JP2005107677A - Communication controller, communication system, communication apparatus, and communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a send and receive system capable of carrying out data transfer by IN transaction of a USB2.0 without problems, even when a channel with a transfer rate that is slower, in comparison with the native speed of the USB2.0 is used between a host and a function. <P>SOLUTION: In a host side controller 100, when reception of an IN packet from a USB host is confirmed, the IN packet is transferred to a function-side controller 110, and a DATA packet is received from the function side. The received DATA packet is temporarily stored in a FIFO 108, and when an IN packet is received from the USB host again, the DATA packet stored in the FIFO 108 is sent to the USB host. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a communication controller that transmits USB signals in the USB standard.

  Universal Serial Bus (hereinafter referred to as USB) is an interface specification developed to increase the degree of freedom of expandability of peripheral devices in personal computers, etc., and is commonly used for communication with various USB compatible devices. It is a serial interface standard that can be used.

  In principle, this USB can connect one host and up to 127 devices on the same bus in one system. These connections are physically a bus having a tree-type network structure, and logically, client software of the USB host and client software of the USB function communicate on a one-to-one basis. In order to maintain such a connection form, the lowest layer protocol communicates in a time division manner, and the host performs scheduling. In USB 1.x, two data transfer rates of 1.5 Mbps in the low speed mode (hereinafter LS) and 12 Mbps in the full speed mode (hereinafter FS) are defined.

  In recent years, USB has been adopted for applications that require high-speed data transfer such as hard disks and DVDs, and the transfer speed has been insufficient. Therefore, a new standard called USB 2.0 was established, and in the USB 2.0 standard, a very high data transfer speed of 480 Mbps was added in the high speed mode (hereinafter referred to as HS).

  Data communication on the USB is performed in units called transactions. This transaction consists of a packet called a token packet, a data packet, and a handshake packet. It always starts with a token packet issued by the host at the start of the transaction, and the corresponding function responds with the address and endpoint contained in the token packet.

  The end point is a FIFO buffer for storing transfer data, and data exchange between the USB host and the USB function is always executed via the end point. A USB function can have up to 16 endpoints, and the endpoints are numbered to recognize multiple endpoints. The USB host performs access using the USB address and end point of the USB function during data transfer. The end point number 0 is called the end point 0 and must always exist in the USB function. This endpoint 0 is used at the time of initialization performed by the SETUP packet at the time of control transfer.

  As types of USB packets, there are a token packet, a data packet, a handshake packet, and a special packet as shown in FIG. Token packets include IN packets, OUT packets, SETUP packets, and SOF packets. Each packet is used for the purpose shown in FIG. Data packets include a DATA0 packet and a DATA1 packet. Handshake packets include ACK packets, NAK packets, STALL packets, and NYET packets. Further, as a special packet, there is a PING packet or the like.

  The USB packet format is shown in FIG. PID is an identifier of a packet and is composed of 8 bits. Further, CRC5 is added to the token packet and CRC16 is added to the data packet, respectively, and it is possible to determine whether or not the contents of the packet are correct by checking the CRC when the packet is received.

  The SOF packet is a packet indicating the start of a frame issued by the host. The SOF packet is issued from the host at a 1 ms cycle in the LS and FS modes and at a 125 us cycle in the HS mode.

[IN transaction]
An IN transaction is a method by which a USB host in the USB 2.0 standard reads data from a USB function. The IN transaction will be described below with reference to FIG.

  First, at timing t2201, an IN packet is transmitted from the USB host toward the USB function. The USB function that has received the IN packet does not have data to transfer at that time, and therefore transmits a NAK packet to that effect to the USB host at t2202. Upon receiving the NAK packet, the USB host recognizes that there is no data to be transmitted in the USB function, and transmits the IN packet to the USB function again at the next transmission timing t2203. In the USB function that has received this, since there is data to be transferred at this time, a DATA packet is transmitted to the USB host at the timing of t2204. When the USB host receives the DATA packet without error within a predetermined time, it transmits an ACK packet indicating that it has been received normally at the timing of t2205 toward the USB function.

  Since a CRC16 code is added to the DATA packet, the data receiving side can check whether there is an error in the received data by checking the CRC. If the CRC 16 determines that there is an error in the data, the USB host does not return any packet to the USB function. That is, the USB function can recognize that data has been transferred normally to the USB host by receiving the ACK packet. If the USB function cannot receive the ACK packet from the USB host within a predetermined time, the USB function recognizes that data transfer to the USB host has not been performed normally, and recognizes that the IN transaction has failed.

  By the above method, an IN transaction is performed, and the USB host can read data from the USB function.

[USB time constraints]
In the USB 2.0 standard, there is a restriction on the propagation time of the data signal.

  In the LS and FS modes, the turnaround time from the USB host to the USB function must be 16 bits time (1333 ns) or less. In other words, if the response packet from the USB function to the packet sent from the USB host to the USB function does not reach the USB host within 1333 ns, the USB host does not normally send the packet sent to the USB function to the USB function. The packet is retransmitted.

  In the HS mode, the turnaround time from the USB host to the USB function must be 721 bit times (1502 ns) or less. If the response packet from the USB function to the packet sent by the USB host to the USB function does not reach the USB host within the 1502 ns, the USB host considers that the packet sent to the USB function has not normally reached the USB function. , Resend the packet.

In the IN transaction, the predetermined time that the USB host waits after transmitting the IN packet and the predetermined time that the USB function waits after transmitting the DATA packet are 1333 ns in the LS and FS modes defined as USB time constraints. And 1502 ns in the HS mode. In each transfer mode, if the DATA packet or the ACK packet cannot be received within the restricted time, the IN transaction does not end normally.
JP 2000-284872 A (publication date October 13, 2000)

  In recent years, USB has been installed in digital cameras, PDAs (Personal Digital Assistants), and the like. The data transmission means in these mobile devices often use the cradle method, and USB transmission is possible by connecting the USB connector attached to the cradle and the USB connector of the mobile device. Since these connectors have physical contacts, there is a possibility that the deterioration of the connectors will progress due to the insertion / removal of the connectors, and high-quality data transfer will be difficult.

  As a method of eliminating the physical contact, there is a method of performing spatial transmission using light. In order to perform spatial transmission of 480 Mbps of USB 2.0 as it is, CDR (Clock Data Recovery) in the optical system and the receiving unit is used. ), Etc., require high performance, leading to increased costs. In order to reduce the cost of CDR in the optical system and the receiving unit, it is conceivable to perform USB 2.0 data transfer at a lower transfer speed, but in this case, there are the following problems.

  FIG. 24 shows the state of an IN transaction when the transfer speed of the optical communication path is, for example, 100 Mbps and a transfer speed slower than the native speed 480 Mbps of USB 2.0.

  The IN packet transmitted by the USB host at timing t2301 is converted into an optical signal by the host-side controller and transmitted to the function-side controller. The function-side controller extracts the USB packet from the received optical signal and transmits it to the USB function. Here, the timing at which the function-side controller starts transmission to the USB function is t2302, because USB native 480 Mbps transfer is performed for transmission to the USB function.

  When the USB function completes receiving the IN packet at t2303, the DATA packet is transmitted to the USB host at t2304. The function-side controller converts the DATA packet from the USB function into an optical signal and transmits it to the host-side controller. The host-side controller waits for the completion of the reception of the DATA packet in the same manner as the function-side controller, and then transmits the DATA packet toward the USB host at t2305. The USB host can receive the DATA packet from the USB function for the first time at t2306.

  Here, when the data transfer speed between the host and the function is slower than the native speed of USB 2.0 (particularly when the DATA packet length is long), the time from t2301 to t2306 (turnaround time) becomes long. The maximum turnaround time (1502 ns in the HS mode) will be exceeded, and the IN transaction will not end normally.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a communication path (for example, an optical communication path of 100 Mbps) having a lower transfer speed than the native speed of USB 2.0 between the host and the function. Even when it is used, it is to realize a transmission / reception circuit capable of performing data transfer by USB 2.0 IN transaction without any problem.

  In order to solve the above-described problem, the communication controller according to the present invention transfers an IN packet transmitted from the host device to the function device when performing an IN transaction as data communication on the USB, and responds to the IN packet. Is a communication controller that functions as a host-side controller that transfers the DATA packet to the host device, and stores reception confirmation means for confirming reception of the IN packet from the host device, and stores the DATA packet transmitted from the function device side Storage means for confirming reception of an IN packet from the host device by the reception recognition means, data storage confirmation means for confirming whether a DATA packet is stored in the storage means, and the data storage confirmation Means to store the above DATA packet. When it is confirmed that the data packet is not received, the IN packet received from the host device is transferred to the function device side. When the data storage confirmation means confirms that the DATA packet is stored, the DATA packet is transmitted to the host device. And a transmission control means for transmitting.

  The communication controller also functions as a function-side controller that transfers a USB standard IN packet transmitted from the host device side to the function device and forwards a DATA packet as a response to the IN packet to the host device side. When an IN packet is received from the host device side, the IN packet is retained. When an ACK packet for the DATA packet transmitted to the host device side is received from the host device side, the IN packet held in the USB function is retained. And when the DATA packet corresponding to the IN packet is received from the function device, an ACK packet is transmitted to the function device.

  In the communication controller, the transfer rate related to the reception of the IN packet from the host device and the transmission of the DATA packet to the host device is the transfer rate defined in the USB standard, and the transmission of the IN packet to the function device side and The transfer rate for receiving DATA packets from the function device side is lower than the transfer rate stipulated in the USB standard, and the amount of data stored when storing the DATA packets received from the function device side in the storage means is confirmed. A data amount confirming unit configured to transmit the DATA packet to the host device when the received data amount confirmed by the data amount confirming unit exceeds a predetermined value. It is characterized by starting.

  The communication controller has error analysis means for analyzing whether or not the DATA packet received from the function device side contains an error. The transmission control means uses the error analysis means to receive the received DATA packet. If it is determined that the data packet is incorrect, the DATA packet is discarded and not transferred to the host device.

  The communication controller has error analysis means for analyzing whether or not the DATA packet received from the function device side contains an error. The transmission control means uses the error analysis means to receive the received DATA packet. If it is determined that the data is wrong, the transmission of the DATA packet to the host device is stopped at that time.

  In the communication controller, the reception confirmation unit transmits a DATA packet to the host device, and then confirms whether or not an ACK packet for the DATA packet is returned from the host device. If the reception of the next IN packet is confirmed without confirming the reception of the ACK packet by the reception confirmation means after the DATA packet is transmitted to the host device, the same DATA packet as the DATA packet transmitted to the previous host device is transmitted. It is characterized by performing retransmission processing to be transmitted to the host device.

  Further, the communication controller has error analysis means for analyzing whether or not the DATA packet received from the function device side contains an error, and the transmission control means performs the retransmission processing by the error analysis means. It is characterized in that it is performed only when it is confirmed that there is no error in the DATA packet held by the device.

  In addition, the communication controller is configured to analyze whether or not the DATA packet received from the function device side includes an error, and when the received DATA packet is determined to be incorrect by the error analysis unit. The function device side has a retransmission request means for requesting retransmission of the DATA packet.

  The communication controller also functions as a function-side controller that transfers a USB standard IN packet transmitted from the host device side to the function device and forwards a DATA packet as a response to the IN packet to the host device side. When a retransmission request is received from the host-side controller, a retransmission process for transmitting the same DATA packet as the DATA packet transmitted to the host-side controller to the host-side controller is performed.

  Further, the communication controller has error analysis means for analyzing whether or not the DATA packet received from the function device includes an error, and the transmission control means performs the retransmission processing by using the error analysis means. This is performed only when it is confirmed that there is no error in the DATA packet held by.

  In addition, the communication controller, when it is confirmed by the error analysis means that there is no error in the DATA packet held by the device, an error is detected in the DATA packet during the packet format of the DATA packet transmitted to the host device. It is characterized by setting a flag indicating that there is no.

  Further, the communication controller receives a DATA packet from the function side controller, and when the error analyzing means detects that there is an error in the DATA packet, the function controller side uses the flag set in the DATA packet. The retransmission request is made only when it is confirmed that an error-free DATA packet is held.

  The communication controller also functions as a function-side controller that transfers a USB standard IN packet transmitted from the host device side to the function device and forwards a DATA packet as a response to the IN packet to the host device side. When a retransmission request is received from the host-side controller, an IN packet is transmitted to the function device, and the received DATA packet is transmitted to the host-side controller.

  In addition, the communication controller adjusts the transfer rate with the communication controller on the communication partner side before executing the IN transaction.

  In addition, when the communication controller determines that communication can be performed at the transfer speed defined in the USB standard in the transfer speed adjustment, each packet transmitted to the communication controller on the communication partner side is It is characterized in that, without performing transmission timing control, only modulation / demodulation is performed and transfer to the communication controller on the other side is performed.

  The communication controller analyzes the error rate in the communication path with the communication controller on the communication partner side, and determines that the error rate is worse than a predetermined error rate, the transfer rate adjustment To reduce the transfer speed.

  The communication controller performs full duplex communication with a communication controller on the communication partner side.

  Further, the communication controller is characterized in that communication with the communication controller on the communication partner side is performed by a communication path using an optical fiber.

  The communication controller is characterized in that communication with the communication controller on the communication partner side is performed by radio using radio waves.

  Further, the communication controller is characterized in that communication with the communication controller on the communication partner side is performed by spatial transmission using light.

  In order to solve the above problems, another communication controller according to the present invention transfers a USB standard IN packet transmitted from the host device side to the function device when performing an IN transaction as data communication on the USB. A communication controller that functions as a function-side controller that transfers a DATA packet that is a response to the IN packet to the host device side. When the IN packet is received from the host device side, it is held and transmitted to the host device side. When the host device receives an ACK packet for the received DATA packet, the IN packet held above is transmitted to the USB function, and when the DATA packet for the IN packet is received from the function device, the ACK packet is It is characterized by transmitting to the location.

  In order to solve the above-described problem, another communication controller according to the present invention transmits a USB standard IN packet transmitted from the host device side to the function device when performing an IN transaction as data communication on the USB. A communication controller that functions as a function-side controller that forwards and transfers a DATA packet that is a response to the IN packet to the host device side. When a retransmission request is received from the host-side controller, it is sent to the previous host-side controller. A retransmission process is performed in which the same DATA packet as the transmitted DATA packet is transmitted to the host-side controller.

  Further, the communication controller analyzes whether or not the DATA packet received from the function device includes an error, and confirms that the retransmission process is performed by the above analysis and that the DATA packet held by the own device is correct. It is characterized by being performed only in the case of.

  In addition, when the communication controller confirms that there is no error in the DATA packet held by the device, the communication controller has no error in the DATA packet during the packet format of the DATA packet transmitted to the host device. It is characterized by setting a flag indicating that.

  In order to solve the above-described problem, another communication controller according to the present invention transmits a USB standard IN packet transmitted from the host device side to the function device when performing an IN transaction as data communication on the USB. A communication controller that functions as a function-side controller that forwards and transfers a DATA packet that is a response to the IN packet to the host device side. When a retransmission request is received from the host-side controller, the communication device It is characterized by transmitting a packet and transmitting the received DATA packet to the host-side controller.

  In order to solve the above problems, the communication system according to the present invention transfers the USB controller IN packet transmitted from the host device side to the function device and the communication controller functioning as the host side controller described above, And a communication controller functioning as a function-side controller for transferring a DATA packet as a response to the IN packet to the host device side.

  In addition, a communication device according to the present invention includes the communication controller described above in order to solve the above-described problem.

  In addition, in order to solve the above-described problem, the communication method according to the present invention confirms whether an IN packet is received from the host device, and determines whether or not a DATA packet that is a response to the IN packet is received at that time. If the DATA packet is received, the DATA packet is transmitted to the host device in response to the received IN packet. If the DATA packet is not received, the received IN packet Is transmitted to the function device side, and a NAK packet is transmitted to the host device.

  As described above, the communication controller according to the present invention includes a reception confirmation unit that confirms reception of an IN packet from a host device, a storage unit that stores a DATA packet transmitted from the function device side, and the reception recognition unit. When the reception of the IN packet from the host device is confirmed by the above, the data storage confirmation means for confirming whether or not the DATA packet is stored in the storage means, and the DATA packet is stored by the data storage confirmation means. When it is confirmed that there is no data, the IN packet received from the host device is transferred to the function device side. When the data storage confirmation means confirms that the DATA packet is stored, the host device receives the DATA packet. Transmission control means for transmitting The DATA packet transmitted from the function device as a response to the IN packet received from the host device is stored in the storage means, and the DATA stored in the storage means when the IN packet is retransmitted from the host device. Send the packet to the host device. Therefore, there is no need to have the DATA device send the DATA packet again for the IN packet retransmitted from the host device, and the transfer rate between the host and function is low, or between the host and function. Even when the transfer path is long, the IN transaction processing can be completed within the restricted time defined by USB transmission.

  The communication controller also functions as a function-side controller that transfers a USB standard IN packet transmitted from the host device side to the function device and forwards a DATA packet as a response to the IN packet to the host device side. When an IN packet is received from the host device side, the IN packet is retained. When an ACK packet for the DATA packet transmitted to the host device side is received from the host device side, the IN packet held in the USB function is retained. When the DATA packet corresponding to the IN packet is received from the function device, an ACK packet is transmitted to the function device. Therefore, when an error occurs in the DATA packet in the communication path between the host and the function, the function-side controller does not transmit the ACK packet to the function device, so that the IN transaction can be prevented from being terminated abnormally. There is an effect that stable packet transfer can be performed.

  The communication controller confirms the amount of data stored when the DATA packet received from the function device side is stored in the storage means by the data amount confirmation means, and the transmission control means confirms that the received data amount is Since the transmission of the DATA packet to the host device is started when the value exceeds the predetermined value, the transfer rate in the communication path between the host and the function is the transfer rate between the host-side controller and the host device. Even if the transfer rate is lower than (the transfer rate defined in the USB standard), the storage means becomes EMPTY even if the predetermined value starts to transfer the DATA packet to the host device at that time. If the value is greater than the value that does not exist, the DATA packet is not waited for the completion of reception of the DATA packet from the function device. It is possible to initiate the transmission of Tsu door. Therefore, it is possible to advance the transmission timing of the DATA packet, and it is possible to improve the transfer rate as a whole.

  Further, the communication controller analyzes whether or not the DATA packet received from the function device side includes an error by an error analysis unit, and the transmission control unit uses the error analysis unit to erroneously receive the received DATA packet. If it is determined, the DATA packet is discarded and not transferred to the host device. Therefore, it is possible to reduce the power required for transmission and to suppress the unexpected abnormal operation caused by the USB host receiving an erroneous packet.

  Further, the communication controller analyzes whether or not the DATA packet received from the function device side includes an error by an error analysis unit, and the transmission control unit uses the error analysis unit to erroneously receive the received DATA packet. If it is determined that there is, the transmission of the DATA packet to the host device is stopped at that time. Therefore, by stopping the transmission of the DATA packet even during the transfer, there is an effect that the deterioration of the transfer efficiency of the low-speed communication path can be suppressed.

  In addition, after the communication controller transmits the DATA packet to the host device, the reception controller confirms whether or not the ACK packet for the DATA packet has been returned from the host device. If the reception of the next IN packet is confirmed without confirming the reception of the ACK packet by the reception confirmation means after the DATA packet is transmitted to the host device, the same DATA packet as the DATA packet transmitted to the previous host device is transmitted. Performs retransmission processing to be sent to the host device. Therefore, when a data error occurs between the host device and the host-side controller when the host-side controller transmits a DATA packet to the host device, the function device side is requested to send the DATA packet again. In this way, the data packet can be retransmitted.

  In addition, the communication controller analyzes whether or not the DATA packet received from the function device side contains an error by an error analysis unit, and the transmission control unit performs the retransmission process by the error analysis unit. This is performed only when it is confirmed that there is no error in the held DATA packet. Therefore, when the communication controller functions as a host-side controller, there is an effect that retransmission processing to the host device can be performed only when the received DATA packet is determined to be correct.

  Further, the communication controller analyzes whether or not the DATA packet received from the function device side includes an error by the error analysis means, and when the error analysis means determines that the received DATA packet is incorrect Then, the retransmission request means makes a retransmission request for the DATA packet to the function device side. Therefore, by performing the above operation, if an error occurs in the DATA packet in the communication path between the host and the function, the host controller can notify the function device to that effect. There is an effect.

  The communication controller also functions as a function-side controller that transfers a USB standard IN packet transmitted from the host device side to the function device and forwards a DATA packet as a response to the IN packet to the host device side. When a retransmission request is received from the host-side controller, a retransmission process for transmitting the same DATA packet as the DATA packet transmitted to the host-side controller last time to the host-side controller is performed. Therefore, it is possible to perform retransmission processing from the function-side controller based on a retransmission request from the host-side controller.

  In addition, the communication controller analyzes whether or not the DATA packet received from the function device contains an error by an error analysis unit, and the transmission control unit owns the retransmission process by the error analysis unit. This is performed only when it is confirmed that there is no error in the DATA packet being processed. Therefore, when the communication controller functions as a function-side controller, there is an effect that retransmission processing to the host-side controller can be performed only when the received DATA packet is determined to be correct.

  In addition, the communication controller, when it is confirmed by the error analysis means that there is no error in the DATA packet held by the device, an error is detected in the DATA packet during the packet format of the DATA packet transmitted to the host device. Set a flag to indicate that there is no. Therefore, there is an effect that it is possible to notify the host device side of information indicating whether or not the DATA packet held by the function-side controller is a retransmittable packet.

  Further, the communication controller receives a DATA packet from the function side controller, and when the error analysis means detects that there is an error in the DATA packet, an error is detected on the function device side by the flag set in the DATA packet. The retransmission request is made only when it is confirmed that a DATA packet with no packet is held. Therefore, when it is determined that there is an error in the received DATA packet, there is an effect that a retransmission request can be made to the function side controller.

  The communication controller also functions as a function-side controller that transfers a USB standard IN packet transmitted from the host device side to the function device and forwards a DATA packet as a response to the IN packet to the host device side. When a retransmission request is received from the host-side controller, an IN packet is transmitted to the function device, and the received DATA packet is transmitted to the host-side controller. Therefore, it is possible to perform retransmission processing from the function-side controller based on a retransmission request from the host-side controller.

  The communication controller adjusts the transfer rate with the communication controller on the communication partner side before executing the IN transaction. Therefore, in the communication path between the host and the function, it is possible to set a transfer rate at which actual communication is possible and a transfer rate that does not lower the transfer rate more than necessary.

  In addition, when the communication controller determines that communication can be performed at the transfer speed defined in the USB standard in the transfer speed adjustment, each packet transmitted to the communication controller on the communication partner side is Without performing transmission timing control, only modulation / demodulation is performed and transfer to the communication controller on the other side is performed. Therefore, if it is determined that the transfer speed on the communication path between the host and the function is sufficient to satisfy the above-mentioned maximum turnaround, the USB 2.0 data transfer is performed without causing a decrease in the data transfer speed. There is an effect that can be performed.

  The communication controller analyzes the error rate in the communication path with the communication controller on the communication partner side, and determines that the error rate is worse than a predetermined error rate, the transfer rate adjustment To reduce the transfer speed. Therefore, if it is determined that the quality of the communication path between the host and the function is poor, it is possible to transfer the data on the communication path with a good quality by reducing the transfer speed.

  In addition, since the communication controller performs full-duplex communication with the communication controller on the communication partner side, it is possible to eliminate the preamble required for half-duplex communication in host-function communication. There is an effect that the use efficiency of the communication path can be improved.

  In addition, since the communication controller communicates with the communication controller on the communication partner side through a communication path using an optical fiber, there is an effect that long-distance transmission is possible in communication between the host and the function. .

  In addition, since the communication controller performs communication with the communication controller on the communication partner side by radio using radio waves or by spatial transmission using light, in communication between the host and function, Because it is cableless, it has the effect of improving convenience.

[Embodiment 1]
An embodiment of the present invention will be described below with reference to FIGS.

  First, FIG. 1 shows a schematic configuration of the transmission / reception system according to the first embodiment. The transmission / reception system shown in FIG. 1 includes a host-side controller 100 and a function-side controller 110. In addition, communication between a device serving as a USB host (host device) and a device serving as a USB function (function device) is performed by a host-side controller 100 connected to the USB host side and a function connected to the USB function side. This is performed with the side controller 110.

  In addition, communication between the host-side controller 100 and the function-side controller 110 in FIG. 1 is performed by optical communication means, and the optical communication means has a transfer speed equal to or lower than the transfer speed defined in the USB standard. Suppose you are.

  When receiving a signal from the USB host, the host-side controller 100 transmits it to the function-side controller 110, and when receiving a signal from the function-side controller 110, transmits it to the USB host. The host-side controller 100 may be connected to the downstream port of the USB hub via a USB cable in addition to being connected to the USB host via a USB cable. Further, it may be configured as a part of a USB host or a USB hub.

  When the function-side controller 110 receives a signal from the host-side controller 100, the function-side controller 110 transmits the signal to the USB function. When the function-side controller 110 receives a signal from the USB function, the function-side controller 110 transmits the signal to the host-side controller 100. The function-side controller 110 may be connected to the upstream port of the USB hub via a USB cable, in addition to being connected to the USB function via a USB cable. Moreover, you may comprise as a part of USB function or USB hub.

  Hereinafter, each component of the host-side controller 100 and the function-side controller 110 will be described.

  The host-side controller 100 includes a host-side state machine 101, a USB receiver 102, a FIFO 103, a modulation circuit 104, an optical transmitter 105, an optical receiver 106, a demodulation circuit 107, a FIFO 108, and a USB transmitter 109. The function-side controller 110 includes a function-side state machine 111, an optical receiver 112, a demodulation circuit 113, a FIFO 114, a USB transmitter 115, a USB receiver 116, a FIFO 117, a modulation circuit 118, and an optical transmitter 119.

  In the host-side controller 100, the USB signal transmitted from the USB host and received by the USB receiver 102 is subjected to signal and packet analysis by the host-side state machine 101, and packets are stored by the FIFO 103. Since the communication path between the host-side controller 100 and the function-side controller 110 is the same or slower than the USB communication path, the FIFO 103 performs timing adjustment when transferring a packet to the communication path.

  When the received packet from the USB host is an IN packet or an ACK packet, the host-side state machine 101 performs packet transfer to the function-side controller 110. In other words, when the host-side controller 100 receives from the USB host a packet that can be transferred, the host-side state machine 101 notifies the modulation circuit 104 of the transmission of the packet and the start of modulation. Thus, the packet stored in the FIFO 103 is modulated by the modulation circuit 104 and transmitted to the function-side controller 110 by the optical transmitter 105.

  In the description according to the present embodiment, since the communication path between the host-side controller 100 and the function-side controller 110 (hereinafter referred to as host-function) is an optical communication path, the optical transmitter 105 is, for example, a light-emitting diode, Although it is a laser, there is no problem whether the optical communication path is a wired communication path using an optical fiber or spatial communication. When an optical fiber is used, long-distance transmission is possible, and in the case of spatial communication, convenience is improved because it is cable-free.

  In the modulation circuit 104, when the communication path between the host and the function is optical communication, a modulation method such as 8B10B is selected. However, the communication path is not necessarily limited to light, and may be wireless, for example. . In that case, the modulation circuit 104 may use another modulation method. The communication method between the host and function may be selected from half duplex communication or full duplex communication. However, when full duplex communication is selected, the optical transmitter 105 always emits light. There is no need to add a preamble to the packet, which leads to an improvement in communication path usage efficiency.

  When the host controller 100 receives an IN packet or an ACK packet from the USB host, the host controller 100 has not received a DATA packet from the function controller 110 at this time. For this reason, the host-side state machine 101 transmits a NAK packet to the USB host via the FIFO 108 and the USB transmitter 109. By doing so, the host-side controller 100 can notify the USB host that there is no DATA packet received from the function-side controller 110.

  On the other hand, when the optical signal transmitted from the host-side controller 100 to the function-side controller 110 is received by the optical receiver 112 of the function-side controller 110, the demodulating circuit 113 demodulates, for example, 8B10B, and then the function-side state. The machine 111 interprets the contents of the packet. Here, the optical receiver 112 is, for example, a photodiode. As described above, the optical receiver 112 differs depending on the type of the communication path between the host and the function. When it is determined that the packet is an IN packet or an ACK packet from the host-side controller 100, the packet is stored in the FIFO 114. Also, the function-side state machine 111 waits for completion of reception of the packet from the host-side controller 100, and transmits the packet as a USB signal to the USB function through the USB transmitter 115.

  Thus, when the USB function receives the IN packet transmitted from the USB transmitter 115 of the function-side controller 110, the USB function receives a DATA packet if it has DATA to be transmitted, and there is no DATA to be transmitted. In this case, a NAK packet is transmitted to the function-side controller 110. The DATA packet or NAK packet received by the USB receiver 116 of the function-side controller 110 is interpreted by the function-side state machine 111 and stored in the FIFO 117. Then, for example, 8B10B modulation is performed by the modulation circuit 118 and transmitted to the host-side controller 100 as an optical signal via the optical transmitter 119.

  The signal received by the optical receiver 106 of the host-side controller 100 is demodulated by, for example, 8B10B by the demodulation circuit 107. When the host-side state machine 101 recognizes that the received signal is a DATA packet or NAK packet, the FIFO 108 To store the packet.

  In addition, as described above, the USB host returns the NAK packet from the host-side controller 100 in response to the transmission of the first IN packet. When the host-side controller 100 receives the IN packet again by the USB receiver 102, if there is the DATA packet or NAK packet stored in the FIFO 108, the host-side controller 100 transmits this packet to the USB host.

  Further, regarding the NAK packet, even when the host-side controller 100 receives an IN packet from the USB host and does not receive a DATA packet from the function-side controller 110, the NAK packet is received from the function-side controller 110. Regardless, it is transmitted from the host-side controller 100 to the USB host.

  As described above, the host-side controller 100 stores the DATA packet or NAK packet as a response to the IN packet first received from the USB host in the FIFO 108, and when the IN packet is retransmitted from the USB host, The stored DATA packet or NAK packet is transmitted to the USB host. As a result, even if a communication path slower than the USB standard exists between the USB host and the USB function, communication between the host and the function is not performed again for the retransmitted IN packet. Since the DATA packet or the NAK packet can be reliably transmitted to the USB host within the limited time, the IN transaction can be performed without any problem.

  Here, the operation of the host-side state machine 101 of the host-side controller 100 according to Embodiment 1 of the present invention will be described with reference to FIG.

  S201 is a step of determining whether or not the packet received from the USB host is an IN packet. If it is an IN packet, the process proceeds to S202. If it is a packet other than an IN packet, the process proceeds to S201 again.

  S 202 is a step of transmitting an IN packet to the function-side controller 110. After the transmission is completed, the process proceeds to S203.

  S203 is a step of determining whether or not a DATA packet is received from the function-side controller 110. If a DATA packet has been received, the process proceeds to S205, and if not, the process proceeds to S204.

  S204 is a step of transmitting a NAK packet to the USB host. After transmitting the NAK packet, the process proceeds to S201.

  S205 is a step of determining whether or not the received DATA packet is correct. If the DATA packet is not correct, the process proceeds to S206. If the DATA packet is correct, the process proceeds to S207.

  S206 is a step of requesting the USB function to retransmit the DATA packet. After this retransmission request, the process proceeds to S201.

  S207 is a step of transmitting a DATA packet to the USB host. After transmitting the DATA packet, the IN transaction is terminated.

  Next, the operation of the function side state machine 111 of the function side controller 110 in the first embodiment of the present invention will be described with reference to FIG.

  S301 is a step of determining whether or not the packet received from the host-side controller 100 is an IN packet. If it is an IN packet, the process proceeds to S302, and if it is any other packet, the process proceeds to S302 again.

  S302 is a step of transmitting an IN packet to the USB function. After transmitting the IN packet, the timer is started and then the process proceeds to S303.

S303 is a step of determining a packet received from the USB function. If it is a DATA packet, the process proceeds to S305, if it is a NAK packet, the process proceeds to S304, and if a predetermined time has elapsed and timed out, the process proceeds to S301. S304 transmits a NAK packet to the host-side controller 100. It is a step. After transmitting the NAK packet, the process proceeds to S301.

  S305 is a step of transmitting a DATA packet to the host-side controller 100. After transmitting the DATA packet to the host-side controller 100, the process proceeds to S306.

  S306 is a step of transmitting an ACK packet to the USB function. After transmitting the ACK packet, the IN transaction is terminated.

  As described above, the host-side controller 100 implements a state machine that performs the operation shown in FIG. 2, and the function-side controller 110 implements a state machine that performs the operation shown in FIG. Even if the communication path between the host-side controller 100 and the function-side controller 110 is the same as or slower than the USB, an IN transaction can be performed without any problem.

  In the process of FIG. 2, the host-side controller 100 transfers the IN packet received from the USB host to the function-side controller 110 in S202. However, when the host-side controller 100 can send a DATA packet to the USB host, it is not necessary to send the IN packet to the function-side controller 110. Strictly speaking, if this IN packet arrives at the USB function, the USB function may generate a new DATA packet. In such a case, it is better not to transfer the IN packet to the USB function. It is done.

  For this reason, when the host-side controller 100 receives a DATA packet from the function-side controller 110 at the time when the host-side controller 100 receives an IN packet from the USB host, for example, control is performed so that the IN packet is not transmitted to the function-side controller 110. It is possible to do. Alternatively, after the function-side controller 110 transmits a DATA packet, an IN packet from the host-side controller 100 is ignored until an ACK packet is received from the host-side controller 100.

[Embodiment 2]
Another embodiment of the present invention will be described below with reference to FIGS.

  The schematic configuration of the transmission / reception system according to the second embodiment is the same as the configuration shown in FIG. 1 in the first embodiment, and each component has the same function as the transmission / reception system according to the first embodiment. Detailed explanation is omitted.

  First, the operation of the host-side state machine 101 of the host-side controller 100 according to the second embodiment will be described with reference to FIG.

  S401 is a step of determining whether or not the packet received from the USB host is an IN packet. If it is an IN packet, the process proceeds to S402, and if it is any other packet, the process proceeds to S401 again.

  S <b> 402 is a step of transmitting an IN packet to the function-side controller 110. After completing the transmission of the IN packet, the process proceeds to S403.

  S403 is a step of determining whether or not a DATA packet has been received from the function-side controller 110. If a DATA packet has been received, the process proceeds to S405. If not, the process proceeds to S404.

  S404 is a step of transmitting a NAK packet to the USB host. After the NAK packet transmission is completed, the process proceeds to S401.

  S405 is a step of transmitting a DATA packet to the USB host. After the completion of the DATA packet transmission, the timer is started and then the process proceeds to S406.

  S406 is a step of determining whether or not an ACK packet has been received from the USB host. If an ACK packet is received, the process proceeds to S407. If a predetermined time has elapsed without receiving an ACK packet and a time-out occurs, the process proceeds to S401.

  S 407 is a step of transmitting an ACK packet to the function-side controller 110. After transmitting the ACK packet, the IN transaction is terminated.

  Next, the operation of the function side state machine 111 of the function side controller 110 according to the second embodiment will be described with reference to FIG.

  S501 is a step of determining whether or not the packet received from the host-side controller 100 is an IN packet. If the packet is an IN packet, the process proceeds to S502. If the packet is any other packet, the process proceeds to S501 again.

  S502 is a step of holding an IN packet. After holding the IN packet, the process proceeds to S503.

  S503 is a step of transmitting an IN packet to the USB function. After completing the IN packet transmission, the timer is started, and then the process proceeds to S504.

  S504 is a step of determining a packet received from the USB function. If the packet is a DATA packet, the process proceeds to S506. If the packet is a NAK packet, the process proceeds to S505. If neither a DATA packet nor a NAK packet is received and a predetermined time elapses, the process proceeds to S501.

  S505 is a step of transmitting a NAK packet to the host-side controller 100. After the NAK packet transmission is completed, the process proceeds to S501.

  S506 is a step of determining whether or not an ACK packet has been received from the host-side controller 100. If an ACK packet has been received, the process proceeds to S508. If not, the process proceeds to S507.

  S507 is a step of transmitting a DATA packet to the host-side controller 100. After completion of the DATA packet transmission, the process proceeds to S501.

  S508 is a step of transmitting the previously stored IN packet to the USB function. After completing the IN packet transmission, the process proceeds to S522.

  S509 is a step of receiving a DATA packet from the USB function. After completion of the DATA packet, the process proceeds to S510.

  S510 is a step of transmitting an ACK packet to the USB function. After sending the ACK packet to the USB function, the IN transaction is finished.

  As described above, the host-side controller 100 implements the state machine that performs the operation as shown in FIG. 4, and the function-side controller 110 implements the state machine that performs the operation as shown in FIG. Even if the communication path between the side controller 100 and the function side controller 110 is the same as or slower than the USB, an IN transaction can be performed without any problem. 4 and FIG. 5 is summarized as a timing chart shown in FIG.

  If the DATA packet received from the function-side controller 110 and sent to the USB host is incorrect, the host-side controller 100 does not receive the ACK packet from the USB host, so send the ACK packet to the USB function. Therefore, the IN transaction can be normally terminated only when the DATA packet is correctly transferred. In other words, in the above processing, if an error occurs in the DATA packet in the communication path between the host and the function, the function side controller 110 does not transmit the ACK packet to the USB function, so that the IN transaction ends abnormally. Can be prevented, and more stable packet transfer can be performed.

  In the first embodiment and the second embodiment, the host-side controller 100 only receives the DATA packet from the function-side controller 110 when receiving the IN packet from the USB host. It was possible to send a DATA packet. This is because there is no field indicating the length of the packet in the packet format of the DATA packet. When receiving data from the low-speed communication path is transferred to the USB high-speed communication path, the data is transferred without omission. This is to ensure that However, the upper limit of the packet length of the DATA packet is set to the maximum packet length in each transfer mode in USB 2.0 as shown in FIG.

[Embodiment 3]
Still another embodiment of the present invention will be described with reference to FIG.

  First, FIG. 8 shows a schematic configuration of a transmission / reception system according to the third embodiment. The transmission / reception system shown in FIG. 8 includes a host-side controller 120 and a function-side controller 110. The host-side controller 120 includes a host-side state machine 101, a USB receiver 102, a FIFO 103, a modulation circuit 104, an optical transmitter 105, an optical receiver 106, a demodulation circuit 107, a FIFO 108, a USB transmitter 109, and a counter 121. . In the host-side controller 120, all the components other than the counter 121 have the same configuration and function as the host-side controller 100 shown in FIG. Further, the function-side controller 110 in FIG. 8 is the same as the function-side controller 110 shown in FIG.

  The counter 121 is a counter whose value increases by the amount of the written DATA packet when the DATA packet received from the function-side controller 110 is written to the FIFO 108.

  In the first and second embodiments, transmission of the DATA packet from the host-side controller 100 to the USB host is started after the host-side controller 100 has completely received the DATA packet. This is because when the transfer speed in the communication path between the host and the function is lower than the transfer speed between the host-side controller 100 and the USB host (transfer speed defined in the USB standard), the function-side controller 110 This is because if transfer of the DATA packet to the USB host is started before reception of the DATA packet is completed, normal transfer processing may not be performed. That is, in the above-described case, the FIFO 108 that stores the DATA packet in the host-side controller 100 becomes EMPTY before receiving the DATA packet from the function-side controller 110, and the DATA packet cannot be continuously transferred to the USB host. Such a problem may occur.

  However, for example, when the transfer between the host-side controller 100 and the USB host is isochronous transfer, the data amount of the DATA packet stored in the FIFO 108 is the maximum at the time of isochronous transfer shown in FIG. Even if the transmission of the DATA packet to the USB 2.0 communication path is started without reaching the value corresponding to the packet length of 3072 bytes, if the FIFO 108 does not become EMPTY in the subsequent transmission, the function-side controller 110 Even if the DATA packet is transmitted to the USB communication path without waiting for the completion of the reception of the DATA packet from the above, the above problem does not occur.

  For this reason, when the host-side controller 120 according to the third embodiment receives a DATA packet from the function-side controller 110 and stores the DATA packet in the FIFO 108, the value of the data amount of the stored DATA packet is set to the counter 121. Manage with. If the value managed by the counter 121 is equal to or greater than the value at which the FIFO 108 does not become EMPTY even if the transfer of the DATA packet to the USB host is started at that time, the value from the function-side controller 110 is By starting the transmission of the DATA packet to the USB host without waiting for the completion of the reception of the DATA packet, the transmission timing of the DATA packet can be advanced, and the transfer rate as a whole can be improved.

  If the transfer method between the host-side controller 100 and the USB host is not isochronous transfer, and the application performs bulk transfer in which the maximum data length is smaller than that of isochronous transfer, the setting value of the counter is lowered. It becomes possible to improve the transfer speed as a whole.

[Embodiment 4]
Still another embodiment of the present invention will be described with reference to FIG.

  First, FIG. 9 shows a schematic configuration of a transmission / reception system according to the fourth embodiment. The transmission / reception system shown in FIG. 9 includes a host-side controller 130 and a function-side controller 110. The host-side controller 130 includes a host-side state machine 101, a USB receiver 102, a FIFO 103, a modulation circuit 104, an optical transmitter 105, an optical receiver 106, a demodulation circuit 107, a FIFO 108, a USB transmitter 109, and a CRC check circuit 131. ing. In the host-side controller 130, all the components other than the CRC check circuit 131 have the same configuration and function as those of the host-side controller 100 shown in FIG. Further, the function-side controller 110 in FIG. 9 is the same as the function-side controller 110 shown in FIG.

  The CRC check circuit 131 can calculate a CRC (Cyclic Redundancy Check) 16 in the DATA packet received from the function-side controller 110 and determine whether or not there is an error in the received DATA packet. The DATA packet determined to have an error by the CRC check circuit 131 is discarded by the host-side state machine 101 and is not transmitted as a USB packet, so that the power required for transmission is reduced and the USB host receives an erroneous packet. This makes it possible to suppress unexpected abnormal operations that occur.

[Embodiment 5]
Still another embodiment of the present invention will be described with reference to FIG.

  First, FIG. 10 shows a schematic configuration of a transmission / reception system according to the fifth embodiment. The transmission / reception system shown in FIG. 10 includes a host-side controller 100 and a function-side controller 140. The function-side controller 140 includes a function-side state machine 111, an optical receiver 112, a demodulation circuit 113, a FIFO 114, a USB transmitter 115, a USB receiver 116, a FIFO 117, a modulation circuit 118, an optical transmitter 119, and a CRC check circuit 141. ing. In the function-side controller 140, all the components other than the CRC check circuit 141 have the same configuration and functions as those of the function-side controller 110 shown in FIG. Further, the host-side controller 100 in FIG. 10 is the same as the host-side controller 100 shown in FIG.

  The CRC check circuit 141 can calculate the CRC 16 in the DATA packet received from the USB function and determine whether or not there is an error in the received DATA packet. If there is an error in the DATA packet received from the USB function, there is no point in transferring it to the host-side controller 100. In this case, the transfer of the DATA packet to the low-speed communication path between the host and the function is as follows: It becomes useless. For this reason, a DATA packet determined to have an error by the CRC check circuit 141 can be prevented from deteriorating the transfer efficiency of the low-speed communication path by stopping the transmission of the packet even during the transfer.

[Embodiment 6]
Still another embodiment of the present invention will be described with reference to FIGS. 11 and 12 as follows.

  First, FIG. 11 shows a schematic configuration of a transmission / reception system according to the sixth embodiment. The transmission / reception system shown in FIG. 11 includes a host-side controller 150 and a function-side controller 110. The host-side controller 150 includes a host-side state machine 101, a USB receiver 102, a FIFO 103, a modulation circuit 104, an optical transmitter 105, an optical receiver 106, a demodulation circuit 107, a FIFO 151, a USB transmitter 109, and a CRC check circuit 131. ing. In the host-side controller 150, all the components other than the FIFO 151 have the same configuration and functions as those of the host-side controller 130 shown in FIG. Further, the function side controller 110 in FIG. 11 is the same as the function side controller 110 shown in FIG.

  When the host-side controller 150 receives the DATA packet from the function-side controller 110, the host-side controller 150 controls to write the DATA packet received by the host-side state machine 101 into the FIFO 151. When the host-side controller 150 re-receives the IN packet from the USB host while the DATA packet is stored in the FIFO 151, the DATA packet stored in the FIFO 151 is transmitted to the USB host.

  The FIFO 151 holds a read pointer value in advance when a DATA packet is transmitted. If the host-side state machine 101 does not receive an ACK packet from the USB host for a predetermined time after sending the DATA packet to the USB host, the host-side state machine 101 uses the communication path between the USB host and the host-side controller 150. It is determined that a data error has occurred. Then, the host-side state machine 101 sets the read pointer to the value of the read pointer described above, and after receiving the next IN packet from the USB host, transmits the same DATA packet to the USB host again.

  In this case, the retransmission of the DATA packet is realized by the control of the read pointer in the FIFO 151, but this retransmission process can be realized by holding the start address in the RAM or the like. When the CRC check circuit 131 is provided, the CRC check circuit 131 can determine whether the received DATA packet from the function-side controller 110 is correct. Therefore, when the received DATA packet is determined to be correct. It is also possible to perform control such as performing the retransmission processing.

  Here, the operation of the host-side state machine 101 of the host-side controller 150 according to the sixth embodiment of the present invention will be described with reference to FIG.

  S1101 is a step of determining whether or not an IN packet has been received from the USB host. If an IN packet is received, the process proceeds to S1102, and if a packet other than the IN packet is received, the process proceeds to S1101 again.

  S 1102 is a step of transmitting an IN packet to the function-side controller 110. After the IN packet transmission is completed, the process proceeds to S1103.

  S1103 is a step of determining whether or not a DATA packet has been received from the function-side controller 110. If a DATA packet has been received, the process proceeds to S1105, and if not, the process proceeds to S1104.

  S1104 is a step of transmitting a NAK packet to the USB host. After the transmission of the NAK packet is completed, the process proceeds to S1101.

  S1105 is a step of transmitting a DATA packet to the USB host. After completion of the DATA packet transmission, the timer is started and the process proceeds to S1106.

  S1106 is a step of determining whether or not an ACK packet has been received from the USB host. If an ACK packet is received, the process proceeds to S1107. If a predetermined time has elapsed without receiving an ACK packet, the process proceeds to S1108.

  S1107 is a step of transmitting an ACK packet to the USB function. After the ACK packet transmission ends, the IN transaction ends.

  S1108 is a step of determining whether or not an IN packet has been received from the USB host. If an IN packet is received, the process proceeds to S1105. If any other packet is received, the process proceeds to S1108 again.

  By performing the state machine operation as described above in the host-side controller 150, when the host-side controller 150 transmits a DATA packet to the USB host, a data error occurs between the USB host and the host-side controller 150. Even when this occurs, it is possible to perform retransmission processing of the DATA packet.

[Embodiment 7]
Still another embodiment of the present invention will be described with reference to FIGS.

  First, FIG. 13 shows a schematic configuration of a transmission / reception system according to the seventh embodiment. The transmission / reception system shown in FIG. 13 includes a host controller 100 and a function controller 160. The function-side controller 160 includes a function-side state machine 111, an optical receiver 112, a demodulation circuit 113, a FIFO 114, a USB transmitter 115, a USB receiver 116, a FIFO 161, a modulation circuit 118, an optical transmitter 119, and a CRC check circuit 141. ing. In the function-side controller 160, all the components other than the FIFO 161 have the same configuration and function as those of the function-side controller 140 shown in FIG. Further, the host-side controller 100 in FIG. 13 is the same as the host-side controller 100 shown in FIG.

  When receiving the DATA packet from the USB function, the function-side controller 160 controls the function-side state machine 111 to write the received DATA packet into the FIFO 161. The DATA packet is modulated by, for example, 8B10B by the modulation circuit 118 and transmitted to the host-side controller 100.

  This FIFO 161 holds the value of the read pointer in advance when transmitting a DATA packet. When the function-side state machine 111 receives a retransmission request from the host-side controller 100, the function-side state machine 111 sets the read pointer to the aforementioned read pointer value and transmits the same DATA packet toward the host-side controller 100 again.

  In this case, the retransmission of the DATA packet is realized by the control of the read pointer of the FIFO 161, but this retransmission process can be realized by holding the start address in a RAM or the like. When the CRC check circuit 141 is provided, the CRC check circuit 141 can determine whether or not the received DATA packet from the USB function is correct. Therefore, only when the received DATA packet is determined to be correct, It is also possible to perform control such as performing the above retransmission processing.

  Here, the operation of the host-side state machine 101 of the host-side controller 100 according to the seventh embodiment of the present invention will be described with reference to FIG. The host-side state machine 101 related to this retransmission process may be incorporated in the state machine of the host-side controller 100 shown in the first or second embodiment, or may exist alone.

  S1301 is a step of determining whether or not the packet received from the function-side controller 160 is a DATA packet. If it is a DATA packet, the process proceeds to S1302, and if it is any other packet, the process proceeds to S1301 again.

  S1302 is a step of determining whether or not there is an error in the received DATA packet. If there is no error, the process is terminated without making a retransmission request. If there is an error, the process proceeds to S1303.

  In step S1303, the function-side controller 160 is requested to retransmit the DATA packet. After the retransmission request is completed, the process proceeds to S1301.

  By performing the above operation, if an error occurs in the DATA packet in the communication path between the host-side controller 100 and the function-side controller 160, the host-side controller 100 sends the error to the function-side controller 160. It is possible to notify the effect.

  Next, the operation of the function side state machine 111 of the function side controller 160 according to the seventh embodiment will be described with reference to FIG. Note that the function-side state machine 111 relating to this retransmission processing may be incorporated into the state machine of the function-side controller 160 shown in the first or second embodiment, or may exist alone.

  S1401 is a step of determining whether or not the packet received from the USB function is a DATA packet. If it is a DATA packet, the process proceeds to S1402, and if it is any other packet, the process proceeds to S1401 again.

  S1402 is a step of transmitting a DATA packet to the host-side controller 100. After the completion of DATA packet transmission, the process proceeds to S1403.

  S1403 is a step of discriminating a signal received from the host-side controller 100. If the request is a retransmission request, the process proceeds to S1402. If the request is an ACK packet, the process is terminated without performing the retransmission process.

  By performing the above operation, the function-side controller 160 resets the read pointer of the FIFO 161, for example, based on the retransmission request from the host-side controller 100, thereby enabling retransmission processing.

  Further, when receiving a retransmission request from the host-side controller 100, the function-side controller 160 may send an IN packet to the USB function and send a DATA packet received as a response to the USB host.

[Embodiment 8]
Still another embodiment of the present invention will be described with reference to FIG.

  FIG. 16 shows a packet format according to the eighth embodiment. In FIG. 16, a USB packet is a packet format of a data packet communicated at a transfer rate defined by USB, and a low-speed packet is a packet format converted for a low-speed communication path. That is, the low-speed packet is a packet format when the function-side controller transmits a DATA packet to the host-side controller.

  As shown in FIG. 16, in the low-speed packet, a field CRC_OK is provided after the CRC 16 of the USB packet. When there is no error in the DATA packet held by the function-side controller, a value indicating that is put in the CRC_OK field (a flag indicating that is set), and there is an error in the held DATA packet. In this case, the DATA packet is transmitted to the host-side controller with the same effect. By doing so, it is possible to notify the host-side controller of information on whether or not the DATA packet held by the function-side controller is a retransmittable packet. By monitoring the CRC_OK field, the host-side controller can control whether to make a retransmission request to the function-side controller if it is determined that there is an error in the received DATA packet. It becomes.

[Embodiment 9]
Still another embodiment of the present invention will be described with reference to FIGS.

  First, FIG. 17 shows a schematic configuration of a transmission / reception system according to the ninth embodiment. The transmission / reception system shown in FIG. 17 includes a host-side controller 170 and a function-side controller 180. The host-side controller 170 includes a host-side state machine 101, a USB receiver 102, a FIFO 103, a modulation circuit 104, an optical transmitter 105, an optical receiver 106, a demodulation circuit 107, a FIFO 108, a USB transmitter 109, a speed negotiation state machine 171, An error detection circuit 172 and a timer 173 are provided. In the host-side controller 170, all the components other than the speed negotiation state machine 171 and the error detection circuit 172 have the same configuration and functions as those of the host-side controller 100 shown in FIG. The function-side controller 180 includes a function-side state machine 111, an optical receiver 112, a demodulation circuit 113, a FIFO 114, a USB transmitter 115, a USB receiver 116, a FIFO 117, a modulation circuit 118, an optical transmitter 119, and a speed negotiation state machine. 181, an error detection circuit 182, and a timer 183. In the function-side controller 180, all the components other than the speed negotiation state machine 181 and the error detection circuit 182 have the same configuration and functions as those of the function-side controller 110 shown in FIG.

  The speed negotiation state machines 171 and 181 perform state negotiation (transfer speed adjustment) between the host-side controller 170 and the function-side controller 180 and select one transfer speed from a plurality of transfer speeds. It is. The error detection circuits 172 and 182 are circuits that perform error detection on a low-speed communication path (in FIG. 17, an optical communication path between the host and the function). This speed negotiation is performed before the execution of the IN transaction.

  The speed negotiation operation will be described with reference to FIG. The speed negotiation protocol in FIG. 18 is an example, and the present invention is not limited to this protocol.

  The speed negotiation state machine 171 of the host-side controller 170 starts transmitting a keep_speed signal at a predetermined transfer speed A at t1401, and starts a timer simultaneously with the transmission of the keep_speed signal. The keep_speed signal is one of transmission codes (request signals) for determining the transfer rate, and is a signal for requesting the function-side controller 180 to maintain the current transfer rate.

  On the other hand, when the function-side controller 180 confirms reception of the keep_speed signal with the signal detect signal, the function-side controller 180 starts a timer and starts transmission of the keep_speed signal to the host-side controller 170 at t1402.

  Each of the host-side controller 170 and the function-side controller 180 continues to transmit a specific transmission code during a predetermined time T.

  If the keep_speed signal transmitted from the host-side controller 170 at t1403 is pitted in the optical communication path and the function-side controller 180 cannot receive normally, the function-side controller 180 replaces the keep_speed signal at t1404, A lower_speed signal is transmitted to the host-side controller 170. This lower_speed signal is one of request signals for determining the transfer rate, and is a signal for requesting the transmission destination (host-side controller 170) to lower the transfer rate.

  The host-side controller 170 that has received the lower_speed signal from the function-side controller 180 recognizes that the function-side controller 180 cannot normally receive at the current transfer rate A. Then, a lower_speed signal is transmitted to the function-side controller 180 (at t1405, the transmission code is switched to lower_speed).

  The function-side controller 180 receives the lower_speed signal from the host-side controller 170 at t1406, thereby determining that the lower-speed signal transmitted by the function-side controller 180 has been recognized by the host-side controller 170.

  Then, after a predetermined time T has elapsed in each of the host-side controller 170 and the function-side controller 180, the host-side controller 170 and the function-side controller 180 have a transfer rate that is the lower_speed signal because the signal being transmitted and received at that time is For example, it is reduced to half (A / 2).

  That is, at t1407, the host-side controller 170 starts transmitting a keep_speed signal at the transfer rate A / 2 and restarts the timer. On the other hand, the function-side controller 180 also starts transmitting a keep_speed signal at the transfer rate A / 2 at t1408 and restarts the timer.

  Then, when a predetermined time T has elapsed without an error being detected by both the host-side controller 170 and the function-side controller 180, the host-side controller 170 and the function-side controller 180 indicate a speed negotiation end signal (end) at t1409 and t1410. Transmission of an End_Nego signal, which is a request). Each of the host-side controller 170 and the function-side controller 180 ends the speed negotiation when it receives the End_Nego signal from the counterpart device, and transitions to the active state.

  Here, the operation of the speed negotiation state machine 171 in the host-side controller 170 will be described with reference to FIG.

  State ST0 is a speed negotiation start state. Here, the speed negotiation state machine 171 uses the transmission code as a keep_speed signal, restarts the timer, and then transitions to the state ST1.

  The state ST1 is a state for performing speed negotiation. Here, the speed negotiation state machine 171 switches the transmission code to lower_speed when there is an error in the reception code or when a lower_speed signal is received from the counterpart device (function-side controller 180).

  Further, after a predetermined time T has elapsed, the speed negotiation state machine 171 transitions to the state ST0 when the transmission code is a lower_speed signal, and transitions to the state ST2 when the transmission code is keep_speed.

  Here, when transitioning to the state ST0, the transfer rate is halved with respect to the current transfer rate, for example (the width (degree) of decrease in the transfer rate can be set to a value desired by the user. This width is stored in advance in the speed negotiation state machine 171).

  On the other hand, when transitioning to the state ST2, the transmission code is switched to the End_Nego signal. This state ST2 is a state for confirming the end of the speed negotiation. When the End_Nego signal is received from the counterpart device (function side controller 180), the speed negotiation is terminated and the state transits to the active state.

  Next, the operation of the speed negotiation state machine 181 in the function-side controller 180 will be described with reference to FIG.

  The operation in each of the states ST0, ST1, and ST2 is the same as the operation of the speed negotiation state machine 171.

  State ST4, which is a state before state ST0, is a state for determining whether or not a request signal has been received from host-side controller 170. When receiving a signal detect signal from the optical receiver 112 (or other received signal detection circuit), the speed negotiation state machine 181 transitions to the state ST0.

  By configuring the state machine with the host-side controller 170 and the function-side controller 180, one transfer rate can be determined from a plurality of transfer rates.

  The error detection circuits 172 and 182 detect bit errors in the optical communication path between the host and the function. Specifically, for example, table lookup is performed at the time of 8B10B demodulation, and an error occurs when a character not in the table is received. I will not mention the definition of this error.

  When an active state is established after the speed negotiation is completed, the number of errors (error rate) in a fixed time can be measured from the number of errors obtained by the error detection circuits 172 and 182 and the measured values of the timers 173 and 183. When the error rate is larger than a predetermined value, the quality of the communication path is deteriorated (for example, a change in the communication distance between the mobile device and the PC in communication between the mobile device and the PC (Personal Computer)). Therefore, after giving up communication at the current transfer rate, performing speed negotiation again, re-determining the transfer rate at which normal communication is possible, and then performing data transfer normally by performing an IN transaction. Is possible.

  In the description according to the present embodiment, it is assumed that the optical communication path between the host and the function has a transfer speed lower than the native speed of USB. However, an inexpensive and faster optical transceiver will be used in the future. If it can be manufactured, it is possible to use a communication means capable of transferring data at the USB native speed on the optical communication path between the host and the function. In such a case, first, speed negotiation is performed at a speed corresponding to the native speed of USB (600 Mbps in the case of 8B10B modulation). If the error rate is not bad, packet control by the state machine of the present invention is not performed. In addition, it is possible to perform pure opticalization of USB 2.0 by performing pure repeat, and it is possible to prevent a decrease in data transfer speed.

  If communication cannot be performed normally at 600 Mbps, the packet can be controlled by the state machine of the present invention after the transfer rate is lowered, and an IN transaction can be performed. That is, it is possible to perform packet transfer by the most efficient method by determining ON / OFF of packet control by the state machine based on the result of speed negotiation.

  In the description of the first to ninth embodiments, the communication speed between the host and the function is lower than the native speed of the USB. In the conventional transmission method, communication within the restricted time defined by the USB is possible. It is described as solving the problem of not completing. However, even when the host-function communication speed is equal to the USB native speed, if the host-function communication path is very long (for example, an optical fiber of several hundred meters), the turnaround time is There is a possibility that the IN transaction cannot be completed within the restricted time. This is because in the USB standard, the maximum turnaround time is determined by the repeat time of the number of stages of the USB hub (maximum of 6 stages) and the cable length of the USB (maximum of 5 m). The transmission method of the present invention can be applied even when the communication path between the host and the function becomes very long as described above, and the conventional transmission method does not complete communication within the restricted time defined by USB. is there.

  In the description of the first to ninth embodiments, the USB 2.0 standard is assumed. In the USB 2.0 standard, the functions on the host side and the function side are fixed. That is, data exchange under the USB 2.0 standard is performed by connecting a device (digital camera, printer, or the like) serving as a USB function to the PC using the PC as a USB host.

  However, in recent years, a standard called USB-OTG (USB-On-The-Go) has been established, and a PC (USB host) that is normally required in a USB system is no longer necessary. That is, in the USB-OTG standard, data can be transmitted and received between USB devices without a PC (USB host), so that convenience is improved. The USB-OTG can operate as a USB host or a USB function depending on the type of connector of the connected cable.

  USB-OTG supports transfer rates of LS (1.5 Mbps), FS (12 Mbps), and HS (480 Mbps) as in USB 2.0. Further, the USB-OTG compatible device can operate as a USB host or a USB function. In the USB-OTG standard, a new connector type called miniAB has been added. This miniAB can be connected to a cable having both miniA and miniB plugs. Depending on the shape of the plug of the connected cable, when miniA is connected, it operates as a USB host, and miniB When is connected, it operates as a USB function. In addition, a new protocol called HNP (Host Negotiation Protocol) has added a mechanism for dynamically changing the function of the host and the function while the cable is connected. In other words, in USB-OTG, whether the connected device is a USB host or a USB function is determined by the type of cable connector or HNP (Host Negotiation Protocol) defined by USB-OTG.

  That is, when the present invention is applied to the USB-OTG, the roles of the USB host and the USB function are not fixed, and the roles may be switched depending on the direction of data to be transmitted. Similarly, the roles of the host-side controller and the function-side controller are not fixed, and the roles can be switched depending on the direction of the transmitted data. It is preferable to have both functions of the side controller. For this purpose, it is only necessary to incorporate a program operable as a function of both the host-side controller and the function-side controller in the state machine of each controller.

  In the description of the first to ninth embodiments, communication between the host-side controller and the function-side controller is full-duplex communication. By doing so, it is possible to eliminate the preamble necessary for half-duplex communication in the communication between the host and the function, and the use efficiency of the communication path can be improved. Of course, there is no problem even if the system is constructed with half-duplex communication.

  In the transmission / reception system according to the present invention, as described in the above embodiment, data transfer between the USB host, the host side controller, the function side controller, and the USB function at a speed (for example, 100 Mbps) slower than the USB native speed. Even when performing the above, there may be a case where almost the same transfer speed as a whole can be obtained as compared with the case where the data transfer between the USB host and the USB function is performed at the USB native speed (480 Mbps).

  For example, when an application for low-speed data transfer (50 Mbps) such as a flash memory is used, if the above IN transaction is continuously performed, compared to a case where an application such as HDD that requires high-speed data transfer (about 200 Mbps) is used. It is necessary to take a long time between IN transactions. That is, the time between transactions is short when using an application for high-speed data transfer, and the time between transactions is long when using an application for low-speed data transfer.

  For this reason, when an IN transaction is performed by the method according to the present invention, the time for one IN transaction is longer than that when performing data transfer between a host and a function at a USB native transfer rate. If it is completed within the time required, the next IN transaction start time is not delayed compared to the IN transaction start time in the case of the USB native speed. That is, comparing the case where the low-speed communication path is used between the host and the function and the case where communication is performed at the USB native speed, the result is that the transfer speed does not change as a whole.

  In addition, in the case where the USB 2.0 is simply made optical, for example, if an 8B10B modulation method is used, an optical transceiver having a bandwidth of 480 × 10/8 = 600 Mbps is required. An optical transceiver that satisfies this requirement is an LD (laser diode). On the other hand, when USB 2.0 can be transferred over a low-speed communication path using the present invention, when the low-speed communication path is, for example, 100 Mbps, the optical transceiver satisfying this is an LED (light emitting diode). Compared with the LD and the LED, the LED is overwhelmingly less expensive, and the configuration of the present invention enables the cost of the optical transceiver to be reduced.

  Furthermore, in the controller, for example, when the host-side controller is integrated with the USB host, and other metal ports are eliminated and only the optical port is configured, the bandwidth required by the controller is greatly reduced from 600 Mbps to 100 Mbps. Become. This means that the controller can be created by an inexpensive manufacturing process, and the present invention can also reduce the cost.

  As described above, when a low-speed application is used, the present invention can reduce the cost. For example, the present invention is effective in a low-speed application such as a mobile phone or a digital camera equipped with a flash memory. Conceivable.

  Even if the transfer rate between the host and the function is low, the present invention can be applied to various communication devices that perform data communication with USB by a transmission / reception system that can normally perform IN transactions without being aware of turnaround time.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates an embodiment of the present invention and is a block diagram illustrating a main configuration of a transmission / reception system according to a first embodiment. 4 is a flowchart showing the operation of the state machine of the host-side controller of the transmission / reception system in the first embodiment. 3 is a flowchart showing the operation of the state machine of the function-side controller of the transmission / reception system in the first embodiment. 10 is a flowchart illustrating an operation of a state machine of a host-side controller of the transmission / reception system according to the second embodiment. 10 is a flowchart showing the operation of the state machine of the function-side controller of the transmission / reception system in the second embodiment. 10 is a timing chart illustrating an IN transaction in the transmission / reception system according to the second embodiment. It is a figure which shows the DATA packet maximum length in each transfer mode in USB2.0. FIG. 10 is a block diagram showing a main configuration of a transmission / reception system in a third embodiment. FIG. 10 is a block diagram illustrating a main configuration of a transmission / reception system in a fourth embodiment. FIG. 10 is a block diagram illustrating a main configuration of a transmission / reception system in a fifth embodiment. FIG. 20 is a block diagram showing a main configuration of a transmission / reception system in a sixth embodiment. 20 is a flowchart illustrating the operation of a state machine of a host-side controller of a transmission / reception system according to a sixth embodiment. FIG. 20 is a block diagram showing a configuration of main parts of a transmission / reception system in a seventh embodiment. 20 is a flowchart illustrating the operation of a state machine of a host-side controller of a transmission / reception system in a seventh embodiment. 18 is a flowchart showing the operation of a state machine of a function-side controller of a transmission / reception system in a seventh embodiment. FIG. 20 is a diagram illustrating a USB packet and a packet format in a low-speed communication path in the eighth embodiment. 209 is a block diagram illustrating a main configuration of a transmission / reception system according to Embodiment 9. FIG. 10 is a timing chart illustrating a speed negotiation process according to the ninth embodiment. FIG. 40 is a timing chart illustrating an operation of a speed negotiation state machine of the host-side controller of the transmission / reception system according to the ninth embodiment. FIG. 40 is a timing chart showing the operation of the speed negotiation state machine of the function-side controller of the transmission / reception system in the ninth embodiment. It is a figure which shows the kind of packet in USB2.0. It is a figure which shows the packet format of the typical packet in USB2.0. It is a timing chart which shows IN transaction in USB2.0. It is a timing chart which shows the mode of the packet transfer in the case of performing IN transaction in USB2.0 by a low-speed communication path.

Explanation of symbols

100, 120, 130, 150, 170
Host-side controller 101 Host-side state machine
(Reception confirmation means, data storage confirmation means, transmission control means, retransmission request means)
108,151 FIFO (storage means)
110, 140, 160, 180
Function-side controller 111 Function-side state machine 121 Counter (data amount confirmation means)
131, 141 CRC check circuit (error analysis means)

Claims (28)

When performing an IN transaction as data communication over USB, it functions as a host-side controller that transfers an IN packet transmitted from the host device to the function device and transfers a DATA packet that is a response to the IN packet to the host device. A communication controller,
A reception confirmation means for confirming reception of an IN packet from the host device;
Storage means for storing a DATA packet transmitted from the function device side;
Data storage confirmation means for confirming whether or not a DATA packet is stored in the storage means when the reception recognition means confirms reception of an IN packet from the host device;
When it is confirmed by the data storage confirmation means that the DATA packet is not stored, the IN packet received from the host device is transferred to the function device side, and a NAK packet is transmitted to the host device to confirm the data storage. A communication controller, comprising: a transmission control means for transmitting the DATA packet to a host device when the means confirms that the DATA packet is stored. The communication controller also functions as a function-side controller that transfers a USB standard IN packet transmitted from the host device side to the function device and transfers a DATA packet as a response to the IN packet to the host device side. ,
When receiving an IN packet from the host device side, hold this,
When an ACK packet for the DATA packet transmitted to the host device is received from the host device, the IN packet held above is transmitted to the USB function, and when the DATA packet for the IN packet is received from the function device. A communication controller that transmits an ACK packet to a function device. The transfer rate related to the reception of the IN packet from the host device and the transmission of the DATA packet to the host device is the transfer rate defined in the USB standard, and the transmission of the IN packet to the function device side and the DATA packet from the function device side The transfer speed related to the reception is lower than the transfer speed defined in the USB standard,
Furthermore, it has a data amount confirmation means for confirming the storage data amount when storing the DATA packet received from the function device side in the storage means,
The transmission control means starts transmission of a DATA packet to the host device when the amount of received data confirmed by the data amount confirmation means exceeds a predetermined value. The communication controller according to 1. Having an error analysis means for analyzing whether the DATA packet received from the function device side contains an error,
2. The communication according to claim 1, wherein when the error analysis unit determines that the received DATA packet is incorrect, the transmission control unit discards the DATA packet and does not transfer it to the host device. controller. Having an error analysis means for analyzing whether the DATA packet received from the function device side contains an error,
2. The transmission control unit according to claim 1, wherein when the error analysis unit determines that the received DATA packet is incorrect, the transmission control unit stops transmission of the DATA packet to the host device at that time. Communication controller. The reception confirmation means confirms whether or not an ACK packet for the DATA packet is returned from the host device after transmitting the DATA packet to the host device.
After transmitting the DATA packet to the host device, the transmission control unit transmits to the host device the previous time when the reception of the next IN packet is confirmed without confirming the reception of the ACK packet by the reception confirmation unit. The communication controller according to claim 1, wherein retransmission processing is performed to transmit the same DATA packet as the transmitted DATA packet to the host device. Having an error analysis means for analyzing whether the DATA packet received from the function device side contains an error,
7. The communication controller according to claim 6, wherein the transmission control unit performs the retransmission process only when it is confirmed by the error analysis unit that there is no error in the DATA packet held by the own device. Error analysis means for analyzing whether or not the DATA packet received from the function device side contains an error;
2. The apparatus according to claim 1, further comprising: a retransmission request unit configured to request a retransmission of the DATA packet on the function device side when the error analysis unit determines that the received DATA packet is incorrect. Communication controller. The communication controller also functions as a function-side controller that transfers a USB standard IN packet transmitted from the host device side to the function device and transfers a DATA packet as a response to the IN packet to the host device side. ,
2. The communication controller according to claim 1, wherein when a retransmission request is received from the host-side controller, retransmission processing is performed to transmit the same DATA packet as the DATA packet transmitted to the host-side controller to the host-side controller last time. . Having an error analysis means for analyzing whether or not the DATA packet received from the function device contains an error;
The communication controller according to claim 9, wherein the transmission control unit performs the retransmission process only when it is confirmed by the error analysis unit that there is no error in the DATA packet held by the own device.   When it is confirmed by the error analysis means that there is no error in the DATA packet held by the own device, a flag indicating that the DATA packet has no error is included in the packet format of the DATA packet to be transmitted to the host device. The communication controller according to claim 10, wherein the communication controller is set up. When a DATA packet is received from the function side controller, and the error analysis means detects that there is an error in the DATA packet,
The flag indicating whether there is an error in the DATA packet held by the function side controller is set in the received DATA packet, and it is confirmed by the flag that the DATA packet without error is held on the function device side. The communication controller according to claim 8, wherein the retransmission request is made only in the case of a failure. The communication controller also functions as a function-side controller that transfers a USB standard IN packet transmitted from the host device side to the function device and transfers a DATA packet as a response to the IN packet to the host device side. ,
2. The communication according to claim 1, wherein when a retransmission request is received from the host-side controller, an IN packet is transmitted to the function device, and the received DATA packet is transmitted to the host-side controller. controller.   2. The communication controller according to claim 1, wherein transfer rate adjustment is performed with a communication controller on a communication partner side before execution of the IN transaction. In the above transfer speed adjustment, when it is determined that communication is possible at the transfer speed defined in the USB standard,
15. The communication according to claim 14, wherein each packet transmitted to the communication controller on the other side of the communication is transferred to the communication controller on the other side by performing only modulation / demodulation without performing packet transmission timing control. controller.   Analyzing the error rate on the communication path with the communication controller on the communication partner side, and if it is determined that the error rate is worse than a predetermined error rate, the transfer rate is adjusted to reduce the transfer rate The communication controller according to claim 14.   The communication controller according to any one of claims 1 to 16, wherein full-duplex communication is performed with a communication controller on a communication partner side.   The communication controller according to any one of claims 1 to 17, wherein communication with a communication controller on a communication partner side is performed through a communication path using an optical fiber.   The communication controller according to any one of claims 1 to 16, wherein communication with a communication controller on a communication partner side is performed by radio using radio waves.   The communication controller according to any one of claims 1 to 17, wherein communication with a communication controller on a communication partner side is performed by spatial transmission using light. When performing an IN transaction as data communication over USB, the function side transfers a USB standard IN packet transmitted from the host device side to the function device, and transfers a DATA packet as a response to the IN packet to the host device side A communication controller that functions as a controller,
When receiving an IN packet from the host device side, hold this,
When an ACK packet for the DATA packet transmitted to the host device is received from the host device, the IN packet held above is transmitted to the USB function, and when the DATA packet for the IN packet is received from the function device. A communication controller that transmits an ACK packet to a function device. When performing an IN transaction as data communication over USB, the function side transfers a USB standard IN packet transmitted from the host device side to the function device, and transfers a DATA packet as a response to the IN packet to the host device side A communication controller that functions as a controller,
A communication controller that performs a retransmission process for transmitting to the host controller the same DATA packet as the DATA packet that was previously transmitted to the host controller when a retransmission request is received from the host controller.   Analyzing whether or not the DATA packet received from the function device includes an error, and performing the retransmission process only when it is confirmed by the analysis that the DATA packet held by the own device is free of errors. The communication controller according to claim 22.   If it is confirmed by the above analysis that there is no error in the DATA packet held by the device, a flag indicating that the DATA packet has no error is set in the packet format of the DATA packet transmitted to the host device. The communication controller according to claim 23. When performing an IN transaction as data communication over USB, the function side transfers a USB standard IN packet transmitted from the host device side to the function device, and transfers a DATA packet as a response to the IN packet to the host device side A communication controller that functions as a controller,
A communication controller, wherein when a retransmission request is received from a host-side controller, an IN packet is transmitted to the function device, and the received DATA packet is transmitted to the host-side controller. A communication controller functioning as a host-side controller according to any one of claims 1, 3, 4, 5, 6, 7, 8, 12, 14, 15, and 16;
A communication controller that functions as a communication controller that functions as a function-side controller that transfers a USB standard IN packet transmitted from the host device side to the function device and transfers a DATA packet that is a response to the IN packet to the host device side; A communication system comprising:   A communication device comprising the communication controller according to any one of claims 1 to 26. When the reception of the IN packet from the host device is confirmed, it is confirmed whether or not a DATA packet that is a response to the IN packet is received at that time.
If the DATA packet is received, the DATA packet is transmitted to the host device in response to the received IN packet,
A communication method, wherein when the DATA packet is not received, the received IN packet is transferred to the function device side and a NAK packet is transmitted to the host device.

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