JPH11261608A - Data communication system, data communication equipment, data communication method and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily transfer data at high speed and to surely transfer data by requesting a part of information data through the use of connection ID, after a data communication system has been initialized. SOLUTION: Image data is shuffled with a purpose of making it resistant against a transmission line error. A burst error which is a continuous code error is converted into a random error being a discrete error, which is easily corrected and interpolated with the processing. For making much of the uniformity of the bias of the occurrence of information quantity by coarseness/fineness of an image in a screen, a case when the variable length codes of run length and the like are used is convenient, when this processing process is performed prior to a compression processing. Then, data identification(ID) information for restoring data shuffling is added. ID added in an ID addition operation is used as auxiliary information, when an information quantity expansion processing is executed at the time of reproduction with mode information of a system, which has been recorded at the some time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data communication system, a data communication device, a data communication method, and a storage medium, and more particularly, to a plurality of electronic devices using a data communication bus capable of communicating control signals and data in a mixed manner. Equipment (hereinafter,
It is suitable for use in a system in which devices are connected to perform data communication between the devices.

[0002]

2. Description of the Related Art Among personal computer peripheral devices, hard disk drives and printers are most frequently used, and these peripheral devices are digital interfaces (hereinafter referred to as digital interfaces) which are typical general-purpose interfaces for small computers.
A connection is made between personal computers using SCSI (I / F) or the like, and data communication is performed.

A recording / reproducing device such as a digital camera or a digital video camera is also one of the peripheral devices as an input means to a personal computer (hereinafter, referred to as a PC). Such images are imported to a PC and stored on a hard disk,
Or the technology in the field of color printing on a printer after editing on a PC has advanced, and the number of users is increasing.

When the captured image data is output from a PC to a printer or a hard disk, data communication is performed via the above-described SCSI or the like. In such a case, the data amount is large as in the case of image data. In order to send information, these digital I / Fs must have high transfer data rates and versatility.

FIG. 8 shows a conventional digital camera,
FIG. 2 shows a block diagram when a PC and a printer are connected. In FIG. 8, 101 is a digital camera, 102 is a personal computer (P
C) and 103 are printers. Further, 104 is a memory as a recording unit of the digital camera, 105 is an image data decoding circuit, 106 is an image processing unit, 107 is a D / A converter, 108 is an EVF as a display unit, and 109 is a digital I / O of the digital camera. /
O part, 110 is digital I / O with digital camera of PC102
111, an operation unit such as a keyboard and a mouse, 112, a decoding circuit for image data, 113, a display, 114, a hard disk device, 115, a memory such as RAM, and 116, an MPU of an arithmetic processing unit.

[0006] 117 is a PCI bus, 118 is a digital I / F SC
SI interface (board), 119 is the SCSI interface of the printer connected to PC 102 by SCSI cable, 120
Denotes a memory, 121 denotes a printer head, 122 denotes a printer controller of a printer control unit, and 123 denotes a driver.

A procedure for taking an image captured by a digital camera into the PC 102 and outputting the image from the PC 102 to a printer will be described. When the image data stored in the memory 104 of the digital camera 101 is read, one of the read image data is decoded by the decoding circuit 105, and the image processing for display by the image processing circuit 106 is performed. Is performed, and is displayed on the EVF 108 via the D / A converter 107.
On the other hand, the digital I / O unit 10
9 through the cable to the digital I / O section 11 of the PC102.
Leads to 0.

In the PC 102, the image data input from the digital I / O unit 110 is stored in the hard disk 114 when the image data input from the digital I / O unit 110 is stored by using the PCI bus 117 as a bus for mutual transmission.
In the case of displaying, after being decoded by the decoding circuit 112, it is stored as a display image in the memory 115 and
Displayed after being converted to analog signal by 3. PC102
Operation input for editing, etc. on the
The entire process is performed by the MPU 116.

When an image is printed out, a PC 10
2 The image data is transmitted from the SCSI interface board 118 in the SCSI
The print image data received by the interface 119 is formed as a print image in the memory 120, and the print head 121 and the driver 123 operate under the control of the printer controller 122 to print the print image data read from the memory 120.

The above is the procedure for taking the conventional image data into the PC 102 or printing it. As described above, conventionally, each device is connected to the PC 102 serving as a host, and the image data captured by the recording / reproducing apparatus is printed via the PC 102.

Also, AV devices such as digital VTRs, TVs, tuners, etc., and personal computers (hereinafter, referred to as PCs) are connected to each other using an IEEE 1394 serial bus (hereinafter, referred to as 1394). Communication systems for transmitting and receiving digital video signals, digital audio signals, and the like between them have been proposed.

In these systems, since it is important to transfer data in real time, so-called synchronous communication (hereinafter referred to as isochronous communication) is used.
Data communication is being performed. In this case, the real-time property of data transfer is guaranteed, but it is not guaranteed that communication is performed reliably.

[0013]

However, as the problems of the digital interface mentioned in the above conventional example, SCSI has a low transfer data rate, a thick cable for parallel communication, and a peripheral device to be connected. There are restrictions on types, numbers, connection methods, etc., and inconveniences in many aspects have been pointed out.

Further, in the case of the conventional 1394 communication, since synchronous communication is performed, it is not guaranteed that the communication is reliably performed. Therefore, the conventional 1394 isochronous communication cannot be used in order to reliably transfer data.

In the conventional 1394 isochronous communication,
The total number of communications is also limited to 64, even if there is a vacancy in the communications band. For this reason, when it is desired to perform a large number of communications that do not require much communication bandwidth, the conventional 1394 isochrono
There was a problem that us communication could not be used.

In the conventional 1394 communication system, it is conceivable that the data transfer is interrupted due to a bus reset or an error during the data transfer. In this case, the conventional 1394
In the communication method, it is not possible to know what data content has been lost. Therefore, the conventional 1394 communication method has a problem in that it is required to take a very complicated communication procedure in order to recover from the interruption of the data transfer.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has been made to solve the inconvenience of the conventional communication system, to transfer data easily and at high speed, and to surely transfer data. This is the first purpose. A second object is to perform a large number of communications simultaneously when a communication band is not used much. Further, it is a third object of the present invention to easily detect data lost due to interruption of data transfer, and to surely and easily recover from the interruption of data transfer. Also, when a plurality of control nodes exist on the network, a means for identifying a logical connection set by each control node is provided, and data can be transmitted from one source node to a plurality of destination nodes. The fourth object is to do so. A fifth object is to simplify a communication procedure for returning from interruption of data transfer.

[0018]

SUMMARY OF THE INVENTION The data communication system of the present invention solves the conventional problems by using a digital communication system which solves the problems of the conventional digital I / F as much as possible. Using a general-purpose digital I / F (for example, a high-performance serial bus of the IEEE1394-1995 standard) that can be installed in a unified manner, PCs, printers, other peripheral devices, digital cameras and digital VTR recording and playback devices, etc. It realizes data communication between devices when connected in a network configuration, captures video data and other data from a recording / reproducing device to a PC, and directly transfers video data to a printer for printing.

In such a network, a protocol for transmitting various data by dividing each data into a plurality of data by an asynchronous transaction is provided. An ID, which is unique node information of the control node and does not change even by a bus reset or the like, is added to the payload. The control node announces the number of destinations logically connected to the source.

The source node combines the acknowledgment packets from the destination for each buffer size from the destination and transmits the next segment packet. Each destination for the packet indicating the end of the transmission data from the source node,
Returns the acknowledgment packet.

A data communication system according to the present invention is a data communication system for performing communication using a connection ID indicating a logical connection between a transmitting device for transmitting information data and a receiving device for receiving the information data. After the initialization of the data communication system, a part of the information data is requested using the connection ID. Data communication system. According to another feature of the data communication system of the present invention, the data communication system includes a management device having a function of managing the connection ID, and the transmission device and the reception device are provided using the management device. It is characterized in that a logical connection with a device is set. According to another feature of the data communication system of the present invention, the management device uses the node ID indicating each device constituting the data communication system to connect the transmission device and the reception device with the connection ID. Is transmitted. Other features of the data communication system of the present invention include:
The management device transmits unique ID information unique to the management device together with the connection ID to the transmission device and the reception device. Another feature of the data communication system of the present invention is that the transmitting device and the receiving device are each provided with the unique I
It is characterized by using D information to identify a management device for which a connection ID is set. Another feature of the data communication system of the present invention is that the management device is an asynchronous compliant device conforming to the IEEE 1394 standard.
It is characterized in that the connection ID is transmitted using a transfer method. Another feature of the data communication system of the present invention is that the management device manages additional information relating to the plurality of connection IDs using a table. Another feature of the data communication system according to the present invention is that the initialization of the data communication system is performed by changing a connection configuration of the data communication system or by turning on / off a power supply of a device included in the data communication system. It is characterized in that it is executed in accordance with any of OFF. Another feature of the data communication system of the present invention is that the data communication system requests a part of the information data when the initialization occurs during the communication of the information data. Features. Another feature of the data communication system of the present invention is that a part of the requested information data requests information data after the normally received data. Another feature of the data communication system of the present invention is that, when a part of the information data is requested from a plurality of receiving devices, the transmitting device determines continuity of data received by each receiving device. It is characterized in that a part of the information data is transmitted so as to secure it. Another feature of the data communication system of the present invention is that the data requesting a part of the information data is transferred to all the devices constituting the data communication system. Another feature of the data communication system of the present invention is that the connection ID indicates a logical connection between a pair of transmitting device and receiving device. Another feature of the data communication system of the present invention is that the connection ID indicates a logical connection between one transmitting device and a plurality of receiving devices. Another feature of the data communication system of the present invention is that the connection I
D indicates a logical connection between a plurality of transmitting devices and one receiving device. Another feature of the data communication system of the present invention is that the connection ID indicates a logical connection between a plurality of transmitting devices and one receiving device. Another feature of the data communication system of the present invention is that communication between the transmitting device and the receiving device is executed using the connection ID. According to another feature of the data communication system of the present invention, information data output from the transmitting device and the receiving device is transferred to all devices constituting the data communication system. I have. Further, another feature of the data communication system of the present invention is that the transmitting device uses a communication packet formed by a broadcast ID and the connection ID designating all devices constituting the data communication system. And transmitting the information data. Another feature of the data communication system of the present invention is that the information data output from the transmitting device is an Asyn compliant with the IEEE 1394 standard.
It is characterized by being transferred using the chronous transfer method. According to another feature of the data communication system of the present invention, the management device recognizes that the communication of the information data has been completed based on an end flag transmitted from the transmission device. . Also,
Another feature of the data communication system of the present invention is that the logical connection between the transmitting device and the receiving device is released by the management device or the receiving device. Another feature of the data communication system of the present invention is that the receiving device responds to the connection request of the transmitting device by receiving a size of a receiving buffer, address information indicating a predetermined area in a memory space, and data. A packet including at least one of a sequential number indicating a start pointer and information indicating completion of preparation is returned. Another feature of the data communication system of the present invention is that the receiving device includes a bit indicating that data has been received normally. Another feature of the data communication system of the present invention is that the transmitting device measures a response from the receiving device for a predetermined period, and detects a communication abnormality based on the period. According to another feature of the data communication system of the present invention, the transmitting device automatically starts the retransmission operation of the information data when the communication device detects a communication abnormality by timing the response for a predetermined period. It is characterized by: Another feature of the data communication system of the present invention is that in a data communication system for transmitting the same information to a plurality of devices using ID information indicating a logical connection between the plurality of devices, After initialization of the data communication system, a request is made for retransmission of information that has become unreceivable using the ID information. Also,
According to another feature of the data communication system of the present invention, the initialization of the data communication system is performed by changing a connection configuration of the data communication system or by turning on / off a power supply of a device included in the data communication system. It is characterized by being executed according to any of them. Another feature of the data communication system of the present invention is that in a data communication system in which communication between a plurality of different devices is determined by a plurality of different ID information, the ID information is initialized after the data communication system is initialized. It is characterized in that retransmission processing is performed for the communication determined in step (1). Another feature of the data communication system according to the present invention is that the ID information is information for specifying communication between the devices, and the initialization of the data communication system is performed based on a connection configuration of the data communication system. Is executed in response to a change in.

A data communication apparatus according to the present invention is connected to a data communication system which performs communication using a connection ID indicating a logical connection between a transmitting device for transmitting information data and a receiving device for receiving the information data. A possible data communication apparatus, comprising: an initialization unit for initializing the information data communication system; and a communication unit for requesting a part of the information data from the transmitting device using the connection ID. And Another feature of the data communication device of the present invention is that it can be connected to a data communication system that transmits the same information to a plurality of devices using ID information indicating a logical connection between the plurality of devices. Such a data communication apparatus is characterized by comprising: an initialization unit for initializing the data communication system; and a communication unit for requesting retransmission of information that has become unreceivable using the ID information. Another feature of the data communication device of the present invention is that in a data communication device connectable to a data communication system that determines communication between a plurality of different devices by a plurality of different ID information, It is characterized by comprising initialization means for performing initialization, and communication means for performing retransmission processing for communication determined by the ID information.

The data communication method of the present invention is a data communication method for performing communication using a connection ID indicating a logical connection between a transmitting device for transmitting information data and a receiving device for receiving the information data. After the initialization of the data communication system, a part of the information data is requested using the connection ID. Another feature of the data communication method of the present invention is that in the data communication method of transmitting the same information to a plurality of devices using ID information indicating a logical connection between the plurality of devices, After initialization of the data communication system, a request is made for retransmission of unreceivable information using the ID information. Another feature of the data communication method of the present invention is that in the data communication method for determining communication between a plurality of different devices by a plurality of different pieces of ID information, the data communication method includes the steps of:
It is characterized in that retransmission processing is performed for communication determined by D information.

The storage medium of the present invention is characterized in that a program for causing a computer to function as each of the above means is stored. Another feature of the storage medium of the present invention is that a program for causing a computer to execute the procedure of the data communication method is stored.

[0025]

Since the present invention comprises the above technical means, an independent connection ID uniquely determined in the network is set by the controller node, a logical connection is established between the source and destination nodes, and each logical connection is established. The connection ID is assigned to the appropriate connection. Thereafter, in the handshake communication between the source and destination nodes, a so-called broadcast Asynchronous including a connection ID number set by the controller in a field in the payload.
Communicate using transactions.

Each node determines the connection ID in the payload, determines whether or not the connection is set between its own nodes, and excludes itself except for the set connection ID.

The source node transmits a broadcast packet having a connection request flag to the destination node, and the destination node immediately receives the buffer size information and the data which can be received as soon as the node is ready to receive the data. It includes the data sequence number indicating the packet start order, and sets the Ack bit to
Communicate using transactions. The source node is
It receives the packet transmitted by broadcast, determines the connection ID, and confirms that it is an Ack response from the destination node. From the above,
Data transfer is started.

Also, the source and destination nodes are logically individually set between the source and destination by the world wide unique ID, which is the unique information of the control node in the payload, and the connection ID set by the control node. Identify.

Further, data is transmitted to a plurality of connected destinations using a single connection ID.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS. In FIG. 1, 10
Is a computer, 12 is an arithmetic processing unit (MPU), 14 is a first 1394 interface, 16 is a first operation unit such as a keyboard, 18 is a first decoder, 20 is a display device such as a CRT display, 22 is A hard disk 24 is a first memory and is an internal memory of the computer 10 according to the present invention, and 26 is a computer internal bus such as a PCI bus.

Reference numeral 28 denotes a VCR, reference numeral 30 denotes an image pickup optical system,
32 is an analog-digital (A / D) converter, 34 is a video processing unit, 36 is a compression / expansion circuit, 38 is a first memory, 40 is a second memory, 42 is a first data selector, and 44 is a The second 1394 interface, 46 is the first memory control circuit, 48 is the second memory control circuit, 50 is the system controller, 52 is the second operation unit, 54 is the finder, 56 is the D / A converter, 58 is It is a recording unit.

Further, reference numeral 60 denotes a printer, and 62 denotes a third printer.
1394 interface, 64 is the second data selector, 66
Is a third operation unit, 68 is a printer controller, 70 is a second decoder, 72 is a third memory, 74 is an image processing unit, 76 is a driver, and 78 is a printer head.

The computer 10, the VCR 28, and the printer 60
Means that the first to third 1394 interfaces 14, 44 and 62 constitute a 1394 serial bus node,
They are interconnected via the first to third 1394 interfaces 14, 44, and 62, and can transmit and receive data, control by commands, and the like.

In this embodiment, for example,
Operates as a controller for transmitting and receiving image signals on the 1394 serial bus. In the computer 10 according to the present invention, for example, by a computer internal bus 26 such as a PCI bus, 12 is an arithmetic processing unit (MPU), a 1394 interface 14, a keyboard 16, a decoder 18, a CRT display 20, a hard disk 22, and an internal memory 24. And other internal devices are interconnected.

Reference numeral 12 denotes an arithmetic processing unit (MPU) which executes software recorded on the hard disk 22 and moves various data to the internal memory 24. Also,
Reference numeral 12 denotes an arithmetic processing unit (MPU) that also performs arbitration operation of each device connected by the PCI bus 26.

The 1394 interface 14 receives an image signal transferred on the 1394 serial bus, and receives an image signal recorded on the hard disk 22 and an internal memory.
The image signal stored in 24 is transmitted. The 1394 interface 14 transmits command data to other devices connected on the 1394 serial bus. Further, the 1394 interface 14 transfers a signal transferred on the 1394 serial bus to another 1394 node.

An operator causes the MPU 12 to execute software recorded on the hard disk 22 through an operation unit such as the keyboard 16. Information on the software etc.
It is presented to the operator by a display device 20 such as a CRT display. The decoder 18 decodes an image signal received from the 1394 serial bus through the software. The decoded image signal is also presented to the operator by a display device 20, such as a CRT display.

In the present embodiment, for example, the VCR 28 operates as an image signal input device. The luminance signal (Y) and the color difference signal (C) of the image input from the imaging optical system 30 are respectively
The data is converted into digital data by the A / D converter 32. The digital data is multiplexed by the video processing unit 34. Thereafter, the compression / expansion circuit 36 compresses the data amount of the image information. In general, the compression processing circuit is provided independently for YC. Here, for simplification of description, an example of compression processing in YC time division will be described.

Next, a shuffling process is performed to make the image data resistant to transmission path errors. The purpose of this processing is to convert a burst error, which is a continuous code error, into a random error, which is a discrete error that can be easily corrected and interpolated. In addition, in the case where importance is placed on the purpose of equalizing the unevenness of the amount of information due to the density in the screen of the image, if this processing step is brought before the compression processing, variable-length codes such as run-lengths are encoded. It is convenient when used.

In response to this, data identification (ID) information for restoring data shuffling is added. The ID added by the ID addition operation is used as auxiliary information together with the system mode information and the like recorded at the same time in the decompression process (information amount expansion process) at the time of reproduction.

Error correction (ECC) information is added in order to reduce errors in reproducing these data. Processing up to the addition of such a redundant signal is performed for each independent recording area corresponding to each information such as video and audio. As mentioned above, ID information and
The image signal to which the ECC information has been added is recorded on a recording medium such as a magnetic tape by the recording unit 58, and is temporarily stored in a first memory 38 described later.

On the other hand, the image data multiplexed by the video processing unit 34 is digital-to-analog converted by a D / A converter 56 and observed by an operator in an electronic viewfinder 54. In addition, the operator, via the second operation unit 52,
Various operation information is transmitted to the system controller 50, and the system controller 50 controls the entire VCR based on the operation information.

The image data multiplexed by the video processing unit 34 is output to the second memory 40 and is temporarily stored. The operations of the first memory 38 and the second memory 40 described above are controlled by a system controller 50 via a first memory control circuit 46 and a second memory control circuit 48, respectively.

The first data selector 42 selects data from the first memory 38 and the second memory 40 described above,
Hand over to the second 1394 interface 44, or
Data from the second 1394 interface 44 is selected and passed to either the first memory 38 or the second memory 40. With the above operation, compressed image data and uncompressed image data can be selected and output from the second 1394 interface 44 of the VCR 28 by the operator.

The second 1394 interface 44 receives command data for controlling the VCR 28 via the 1394 serial bus. The received command data is passed through the first data selector 42 to the system controller 50.
Is input to The stem controller 50 creates response data for the command data, and outputs the first data selector 42 and the second 1394 interface.
The data is transmitted to the 1394 serial bus through 44.

In this embodiment, for example, the printer 60
Operates as an image printout device. The third 1394 interface 62 receives an image signal transferred on the 1394 serial bus and command data for controlling the printer 60 via the 1394 serial bus. Further, the third 1394 interface 62 transmits response data to the command.

The received image data is input to the second decoder 70 through the second data selector 64. The second decoder 70 decodes the image data and outputs it to the image processing unit 74. The image processing unit 74 temporarily stores the decoded image data in the third memory 72.

On the other hand, the received command data is passed through the second data selector 64 to the printer controller 68.
Is input to The printer controller 68 performs various printing-related controls, such as paper feed control by the driver 76 and position control of the printer head 78, based on the command data. Also, the printer controller 68 has a third memory
The image data temporarily stored in 72 is transmitted to the printer head 78 as print data, and a printing operation is performed.

As described above, the first to third 1394 interfaces 14, 44, and 62 according to the present embodiment each constitute a 1394 serial bus node. The first 1394 interface 14 operates as a control node or a controller, and the second 1394 interface 44
Operates as a source node for image data and the third 1394
The interface 44 operates as a destination node.

The operation of each node according to the present embodiment will be described below with reference to FIG. In FIG. 2, reference numeral 200 denotes a controller, 202 denotes a source node, 204 denotes a destination node, 206 denotes a subunit inside the source node, and 208 denotes a subunit.
Is an object such as image data, 210 is the first memory space inside the destination node, 212 is the first connection, 214 is the nth memory space of the destination, 21
6 is the nth connection.

The controller 200 is a node that manages a connection ID for establishing a connection between the source node 202 and the destination node 204 that perform data transfer. Controller 200 is a source node 202
, And a node independent of the destination node 204, or the source node or the destination node and the controller may be the same.

In the latter case, a transaction between the controller and the source node or the destination node, which is the same node as the controller, is unnecessary. In the present embodiment, an example in which the controller 200 exists in a node different from the source node 202 and the destination node 204 will be described.

In the communication device according to the present embodiment, it is possible to establish a plurality of connections. The source node 202 writes an object 208 such as image data from the internal subunit 206 to the first memory space 210 inside the destination node via, for example, the first connection 212. The transmission and reception of data through the above-described connection is performed using, for example, an asynchronous packet.

Next, the operation of each of the controller 200, the source node 202, and the destination node 204 will be described with reference to FIG. The controller transmits a data packet for making a connection to the source node and the destination node selected by the user. This packet is an asynchronous packet, and a connection ID for identifying this connection is written in the payload.

Following this packet, the controller sends a send command packet to the source node. Upon receiving the transmission command packet, the source node and the destination node perform a broadcast transaction using the assigned connection ID, and start data transfer. When the data transfer ends, the source
send a broadcast packet indicating gment end,
The controller that receives this packet connects
Release the ID and end the data transfer.

The source node, which has received the connection ID notification packet and the transmission command packet from the controller, sends an inquiry to the destination node.
Send an Asynchronous broadcast packet. This packet contains the connection specified by the controller.
ID has been written.

The destination node receives this packet and sends out a response broadcast packet. The same connection ID is also written in this packet, and the source node checks this ID to determine whether or not the packet is addressed to this source node. The buffer size and offset address of the destination node are written in the response packet, and the subsequent data transfer is performed by a write transaction for that address.

The source node responds to the offset address received from the destination node by Asynchro
Write using a nous broadcast packet. In this packet, the connection ID and the data sequence number are written.

After transmitting the broadcast packet,
The source node waits for a response from the destination node. From the destination node, a response packet in which the connection ID and the sequence number are written is transmitted as an asynchronous broadcast packet. Upon receiving this packet, the source node increments the sequence number and transmits the next data in the same manner. By repeating this procedure, the source node performs data transfer.

The maximum time for waiting for a response from the destination node is predetermined.
If no response returns after that time,
The same data is retransmitted using the same sequence number. When a response packet for a retransmission request is transmitted from the destination node, the data of the designated sequence number is retransmitted by broadcast.
When all data has been transferred, the source node is segm
send a broadcast packet indicating ent end,
End the data transfer.

The destination node receiving the connection ID notification packet from the controller waits for an asynchronous broadcast packet for an inquiry from the source node. Upon receiving the broadcast packet, the destination node compares the connection ID written in the packet with the connection ID notified from the controller, and determines whether the packet is a packet from the source node.

Upon receiving the inquiry packet from the source node, the destination node
A response packet in which the ID, the buffer size for data reception, and the offset address are written is transmitted by broadcast. Data from the source node is written to this address.

When data is written from the source node, the destination node checks the connection ID in the payload. If the ID matches the ID notified by the controller, the data is received, and a response packet in which the connection ID and the sequence number in the received data are written is transmitted by broadcast.
When inconsistency is detected in the sequence number of the received data, a response indicating a retransmission request is transmitted, and data can be requested again from the source node.

When all data transfer is completed, a broadcast packet indicating segment end is transmitted from the source node. When this packet is received, the data transfer process ends.

In order to transfer data reliably, it is desirable that the data transfer be promptly restarted even if the data transfer is interrupted due to the occurrence of a bus reset or some error. In the present embodiment, the problem is solved by providing a procedure for a retransmission request. Next, the procedure of the retransmission request will be described with reference to FIG.

For example, when data transfer is interrupted when the sequence number is i, each node first reconstructs a bus according to a procedure defined by the standard. After the completion of the bus reconstruction, the destination node transmits a resend request packet (resend request) in which the connection ID and the sequence number i are written in a broadcast packet.

The source node collates the connection ID of the received packet, and transmits data subsequent to the requested sequence number, that is, data of a data sequence starting with the sequence number (i + 1) as a broadcast packet.

According to the above-described procedure, the source node, the destination node, and the controller node can stop the data transfer without taking the node ID into consideration.
Subsequent data transfer can be easily and reliably restarted. As described above, in the present embodiment,
Even when the data transfer is interrupted, the control procedure of the controller can be simplified.

Next, referring to FIG. 4, the above-mentioned Asynchronous
The packet will be described. Asynch according to the present embodiment
The ronous packet is, for example, a data packet in units of 4 bytes (32 bits, hereinafter referred to as a quadlet).

In the Asynchronous packet, the first 16
bits is a destination ID field, and this field indicates a node ID of a reception destination. When broadcasting is performed as in the present embodiment, the value of this field is FFFF (hexadecimal).

The next 6 bits field is a transaction label (tl) field, and is a tag unique to each transaction. The next 2 bits field is a retry (rt) code, which specifies whether the packet will try to retry.

The next 4 bits field is a transaction code (tcode). tcode specifies the format of the packet and the type of transaction that must be performed.

In this embodiment, for example, a transaction of a data block write request whose value is 0001 (binary number) is used. The next 4 bits field is a priority (pri) field, and specifies the priority. In the present embodiment, Asynchro
Since nous packet is used, the value of this field is
0000 (binary).

The next 16 bits are a source ID field, and indicate a node ID on the transmitting side. The next 48 bits are destinat
This field is the ion offset field, and the lower 48 bits of the destination node address of the packet are specified by this field.

The next 16 bits are a data length field, and indicate the length of a data field described later in bytes. The next 16 bits are an extended tcode field, and this value is 0000 (hexadecimal) in a data block write request transaction used in the present embodiment.

The next 32 bits are a header CRC field, and extend from the destination ID field described above.
Up to the ed tcode field is called the packet header,
Used for error detection of the header packet.

The next field is a variable length data field, and this data field is called the payload of the packet. In the present embodiment, if the data field is not a multiple of a quadlet, bits less than the quadlet are filled with zeros.

The next 32 bits field is a data CRC field, and is used for error detection in the data field, similarly to the header CRC field. FIG. 5 is a diagram in which fixed data is added to the above-described fields in the Asynchronous packet header according to the present embodiment.

FIG. 6 is a diagram showing a structure of a data field of an asynchronous packet used in the present embodiment. In FIG. 6, data having the same functions as in FIG. 4 will not be described.

The first six quadlets are header information, in which a connection ID for identifying the above-mentioned connection and the like are written. The sixth and subsequent quadlets are variable-length data blocks. In this embodiment, if the data block is not a multiple of a quadlet, the bits less than the quadlet have 0s.
Is packed.

FIG. 7 is a diagram showing the structure of the header information. The first two quadlets are the world wide unique ID of the control node, and the source and destination identify the control node that has set the connection based on the data.

This world wide unique ID is an IEEE
Complies with the 1394-1995 standard. Here, the world wide unique ID compliant with the IEEE1394-1995 standard is used to identify each control node. However, even if a bus reset occurs, any unique information that can identify each node that does not change even if a bus reset or the like occurs. Anything is fine.

The next 16 bits are the connection ID described above.
(connection ID) field for identifying a connection by the data. Even when a plurality of controllers set the same connection ID, each node identifies an absolute logical connection based on the unique ID of the control node and the connection ID.

Further, each controller allows the connection ID number set by another controller to be duplicated, and the controller sets the ID set by another controller.
May be used.

The next 8 bits are the protocol type (protoco
l type) field, which indicates a procedure for data transfer using the header information. In the figure, Rese
Indicated as rved. For example, a value of 01 (hexadecimal number) is used in the exchange procedure of the present embodiment.

The next 8 bits are a control flag (control
flags) field, in which control data is written.
The most significant bit of the control flag field is, for example, a resend request flag. When the value of this bit is 1, it indicates that a data resend request has occurred.

The next 16 bits are the sequence number (sequence number).
nce number) field. As described above, the sequence number field contains a specific connection ID.
A continuous value is used for the data packet transmitted and received by the. The destination node monitors the continuity of significant data by using the sequence number field, and if a mismatch occurs, requests a retransmission to the source node.

The next 16 bits are a confirmation response number (reconfirm
ation number) field. This field is meaningful only when the value of the retransmission request flag is 1. When the value of the retransmission request flag is 1, this field indicates the sequence number of the start packet in which the retransmission request has occurred.

The next 16 bits indicate the buffer size of the destination node. The next 48 bits indicate the offset address in the 1212 address space of the destination node.

FIG. 9 shows a configuration in which two controllers set the same connection ID on the network. The controller node 1 in the figure is a node unique identification I that does not change even when a bus reset or the like occurs.
D. Here, it is assumed that the world wide unique ID of the IEEE1394-1995 standard = 1.

Similarly, controller node 2 in the figure
Indicates that the node has a node unique identification ID which does not change even when a bus reset or the like occurs as in the case of the controller node 1. Here, it is assumed that the world wide unique ID of the IEEE1394-1995 standard is 4. Each controller sets a logical connection between the source and destination, and here, each logical connection ID is 0.

As described above, even when the same connection ID is set by each controller, it is not necessary to negotiate between the control nodes so that the connection IDs do not overlap.

The controller notifies the connection ID and the unique node ID of the controller between the source and destination before setting the connection. The source and the destination respectively identify the controller that has set the connection by the above procedure.

FIG. 10 shows a general flow between the controller, the source, and the destination according to the present embodiment, which supplements the flow described with reference to FIG. 3A. (1) First, the controller sets the maximum Asynchronous tolerable for the destination.
IEEE indicating payload size of Write transaction
Inquires about the max_rec size conforming to the 1394-1995 standard and at the same time announces the unique connection ID set by the controller. In response to the command from the controller, the destination indicates a max rec size and returns as a response that the connection ID has been set.

(2) Next, the controller sets the unique connection ID set by the controller for the source and the total number N of destinations that the controller logically connects between the source and the destination.
And the broadcast Asynchronous sent by the source
Advertises the size of the write transaction payload. The source returns a response to the command from the controller that the respective settings have been made.

(3) The controller selects one object from the object data of the source desired to be transmitted to the source. The source returns a response indicating that the object has been selected to the controller. The selected object may be a still image or a moving image. Further, the data may be text data or binary data.

(4) When the controller knows that the source can transmit the object in response to the response from the source, the controller issues a command for instructing the source to start transmitting the selected object to the destination. Send.

(5) Upon receiving the transmission start command from the controller, the source starts transmitting the selected object.

(6) When the transmission of the object from the source ends, the controller releases the selected object to the source.

(7) At this point, if the controller wants to transmit another object, the controller repeats the above-mentioned procedures (3) to (6).

(8) When all objects have been transmitted, the controller may release the previously set unique connection ID.

FIG. 11 shows a configuration in which one controller sets the same connection ID on a network between one source and N destinations. Here, the unique connection ID is FFFF (hexadecimal), but may be another number. The controller is shown in FIG.
The procedure (1) of the entire flow shown in (1) is performed for each destination, and is repeated N times for convenience.

FIG. 12 shows a case where the destinations have the same receiving buffer size and the object data size is equal to the receiving buffer in the network configuration as shown in FIG. Here, the number of destinations is set to N = 3 for simplicity. The controller has already notified the controller that the number of destinations connected by the same connection ID = 3 from the controller.

(A) When the transmission start command from the controller is transmitted to the source, the source is switched to the state shown in FIG.
The connection request is transmitted according to the procedure described in. (B) Each of the three destinations returns an Ack response to which its own reception buffer size is added when the preparation for reception is completed. (C) After confirming that three Acks have returned, the source determines from the reception buffer size in the Ack response:
The object is divided into designated payload sizes and transmitted until the buffer size of the destination is reached.

(D) A segment end flag indicating the end of the segment is set for the last segment in which all data has been transmitted, and then transmitted. (E) Upon receiving the segment end packet, each destination returns a segment end receive response indicating that all the data has been received. (F) The controller and the source recognize that the segment end receive response has returned from all destinations and recognize that the data transfer has been completed.

FIG. 13 shows a model of the transfer of the object data described in FIG. In this figure, the object data is a still image having a data size of 128 Kbytes, and the payload size is 256 bytes, divided into 500 and transferred to the destination.

FIG. 14 shows the flow of data transfer in the network in FIG. 11 in which each of the three destinations has a different receive buffer size. Here, for simplicity, the number of destinations is N
= 3. The controller has already notified the controller that the number of destinations connected by the same connection ID = 3 from the controller.

(G) When the transmission start command from the controller is transmitted to the source, the source is switched to the state shown in FIG.
The connection request is transmitted according to the procedure described in. (H) Each of the three destinations returns an Ack response to which the own receiving buffer size is added when the preparation for reception is completed.

(Re) After confirming that three Ackes have returned, the source divides the object into the designated payload size from the field indicating the reception buffer size in each Ack response, and It transmits until the buffer size becomes the minimum among the destinations, and waits for a receive response from the destination having the minimum buffer size to be transmitted.

(N) Upon receiving a receive response from the destination having the smallest receive buffer, the source continues to transmit up to the buffer size of the destination node having the next largest receive buffer, and the receive response from the destination is received. Wait for it to be sent.

(L) Upon receiving the receive response from the destination, the source continues to transmit up to the buffer size of the destination node having the next larger receive buffer, and the receive response from the destination is transmitted. To wait.

(ヲ) When all the data has been transmitted, the source transmits the last segment with the segment end flag, and waits for a segment end receive response from each destination. (W) When all the segment end receive responses are received, the controller and the source recognize that the data transmission has been completed.

FIG. 15 shows the case of the different receiving buffers shown in FIG. 14, and here, the number of destinations is set to N = 2 for simplicity. The source object here has a data size of 128Kby
Although it is a still image of te, the data size is variable and is not specified in the present embodiment. Also,
The object can handle not only still images but also various data such as moving images, texts, binary data, and the like.

The source divides the object into 500 into a payload size of 256 Bytes, and
1 and the destination returns a receive response, and the source continues # 2.
The transmission is continued until the destination receive buffer becomes available.

Here, the buffer size of the destination # 2 is twice as large as the buffer size of the destination # 1, but the buffer size between the destinations is not specified at all. The destination of # 1 returns three send-receive responses for convenience, and the destination of # 2 returns one send-receive response.

Next, a return procedure when a bus reset occurs while a transaction is being performed between one source and a plurality of destinations will be described with reference to FIG. Here, the bus reset is caused by a change in the connection configuration,
It starts when the power of each node is turned ON / OFF.

This example shows a case where data from a source is received by three destinations.
When the bus is reset at the time when the source has finished transmitting the data of the sequence number i, each node on the bus initializes the procedure defined by the standard and performs reconfiguration.

After the completion of the bus rebuilding, each destination node sends a retransmission request packet (resend) in which the connection ID and the sequence number of the data correctly received before the bus reset occurs are written.
request) in a broadcast packet. In this example, destinations # 1 and # 2 can correctly receive data up to sequence number i, and destination # 3 can correctly receive data up to sequence number (i-1). Therefore, the source starts retransmission from the data of sequence number i.

In the case of FIG. 16 (a), the source selects the smallest number from the sequence numbers indicated by each retransmission request packet ((i-1) in this example), and starts transfer from the data of sequence number i. I do.

Further, as shown in FIG. 16 (b), the source receives each retransmission request packet, but can start retransmission from the data of sequence number 0 without determining the minimum sequence number. In this case, the function of determining the minimum sequence number can be omitted.

In this way, even if a bus reset occurs when a plurality of destinations exist, data transfer can be resumed without losing data in all destinations.

(Other Embodiments of the Present Invention) The present invention can be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), but can be applied to an apparatus including one device. You may.

Further, in order to realize various functions so as to realize the functions of the above-described embodiment, the functions of the above-described embodiments are realized by a device connected to the various devices or a computer in a system. The present invention also includes a program that is implemented by supplying the program code of the software described above and operating the various devices according to a program stored in a computer (CPU or MPU) of the system or apparatus.

Further, in this case, the program code of the software implements the functions of the above-described embodiment, and the program code itself and means for supplying the program code to the computer,
For example, a storage medium storing such a program code constitutes the present invention. As a storage medium for storing such a program code, for example, a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM,
A magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

When the computer executes the supplied program code, not only the functions of the above-described embodiment are realized, but also the OS (operating system) or other operating system running on the computer. Needless to say, the program code is also included in the embodiment of the present invention when the functions of the above-described embodiment are realized in cooperation with application software or the like.

Further, after the supplied program code is stored in the memory provided in the function expansion board of the computer or the function expansion unit connected to the computer, the function expansion board or the function expansion unit is specified based on the instruction of the program code. It is needless to say that the present invention also includes a case where a CPU or the like provided in the first embodiment performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

[0127]

As described above, the present invention has the effect of solving the inconvenience of the conventional communication system. In addition, even in data transfer that does not require real-time processing, there is an effect that data can be transferred easily and at high speed. According to the present invention,
When the communication band is not used much, there is an effect that a large number of communications can be performed simultaneously. Further, according to the present invention, it is possible to easily detect data lost due to interruption of data transfer, and to reliably and easily return from interruption of data transfer. There is.

Further, according to the present invention, there is no need to adjust the connection ID so as not to be duplicated among a plurality of controls, so that the controller can easily and surely set the connection.

According to the present invention, a plurality of control nodes individually source a plurality of logical connections,
Also in the case of setting between destinations, each node can determine the controller that has set the connection by a unique node ID such as a world wide unique ID which is information unique to the node. The node has an effect that the logical connection can be reliably identified.

Further, according to the present invention, data can be easily transmitted to a plurality of destinations in a single segment packet by one logical connection ID, so that traffic on the bus is reduced. effective.

Further, according to the present invention, the connection ID
It is not necessary to set a plurality of connection IDs, so that there is an effect that initial setting of the connection ID of the controller becomes easy. Also,
Even if the receiving buffer of each destination is different, the source only needs to manage and transmit only the receiving buffer size of each destination, so the source may have the same data flow and the implementation is easy. effective. Further, according to another feature of the present invention, there is an effect that a communication procedure for performing recovery from interruption of data transfer can be simplified.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an embodiment of the present invention.

FIG. 2 is a block diagram showing the operation of each node according to the present invention.

FIG. 3 is a diagram illustrating a diagram showing transmission and reception of commands and data between nodes according to the present invention.

FIG. 4 is a diagram showing an asynchronous packet according to the present invention.

FIG. 5 shows an Asynchronous used in the embodiment of the present invention.
It is a figure showing a packet.

FIG. 6 shows an Asynchronous used in the embodiment of the present invention.
FIG. 3 is a diagram illustrating a structure of a data field of a packet.

FIG. 7 is a diagram showing a structure of a header in a data field used in the embodiment of the present invention.

FIG. 8 is a diagram showing a conventional example.

FIG. 9 is a diagram showing unique identification information of a control node used in the embodiment of the present invention.

FIG. 10 is a diagram for explaining a diagram showing an overall flow supplementing the flow described in FIG. 3A used in the embodiment of the present invention.

FIG. 11 illustrates a case where one controller used in the embodiment of the present invention has the same connection ID on the network.
FIG. 3 is a diagram illustrating a configuration set between one source and N destinations.

FIG. 12 is a diagram for explaining a diagram showing a data flow when each destination used in the embodiment of the present invention has the same receiving buffer size and the object data size is equal to the receiving buffer.

FIG. 13 is a diagram showing a model of transfer of object data used in the embodiment of the present invention.

FIG. 14 is a diagram for explaining a diagram showing a flow of data transfer in a network in which each of three destinations has a different reception buffer size used in the embodiment of the present invention.

FIG. 15 is a diagram showing a case where destinations used in the embodiment of the present invention have reception buffers of different sizes.

FIG. 16 is a diagram illustrating a diagram showing a data flow when a bus reset occurs when a plurality of destinations exist, which is used in the embodiment of the present invention.

[Explanation of symbols]

10 computer 12 Processing unit (MPU) 14 First 1394 interface 16 First operation unit such as keyboard 18 First decoder 20 Display device such as CRT display 22 Hard disk 24 First memory 26 Internal bus of computer such as PCI bus 28 VCR 30 Imaging optical system 32 A / D converter 34 Video processing unit 36 Compression / expansion circuit 38 First memory 40 Second memory 42 First data selector 44 Second 1394 interface 46 First memory control circuit 48 Second memory control circuit 50 System controller 52 Second operation unit 54 Electronic viewfinder 56 D / A converter 58 Recording unit 60 Printer 62 Third 1394 interface 64 Second data selector 66 Third operation unit 68 Printer Controller 70 Second decoder 72 Third memory 74 Image processing unit 76 Driver 78 Printer head 200 Control node 202 Source node 20 4 Destination node 206 Subunit inside source node 208 Object such as image data 210 First memory space inside destination node 212 First connection 214 nth memory space inside destination node 216 nth connection

Claims (38)

[Claims] 1. A data communication system for performing communication using a connection ID indicating a logical connection between a transmitting device that transmits information data and a receiving device that receives the information data. A data communication system, wherein after the initialization, a part of the information data is requested using the connection ID. 2. The data communication system according to claim 1, wherein the data communication system includes a management device having a function of managing the connection ID, and the transmission device and the reception device using the management device. A logical connection between the data communication system and the data communication system. 3. The data communication system according to claim 2, wherein the management device assigns the connection ID to the transmitting device and the receiving device by using a node ID indicating each device constituting the data communication system. A data communication system for transmitting. 4. The data communication system according to claim 3, wherein the management device transmits unique ID information unique to the management device together with the connection ID to the transmission device and the reception device. Data communication system. 5. The data communication system according to claim 4, wherein said transmitting device and said receiving device identify a management device for which a connection ID has been set using said unique ID information. system. 6. The data communication system according to claim 2, wherein the management device is an Asyn compliant with the IEEE 1394 standard.
A data communication system, wherein the connection ID is transmitted using a chronous transfer method. 7. The data communication system according to claim 2, wherein the management device manages additional information on the plurality of connection IDs using a table. system. 8. The data communication system according to claim 1, wherein the initialization of the data communication system changes a connection configuration of the data communication system or configures the data communication system. A data communication system which is executed in accordance with one of ON / OFF of a power supply of a device. 9. The data communication system according to any one of claims 1 to 8, wherein the data communication system performs one of the information data when the initialization occurs during the communication of the information data. A data communication system for requesting a part. 10. The data communication system according to claim 1, wherein a part of the requested information data requests information data subsequent to the normally received data. Data communication system. 11. The data communication system according to claim 1, wherein when a plurality of receiving devices request a part of the information data, the transmitting device receives the information data from each of the receiving devices. A data communication system for transmitting a part of the information data so as to ensure continuity of data to be transmitted. 12. The data communication system according to claim 1, wherein the data requesting a part of the information data is transferred to all devices constituting the data communication system. A data communication system, comprising: 13. The data communication system according to claim 1, wherein the connection ID indicates a logical connection between a set of transmitting device and a receiving device. Data communication system. 14. The data communication system according to claim 1, wherein the connection ID indicates a logical connection between one transmitting device and a plurality of receiving devices. Data communication system. 15. The data communication system according to claim 1, wherein the connection ID indicates a logical connection between a plurality of transmitting devices and one receiving device. Data communication system. 16. The data communication system according to claim 1, wherein the connection ID indicates a logical connection between a plurality of transmitting devices and one receiving device. Data communication system. 17. The data communication system according to claim 1, wherein communication between the transmitting device and the receiving device is performed using the connection ID. Data communication system. 18. The data communication system according to claim 1, wherein information data output from said transmitting device and said receiving device are transferred to all devices constituting said data communication system. A data communication system, comprising: 19. The data communication system according to claim 18, wherein the transmitting device uses a communication packet configured by a broadcast ID designating all devices constituting the data communication system and the connection ID. A data communication system for transmitting the information data. 20. The data communication system according to any one of claims 1 to 19, wherein the information data output from the transmitting device is IEEE1
A data communication system wherein data is transferred using an asynchronous transfer method conforming to the 394 standard. 21. The data communication system according to claim 2, wherein the management device recognizes that the communication of the information data has ended based on an end flag transmitted from the transmitting device. A data communication system, comprising: 22. The data communication system according to claim 2, wherein the logical connection between the transmitting device and the receiving device is released by the management device or the receiving device. A data communication system, comprising: 23. The data communication system according to claim 1, wherein the receiving device responds to the connection request of the transmitting device by setting a size of a receiving buffer and a predetermined area in a memory space. A data communication system comprising: returning a packet including at least one of address information indicating a data start, a sequential number indicating a data start pointer, and information indicating preparation completion. 24. The data communication system according to claim 1, wherein the receiving device is provided with a bit indicating that data has been received normally. 25. The data communication system according to claim 1, wherein the transmitting device measures a response from the receiving device for a predetermined period, and detects a communication abnormality based on the period. Characteristic data communication system. 26. The data communication system according to claim 25, wherein the transmitting device automatically starts the retransmission operation of the information data when the communication device detects a communication abnormality by measuring the response for a predetermined period. A data communication system, comprising: 27. An I indicating a logical connection between a plurality of devices.
In a data communication system for transmitting the same information to a plurality of devices using D information, after initialization of the data communication system, a request is made to retransmit unreceivable information using the ID information. Data communication system. 28. The data communication system according to claim 27, wherein the initialization of the data communication system is performed by changing a connection configuration of the data communication system or turning on / off a power supply of a device included in the data communication system. A data communication system, which is executed according to any of the above. 29. A data communication system for determining communication between a plurality of different devices by a plurality of different ID information, wherein after the data communication system is initialized, retransmission processing is performed on the communication determined by the ID information. A data communication system, comprising: 30. The data communication system according to claim 29, wherein the ID information is information for specifying communication between the devices, and the initialization of the data communication system is performed based on a connection configuration of the data communication system. A data communication system that is executed according to a change. 31. A data communication device connectable to a data communication system that performs communication using a connection ID indicating a logical connection between a transmitting device that transmits information data and a receiving device that receives the information data. A data communication apparatus comprising: an initialization unit configured to initialize the information data communication system; and a communication unit configured to request a part of the information data from the transmission device using the connection ID. 32. An I indicating a logical connection between a plurality of devices.
In a data communication device connectable to a data communication system that transmits the same information to a plurality of devices using D information, initialization means for initializing the data communication system, and reception failure using the ID information And a communication unit for requesting retransmission of the information. 33. A data communication device connectable to a data communication system for determining communication between a plurality of different devices by a plurality of different ID information, an initialization unit for initializing the data communication system, and the ID information A communication means for performing a retransmission process for the communication determined in (1). 34. A data communication method for performing communication using a connection ID indicating a logical connection between a transmitting device that transmits information data and a receiving device that receives the information data, comprising: Requesting a part of the information data by using the connection ID after the conversion. 35. An I indicating a logical connection between a plurality of devices.
A data communication method for transmitting the same information to a plurality of devices using D information, wherein after initializing the data communication system, a request is made to retransmit unreceivable information using the ID information. Data communication method. 36. A data communication method for determining communication between a plurality of different devices by a plurality of different ID information, wherein after the data communication system is initialized, retransmission processing is performed on the communication determined by the ID information. A data communication method, comprising: 37. A storage medium storing a program for causing a computer to function as each of the means according to claim 31 to 33. 38. A storage medium storing a program for causing a computer to execute the procedure of the data communication method according to any one of claims 34 to 36.