JP2006195607A - Method and circuit for determining bulk-out transfer end - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately determine end of bulk-out transfer to an own USB device even when the transfer period of bulk-out transfer is reduced by connection of two or more USB devices to a host device. <P>SOLUTION: In this determination method, a SOF packet counter counting SOF packets is used, and the increment value of the SOF packet counter is set to "2" when only SOF packets are transferred, or when no packet is transferred to any USB device to increase a count value increment rate. When packets to USB devices other than the own device are transferred, the increment value is set to "1" to reduce the count value increment rate, and when the count value of the SOF packet counter is a predetermined value, end of bulk-out transfer to the own USB device is determined. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method and a circuit for determining the end of a bulk-out transfer performed from a host device such as a USB host device to a peripheral device such as a USB device.

  First, USB will be briefly described. Data transferred by USB is composed of a token packet, a data packet, and a handshake packet, and one data transfer composed of these three packets is called a transaction.

  The token packet stores the PID (identifier) indicating the type of transaction, the address of the USB device that is the counterpart of the data transfer, and the endpoint, and between the USB device and the host device that conforms to the information of this token packet. Data transfer becomes possible. Transfer data is stored in the data packet. The handshake packet stores information indicating whether or not the data transfer has been normally completed.

  There are three types of transactions: IN transactions, OUT transactions, and SETUP transactions. In the IN transaction, data is transferred from the USB device to the host device. In the OUT transaction, data is transferred from the host device to the USB device. The SETUP transaction is used when a command specified by the standard is transferred from the host device to the USB device. These three transactions constitute a transfer called bulk transfer, control transfer, isochronous transfer, or interrupt transfer.

  Bulk transfer is used for transferring a large amount of data aperiodically, and is performed by repeating an IN transaction or an OUT transaction. Hereinafter, the bulk transfer performed by repeating the OUT transaction is particularly referred to as “bulk-out transfer”. The control transfer is a transfer used for exchanging information necessary for controlling the peripheral device, and starts with a SETUP transaction and includes an IN transaction and an OUT transaction. Isochronous transfer is used for continuous and periodic communication, and is a sequence of IN or OUT transactions without handshake packets. An interrupt transfer is a single IN transaction used for periodic and low bandwidth data transfers.

  These various transfers are arranged in a certain period called a frame (1 ms in the full speed mode, 125 μs in the high speed mode) and transferred in units of one frame. The start of the frame is notified by a special packet called an SOF (Start of Frame) packet.

  When transferring a large amount of data from a USB host device such as a PC (personal computer) to a USB device such as a printer or scanner, the data is divided into a plurality of packets in units of USB protocol packets by the bulk-out transfer described above. Transferred. For example, in a device having a USB 2.0 high-speed mode function, as shown in FIG. 8, the data is divided into 512-byte units (maximum packet size) and transmitted.

  FIG. 8A shows a case where transfer data is not divisible by 512 bytes, and the remaining data (1 to 511 bytes) is transferred to the last bulk-out transfer packet. In each packet, “OUT” is a token packet indicating data transmission from the USB host toward the USB device, “512 bytes” is a data packet to be transferred, and “ACK” is a hand indicating that the data packet has been received without error. This is a shake packet and is transferred from the USB device to the USB host device. The last bulk-out transfer packet in FIG. 8A is called a short packet. FIG. 8B shows a case where 512 bytes are divisible, and 0-byte data is transferred in the last bulk-out transfer packet. This last bulk-out packet is called a Null packet.

  In this way, on the USB device side, the end of the transfer data by the bulk-out transfer is received by receiving a packet different from the maximum packet size (512 bytes in the above case), that is, receiving a short packet or a Null packet. It is common to judge.

  However, in bulk-out transfer, a null packet may not be transmitted from the USB host device in some devices, such as data transfer to a printer device. Therefore, in the case of data transfer that is divisible by the maximum packet size, there is a problem that the end of transfer cannot be determined.

  Therefore, as a determination method other than detecting the end of a short packet or Null packet and determining the end of bulk-out transfer, the USB device side has a timer function, and data is not received within a fixed period set by the timer. (For example, Patent Document 1) that detects that the received data on the USB device side is not updated and determines the end of bulk-out transfer, or the timer time is set to transfer speed or the like so as not to decrease the processing speed of the apparatus A technique (for example, Patent Document 2 and Patent Document 3) that switches to an optimum value in response to this has been proposed.

JP 2003-249965 A JP 2004-118517 A JP 2004-133537 A

  As described above, the USB bulk-out transfer is not a transfer method in which the transfer cycle is guaranteed, but is an aperiodic transfer that is transferred when the USB bus is free, so that multiple USB devices are connected to the USB host device. In this case (a maximum of 127 USB devices can be connected to one USB host device), the USB host device controls a plurality of USB devices, and therefore the data transfer cycle to each USB device is delayed. For this reason, when the end of data is determined by the timer, the time-out may be reached even though the bulk-out transfer has not yet ended, and the end of data may be determined to be erroneous.

  It is an object of the present invention to accurately determine the end of bulk-out transfer even when a data transfer cycle is reduced due to a plurality of peripheral devices such as USB devices connected to a host device such as a USB host device. An object of the present invention is to provide a bulk-out transfer end determination method and circuit.

  According to the first aspect of the present invention, when two or more peripheral devices are connected to the host device and bulk-out transfer is performed from the host device to at least one of the peripheral devices, the peripheral device side In the method for determining the end of bulk-out transfer, each peripheral device is provided with a counting means that is incremented by an SOF packet periodically transferred from the host device to each peripheral device. When a bulk-out packet is transferred, the counting means is cleared. When a packet addressed to a peripheral device other than itself is transferred, the increment value of the counting means is set to the first value, and only the SOF packet is transferred. When this happens, the increment value is set to a second value larger than the first value, and the count value of the counting means is preliminarily set. Upon reaching the set predetermined value, the bulk-out transfer to the self peripherals and judging to be complete.

  The invention according to claim 2 is the bulk out transfer end determination method according to claim 1, wherein when the bulk out packet addressed to its own peripheral device is a short packet or a null packet, the counting means is cleared and the bulk A method characterized by determining that the out transfer has been completed.

  The invention according to claim 3 is the bulk-out transfer end determination method according to claim 1 or 2, wherein when the counting unit is incremented, the increment value is set to the second value. To do.

  According to a fourth aspect of the present invention, there is provided a bulk-out transfer end determination circuit which is incorporated in a peripheral device connected to two or more host devices and determines the end of a bulk-out transfer performed by the host device. Count means that is incremented by a SOF packet periodically transferred and cleared when a bulk-out packet addressed to its own peripheral device is received, and when a packet other than a bulk-out packet addressed to its own peripheral device is received An increment value control means for setting the increment value of the count means to a first value and setting an increment value to a second value larger than the first value when only the SOF packet is received; Means for comparing the count value of the means with a preset value set in advance, When the count value of the unit reaches the preset value, and judging said to self peripherals bulk-out transfer is completed.

  According to a fifth aspect of the present invention, in the bulk-out transfer end determination circuit according to the fourth aspect, when the bulk-out packet addressed to its own peripheral device is a short packet or a null packet, the counting means is cleared and the bulk Packet identification means for determining that the out transfer has been completed is provided.

  According to a sixth aspect of the present invention, in the bulk-out transfer end determination circuit according to the fourth or fifth aspect, the increment value control means sets the increment value to the second value when the count means is incremented. It is characterized by setting.

  According to the present invention, the counting means for counting SOF packets is used, and when only the SOF packet is transferred, the increment value of the counting means is increased to increase the count value increase rate, When the packet addressed to the device is being transferred, the increment value is set to a small value to decrease the count value increase rate, so that the count value (preset value) of the counting means for setting the end point of the bulk-out transfer addressed to its own peripheral device ) Is appropriately set, it is possible to accurately determine the end of the bulk-out transfer even if the transfer period of the bulk-out transfer is reduced due to two or more peripheral devices connected to the host device. . The present invention is particularly effective when two or more USB devices are connected to one USB host device and data transfer is mixed.

  As shown in FIG. 1, when a plurality (three examples are shown) of USB devices 2A, 2B, and 2C are connected to one USB host device 1, each USB device 2A, 2B, and 2C is connected to each USB device 2A, 2B, and 2C. Are assigned addresses A1, A2 and A3 by the USB host device 1. Then, each USB device 2A, 2B, 2C confirms the address included in the token packet transferred from the USB host device 1, and the packet is sent to its own USB device or sent to another USB device. To determine whether it is a packet.

  FIG. 2 is a diagram showing an outline of this processing, and shows a case where data is transferred from the USB host device 1 in the order of USB devices 2A → 2B → 2C → 2A. In the USB device 2A, the handshake packet ACK is returned for the packet of the self address A1, and the transmitted data Data is stored, but the handshake packet is not returned for the packets of the other addresses A2 and A3. Ignore the data.

  Also, as shown in FIG. 3, the USB host device 1 transfers various packets to be transferred to a plurality of USB devices in one frame. An SOF packet is added to the head of this frame. As described above, the SOF packet is periodically transmitted to all the USB devices 2A, 2B, and 2C at a constant period. When data transfer is not performed, the frame is only the SOF packet.

  FIG. 4 is a block diagram showing the configuration of the USB device 2 of this embodiment. The USB device 2 includes a USB device controller 21, an MPU 22 that controls USB operation, a memory (RAM) 23 for storing data, a memory controller 24 that controls the memory 23, and an internal bus 25.

  FIG. 5 is a block diagram showing an internal configuration of the USB device controller 21 shown in FIG. The USB device controller 21 includes a USBPHY 211 that controls input / output of packets, a packet control circuit 212 that controls packets to be input / output, an endpoint buffer 213, a DMA controller 214, and a control register 215.

  FIG. 6 is a block diagram showing an internal configuration of a partial circuit 212A related to the present invention in the packet control circuit 212 shown in FIG. Reference numeral 2121 denotes a packet identification circuit for identifying a packet transmitted from the USB host device 1, 2122 denotes an SOF packet counter incremented by the SOF packet identified by the packet identification circuit 2121, and 2123 denotes a bulk-out packet addressed to its own USB device. When the other packet is received, the increment value of the counter 2122 is set to “1”, and when the SOF packet counter 2122 is incremented, it is set to “2”. The increment value control circuit 2124 sets the count value of the SOF packet counter. This is a count value comparison circuit that compares with a preset value set in advance and notifies the control register 215 of the end of transfer if they match.

  The packet control circuit 212 including the above-described circuit 212A can be realized only by adding a simple functional circuit to the functions originally provided in a general USB device controller, and the hardware load is light. Further, if the notification of the function (transfer end) obtained by the circuit 212A to the firmware is made the same as the notification method when a short packet or a null packet is received, the load on the firmware is reduced. Further, timer measurement with firmware is not required (for example, an interrupt signal is output as a notification method).

  FIG. 7 is a flowchart for determining the end of the bulk-out transfer according to this embodiment. In this embodiment, the received SOF packet is counted by the SOF packet counter 2122, and when the count value reaches a preset value, the end of the bulk-out transfer is notified. At this time, the counter 2122 sets the default increment value to “2”, and when the SOF packet is counted, the increment value is set to “2”. When the bulk-out packet to the own USB device is received, When the packet is cleared and a packet addressed to another USB device is received, the increment value is set to “1”. The increment value can be determined by determining the number of other USB devices to be received by the address and increasing the number of types.

  The USB device 2 first waits for reception of a packet (S1), and when it is received (S2), the packet identification circuit 2121 confirms it (S3). If it is an SOF packet (S4), the current increment is made. The value is confirmed by the increment value control circuit 2123 (S5), and the SOF packet counter 2122 is incremented (S6). After the increment value is set to “2” (S7), the counter comparison circuit 2124 compares the count value with the preset value P (S8) to determine whether or not they match (S9). It is determined that the bulk-out transfer addressed to the USB device has been completed.

  If the packet is not an SOF packet (S4), the packet identification circuit 2121 determines whether it is a bulk-out packet addressed to its own USB device (S10). If it is a bulk-out packet addressed to its own USB device, the SOF packet counter 2122 is cleared (S11), it is determined whether it is a short packet or a null packet (S12), and the short packet or null packet is determined. In this case, it is determined that the bulk-out transfer to itself has been completed.

  If it is determined in step S10 that the packet other than the SOF packet is not a bulk-out packet addressed to its own USB device, the increment value control circuit 2123 sets the increment value to “1”.

  As described above, when the bulk-out transfer is continuously performed only to the own USB device 2, the SOF packet counter 2122 counts the SOF packet, but the SOF packet counter 2122 receives the own USB device that arrives thereafter. Since the count value does not reach the preset value because it is cleared upon reception of the bulk-out packet addressed to the device, it is determined that the bulk-out transfer is completed when a short packet or a null packet arrives. The short packet or the null packet is identified by the packet identification circuit 2121.

  When packet transfer is performed not only to the bulk-out transfer addressed to the own USB device but also to another USB device, the increment value is set to “1” when the packet transfer addressed to another USB device is performed. When the SOF packet is set and every subsequent SOF packet is addressed to another USB device, the SOF packet counter 2122 is incremented by “1” every time the SOF packet arrives. However, if bulk-out transfer addressed to its own USB device is performed before the count value of the SOF packet counter 2122 reaches the preset value P, the SOF packet counter 2122 is cleared, so that the bulk-out transfer is completed. It will not be judged.

  When the bulk-out transfer addressed to the own USB device is not performed and the packet transfer addressed to another USB device is performed, the increment value is set to “1”, and the SOF packet counter 2122 is incremented by the SOF packet that arrives thereafter. Although the increment value is once switched to “2”, but immediately after that, the increment value is switched to “1”. Therefore, when the increment value “1” increments and the count value reaches the preset value P, the bulk-out transfer is completed. It is determined.

  When the bulk-out transfer addressed to the own USB device is not performed and the packet transfer to another USB device is not performed, the SOF packet is set by the incoming SOF packet with the increment value set to “2”. Since the packet counter 2122 is incremented, the increment by the increment value “2” proceeds, and when the count value reaches the preset value P, it is determined that the bulk-out transfer is completed. The time required to reach the preset value P at this time is half that in the case where packet transfer only to other USB devices is performed.

  That is, in this embodiment, when only the SOF packet is transferred, the increment value is increased to increase the count value increase rate, and when a packet addressed to a USB device other than itself is transferred, the increment value is increased. Therefore, it is determined that the bulk-out transfer addressed to the self-USB device is completed at a fast timing in the former case, and the state of the other USB device is taken into consideration in the latter case. Since it is determined that the bulk-out transfer addressed to the self USB device is completed at a later timing, two or more peripheral devices are connected to the host device by appropriately setting the preset value P of the count value comparison circuit 2124. Even if the transfer period of bulk-out transfer is reduced due to the It is possible to determine.

  In the above description, the case where the present invention is applied to the USB system has been described as an example. However, the present invention is not limited to this, and the present invention can also be applied to other similar systems. is there.

It is a block diagram which shows the structure of a USB system. It is explanatory drawing of the packet transferred to each USB device from a USB host apparatus. It is explanatory drawing of the flame | frame in a USB system. It is a block diagram which shows schematic structure of a USB device. FIG. 5 is a block diagram illustrating a configuration of a USB device controller in FIG. 4. FIG. 6 is a block diagram illustrating a configuration of a packet control circuit in FIG. 5. It is a flowchart of the completion | finish determination of the bulk-out transfer of a present Example. It is explanatory drawing of the completion determination of the conventional bulk-out transfer.

Explanation of symbols

  212: Packet control circuit, 212A: Partial circuit of packet control circuit, 2121: Packet identification circuit, 2122: SOF packet counter, 2123: Increment value control circuit, 2124: Count value comparison circuit

Claims (6)

When two or more peripheral devices are connected to the host device and bulk-out transfer is performed from the host device to at least one of the peripheral devices, the end of the bulk-out transfer is determined on the peripheral device side. In the method
Each peripheral device is provided with a counting means that is incremented by an SOF packet periodically transferred from the host device to each peripheral device,
When a bulk-out packet addressed to its own peripheral device is transferred, the counting means is cleared. When a packet addressed to a peripheral device other than itself is transferred, the increment value of the counting means is set to the first value. , When only the SOF packet is transferred, the increment value is set to a second value larger than the first value,
When the count value of the counting means reaches a predetermined value set in advance, it is determined that the bulk-out transfer to the peripheral device is completed. The bulk-out transfer end determination method according to claim 1,
When the bulk-out packet addressed to its own peripheral device is a short packet or a null packet, the counting means is cleared and it is determined that the bulk-out transfer is completed. In the bulk-out transfer end determination method according to claim 1 or 2,
When the counting means is incremented, the increment value is set to the second value. A bulk-out transfer end determination circuit that is incorporated in a peripheral device connected to two or more host devices and determines the end of bulk-out transfer performed by the host device,
A counting means which is incremented by a SOF packet periodically transferred from the host device and cleared when a bulk-out packet addressed to its own peripheral device is received;
When a packet other than a bulk-out packet addressed to its own peripheral device is received, the increment value of the counting means is set to a first value, and when only the SOF packet is received, a value larger than the first value is set. An increment value control means for setting an increment value to a value of 2,
Comparing means for comparing the count value of the counting means with a preset value set in advance,
A bulk-out transfer end determination circuit, wherein when the count value of the counting means reaches the preset value, it is determined that the bulk-out transfer to its own peripheral device has ended. The bulk-out transfer end determination circuit according to claim 4,
When the bulk-out packet addressed to its own peripheral device is a short packet or a null packet, it comprises a packet identification means for clearing the counting means and determining that the bulk-out transfer has been completed. End determination circuit. In the bulk-out transfer end determination circuit according to claim 4 or 5,
The bulk-out transfer end determination circuit, wherein the increment value control means sets the increment value to the second value when the count means is incremented.

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