JP2014168144A - Communication method and switching hub - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the communication time of USB communication.SOLUTION: A communication method of the invention is a communication method for a host device (11) and n target devices (TGT_1 to TGT_3) to perform USB communication via a switching hub (12) and is made switchable between a first communication mode in which data can be transmitted and received to and from the host device per target device and a second communication mode in which data of a plurality of target devices can be transmitted to the host device in bulk. The communication method includes the following processes: a process for the host device to dictate the communication mode to the other target devices when the host device performs communication with one target device; if the second communication mode is dictated, a process for the other target devices to store their transfer data in the storage unit of the one target device together; and after the communication has completed, a process for the one target device to transmit its own transfer data and the stored transfer data together to the host device.

Description

  The present invention relates to a communication method, a switching hub, and a data transfer system for transmitting / receiving data in accordance with a USB (Universal Serial Bus) standard, and more particularly, a plurality of target devices transmit / receive data to / from a host device via the switching hub. The present invention relates to a technology that is effective when applied to a communication method.

  USB is known as a general-purpose interface for connecting a peripheral device (hereinafter also referred to as a target device) such as a hard disk drive, a memory card reader, a printer, or a digital camera to a host device such as a personal computer or a home multimedia device. . In USB, by using a hub, a plurality of target devices can be connected to one port of a host device to communicate. For example, Patent Document 1 discloses a related art related to a hub in a data transfer system that performs communication based on the USB standard (hereinafter also simply referred to as USB communication).

  Conventionally, a method for performing communication between one host device and a plurality of peripheral devices in a field other than USB communication is known. For example, Patent Document 2 discloses a master / slave communication method for performing communication between a master device and a plurality of slave devices by broadcast communication. In this document, when a master device controls and monitors a plurality of slave devices, the master device transmits a monitoring / control command to each slave device by broadcast communication, and each slave device responds to it. A method is disclosed in which a response is transmitted to a relay device designated by the master device, and the relay device transmits a response from each slave device to the master device.

  On the other hand, in the USB communication data transfer system, communication between the host device and each target device is realized by polling in which the host device sequentially inquires each target device.

Special table 2008-53885 gazette JP 2008-60753 A

  As described above, communication according to the USB standard (hereinafter also simply referred to as USB communication) is a communication method led by the host device. For example, a period during which one target device communicates with the host device Target devices cannot communicate or are restricted even if they can communicate. For example, in a data transfer system in which three target devices are connected to a host device via a hub, consider a case where one target device exchanges a large amount of data with the host device. The data transfer schedule is delimited by each frame repeated every predetermined time, and a transfer time is allocated to each target device within the frame. In this case, in conventional USB communication, the host device assigns a long transfer time to the one target device that handles large-capacity transfer data, and assigns a short transfer time to the remaining two target devices. Therefore, the amount of data that can be transferred in one frame in the remaining two target devices is limited, and the number of transactions required to complete the target data transfer increases. In addition, since communication is performed in one transaction by a procedure of token packet transfer, data packet transfer, and handshake packet transfer, the total amount of data to be transferred by the remaining two target devices is small. However, if the number of transactions increases, the communication overhead increases and the throughput deteriorates. As a result, there is a problem that the communication time of USB communication becomes longer and the response becomes worse.

  Means for solving such problems will be described below, but other problems and novel features will become apparent from the description of the present specification and the accompanying drawings.

  An outline of representative ones of the embodiments disclosed in the present application will be briefly described as follows.

  That is, this communication method is a communication method for performing USB communication between a host device and n target devices via a switching hub, and is a first method capable of transmitting and receiving data to and from the host device for each target device. The communication mode and the second communication mode in which data of a plurality of target devices can be collectively transmitted to the host device can be switched. This communication method includes the following processes. When the host device communicates with one target device, a process of instructing the communication mode to other target devices. When the second communication mode is instructed, the other target devices collectively store the respective transfer data in the storage unit of one target device. After the completion of the communication, the one target device collectively transmits its own transfer data and the stored transfer data to the host device.

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

  In other words, in a data transfer system in which a plurality of target devices are connected to a host device, the communication time for USB communication can be shortened.

1 is a diagram illustrating a data transfer system capable of USB communication according to Embodiment 1. FIG. 7 is a flowchart showing an example of a communication method in a second communication mode in the data transfer system according to Embodiment 1. FIG. FIG. 10 is a flowchart showing another example of the communication method in the second communication mode in the data transfer system according to the first embodiment. It is a figure which illustrates the data transfer system which can perform USB communication based on Embodiment 2. FIG. FIG. 10 is a flowchart showing an example of a communication method in a second communication mode in the data transfer system according to the third embodiment. FIG. 10 is a flowchart showing another example of the communication method in the second communication mode in the data transfer system according to the second embodiment. It is a figure which shows the specific example of the data transfer system to which the communication method which concerns on Embodiment 1 is applied. It is a figure which shows another specific example of the data transfer system to which the communication method which concerns on Embodiment 1 is applied.

1. First, an outline of a typical embodiment disclosed in the present application will be described. Reference numerals in the drawings referred to in parentheses in the outline description of the representative embodiments merely exemplify what are included in the concept of the components to which the reference numerals are attached.

[1] (Communication method in which data is collected between other USB target devices while one USB target device is communicating with the host device, and the collected data is transmitted to the host device after the communication)
A communication method according to a representative embodiment of the present application includes a host device (11) and n (n is an integer of 3 or more) target devices each including a storage unit (101) for temporarily storing data. (TGT_1 to TGT_3) is a communication method for transmitting and receiving data according to the USB standard via the switching hub (12). The host device and the n target devices are a first communication mode capable of transmitting and receiving data to and from the host device for each target device, and a first communication mode in which data of a plurality of target devices can be collectively transmitted to the host device. Communication is possible by switching between the two communication modes. This communication method includes the following processes. When the host device communicates with one target device (TGT_3), a first process (S101, S103) for instructing a communication mode to other target devices (TGT_1, TGT_2) other than the one target device . A second process in which the host device starts communication with the one target device (S105). When the second communication mode is instructed in the first process, the other target devices communicate with each other, thereby transferring one transfer data to be transferred to the host device held by each of the other target devices. Third processing (S110) for storing together in the storage unit in another target device. After the communication between the host device and the one target device is completed, the target device (TGT_1) that collectively stores the transfer data in the storage unit in the third process stores the transfer data and its own storage unit in the storage unit. Fourth processing (S115) for transmitting the transfer data together to the host device.

  According to this, compared with the case where each of the other target devices establishes communication with the host device and transfers data, the transaction required to complete transmission of all transfer data of the other target device. Since the number is reduced, overhead in transfer is reduced and throughput is improved. Further, in the USB standard, when the communication speeds of the target devices connected to the switching hub are different, communication must be performed in accordance with the target device having the slowest communication speed. Thus, it is possible to perform data communication at the fastest communication speed that can be taken by the target device that collectively stores the transfer data. Therefore, according to this communication method, the communication time of USB communication can be shortened in a data transfer system in which a host device and n target devices are connected via a switching hub.

[2] (Data is stored in the target device with the largest buffer storage capacity)
In the communication method according to Item 1, in the one other target device, the storage capacity of the storage unit is maximized among the other target devices.

  According to this, since more data can be stored in the storage unit, the throughput can be further improved.

[3] (Identify the target device with the largest storage capacity and send the transfer data)
In the communication method according to Item 2, the third process includes the following processes. A fifth process (S106, S107) in which the other target devices mutually transmit / receive information on the storage capacity indicating the storage capacity of the storage unit held by each other. Based on the information on the storage capacity, the other target device determines whether the storage capacity of the storage unit is the largest, and the target device that determines that the storage capacity is the largest Sixth processing for notifying the target device that transfer data can be stored (S108). The target device that has received the notification of the sixth process transmits the transfer data for transfer to the host device to the target device that has been determined to have the largest storage capacity, and the target device that has been determined to have the largest storage capacity Is a seventh process of storing the received transfer data in the storage unit (S110).

  According to this, it is possible to easily determine the target device having the storage unit with the largest storage capacity, and it becomes easy for another target device to transmit the transfer data to the determined target device.

[4] (Accumulate data that can be transmitted within a specified time)
In the communication method according to Item 3, in the first process, the host device further transmits information indicating a waiting time until communication with the host device becomes possible to the other target device. In the seventh process, the other target devices calculate the amount of data that can be transmitted before the communication between the host device and the one target device is completed based on the information indicating the standby time, The transfer data corresponding to the calculated data amount is data to be transmitted to the target device determined to have the largest storage capacity.

  According to this, it is possible to store more transfer data in the storage unit during a period in which the host device and the one target device are communicating, which contributes to further improvement of throughput.

[5] (Predicted number of transactions)
In the communication method according to Item 4, the information indicating the waiting time includes information on the number of transactions scheduled for communication between the host device and the one target device.

[6] (Predicted time)
In the communication method according to Item 4, the information indicating the standby time includes information on an estimated time required for communication between the host device and the one target device.

[7] (When one USB target device is communicating with the host device, the data of the other USB target devices are stored together in the buffer memory of the switching hub, and the combined data is transmitted to the host device after the communication. Communication method)
In the communication method according to the representative embodiment of the present application, a host device (11) and n (n is an integer of 3 or more) target devices (TGT_1A to TGT_3A) are connected via a switching hub (22). This is a communication method for transmitting and receiving data according to the USB standard. The host device and the n target devices are a first communication mode capable of transmitting and receiving data to and from the host device for each target device, and a first communication mode in which data of a plurality of target devices can be collectively transmitted to the host device. Communication is possible by switching between the two communication modes. The switching hub includes a storage unit (225) capable of temporarily storing data. This communication method includes the following processes. When the host device communicates with one target device, a first process (S301, S303, S305) for instructing a communication mode to a target device other than the one target device and the switching hub. A second process in which the host device starts communication with the one target device (S307). When the second communication mode is instructed in the first process, the other target device communicates with the switching hub and transfers to the host device held by each of the other target devices. 3rd processing (S308-S313) which stores the transfer data for this in the said memory | storage part in the said switching hub collectively. After the communication between the host device and the one target device is completed, a fourth process (S320) in which the switching hub collectively transmits the transfer data stored in the storage unit to the host device.

  In the communication method, the switching hub accumulates transfer data from another host device as a pseudo host device during a period in which the one target device and the host device are communicating, and the communication The transfer data stored later is collectively transmitted to the host device. According to this, compared with the case where each of the other target devices establishes communication with the host device and transfers data, the transaction required to complete transmission of all transfer data of the other target device. Since the number is reduced, overhead in transfer is reduced and throughput is improved. In the USB standard, when the communication speeds of the target devices connected to the switching hub are different, communication must be performed in accordance with the target device having the slowest communication speed. It is possible to perform data communication with the host device at the fastest communication speed possible. Therefore, according to this communication method, the communication time of USB communication can be shortened in a data transfer system in which a host device and n target devices are connected via a switching hub.

[8] (Details of communication method between switching hub and target device)
In the communication method according to Item 7, the third process includes a fifth process (S308, S310) in which the switching hub notifies the other target device that the transfer data can be stored, and the other process. Including a sixth process (S312 and S313) in which the target device transmits the transfer data to the switching hub and accumulates the transfer data received by the switching hub in the storage unit.

  This facilitates communication between the switching hub and the target device without using the host device.

[9] (Accumulate data that can be transmitted within a predetermined time)
In the communication method according to item 8, in the first process, the host device further transmits information indicating a waiting time until communication with the host device becomes possible to the other target device and the switching hub. To do. In the sixth process, the other target device calculates the amount of data that can be transmitted before the communication between the host device and the one target device is completed based on the information indicating the standby time. The transfer data corresponding to the calculated data amount is data to be transmitted to the switching hub.

  According to this, it is possible to store more transfer data in the storage unit during a period in which the host device and the one target device are communicating, which contributes to further improvement of throughput.

[10] (Predicted number of transactions)
In the communication method according to item 9, the information indicating the waiting time includes information on the number of transactions scheduled for communication between the host device and the one target device.

[11] (Predicted time)
In the communication method according to Item 9, the information indicating the standby time includes information on an estimated time required for communication between the host device and the one target device.

[12] (Switching hub)
The switching hub (22) according to the representative embodiment of the present application is a switching hub capable of communication according to the USB standard. This switching hub has a first input / output port (121) for connection to the host device (11) and n second (n is an integer of 3 or more) second for connection to the target devices (TGT_1A to TGT_3A). Input / output ports (123 to 125). The switching hub further switches the connection between the first input / output port and the second input / output port to connect the host device connected to the first input / output port and the second input / output port. It has a communication control part (220,122) for controlling communication between the said connected target apparatuses, and a memory | storage part (225). When the communication control unit establishes a connection between the first input / output port and one second input / output port, transfer data to be transferred to the host device is transferred to the other second input / output port. The transfer data is stored together in the storage unit. Further, the communication control unit collectively outputs the transfer data stored in the storage unit from the first input / output port after releasing the connection between the first input / output port and the one second input / output port. Is made possible.

  According to this, compared with the conventional switching hub that constructs communication between each of the other target devices and the host device while sequentially switching the second input / output port connected to the first input / output port. Since the number of transactions required to complete transmission of all transfer data of other target devices is reduced, overhead in transfer is reduced and throughput is improved. In addition, in the USB standard, when the communication speed of the target device connected to the switching hub is different, communication must be performed in accordance with the target device having the slowest communication speed. Data communication can be performed at the fastest communication speed that the switching hub can take. Therefore, according to this switching hub, the communication time of USB communication can be shortened.

[13] (Data transfer system)
A data transfer system (1) according to a typical embodiment of the present application includes a host device (11) and n (n is an integer of 3 or more) target devices (TGT_1 to TGT_3). The data transfer system includes a first input / output port (121) to which the host device is connected and n second input / output ports (123 to 125) to which the target devices are connected correspondingly. And a switching hub (12) that enables switching between the connection between the first input / output port and the second input / output port and the connection between the second input / output ports. The target device includes a storage unit (101) for temporarily storing data. When the other target devices communicate with each other, transfer data to be transferred to the host device held by the other target devices is collectively stored in the storage unit in one other target device. Is done. When the communication between the host device and the one target device is completed, the target device that collectively stores the transfer data collectively stores the transfer data held by the target device and the transfer data stored in the storage unit. Send to the host device.

  According to this, the number of transactions required to complete transmission of all transfer data of the other target device is reduced compared to the case where each of the other target devices transfers data to the host device. Transfer overhead is reduced and throughput is improved. Thereby, the communication time of USB communication in a data transfer system can be shortened.

2. Details of Embodiments Embodiments will be further described in detail.

<< Embodiment 1 >>
FIG. 1 illustrates a data transfer system capable of USB communication.

  The data transfer system 1 shown in FIG. 1 includes a host device (HOST) 11, a plurality of peripheral devices (target devices, PRD) TGT_1 to TGT_3, and a switching hub (SW_HUB) 12. The host device 11 And the target devices TGT_1 to TGT_3 (generally referred to simply as TGT) are capable of USB communication via the switching hub 12.

  In general, in USB communication, communication is performed by transferring a data block including a plurality of packets called a frame at a predetermined cycle. The predetermined period is 1 ms in the full speed mode and 125 μs in the high speed mode. The frame is composed of an SOF packet called SOF (Start of frame) and a plurality of transactions. A transaction is a minimum unit of one data transfer realized by exchanging a plurality of packets between a host device and a target device. The transaction consists of a token packet that specifies the type of transfer and the address of the target device, a data packet that contains the data to be transferred, and a handshake packet such as ACK or NAC that indicates normal reception or reception error of the data. Composed. For example, in the case of bulk transfer, there are an OUT token that instructs data transfer from the host device to the target device and an IN token that instructs data transfer from the target device to the host device as token packets. Transactions within one frame can be assigned to each target device as necessary, and transfer time can be assigned to each target device little by little during the period of one frame.

  The host device 11 is interfaced with each of the target devices TGT_1 to TGT_3 via the switching hub 12. The host device 11 is, for example, a personal computer, a server, or a home multimedia device. The host device 11 supports, for example, a low speed mode (1.5 Mbps), a full speed mode (12 Mbps), and a high speed mode (480 Mbps), and the target devices TGT_1 to TGT_3 at any communication speed. Is made accessible.

  The host device 11 includes a central processing unit (CPU) 110, a memory (MRY) 111, a bus 112, a USB host controller (USB_CNT) 113, and other peripheral circuits not shown. Although not particularly limited, the central processing unit 110, the memory 111, the bus 112, the USB host controller 113, and other peripheral circuits (not shown) are formed on a single semiconductor substrate such as single crystal silicon by a known CMOS integrated circuit manufacturing technique. Formed. The host device 11 is a microcontroller, for example.

  The central processing unit 110 executes various arithmetic processes according to a program stored in advance in the memory 111 and performs overall control of each functional unit in the host device 11. The memory 111 includes a RAM that temporarily stores calculation results, programs, and the like in the calculation processing performed by the central processing unit 110, and a ROM that stores programs executed by the central processing unit 110.

  The USB host controller 113 controls USB communication between the host device 11 and the target devices TGT_1 to TGT_3. The USB host controller 113 is commonly connected to the central processing unit 110, the memory 111, and peripheral circuits (not shown) via the bus 112. The USB host controller 113 includes, for example, a control unit (CNT) 1130 and an input / output port (I / O_PRT) 1131. The input / output port 1131 is connected to the upstream port (input / output port 121) of the switching hub 12 so that data can be transmitted and received. Although not shown, the input / output port 1131 includes, for example, a plurality of external terminals and an external interface circuit for receiving data supplied to the external terminals and transmitting data to the external terminals. Is done.

  The control unit 1130 controls USB communication with the target devices TGT_1 to TGT_3 by controlling the input / output port 1131. Although not particularly limited, the control unit 1130 is a program processing device that realizes various functions when the central processing unit executes programs stored in a ROM or a RAM. The control unit 1130 sequentially inquires (polling) the presence / absence of a communication request to the target devices TGT_1 to TGT_3, and establishes communication with the target device having the communication request. At this time, either the first communication mode or the second communication mode is designated for the switching hub 12 and the target devices TGT_1 to TGT_3. The first communication mode is a mode in which data can be transmitted / received to / from the host device 11 for each of the target devices TGT_1 to TGT_3, similarly to the conventional USB communication. The second communication mode is a mode in which data of a plurality of target devices TGT can be collectively transmitted to the host device 11.

  Specifically, the control unit 1130 determines the amount of transfer data to be transferred in communication with one target device TGT, and instructs the second communication mode when determining that the communication time is long. If not, the first communication mode is instructed. For example, when the transfer data is transmitted from the host device 11 to the target device TGT_3, the control unit 1130 completes communication with the target device TGT_3 based on the amount of transfer data to be transmitted to the target device TGT_3. Is calculated and compared with a predetermined threshold. When the calculated required time is smaller than the predetermined threshold value, it instructs the other target devices TGT_1 and TGT_2 other than the target device TGT_3 to perform communication in the first communication mode. On the other hand, when the calculated required time is larger than the predetermined threshold, the host device 11 is instructed to perform communication in the second communication mode to the target devices TGT_1 and TGT_2 other than the target device TGT_3. Information on the waiting time until communication with can be made. The information on the waiting time is, for example, information on the predicted number of transactions scheduled for communication between the host device 11 and the target device TGT_3, information on the predicted time required for communication between the host device 11 and the target device TGT_3, and the like. .

  The switching hub 12 includes an input / output port (I / O_PRT) 121 as an upstream port connectable to the host device 11 and n ports (n is an integer of 3 or more) as downstream ports connectable to the target device TGT. Input / output port (I / O_PRT), a switching circuit (SWCIR) 122, and a control unit (CNT) 120. The figure shows three ports, i.e., input / output ports 123, 124, and 125, as n input / output ports as downstream ports, but the number is limited to three or more. There is no.

  As described above, the input / output port 121 is connected to the input / output port 1131 in the host device 11 so that data can be transmitted and received. The input / output ports 123 to 125 are connected to the input / output ports (I / O_PRT) 104 of the corresponding target devices TGT_1 to TGT_3 to enable data transmission / reception. Although not shown, the input / output ports 121 and 123 to 125 include, for example, a plurality of external terminals, an external interface circuit for receiving data supplied to the external terminals and transmitting data to the external terminals, It is comprised including. The switching circuit 122 switches connection and disconnection between the input / output port 121 and the input / output ports 123 to 125 and switches connection and disconnection between the input / output ports 123 to 125. As a result, various communication paths can be established between the input / output ports 121 and 123 to 125. Although not particularly limited, FIG. 1 illustrates a case where the input / output port 123 and the input / output port 124 are connected and the input / output port 121 and the input / output port 125 are connected.

  The control unit 120 controls the input / output ports 121 and 123 to 125 and the switching circuit 122 to thereby control the host device 11 connected to the input / output port 121 and the target devices TGT_1 to TGT_3 connected to the input / output ports 123 to 125. Control communication with the. For example, the control unit 120 establishes a designated communication path by controlling the switching circuit 122 based on a control signal transmitted from the USB host controller 113 in the host device 11, and establishes a designated communication path with the host device 11 and the target devices TGT_1. TGT_3 communication and communication between target devices TGT_1 to TGT_3 are enabled.

  The target devices TGT_1 to TGT_3 are enabled to perform USB communication between target devices in addition to USB communication with the host device 11. The target device TGT is, for example, a USB device compatible with the OTG (On-The-Go) standard, and is a hard disk drive, a memory card reader, a printer, a digital camera, or the like.

  The target devices TGT_1 to TGT_3 include, for example, a USB target controller 100 and an internal circuit 103. The internal circuit 103 is a functional unit for realizing functions unique to the target devices TGT_1 to TGT_3. The USB target controller 100 communicates with the host device 11 and other target devices via the switching hub 12. The USB target controller 100 includes, for example, a buffer memory 101, a control unit 102, and an input / output port (I / O_PRT) 104. The USB target controller 100 is not particularly limited, but is a one-chip semiconductor integrated circuit formed on a single semiconductor substrate such as single crystal silicon by a known CMOS integrated circuit manufacturing technique. The buffer memory 101 may be configured on the same chip as the control unit 102 or the like, or may be a separate chip, and is not particularly limited. The input / output port 104 is connected to any one of the input / output ports 123 to 125 in the switching hub 12 to enable data transmission / reception. Although not shown, the input / output port 104 includes, for example, a plurality of external terminals and an external interface circuit for receiving data supplied to the external terminals and transmitting data to the external terminals. Is done. The buffer memory 101 is a storage device for storing data. For example, the buffer memory 101 includes a large-capacity volatile storage area. Although not particularly limited, the buffer memory 101 is a RAM.

  The control unit 102 controls the input / output port 104 based on a control signal supplied from the host device 11 via the switching hub 12, thereby communicating with the host device 11 via the switching hub 12 and other targets. Allows communication with the device. For example, when the first communication mode is instructed by a control signal supplied from the host device 11, the control unit 102 sends transfer data to be transmitted to the host device 11 supplied from the internal circuit 103 to the input / output port 104. The transfer data received at the input / output port 104 is supplied to the internal circuit 103 as necessary. On the other hand, when the second communication mode is instructed by the control signal supplied from the host device 11, the control unit 102 performs communication with other target devices. Specifically, the control unit 102 exchanges storage capacity information indicating the storage capacity of the buffer memory 101 with other target devices, and the storage capacity of its own buffer memory 101 is the highest. Determine whether it is larger. When it is determined that the data is the largest, information indicating that data can be accumulated is transmitted to another target device, and transfer data transmitted from the other target device is stored in the buffer memory 101. Then, the transfer data supplied from its own internal circuit 103 and the transfer data stored in the buffer memory 101 are collected and transmitted to the host device 11. On the other hand, if it is determined that the storage capacity of its own buffer memory 101 is smaller than that of the other target device, the control unit 102 transfers the transfer data to be transmitted to the host device 11 to the buffer memory having the largest storage capacity. 101 to the target device having 101. More specifically, the control unit 102 calculates a communicable time with another target device based on the information on the standby time received from the host device 11, and transmits within the calculated time. Calculate the maximum amount of data possible. Then, the transfer data corresponding to the calculated maximum data amount is transmitted to the target device having the buffer memory 101 having the largest storage capacity. When the storage capacity of the buffer memory of the destination target device is smaller than the calculated maximum data amount, transfer data having a data amount that can be stored in the buffer memory is transmitted. Then, after the communication between the host device and the target device is completed, the remaining transfer data may be transmitted again to the host device.

  Next, a communication method in the second communication mode in the data transfer system 1 will be described in detail with reference to FIGS.

  FIG. 2 is a flowchart showing an example of a communication method in the second communication mode in the data transfer system according to the first embodiment. The figure illustrates a communication procedure when the host device 11 transmits a large amount of data to the target device TGT_3, and the target device TGT_1 and the target device TGT_2 transmit a small amount of data to the host device 11. Yes.

  First, the host device 11 calculates a required time until the communication with the target device TGT_3 is completed based on the data amount of transfer data to be transmitted to the target device TGT_3, and compares it with a predetermined threshold value. When the host device 11 determines that the calculated required time is larger than the predetermined threshold, the host device 11 instructs the target device TGT_1 to perform communication in the second communication mode by a bulk communication transaction and communicates with the host device 11. The information of the waiting time until it becomes possible is transmitted (S101). The target device TGT_1 transmits a response (ACK) to the host device 11 to the host device 11 (S102). Similarly, the host device 11 instructs the target device TGT_2 to perform communication in the second communication mode, and transmits information on the standby time (S103). The target device TGT_2 transmits a response (ACK) to the host device 11 to the host device 11 (S104). The host device 11 starts communication with the target device TGT_3 (S105). Specifically, the host device 11 repeatedly transmits the transfer data until the scheduled transmission completion time based on the information on the standby time notified to the other target devices TGT_1 and TGT_2. Even if the data needs to be retransmitted and the transmission of all data is not completed by the original scheduled time for completion of transmission, the transmission of data is stopped when the initial scheduled time for completion of transmission is reached. At this time, the host device 11 does not issue the transactions of the target devices TGT_1 and TGT_2, and transmits data only by the transaction of the target device TGT_3. Thereby, the data transfer to the target device TGT_3 can be completed in a shorter time.

  When communication between the host device 11 and the target device TGT_3 is started in the process S105, communication between the target devices TGT_1 and TGT_2 is started. Specifically, when the transmission of the periodic SOF packet from the host device 11 to the target devices TGT_1 and TGT_2 is stopped, the target devices TGT_1 and TGT_2 start communication using this as a trigger. First, the target device TGT_1 transmits information on the storage capacity of the buffer memory 101 held by itself to the target device TGT_2 (S106). Next, the target device TGT_2 transmits information on the storage capacity of the buffer memory 101 that it owns to the target device TGT_1 (S107). Although not particularly limited, for example, which of the target devices TGT_1 and TGT_2 starts transmission of storage capacity information is performed from the smaller address number for each target device allocated when connected to the host device 11. Shall. The target devices TGT_1 and TGT_2 that have received the storage capacity information determine which buffer memory 101 has the larger storage capacity. When it is determined that the buffer memory 101 of the target device TGT_1 has a larger storage capacity, the target device TGT_1 notifies the target device TGT_2 that data can be accumulated (S108). Receiving the notification, the target device TGT_2 transmits a response (ACK) to the target device TGT_1 to the target device TGT_1 (S109).

  Thereafter, the target device TGT_2 starts transmitting transfer data to be transferred to the host device 11 to the target device TGT_1 (S110). Specifically, the target device TGT_2 calculates the time that can be communicated with the target device TGT_1 based on the information on the standby time received in the process S103, and can transmit the maximum time within the calculated time. Calculate the amount of data. Then, transfer data corresponding to the calculated maximum data amount is transmitted to the target device TGT_1. On the other hand, the target device TGT_1 sequentially stores the transfer data transmitted from the target device TGT_2 in its own buffer memory 101.

  When the transmission of data to the target device TGT_3 is completed, the host device 11 notifies the target device TGT_1 that the transmission has been completed (S111). In addition to the response (ACK) to the response, the target device TGT_1 notifies the host device 11 that the transfer data of the target device TGT_2 is accumulated (S112). Similarly, the host device 11 notifies the target device TGT_2 that transmission has been completed (S113). The target device TGT_2 notifies the host device 11 of a response (ACK) to the target device TGT_2 (S114). Thereafter, the target device TGT_1 collectively transmits the transfer data of the target device TGT_2 stored in the buffer memory 101 and the transfer data to be transferred to the host device 11 held by the target device TGT_1 to the host device 11 (S115). For example, the target device TGT_1 notifies the host device 11 that data has been accumulated in the first bulk notification transaction, and transmits the transfer data collectively in the subsequent transaction. This communication is performed only between the host device 11 and the target device TGT_1. That is, the communication frame does not include the transaction of the target device TGT_2 or the target device TGT_3, and data is transmitted only by the transaction of the target device TGT_1.

  When the data transmission to the host device 11 is completed, the target device TGT_1 notifies the target device TGT_2 that the transfer data stored in the buffer memory 101 has been transferred to the host device 11 (S116). The target device TGT_2 notifies the response (ACK) to the target device TGT_1 (S117). When the above processing is completed, the host device 11 and the target device TGT return to normal operation.

  FIG. 3 is a flowchart showing another example of the communication method in the second communication mode. The figure illustrates a communication procedure when the target device TGT_3 transmits a large amount of data to the host device 11, and the target device TGT_1 and the target device TGT_2 transmit a small amount of data to the host device 11. Yes.

  First, when the target device TGT_3 receives an inquiry about the presence / absence of data transfer from the host device 11 by polling, the target device TGT_3 sends a preferential transmission request for transfer data and information on the data amount of the transfer data to be transmitted 11 (S201). The host device 11 transmits a response to the request to the target device TGT_3 (S202). Based on the received information on the amount of data, the host device 11 calculates a time required for completing communication with the target device TGT_3 and compares it with a predetermined threshold value. When the host device 11 determines that the calculated required time is larger than the predetermined threshold, the host device 11 instructs the target device TGT_1 to perform communication in the second communication mode by a bulk communication transaction and communicates with the host device 11. The information of the waiting time until it becomes possible is transmitted (S101). The target device TGT_1 transmits a response (ACK) to the host device 11 to the host device 11 (S102). Similarly, the host device 11 instructs the target device TGT_2 to perform communication in the second communication mode, and transmits information on a waiting time until communication with the host device 11 becomes possible (S103). . The target device TGT_2 transmits a response (ACK) to the host device 11 to the host device 11 (S104).

  The host device 11 starts communication with the target device TGT_3 (S205). Specifically, the host device 11 repeatedly receives the transfer data until the scheduled transmission completion time based on the information on the standby time notified to the other target devices TGT_1 and TGT_2. Even if the data needs to be retransmitted and reception of all data is not completed before the initial scheduled transmission completion time, the reception of data is stopped when the initial scheduled transmission completion time is reached. At this time, the host device 11 does not issue the transactions of the target devices TGT_1 and TGT_2, and transmits data only by the transaction of the target device TGT_3.

  When communication between the host device 11 and the target device TGT_3 is started in step S205, communication between the target devices TGT_1 and TGT_2 is started. The subsequent processing is the same as the processing S106 to S117 in FIG. As a result, the transfer data of the target device TGT_2 is temporarily stored in the buffer memory 101 of the target device TGT_1. After the communication between the host device 11 and the target device TGT_3 is completed, the target device TGT_1 stores the transfer data in its own buffer data and the buffer memory 101. The accumulated data is collectively transmitted to the host device 11.

  According to the above communication method, the overhead in data transfer can be reduced as compared with the case where each target device transfers data to the host device by a transaction allocated in one frame. For example, in the case of the above example, when the target device TGT_1 collectively transmits the transfer data to the host device 11, the target device TGT_1 and the target device TGT_2 transmit data to the host device 11 separately as compared with the case where the target device TGT_1 transmits data to the host device 11. Since the number of token packet transmissions is reduced, overhead in data transfer is reduced and throughput is improved.

  Further, in the USB standard, when the communication speed of the target device connected to the switching hub is different, the communication speed of the target device having the slowest communication speed must be followed. The data communication can be performed at the fastest communication speed that can be taken by the target device that stores the data in the buffer memory. For example, when the target device TGT_2 is compatible with the low speed mode and the target device TGT_1 is compatible with the full speed mode, the target device TGT_1 and the target device TGT_2 can perform data transmission within one frame only by the target device TGT_2. In addition, the target device TGT_1 needs to communicate in the low speed mode. However, according to the above method, since only the target device TGT_1 communicates with the host device 11, data can be transferred in the full speed mode, and throughput can be improved.

  As described above, according to the data transfer system 1 according to the first embodiment, the communication time of USB communication can be shortened.

<< Embodiment 2 >>
In the first embodiment, the configuration and method of performing communication between other target devices while one target device is communicating with the host device and accumulating transfer data in one of the other target devices are exemplified. However, the second embodiment exemplifies a configuration and method for storing transfer data of other target devices in the switching hub during the period.

  FIG. 4 illustrates a data transfer system capable of USB communication according to the second embodiment.

  The data transfer system 2 shown in the figure includes a host device 11, a plurality of peripheral devices (target devices) TGT_1 to TGT_3, and a switching hub 22, and the host device 11 and the target device TGT are switched. USB communication is enabled via the hub 22. In the figure, the same components as those in the data transfer system according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  The switching hub 22 includes an input / output port 121 as an upstream port that can be connected to the USB host controller 113 of the host device 11 and n ports (n is 3) that can be connected to the target device TGT. (An integer above) input / output ports, a switching circuit 122, a control unit 220, and a buffer memory (BUF) 225. The figure shows three ports, i.e., input / output ports 123, 124, and 125, as n input / output ports as downstream ports, but the number is limited to three or more. There is no. Although not particularly limited, the input / output ports 121, 123, 124, and 125, the switching circuit 122, the control unit 220, and the buffer memory 225 may be a single semiconductor substrate such as single crystal silicon by a known CMOS integrated circuit manufacturing technique. Formed. The buffer memory 225 may be configured on the same chip as the control unit 220 or the like, or may be a separate chip, and is not particularly limited.

  The buffer memory 225 is a storage device for storing data. For example, the buffer memory 225 includes a large-capacity volatile storage area. Although not particularly limited, the buffer memory 225 is a RAM.

  The control unit 220 controls the input / output ports 121 and 123 to 125 and the switching circuit 122, so that the host device 11 connected to the input / output port 121 and the target devices TGT_ 1 </ b> A to TGT_ <b> 3 </ b> A connected to the input / output ports 123 to 125. Control communication with the. For example, when the first communication mode is instructed by the control signal transmitted from the USB host controller 113 in the host device 11, the control unit 220 inputs / output ports 123 to 125 to which the designated target device TGT is connected. Communication between the host device 11 and the designated target device TGT is enabled. On the other hand, when the second communication mode is instructed by the control signal transmitted from the USB host controller 113, the control unit 220 sets the communication path between one target device and the host device 11 as in the first communication mode. At the same time, as a pseudo host device, data transmission / reception between other target devices and the switching hub 22 is enabled. Specifically, when receiving the control signal instructing the second communication mode, the control unit 220 notifies the other target devices that data can be stored, and transmitted from each of the notified target devices. Are transferred to the buffer memory 225 and stored together. Then, the transfer data stored in the buffer memory 225 is collectively transmitted to the host device 11. When the transfer data transmitted from another target device is larger than the storage capacity of the buffer memory 225, only the transfer data having a data amount that can be stored in the buffer memory is received. Then, after the communication between the host device and the target device is completed, the remaining transfer data may be transmitted again from the target device having the remaining transfer data to the host device 11 in the first communication mode.

  The target devices TGT_1A to TGT_3A are enabled to perform USB communication with the switching hub in addition to USB communication with the host device 11. The target devices TGT_1A to TGT_3A are configured to include a USB target controller 200 and an internal circuit 103, for example. The USB target controller 200 communicates with the host device 11 via the switching hub 22 and also communicates with the switching hub 22 as a pseudo host device. The USB target controller 200 includes, for example, a control unit 202 and an input / output port (I / O_PRT) 104.

  When the first communication mode is instructed by the control signal supplied from the host device 11, the control unit 202 transmits transfer data to be transmitted to the host device 11 supplied from the internal circuit 103 from the input / output port 104. At the same time, the transfer data received at the input / output port 104 is supplied to the internal circuit 103. On the other hand, when the second communication mode is instructed by the control signal supplied from the host device 11, the control unit 202 communicates with the switching hub 22 as a pseudo host device. For example, the control unit 202 calculates a communicable time with the switching hub 22 based on the standby time information received from the host device 11, and the maximum amount of data that can be transmitted within the calculated time. Is calculated. When receiving a notification from the switching hub 22 that data can be stored, the transfer data corresponding to the calculated maximum data amount is transmitted to the switching hub 22.

  Next, a communication method in the second communication mode in the data transfer system 2 will be described in detail with reference to FIGS.

  FIG. 5 is a flowchart showing an example of a communication method in the second communication mode in the data transfer system 2. The figure illustrates a communication procedure when the host device 11 transmits a large amount of data to the target device TGT_3A, and the target device TGT_1A and the target device TGT_2A transmit a small amount of data to the host device 11. Yes.

  First, the host device 11 calculates a time required for completing communication with the target device TGT_3A based on the data amount of transfer data to be transmitted to the target device TGT_3A, and compares it with a predetermined threshold value. If the host device 11 determines that the calculated required time is larger than a predetermined threshold, the host device 11 instructs the switching hub 22 to perform communication in the second communication mode by a bulk communication transaction, and The information of the waiting time until the communication becomes possible is transmitted (S301). The switching hub 22 (control unit 220) transmits a response (ACK) to the host 11 (S302). Similarly, the host device 11 instructs the target device TGT_1A to perform communication in the second communication mode, and transmits the waiting time information (S303). The target device TGT_1A transmits a response (ACK) to the target device TGT_1A (S304). Further, the host device 11 instructs the target device TGT_2A to perform communication in the second communication mode, and transmits information on the waiting time (S305). The target device TGT_2A transmits a response (ACK) to the target device TGT_2A to the host device 11 (S306).

  The host device 11 starts communication with the target device TGT_3A (S307). Specifically, the host device 11 repeatedly transmits the transfer data until the scheduled transmission completion time based on the information on the standby time notified to the switching hub 22 and the other target devices TGT_1A and TGT_2A. Even if it is necessary to retransmit the data and transmission of all data is not completed by the initial scheduled transmission completion time, the transmission of the transfer data is stopped when the initial scheduled transmission completion time is reached. At this time, the host device 11 does not issue transactions of the target devices TGT_1A and TGT_2A, and transmits data only by the transactions of the target device TGT_3A.

  When the communication between the host device 11 and the target device TGT_3A is started in the process S307, the communication between the switching hub 22 and the target devices TGT_1A and TGT_2A is started. Specifically, when the transmission of the periodic SOF packet from the host device 11 to the target devices TGT_1A and TGT_2A is stopped, the switching hub 22 starts communication with the target devices TGT_1A and TGT_2A as a pseudo host device using that as a trigger. To do. First, the switching hub 22 transmits to the target device TGT_1A that data can be stored (S308). The target device TGT_1A transmits a response (ACK) to the target device TGT_1A to the switching hub 22 (S309). Similarly, the switching hub 22 transmits to the target device TGT_2A that data can be stored (S310). The target device TGT_2A transmits a response (ACK) to the target device TGT_2A to the switching hub 22 (S311).

  Thereafter, the target device TGT_1A transmits the transfer data to be transferred to the host device 11 to the switching hub 22 (S312). Specifically, the target device TGT_1A calculates a communicable time with the switching hub 22 based on the information on the standby time received in the process S303, and the maximum possible transmission within the calculated time. Calculate the amount of data. Then, transfer data corresponding to the calculated maximum data amount is transmitted to the switching hub 22. On the other hand, the switching hub 22 sequentially stores the transfer data transmitted from the target device TGT_1A in the buffer memory 225. Similarly, the target device TGT_2A transmits transfer data to be transferred to the host device 11 to the switching hub 22 (S313). Specifically, the target device TGT_2 calculates the time that can be communicated with the switching hub 22 based on the information on the standby time received in step S305, and the maximum that can be transmitted within the calculated time. Calculate the amount of data. Then, transfer data corresponding to the calculated maximum data amount is transmitted to the switching hub 22. On the other hand, the switching hub 22 sequentially stores the transfer data transmitted from the target device TGT_2A in the buffer memory 225.

  When the transmission of data to the target device TGT_3A is completed, the host device 11 notifies the switching hub 22 that the transmission has been completed (S314). The switching hub 22 notifies the host device 11 that the transfer data of the target devices TGT_1A and TGT_2A is accumulated in addition to the response (ACK) to the switching hub 22 (S315). Similarly, the host device 11 notifies the target device TGT_1A that the transmission has been completed (S316). The target device TGT_1A notifies the host device 11 of a response (ACK) to the target device TGT_1A (S317). Further, the host device 11 notifies the target device TGT_2A that the transmission has been completed (S318). The target device TGT_2A notifies the host device 11 of a response (ACK) to the target device TGT_2A (S319).

  Thereafter, the switching hub 22 transmits the transfer data of the target device TGT_1A and the target device TGT_2A stored in the buffer memory 225 to the host device 11 (S320). For example, the switching hub 22 notifies the host device 11 that data has been stored in the first bulk notification transaction, and transmits the transfer data collectively in the subsequent transaction. This communication is performed only between the host device 11 and the switching hub 22. That is, this communication frame does not include the transaction of the target device TGT_3A or the transactions of the target devices TGT_1A and TGT_2A, and data is transmitted only by the transaction of the switching hub 22.

  When the data transmission to the host device 11 is completed, the switching hub 22 notifies the target device TGT_1A that the transfer data stored in the buffer memory 225 has been transferred to the host device 11 (S321). The target device TGT_1A notifies the switching hub 22 of a response (ACK) to the target device TGT_1A (S322). Similarly, the switching hub 22 notifies the target device TGT_2A that the transfer data stored in the buffer memory 225 has been transferred to the host device 11 (S323). The target device TGT_2A notifies the switching hub 22 of a response (ACK) to the target device TGT_2A (S324). When the above processing is completed, the host device 11 and the target device TGT return to normal operation.

  FIG. 6 is a flowchart showing another example of the communication method in the second communication mode in the data transfer system 2. The figure illustrates a communication procedure when the target device TGT_3A transmits a large amount of data to the host device 11, and the target device TGT_1A and the target device TGT_2A transmit a small amount of data to the host device 11. Yes.

  First, when the target device TGT_3A receives an inquiry about the presence / absence of data transfer from the host device 11 by polling, the target device TGT_3A sends a preferential transmission request for the transfer data and information on the data amount of the transfer data to be transmitted. 11 (S401). The host device 11 transmits a response to the response to the target device TGT_3A (S402). Based on the data amount information received from the target device TGT_3A, the host device 11 calculates a required time until the communication with the target device TGT_3A is completed, and compares it with a predetermined threshold value. If the host device 11 determines that the calculated required time is greater than a predetermined threshold, the host device 11 instructs the switching hub 22 to perform communication in the second communication mode and can communicate with the host device 11. The information of the waiting time until is transmitted (S301). The switching hub 22 (control unit 220) transmits a response (ACK) to the host 11 (S302). Similarly, the host device 11 instructs the target device TGT_1A to perform communication in the second communication mode, and transmits the waiting time information (S303). The target device TGT_1A transmits a response (ACK) to the target device TGT_1A (S304). Further, the host device 11 instructs the target device TGT_2A to perform communication in the second communication mode, and transmits information on the waiting time (S305). The target device TGT_2A transmits a response (ACK) to the target device TGT_2A to the host device 11 (S306).

  The host device 11 starts communication with the target device TGT_3A (S407). Specifically, the host device 11 repeatedly receives the transfer data until the scheduled transmission completion time based on the standby time information notified to the switching hub 22 and the other target devices TGT_1A and TGT_2A. Even if the data needs to be retransmitted and reception of all data is not completed before the initial scheduled transmission completion time, the reception of data is stopped when the initial scheduled transmission completion time is reached. At this time, the host device 11 does not issue transactions of the target devices TGT_1A and TGT_2A, and transmits data only by the transactions of the target device TGT_3A. When the communication between the host device 11 and the target device TGT_3 is started in the process S407, communication between the switching hub 22 and the target devices TGT_1A and TGT_2A is started. The subsequent processing is the same as the processing S308 to S324 in FIG. As a result, the transfer data of the target devices TGT_1A and TGT_2A is temporarily stored in the buffer memory 225 of the switching hub 22, and after the communication between the host device 11 and the target device TGT_3A is completed, the switching hub 22 is stored in the buffer memory 225. The transfer data is collectively transmitted to the host device 11.

  According to the above communication method, the overhead in data transfer can be reduced as compared with the case where each target device transfers data to the host device by a transaction allocated in one frame. For example, in the case of the above example, the switching hub 22 collectively transmits the transfer data to the host device 11, so that the target device TGT — 1A and the target device TGT — 2A transmit data to the host device 11 separately compared to the case where the data is transferred to the host device 11. Since the number of token packet transmissions is reduced, overhead in data transfer is reduced and throughput is improved.

  Further, data communication can be performed at the fastest communication speed that the switching hub 22 can take. For example, when the target device TGT_1A and the target device TGT_2A are compatible with the low speed mode and the switching hub 22 is compatible with the full speed mode, the target devices TGT_1A and TGT_2A perform data transmission within one frame. Communication between TGT_1 and TGT_2 and the host device 11 needs to be performed in the low speed mode. However, according to the above method, since only the switching hub 22 transmits data, it is possible to communicate with the host device 11 in the full speed mode and to improve the throughput.

  As described above, according to the data transfer system 2 according to the second embodiment, the communication time of USB communication can be shortened.

<< Embodiment 3 >>
FIG. 7 shows a specific example of a data transfer system to which the communication method according to Embodiment 1 is applied. In the data transfer system 1A shown in the figure, a media server (MD_SVR) 11A as a host device 11 is connected via a switching hub 12A to a video camera (VDCCAM) 10A, a smartphone (SMTPH) 10B as a target device TGT, and It is interfaced with a digital camera (DGCAM) 10C by USB.

  The media server 11A can store moving image data, image data, and the like, and can be connected to a monitor (TV or the like) as necessary to reproduce video. The video camera 10A stores a large amount of recorded moving image data. The smartphone 10B has a camera function, for example, and stores a small amount of image data. The USB target controller 100 in the smartphone 10B includes a buffer memory 101 that can temporarily store data. The digital camera 10C stores a small amount of image data.

  Consider a case in which data is transferred from the video camera 10A, the smartphone 10B, and the digital camera 10C to the media server 11A in the data transfer system 1A. In this case, since the transfer data of the video camera 10A has a larger data amount than the transfer data of the other smartphone 10B or the digital camera 10C, first, USB communication is preferentially performed between the media server 11A and the video camera 10A. When starting communication, the media server 11A instructs the smartphone 10B and the digital camera 10C to communicate in the second communication mode and transmits information on the standby time. While the media server 11A and the video camera 10A are communicating, the smartphone 10B and the digital camera 10C communicate with each other. In this communication, the digital camera 10C transmits transfer data as image data to be transferred to the media server 11A to the smartphone 10B, and the transfer data is accumulated in the buffer memory 101 of the smartphone 10B. Thereafter, when the communication between the media server 11A and the video camera 10A is completed, the smartphone 10B establishes USB communication with the media server 11A, and the image data held by the smartphone 10B and the digital camera 10C stored in the buffer memory 101 are stored. Send image data together. As a result, the data transfer from each target device to the host device can be performed more efficiently than the conventional USB communication, and the communication time of the USB communication in the data transfer system can be shortened.

<< Embodiment 4 >>
FIG. 8 shows another specific example of the data transfer system to which the communication method according to the first embodiment is applied. In the data transfer system 1B shown in the figure, a media server 11A as a host device 11 is connected via a switching hub 12A to a smartphone (SMTPH) 10D, a smartphone 10B, and a digital camera 10C as target devices TGT and a USB. Interfaced. In FIG. 8, the same components as those in the data transfer system 1A according to the third embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  The smartphone 10D includes a nonvolatile storage device (for example, a flash memory) that can store a large amount of data. For example, the moving image data stored in the storage device can be reproduced on the go.

  In the data transfer system 1B, consider a case in which moving image data is transferred from the media server 11A to the smartphone 10D and data is transferred from the smartphone 10B and the digital camera 10C to the media server 11A. In this case, since the transfer data (moving image data) transferred from the media server 11A to the smartphone 10D has a larger data amount than the transfer data of the other smartphone 10B or the digital camera 10C, first, the media server 11A and the smartphone 10D USB communication is preferentially performed between them. When starting communication, the media server 11A instructs the smartphone 10B and the digital camera 10C to communicate in the second communication mode and transmits information on the standby time. During a period in which the media server 11A and the smartphone 10D are communicating, the smartphone 10B and the digital camera 10C communicate with each other. In this communication, the digital camera 10C transmits transfer data as image data to be transferred to the media server 11A to the smartphone 10B, and the transfer data is accumulated in the buffer memory 101 of the smartphone 10B. Thereafter, when the communication between the media server 11A and the smartphone 10D is completed, the smartphone 10B establishes USB communication with the media server 11A, and the image data held by itself and the image of the digital camera 10C stored in the buffer memory 101 are established. Send data together. Thereby, similarly to the data transfer system according to the third embodiment, the communication time of USB communication in the data transfer system can be shortened.

  Although the invention made by the present inventor has been specifically described based on the embodiments, it is needless to say that the present invention is not limited thereto and can be variously modified without departing from the gist thereof.

  For example, in the first embodiment, the configuration in which each target device TGT includes the buffer memory 101 in the USB target controller 100 is illustrated, but the present invention is not limited thereto. For example, when the target devices TGT_1 and TGT_2 communicate during a period in which the host device 11 and the target device TGT_3 are communicating, it is only necessary that at least one of the target devices TGT_1 and TGT_2 includes a buffer memory.

  In the first to fourth embodiments, the case where the number of target devices TGT is three has been exemplified. However, the number of target devices TGT is not limited to this, and the number of the target devices TGT is three or more. . For example, in the first embodiment, if four target devices are connected to the switching hub 12, communication is performed between the remaining three target devices while one target device is communicating with the host device. Can do. At this time, the three target devices exchange storage capacity information with each other, and determine whether each target device has the largest storage capacity in its buffer memory. Then, the target device determined to have the buffer memory with the largest storage capacity notifies the remaining two target devices of information indicating that data can be accumulated. By performing the subsequent processing in the same manner as the method described in the first embodiment, the same effect as described above can be obtained.

  In FIGS. 5 and 6 of the second embodiment, the case where the transfer data is transmitted from the target devices TGT_1A and TGT_2A to the host device 11 is illustrated, but the same applies when the transfer data is transmitted from the host device 11 to the target devices TGT_1A and TGT_2B. In addition, the communication time for USB communication can be shortened. For example, first, the transfer data to be transferred to the target devices TGT_1A and TGT_2A are collectively transmitted from the host device 11 to the switching hub 22, and stored in the buffer memory 225. When the host device 11 and the target device TGT_3A start communication, the switching hub 22 may sequentially transfer the transfer data stored in the buffer memory 225 to the target devices TGT_1 and TGT2.

  Although the case where the buffer memories 101 and 225 are volatile storage devices has been illustrated, a rewritable nonvolatile storage device (for example, a flash memory) may be used.

1 Data transfer system 11 Host device TGT, TGT_1 to TGT_3 Peripheral device (target device, PRD)
12 Switching hub 110 Central processing unit (CPU)
111 memory (MRY)
112 bus 113 USB host controller (USB_CNT)
1130 Control unit (CNT)
1131 I / O port (I / O_PRT)
120 Control unit (CNT)
121 I / O port (I / O_PRT, upstream port)
122 Switching circuit (SWCIR)
123, 124, 125 I / O ports (I / O_PRT, downstream ports)
100 USB target controller 101 buffer memory 102 control unit 103 internal circuit 104 input / output port (I / O_PRT)
2 Data transfer system TGT_1A, TGT_2A, TGT_3A
22 Switching hub 220 Control unit (CNT)
225 Buffer memory (BUF)
200 USB target controller 202 Control unit (CNT)
1A, 2A Data transfer system 11A Media server 12A Switching hub 10A Video camera 10B, 10D Smartphone 10C Digital camera

Claims (12)

A host device and n (n is an integer of 3 or more) target devices having a storage unit for temporarily storing data for transmitting and receiving data according to the USB standard via a switching hub A communication method,
The host device and the n target devices are a first communication mode capable of transmitting and receiving data to and from the host device for each target device, and a first communication mode in which data of a plurality of target devices can be collectively transmitted to the host device. It is possible to communicate by switching between 2 communication modes,
When the host device communicates with one target device, a first process for instructing a communication mode to a target device other than the one target device;
A second process in which the host device starts communication with the one target device;
When the second communication mode is instructed in the first process, the other target devices communicate with each other, thereby transferring one transfer data to be transferred to the host device held by each of the other target devices. A third process for storing together in the storage unit in another target device;
After the communication between the host device and the one target device is completed, the target device that collectively stores the transfer data in the storage unit in the third process stores its transfer data and the transfer data stored in the storage unit. 4th process which transmits to a said host apparatus collectively.   The communication method according to claim 1, wherein the one other target device has a storage capacity of the storage unit that is the largest among the other target devices. The third process includes
A fifth process in which the other target devices mutually transmit / receive information on storage capacity indicating the storage capacity of the storage unit held by each other, and
The other target device determines whether or not its storage unit has the largest storage capacity based on the storage capacity information, and the target device that has determined that the storage capacity is the largest is the other target. A sixth process for notifying the apparatus that transfer data can be stored;
The other target device transmits the transfer data to be transferred to the host device to the target device that has been determined to have the largest storage capacity, and the target device that has been determined to have the largest storage capacity has received the received The communication method according to claim 2, further comprising: a seventh process of storing transfer data in the storage unit. In the first process, the host device further transmits to the other target device information indicating a waiting time until communication with the host device becomes possible,
In the seventh process, the other target devices calculate the amount of data that can be transmitted before the communication between the host device and the one target device is completed based on the information indicating the standby time, The communication method according to claim 3, wherein the transfer data corresponding to the calculated data amount is data to be transmitted to a target device determined to have the largest storage capacity.   The communication method according to claim 4, wherein the information indicating the waiting time includes information on the number of transactions scheduled for communication between the host device and the one target device.   The communication method according to claim 4, wherein the information indicating the standby time includes information on an estimated time required for communication between the host device and the one target device. A communication method for transmitting and receiving data in accordance with the USB standard between a host device and n (n is an integer of 3 or more) target devices via a switching hub,
The host device and the n target devices are a first communication mode capable of transmitting and receiving data to and from the host device for each target device, and a first communication mode in which data of a plurality of target devices can be collectively transmitted to the host device. It is possible to communicate by switching between 2 communication modes,
The switching hub includes a storage unit capable of temporarily storing data;
When the host device communicates with one target device, a first process of instructing a communication mode to another target device other than the one target device and the switching hub;
A second process in which the host device starts communication with the one target device;
When the second communication mode is instructed in the first process, the other target device communicates with the switching hub and transfers to the host device held by each of the other target devices. A third process for collectively storing transfer data for storage in the storage unit in the switching hub;
And a fourth process in which the switching hub collectively transmits the transfer data stored in the storage unit to the host device after communication between the host device and the one target device is completed. The third process includes
A fifth process in which the switching hub notifies the other target device that the transfer data can be stored;
The communication method according to claim 2, further comprising: a sixth process in which the other target device transmits the transfer data to the switching hub and accumulates the transfer data received by the switching hub in the storage unit. In the first process, the host device further transmits to the other target device and the switching hub information indicating a waiting time until communication with the host device becomes possible,
In the sixth process, the other target device calculates the amount of data that can be transmitted before the communication between the host device and the one target device is completed based on the information indicating the standby time. The communication method according to claim 9, wherein the transfer data corresponding to the calculated data amount is data to be transmitted to the switching hub.   The communication method according to claim 9, wherein the information indicating the waiting time includes information on the number of transactions scheduled in communication between the host device and the one target device.   The communication method according to claim 9, wherein the information indicating the standby time includes information on an estimated time required for communication between the host device and the one target device. A switching hub capable of communication according to the USB standard,
A first input / output port for connecting to a host device;
N second input / output ports (n is an integer of 3 or more) for connecting to the target device;
The host device connected to the first input / output port and the target device connected to the second input / output port by switching the connection between the first input / output port and the second input / output port A communication control unit for controlling communication with
A storage unit;
When the communication control unit establishes a connection between the first input / output port and one second input / output port, transfer data to be transferred to the host device is transferred to the other second input / output port. The transfer data is stored together in the storage unit and stored in the storage unit after the connection between the first input / output port and the one second input / output port is released. A switching hub capable of collectively outputting transfer data from the first input / output port.

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