (step SA 120 ). 
     On the other hand, when the information processing terminal  10  is connected, the CPU  21  of the host device  20  recognizes the information processing terminal  10  as a removable disk and transmits a command for inquiring whether a storage medium such as a medium is inserted in the removable disk to the information processing terminal  10  (step SA 130 ). In order to virtually show the information processing terminal  10  as the removable disk in which a storage medium is not inserted, the CPU  11  of the information processing terminal  10  transmits a command for replying that a storage medium is not inserted in response to the command, which is transmitted from the host device  20 , to the host device  20  (step SA 140 ). 
     When the command for replying that a storage medium is not inserted is transmitted from the information processing terminal  10 , the CPU  21  of the host device  20  recognizes that a storage medium is not inserted in the information processing terminal  10  (step SA 150 ). According to the OS, the CPU  21  of the host device  20  does not request access to the removable disk in which a storage medium is not inserted. Therefore, the information processing terminal  10  can reject access to the flash ROM  13  by the CPU  21  of the host device  20  by performing such a response. 
     When the information processing terminal  10  is in this connected mode, for example, even if the operation unit  27  of the host device  20  is operated by the user and access to the flash ROM  13  of the information processing terminal  10  is instructed, the CPU  21  of the host device  20  does not perform a request for the access.  FIG. 10  is a diagram showing a screen displayed on the display unit  28  of the host device  20  at this point. When the information processing terminal  10  is in the connected mode, if access to the flash ROM  13  of the information processing terminal  10  is instructed by the user, the CPU  21  of the host device  20  causes the display unit  28  to display a message “removable disk is not ready” as shown in the figure and notifies the user that the flash ROM  13  cannot be accessed. 
     On the other hand, when the operation unit  17  of the information processing terminal  10  is operated by the user, this information processing terminal  10  executes processing instructed by the operation by the user as described above. For example, when operation for instructing processing for causing the display unit  18  to display certain content data D is performed, the CPU  11  of the information processing terminal  10  receives an instruction for processing by the operation by the user (step SA 160  in  FIG. 9 ). Then, this CPU  11  executes the processing instructed by the operation by the user, i.e., processing for reading out the content data D from the flash ROM  13  and causing the display unit  18  to display the content data D (step SA 170 ). Consequently, the content data D designated by the user is displayed on the display unit  18 . 
     Subsequently, operations in the external operation mode are explained with reference to a sequence chart shown in  FIG. 11 . In order to instruct switching to the external operation mode, an SCSI command is used. In the SCSI specification, a command area that a manufacturer can independently use is provided. Therefore, the manufacturer can define a command for instructing switching to the external operation mode using this command area. It is possible to instruct switching to the external operation mode by using the command defined in this way as the operation mode switching order. 
     In a state in which the information processing terminal  10  is connected, when the operation unit  27  of the host device  20  is used by the user and operation for instructing switching to the external operation mode is performed, the CPU  21  of the host device  20  receives an instruction for switching to the external operation mode by the operation (step SB 110 ). Then, this CPU  21  transmits a command for instructing switching to the external operation mode to the information processing terminal  10  (step SB 120 ). When the command for instructing switching to the external operation mode is transmitted from the host device  20 , the CPU  11  of the information processing terminal  10  receives the command using the USB controller  16  and switches the operation mode of the information processing terminal  10  to the external operation mode (step SB 130 ). 
     As an order for processing performed by the host device  20 , in the same manner as described above, the SCSI command defined by the manufacturer is used. For example, if an SCSI command for ordering page turn-over processing for causing the display unit  18  of the information processing terminal  10  to display content data D of the next page is defined by the manufacturer, it is possible to perform page turn-over by using the SCSI command for the order for processing. In other words, the manufacturer can order arbitrary processing from the host device  20  and cause the information processing terminal  10  to execute the processing by defining the SCSI command. 
     As described above, in the external operation mode, the information processing terminal  10  executes the processing ordered by the host device  20 . For example, in this external operation mode, when the operation unit  27  of the host device  20  is used by the user and the operation for instructing the page turn-over processing is performed, the CPU  21  of the host device  20  receives the instruction for the processing by the operation by the user (step SB 140 ). Then, this CPU  21  transmits a command for ordering the page turn-over processing designated by the operation to the information processing terminal  10  (step SB 150 ). When the command for ordering the processing is transmitted from the host device  20 , the CPU  11  of the information processing terminal  10  executes the page turn-over processing ordered by the command (step SB 160 ). 
       FIG. 12  is a diagram showing a screen for receiving operation for instructing the information processing terminal  10  to perform processing. The CPU  21  of the host device  20  executes processing order software, whereby this screen is displayed on the display unit  28  of the host device  20 . For example, when certain content data D is displayed on the display unit  18  of the information processing terminal  10 , the CPU  21  causes the display unit  28  to display a preview image representing contents of the content data D in an area A 1  in this screen and receives operation for instructing the information processing terminal  10  to perform processing using the content data D. When the operation unit  27  of the host device  20  is operated by the user and the page turn-over processing is instructed on this screen, as described above, the CPU  21  of the host device  20  transmits a command for ordering the page turn-over processing to the information processing terminal  10 . When the command for ordering the processing is transmitted from the host device  20 , the CPU  11  of the information processing terminal  10  causes the display unit  18  to display the content data D of the next page according to an order of the command. Consequently, the content data D of the next page is displayed on the display unit  18  of the information processing terminal  10 . 
     Subsequently, operations in the mass-storage mode are explained with reference to a sequence chart shown in  FIG. 13 . When the operation unit  27  of the host device  20  is used by the user and operation for instructing switching from an operation mode (the connected mode or the external operation mode) other than the mass-storage mode to the mass-storage mode is performed, the CPU  21  of the host device  20  receives the instruction for switching to the mass-storage mode by the operation (step SC 100 ). The CPU  21  transmits a command for instructing switching to the mass-storage mode to the information processing terminal  10  as an operation mode switching order (step SC 110 ). 
     When the command for instructing switching to the mass-storage mode is transmitted from the host device  20 , the CPU  11  of the information processing terminal  10  receives the command using the USB controller  16  and, first, writes cache data stored in the RAM  12  in the flash ROM  13  (step SC 120 ). In this RAM  12 , cache data that is a result of processing executed by the CPU  11  is temporarily stored. The cache data stored in the RAM  12  is written in the flash ROM  13  at predetermined timing. For example, when processing for adding tag information representing a tag to certain content data D is executed by the CPU  11 , the content data D is invoked to the RAM  12  and the tag information is added in the RAM  12 . Therefore, in this RAM  12 , the content data D added with the tag information as the cache data is stored. In this way, the tag information is added to the content data D stored in the RAM  12 . However, since there is a time difference until a state of the content data D is reflected on the flash ROM  13 , in a certain period, this tag information is not added to the content data D stored in the flash ROM  13 . 
     In other words, when the CPU  11  writes data in the flash ROM  13 , in general, delay writing is performed by using the RAM  12  as a cache. Since, in general, speed of access to the RAM  12  is higher than speed of access to the flash ROM  13 , contents frequently written are subjected to change or update processing on the RAM  12  and, after the processing is finished, the contents are read out from the RAM  12  and written in the flash ROM  13 . When, for example, a hard disk is used instead of the flash ROM  13 , this hard disk is a block device that cannot be accessed bit by bit and read and written for each block size. Therefore, the CPU  11  needs to store the data on the RAM  12  until the fixed block size is obtained. Because of such circumstances, the RAM  12  is used as a cache. However, unless the contents cached in the RAM  12  are written in the flash ROM  13 , inconsistency occurs in the file system that manages the flash ROM  13 . In the USB terminal in the past, an operation mode is switched according to presence or absence of connection between the USB terminal and the host device. Therefore, when processing for removing the USB terminal from the host device is performed, processing for writing cache data stored in a RAM to a flash ROM is performed. On the other hand, in this embodiment, it is possible to shift the operation mode without removing the USB connector  15  of the information processing terminal  10  from the USB port  25  of the host device  20  and change a management entity of the file system in the flash ROM  13  to the CPU  10  of the information processing terminal  10  or the CPU  21  of the host device  20 . Therefore, before shifting to the mass-storage mode, processing for reflecting the cache data stored in the RAM  12  on the content data D of the flash ROM  13  is necessary. 
     Subsequently, the CPU  11  of the information processing terminal  10  writes work data stored in the RAM  12  in the flash ROM  13  (step SC 130 ). This work data is information representing a work state immediately before the operation mode of the information processing terminal  10  is switched from the operation mode other than the mass-storage mode to the mass-storage mode. The work data is, for example, a file name and a page number of contents displayed on the display unit  18  when the user attempts to write the work data in the flash ROM  13  or an operation history of the operation unit  17 . In other words, the work data is a history of processing executed by the CPU  11 . By performing processing for saving such work data, even if the operation mode of the information processing terminal  10  is switched from the operation mode other than the mass-storage mode to the mass-storage mode and stored contents of the RAM  12  are rewritten by the host device  20 , when the operation mode of the information processing terminal  10  is switched from the mass-storage mode to another operation mode (the connected mode or the external operation mode), it is possible to restore a work state immediately before the operation mode is switched to the mass-storage mode. 
     After writing the data of the RAM  12  in the flash ROM  13 , the CPU  11  of the information processing terminal  10  switches the operation mode of the information terminal  10  to the mass-storage mode (step SC 140 ). As described above, in the mass-storage mode, the information processing terminal  10  accepts access to the flash ROM  13  by the host device  20 . 
     Here,  FIG. 14  is a diagram showing transition of a screen displayed on the display unit  28  of the host device  20  when the CPU  21  of the host device  20  accesses the flash ROM  13  of the information processing terminal  10 .  FIG. 14A  is a diagram showing a screen for managing a device connected to the host device  20 . On this screen, the information processing terminal  10  is displayed as a “removable disk”. When the operation unit  27  of the host device  20  is operated by the user and access to the flash ROM  13  of the information processing terminal  10  is instructed on this screen, a screen shown in  FIG. 14B  is displayed. On this screen, a file name list of the content data D stored in the flash ROM  13  of the information processing terminal  10  is displayed. When the operation unit  27  is operated by the user and display of the content data D with a file name “jkl.bmp” is instructed on this screen, software for displaying this content data D is executed by the CPU  21  and a screen shown in  FIG. 14C  is displayed. On this screen, an image representing the content data D with the file name “jkl.bmp” is displayed. 
     When the operation unit  27  of the host device  20  is used by the user and, for example, operation for instructing processing for adding content data “pqr.bmp” to the flash ROM  13  of the information processing terminal  10  is performed on the screen shown in  FIG. 14B , the CPU  21  of the host device  20  receives the instruction for the processing by the operation by the user (step SC 150  in  FIG. 13 ). Then, this CPU  21  executes processing for accessing the flash ROM  13  of the information processing terminal  10  and adding the content data “pqr.bmp” instructed by the operation (step SC 160 ).  FIG. 15  is a diagram showing screens displayed on the display unit  28  of the host device  20  and the display unit  18  of the information processing terminal  10 . On the display unit  28  of the host device  20 , a message “transferring data to information processing terminal” indicating that content data is being transmitted is displayed. Similarly, on the display unit  18  of the information processing terminal  10 , a message “communicating with PC” indicating that the content data is being transmitted from the host device  20  is displayed. Consequently, the content data “pqr.bmp” is added to the flash ROM  13  of the information processing terminal  10 . 
     When the operation mode of the information processing terminal  10  is the mass-storage mode, when the operation unit  27  of the host device  20  is used by the user and operation for instructing switching from the mass-storage mode to another operation mode is performed, the CPU  21  of the host device  20  receives an instruction for switching to the another operation mode by the operation (step SC 170  in  FIG. 13 ). The another operation mode referred to here is the connected mode or the external operation mode. Next, first, the CPU  21  of the host device  20  writes the cache data temporarily stored in the RAM  22  in the flash ROM  13  (step SC 180 ). In this RAM  22 , in the same manner as described above, cache data that is a result of processing executed by the CPU  21  is stored. For example, when processing for changing contents of certain content data D is executed by the CPU  21 , the content data D acquired by access to the flash ROM  13  is invoked to the RAM  22  and the contents are changed in the RAM  22 . Therefore, in this RAM  22 , the content data D, the contents of which are changed as a result of the processing, is stored. The contents of the content data D stored in the RAM  22  in this way are changed. However, since there is a time difference until a state of the content data D is reflected on the flash ROM  13 , the contents of the content data D stored in the flash ROM  13  may be unchanged from those before the change. Therefore, processing for reflecting the cache data stored in the RAM  22  on the content data D of the flash ROM  13  is necessary. 
     After writing the cache data of the RAM  22  in the flash ROM  13 , the CPU  21  of the host device  20  transmits a command for instructing switching to another operation mode to the information processing terminal  10  as an operation mode switching order (step SC 190 ). When the command for instructing switching to another operation mode is transmitted from the host device  20 , the CPU  11  of the information processing terminal  10  receives the command using the USB controller  16  and switches the operation mode of the information processing terminal  10  from the mass-storage mode to the another operation mode (step SC 200 ). 
     Then, the CPU  11  of the information processing terminal  10  reads the work data written in the flash ROM  13  in step SC 130  in the RAM  12  (step SC 210 ). Consequently, the display contents displayed on the display unit  18  before the operation mode is switched to the mass-storage mode, i.e., a page image specified by the file name and the page number written in the flash ROM  13  in step SC 130  is displayed on the display unit  18  again. Moreover, a history of operation performed before the operation mode is switched to the mass-storage mode is restored. 
     For example, when the operation mode of the information processing terminal  10  is switched from the mass-storage mode to the connected mode in step SC 200 , as described above, the CPU  11  of the information processing terminal  10  executes processing instructed by operation received by the operation unit  17  of the information processing terminal  10 . Therefore, for example, when the user operates the operation unit  17  of the information processing terminal  10  and instructs processing for displaying the content data D “pqr.bmp” added to the flash ROM  13  on the display unit  18 , the CPU  11  causes the display unit  18  to display this content data D. 
     When the connection between the information processing terminal  10  and the host device  20  is cut and the USB connector  15  of the information processing terminal  10  is removed from the USB port  25  of the host device  20 , the information processing terminal  10  and the host device  20  operate alone, respectively. In other words, the CPU  21  of the host device  20  executes processing instructed by operation received by the operation unit  27  and the CPU  11  of the information processing terminal  10  executes processing instructed by operation received by the operation unit  17  using the content data D stored in the flash ROM  13 . 
     According to the embodiment explained above, since the information processing terminal  10  operates in the connected mode, even in a state in which the information processing terminal  10  is connected to the host device  20 , it is possible to execute processing corresponding to operation by the user on the information processing terminal  10 . 
     [Modification] 
     The above is the explanation of the embodiment. Contents of this embodiment can be modified as described below. Respective forms described below may be appropriately combined. 
     (1) In the embodiment described above, the information processing terminal  10  and the host device  20  are connected according to the USB standard. However, the information processing terminal  10  and the host device  20  may be connected to be capable of communicating with each other according to IEEE 1394. In this case, in the information processing terminal  10 , an interface complying with IEEE 1394 detachably attachable to the host device  20  and a controller that communicates with the host device  20  according to IEEE 1394 are provided. In the host device  20 , a connection port to which the interface of the information processing terminal  10  is connected and a controller that communicates with the information processing terminal  10  according to IEEE 1394 are provided. With this configuration, an effect same as that of the embodiment described above is obtained. 
     (2) In the embodiment described above, the information processing terminal  10  operates in the operation mode of any one of the connected mode, the external operation mode, or the mass-storage mode in a state in which the information processing terminal  10  is connected to the host device  20 . On the other hand, the information processing terminal  10  may operate in the operation mode of the connected mode or the mass-storage mode in a state in which the information processing terminal  10  is connected to the host device  20 . 
     (3) In the embodiment described above, switching to the external operation mode and the mass-storage mode is performed according to an instruction of a command transmitted from the host device  20  on the basis of operation by the user received by the operation unit  27  of the host device  20 . On the other hand, switching from the connected mode or the external operation mode to another operation mode may be performed on the basis of operation of the operation unit  17  of the information processing terminal  10  by the user. 
     (4) In the embodiment described above, the example in which the host device  20  is the personal computer and the information processing terminal  10  is the display device called electronic paper is cited and explained. However, the present invention is not limited to this. For example, the information processing terminal  10  described above may be a portable music player or a digital camera. Moreover, for example, when the information processing terminal  10  is the portable music player, the content data D stored in the flash ROM  13  may be sound data used for reproducing music. When the information processing terminal  10  is the digital camera, the content data D may be image data for displaying a picked-up image. Therefore, unit that outputs a result of processing executed by the information processing terminal  10  and the host device  20  is not limited to display unit such as the display unit  18  and the display unit  28  and may be reproducing unit that reproduces the result of the processing as sound or writing unit that writes the result of the processing in a recording medium. 
     (5) In the embodiment described above, processing corresponding to operation received by the operation unit  17  is not executed in the external operation mode. On the other hand, if the processing corresponding to the operation received by the operation unit  17  does not conflict with processing ordered by a command transmitted from the host device  20  and does not cause inconsistency or breakage of data stored in the flash ROM  13 , the CPU  11  of the information processing terminal  10  at the time of the external operation mode may execute the processing corresponding to the operation received by the operation unit  17 . 
     (6) In the embodiment described above, the external operation mode for executing processing ordered by operation received by the operation unit  27  of the host device  20  is provided. In the connected mode, the processing ordered by the operation received by the operation unit  27  of the host device  20  is not executed. On the other hand, the CPU  11  of the information processing terminal  10  at the time of the connected mode may execute the processing ordered by the operation received by the operation unit  27  of the host device  20 . In this case, in a state in which the information processing terminal  10  is connected to the host device  20 , the information processing terminal  10  operates in the two operation modes, i.e., the connected mode and the mass-storage mode. 
     (7) In the embodiment described above, transition of the operation mode may be limited between the mass-storage mode and the external operation mode. For example, the transition of the operation mode is allowed between the connected mode and the mass-storage mode and between the connected mode and the external operation mode and direct transition of the operation mode is disallowed between the mass-storage mode and the external operation mode. This is because, depending on transition between the operation modes, it is likely that contents of the flash ROM are rewritten and consistency of data cannot be maintained after return from the transition between the operation modes. 
     For example, when the operation unit  27  of the host device  20  is operated by the user and switching from the mass-storage mode to the external operation mode is instructed, the information processing terminal  10  may switch the operation mode of the information processing terminal  10  itself from the mass-storage mode to the connected mode once and, then, switch the operation mode to the external operation mode. Consequently, although the operation mode does not directly transition from the mass-storage mode to the external operation mode actually, it is possible to show the operation mode to the user as if the operation mode directly transitions from the mass-storage mode to the external operation mode. 
     (8) In the embodiment described above, programs executed by the CPU  11  of the information processing terminal  10  or the CPU  21  of the host device  20  can be provided in a state in which the programs are recorded in storage media such as a magnetic tape, a magnetic disk, a flexible disk, an optical recording medium, a magneto-optical recording medium, a CD (Compact Disk), a DVD (Digital Versatile Disk), and a flash ROM. 
     The entire disclosure of Japanese Patent Application Nos. 2007-099390 filed on Apr. 5, 2007 and 2007-175369 filed on Jul. 3, 2007 are expressly incorporated by reference herein.