JPH11168489A - Data communication equipment, its method and its system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To permit a user to easily recognize an information signal flow and a connection state between nodes by displaying information by which equipment information and an operation state in respective equipment constituting a communication system and the information signal flow in a network are indicated. SOLUTION: Topology map information indicating connecting relation between respective nodes is generated by using the function of a bus manager in a monitor 406. The topology map information is used so as to display connecting relation between respective nodes to a user through the use of an icon, etc. The monitor 406 manages total information concerning parentage relation between respective nodes and also generates topology map information. The respective nodes on the bus recognize the connecting relation of the bus by using topology map information which is managed by the monitor 406. The monitor 406 generates a table to which equipment information corresponds as against the respective nodes constituting the bus at each bus resetting. Besides, the monitor 406 visibly displays the icon or character information, etc., which represents equipment information of the respective nodes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data communication device, a method and a system, and more particularly to a technique for managing a network constituted by a data communication device having a communication digital interface.

[0002]

2. Description of the Related Art In recent years, image and audio data handled by AV equipment such as digital cameras and digital video cameras have been rapidly digitized. Along with this, a technology has been developed in which peripheral devices (printers, hard disks, etc.) of personal computers (hereinafter, PCs) and digital AV devices are connected using a common digital interface for communication, thereby forming one communication system. .

[0003] One of the technologies used in such a communication system is an I-related technology related to the High Performance Serial Bus.
EEE1394 standard, ie, IEEE Std 1394-1995 (hereinafter IEEE13
94 standards).

[0004] A communication interface (hereinafter, 1394 interface) conforming to the IEEE1394 standard is a digital interface capable of constructing a bus-type network capable of bidirectional communication. Further, the 1394 interface can transmit transmission packets at high speed and serially. 1394
The interface has several features, including:

(1) There are two transfer modes (Isochronous transfer mode and Asynchronous transfer mode). Isochr
The onous transfer mode is effective for real-time transfer of video data and audio data because it guarantees transmission and reception of a fixed amount of packets every communication cycle period (125 μs).
The asynchronous transfer mode is a transfer mode in which control commands, files, and the like are asynchronously transmitted and received as necessary, and has a lower priority than the isochronous transfer mode.

(2) A connection system having a high degree of freedom. Specifically, the daisy-chain method and the node branch method can be mixed, and a highly flexible network can be constructed.

(3) Automatic recognition of the network configuration is possible. In other words, according to changes in the network configuration due to power ON / OFF and addition / deletion of electronic devices, the interface is set to the ID set for each electronic device on the network
It has a function that can automatically set and recognize information.

(4) Since data transmission between the 1394 interfaces is performed serially, the cable is thin and
The connector can be downsized.

[0009]

SUMMARY OF THE INVENTION
The communication system configured using the 1394 interface has the following problems.

For example, it has been difficult for a user to grasp all flows of moving image signals and audio signals that are being communicated in real time on a network.

In order to solve this problem, it is necessary to provide a device which allows the user to easily and visually display the flow of the signals between the devices, but such a device has conventionally existed. Did not.

Therefore, when a user wants to grasp the flow of a signal on a network and manage communication between the devices based on the flow, there is no means for realizing this.

In view of the above background, it is an object of the present invention to provide a data communication device, a method and a system that allow a user to easily understand the flow of an information signal communicated in real time on a network. It is.

[0014]

In order to achieve the above-mentioned object, a data communication apparatus according to the present invention comprises a display means for displaying a flow of an information signal between a plurality of devices, and a display means for displaying the flow of information signals. Selecting means for selecting at least one of the information signal flows, and control means for controlling display of the content of the information signal indicated by the flow selected by the selecting means. It is.

Further, the data communication apparatus of the present invention has a display means for displaying a flow of an image signal between a plurality of devices, and displays the contents of the image information together with the flow of the image signal displayed on the display means. And control means for performing the control.

Further, in the data communication method according to the present invention, a display step of displaying a flow of an information signal between a plurality of devices, and a selection step of selecting at least one of the flow of the information signal displayed in the display step And a control step of controlling to display the content of the information signal indicated by the flow selected in the selection step.

The data communication method according to the present invention further comprises a display step of displaying a flow of an image signal between a plurality of devices, and a control step of controlling the content of the image information to be displayed together with the flow of the image signal. It is characterized by having.

Further, the data communication system of the present invention comprises a display means for displaying a flow of information signals between a plurality of devices, and a selection means for selecting at least one of the information signal flows displayed by the display means. And control means for controlling display of the content of the information signal indicated by the flow selected by the selection means.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a data communication device according to the present invention will be described.
The method and system will be described in detail with reference to the drawings.

(First Embodiment) FIG. 1 is a diagram showing a digital communication system constituted by using a plurality of electronic devices having the above-mentioned 1394 interface.

In FIG. 1, reference numeral 101 denotes a printer;
Is a PC, 103 is a digital video tape recorder-A
(Hereinafter, DVTR-A), 104 is a digital video tape recorder-B (hereinafter, DVTR-B), and 105 is a video disk. Each device is connected via a communication cable 106 conforming to the IEEE1394 standard.

In the communication system shown in FIG. 1, the 1394 interface constantly monitors changes in the connection configuration due to the power ON / OFF of each device, or addition or deletion of devices. When a change in the connection configuration is detected, the 1394 interface of each device automatically recognizes the connection configuration (topology) of the network and sets ID information (hereinafter, node ID) for each device (node). Execute the process.

Recognition of the connection configuration is executed by each node declaring a parent-child relationship after a bus reset (a bus initialization process involving clearing of connection configuration information). Each node determines the parent-child relationship between each node,
The network connection configuration is recognized as a tree structure (hierarchical structure). Finally, the parent (or higher) device of all the devices becomes the root node, and manages arbitration of the right to use the bus.

After determining the root node, the network assigns a physical address (ie, node I) to each node.
D) is set automatically. The setting of the node ID (consisting of the bus number and the node number) is basically such that the parent node allows the setting of the physical address to the child node connected to the communication port having the lower port number, and further, the child node sets its own This is performed by giving the setting permission to the child nodes in order. After the ID setting of all the child nodes is completed, the parent node sets its own node ID.

Hereinafter, the process of automatically setting the node ID in the network will be described with reference to FIG. In this embodiment, a case will be described in which the PC 102 becomes the root node after the connection configuration is recognized. Further, since the network of the present embodiment is configured by the same bus, the bus number of each node is set to the same number.

In FIG. 1, a PC which is a root node
First, the node 102 permits the node connected to the communication port of the port number “# 1”, that is, the printer 101, to set the node ID. The printer 101 sets its own node number to “No. 0” and transfers the result to all devices on the bus as a self-ID packet (broadcast). As a result, all the devices on the network recognize that “node number“ No. 0 ”has been allocated”, and the next device that is permitted to set the node number is “No.
1 ”is set.

After setting the printer 101, the PC 102
The node connected to the communication port having the port number “# 2”, that is, the DVTR-A 103, is permitted to set the node ID. The DVTR-A103 further includes a child node (D
Among the communication ports connected to the VTR-B 104 and the video disk 105), permission is given in order from the communication port with the lowest port number. That is, the DVTR-A 103 gives permission in the order of the DVTR-B 104 and the video disk 105, and the DVTR-B 104 and the video disk 105 that have received the permission respectively have the node numbers "No. 1" and "No. 2".
Is set, and a self-ID packet is broadcast. After setting the DVTR-B 104 and the video disc 105, the DVTR-A 103 sets its own node number to “N”.
o.3 ", and finally the root node (PC102)
Sets its own node number to “No. 4” and ends the recognition of the connection configuration.

With the above processing, each node can automatically recognize the connection configuration of the network, and can automatically assign a node ID to each node.
Each node can perform communication between the nodes by using the node ID.

The 1394 interface is an asynchronous
It has two types of transfer modes called a transfer mode and an isochronous transfer mode. Asynchronous packets are
As shown in FIG. 2, the header 201, the header CRC 20
2, a data section 203 and a data CRC 204. The header section 201 has fields for storing target node ID information (node ID of a destination node), source node ID information (node ID of a node transmitting a packet), and various types of control information. Transferred to the node indicated by the node ID information. Note that a node that receives an Asynchronous packet, unless the packet is broadcast,
It always returns acknowledge, but does not return acknowledged packets.

As shown in FIG. 3, the isochronous packet includes a header section 301, a header CRC 302, and a data section 30.
3. Data CRC 304. The header 301 includes channel number information (a number assigned to a bandwidth in which an isochronous packet can be transferred, and isochronous data output from each node is distinguished by this number) and various control information. There are fields to store. Isochronous packets are broadcast to the entire bus instead of being forwarded to a specific node. Therefore, each node can receive a predetermined isochronous packet by detecting the channel number. The node that has received the isochronous packet does not return an acknowledge.

FIG. 4 is a diagram showing a configuration of a communication system according to this embodiment of the present invention. Here, each device (hereinafter, node) constituting the communication system of FIG. 4 has a 1394 interface.

In FIG. 4, reference numerals 401 to 405 denote camera-integrated digital video tape recorders (hereinafter, camera-integrated DVTRs), and 406 denotes a monitor.

The monitor 406 has a function of a bus manager conforming to the IEEE1394 standard. By using this function, the monitor 406 can create topology map information indicating the connection relationship between the nodes.
Further, the monitor 406 can display the connection relationship between the nodes to the user using icons and the like by using the topology map information.

In the communication system of the IEEE1394 standard, when automatically recognizing the connection relation between the nodes, the relation is recognized as a parent-child relation. The monitor 406, which is a bus manager, collectively manages information on the parent-child relationship between the nodes and creates topology map information. Each node on the bus can recognize the connection relation of the bus by using the topology map information managed by the monitor 406.

In a communication system of the IEEE 1394 standard, communication between nodes is normally performed using a node ID set in a bus initialization process after a bus reset. That is, since each node recognizes the node on the bus by the node ID, it is necessary to inquire the device information (including the device name) of the node in order to know the model of the node to communicate with. There is. Therefore, the monitor 406 according to the present embodiment makes an inquiry about the device information to each node constituting the bus every bus reset, and creates a table in which the node ID of each node is associated with the device information. Further, the monitor 406 visually displays icons, character information, and the like representing device information of each node. Here, when there are a plurality of nodes of the same model with the same maker on the bus, for example, numbers are set in ascending order of the node ID value,
It is displayed in a manner that is easy for the user to understand.

In FIG. 4, for example, a camera-integrated DV
Image data reproduced by TR403
Recorded by VTR401, camera-integrated DVTR402
Image data reproduced by the DVTR40 with camera
4. A case will be described in which recording processing is performed by the camera-integrated DVTR 405.

The image data reproduced and transferred isochronously by the camera-integrated DVTR 403 is packetized into isochronous packets for each predetermined amount of data. I
The detailed structure of the sochronous packet is described in FIG.
Shown in Here, the camera-integrated DVTR 403 is an Isoc
The channel number “0” assigned before the start of the hronous transfer is set in the channel number field of the isochronous packet.

Similarly, image data reproduced and transferred isochronously by the camera-integrated DVTR 402 is packetized into Isochronous packets for each predetermined amount of data. Here, the camera-integrated DVTR 402 is an Isoc
The channel number “1” assigned before the start of the hronous transfer is set in the channel number field of each Isochronous packet.

Camera-integrated DVTR 4 serving as a transmitting node
03 and Is generated by camera-integrated DVTR 402
The ochronous packet is broadcast in a time division manner for each communication cycle. Further, the camera-integrated DVTR 401, the camera-integrated DVTR 404, and the camera-integrated DVTR 405 serving as reception nodes receive the isochronous packet transferred from the communication partner node by detecting the channel number of the packet.

Each node (401 to 406) is provided with a transmission connection register 505 and a reception connection register 506. Each node (401 to 406) on the bus system
By checking the contents of these registers, it is possible to recognize the flow of Isochronous data between nodes. FIG. 5 shows the configuration of each register.

In FIG. 5, each register has a connection count field (501, 502) and a channel field (503, 504). The connection count fields (501, 502) store the number of nodes to be communicated with, and the channel fields (503, 50).
4) stores the channel number of the isochronous packet transferred to the communication partner.

For example, the contents of the transmission connection register 505 of the camera-integrated DVTR 403 as the transmission node and the contents of the reception connection register 506 of the camera-integrated DVTR 401 as the reception node will be described using the example described with reference to FIG. .

The communication partner (transmission destination) of the camera-integrated DVTR 403 (transmission node) is a camera-integrated DVTR 40.
Since it is only 1, “1” is set in the connection count field 501 of the camera-integrated DVTR 403.
In addition, camera-integrated DVTR403 and camera-integrated DVT
Since the channel number of the isochronous packet transferred to R401 is “0”, the camera-integrated DVT
“0” is set in the channel field 503 of R403.

The communication partner (transmission source) of the camera-integrated DVTR 501 (receiving node) is a camera-integrated DVTR 5
Since the number is only 03, “1” is set in the connection count field 502 of the camera-integrated DVTR 401.
In addition, camera-integrated DVTR403 and camera-integrated DVT
Since the channel number of the isochronous packet transferred to R401 is “0”, the camera-integrated DVT
“0” is set in the channel field 504 of R501.

Similarly, using the example described with reference to FIG. 4, the contents of the transmission connection register 505 of the camera-integrated DVTR 402 as the transmission node and the reception connection registers of the camera-integrated DVTR 404 and the camera-integrated DVTR 405 as the reception nodes The contents of 506 will be described.

The communication partner (transmission destination) of the camera-integrated DVTR 402 (transmission node) is a camera-integrated DVTR 40.
4 and 405, “2” is set in the connection count field 501 of the camera-integrated DVTR 402. In addition, a camera-integrated DVTR 402 and a camera-integrated D
Isochronous transferred between VTRs 404 and 405
Since the channel number of the packet is “1”, “0” is set in the channel field 503 of the camera-integrated DVTR 402.

In addition, camera-integrated DVTRs 404 and 405
The communication partner (sender) of the (receiving node) is the camera-integrated D
VTR 402 only. Therefore, the camera-integrated DV
“1” is set in the connection count field 502 of the TRs 404 and 405. In addition, camera-integrated DVTR40
The channel number of the isochronous packet transferred between the camera 2 and the camera-integrated DVTRs 404 and 405 is “1”.
Therefore, “1” is set in the channel field 504 of the camera-integrated DVTRs 404 and 405.

In this embodiment, the monitor 406 checks the transmission connection register 505 and the reception connection register 506 of each node (401 to 406) to manage the flow of Isochronous data transferred on the communication system.
Furthermore, it has a function of displaying them to the user.

FIG. 6 is a block diagram for explaining in detail the configuration of the monitor 406 according to the fourth embodiment.

In FIG. 6, reference numeral 601 denotes a 1394 interface conforming to the IEEE 1394 standard. 602, a signal processing unit that converts image data and audio data input via the 1394 interface 601 into a signal form that can be output;
Reference numeral 03 denotes a monitor unit capable of displaying image data transferred from another node, which can display icons and the like of device information of each node. A display information generation unit 604 generates various display information such as an icon of each node and message information, an operation unit 605 inputs a user's instruction by a predetermined operation, and 606 stores information regarding a connection configuration of the communication system. 607, a speaker for outputting sound, 608, a microcomputer including a microcomputer, a control unit for controlling the operation of various processing circuits (601 to 607) provided in the monitor 406, and 609, data connected to other nodes. It is a bus.

The 1394 interface 601 is a device information (device name) of each node connected to the data bus 609.
And a node ID are associated with each bus reset.
In addition, the 1394 interface 601 inquires the contents of the transmission connection register 505 and the reception connection register 506 of each node as needed in order to manage information on the flow of Isochronous data, and operates the nodes (for example, Playback, recording, variable speed playback, external input,
Inquire about external output, standby, etc.). Here, the control command for inquiring these pieces of information is packetized into the above-described asynchronous packet shown in FIG. 2 and is transmitted asynchronously.

The monitor 406 associates the results of these inquiries with the node ID and the device information, and creates a management table for managing the information.

FIG. 7 is a diagram showing the contents of a management table for managing information on the flow of isochronous data.
Note that the created management table is stored in the memory 606.

In FIG. 7, reference numeral 701 denotes a node ID set to a node on the bus system, 702 denotes device information (device name) of each node, 703 denotes an operation state of each node, and 704 transmits an isochronous packet. Indicates whether or not the node is Reference numeral 705 indicates whether or not the node is receiving an isochronous packet. Reference numeral 706 indicates an isochronous packet.
Indicates the channel number used for ous transfer.

The monitor 406 can display information on the flow of isochronous data on the screen of the monitor unit 603 by using the management table shown in FIG.

FIG. 8 is a diagram showing an example of a screen displayed on the monitor unit 603.

In FIG. 8, reference numerals 801 and 802 denote Isochron.
Icons indicating channel numbers of data being ous-transferred, icons 803 and 804 indicating nodes serving as transmission nodes, 805 to 807 icons indicating nodes serving as reception nodes, and 808 performing isochronous transfer with other nodes. This icon indicates a node that is not present (standby node). Icons 803 to 808 display device information (device name) of the node and information on the operation state of the device. Note that the icons displayed on the monitor unit 603,
The display information such as a message is generated by the display information generation unit 604 based on the contents of the management table shown in FIG.

In FIG. 8, reference numeral 809 denotes a field for displaying an icon indicating a channel number; 810, a field for displaying an icon for a transmitting node; 811, a field for displaying an icon for a receiving node;
Reference numeral 2 denotes a field for displaying an icon indicating a standby node. Reference numeral 81 denotes a pointer for operating each icon and inputting a predetermined designation, and is operated by the operation unit 605.
A field 814 displays the isochronous data of the channel number “0”, and a field 815 displays the isochronous data of the channel number “1”.
This is a field for displaying isochronous data.

By visually displaying information on the flow of the isochronous data as shown in FIG. 8, the user can easily grasp the node using the bus.
Also, the flow of isochronous data on the bus can be recognized.

The monitor 406 of this embodiment changes the actual flow of the isochronous transfer by moving the icons (803 to 808) displayed in FIG. 8 to the display fields 809, 811 and 812. It can also be controlled.

For example, when the icon 806 (indicating the camera-integrated DVTR-D404) is dragged using the pointer 813 and dropped on the display field 809 indicating the channel number “0”, the monitor 406 is moved to the camera-integrated DVTR-D404. A request is made to change the communication destination to the channel number “0”. As a result, the camera-integrated DVTR-D404 is able to operate the I / O of the channel number “0”.
The monitor 406 changes the contents of the management table and the display screen while processing to receive the sochronous data.

Also, an icon 803 (camera integrated DVT)
(Showing the R-C 403) and dropping it on the display field 412 showing the standby node.
Is the camera integrated DVTR-C403 and the camera integrated D
It requests the VTR-A 401 to stop isochronous transfer. Thereby, DVTR-C2103 and DVTR-C
A2101 is both standby nodes, and monitor 406 is
Change the contents of the management table and the display screen.

An icon 80 indicating a channel number
By clicking 1,802, the content of the isochronous data indicated by the icon can be displayed in the fields 814, 815 on the screen of the monitor unit 603. For example, Isochronou indicated by icons 801 and 802
When the s data is an image signal, the monitor 406 displays an image of the image signal in the fields 814 and 815. When the isochronous data indicated by the icons 801 and 802 is an audio signal, the monitor 406 outputs the audio of the audio signal from the speaker 608 and displays a message such as “audio output” in the fields 814 and 815. You may. In this case, the monitor 406 is set to receive the isochronous data of the designated channel number by itself, and receives the isochronous data broadcasted from the transmitting node every predetermined communication cycle.

Further, the monitor unit 603 of the monitor 406
Information on the flow of ochronous data can be displayed as shown in FIG. In FIG. 9, each icon is composed of an image indicating device information and an operation state of each node and character information. Arrows and character information between each node (between the transmitting node and the receiving node) are Isoc.
It shows the flow of hronous data and channel numbers. In FIG. 9, the monitor 406 also outputs the content (image or sound) of the isochronous data of each channel.

The user can instruct the standby node to receive Isochronous data indicated by the arrow by dragging the icon displayed in the field indicating the standby node and dropping it on the illustrated arrow. With this operation, the monitor 406 requests the specified standby node to receive the specified isochronous data, and changes the contents of the management table and the display screen.

As described above, in the present embodiment, display information (consisting of icons and character information) indicating the device information and operation status of each node constituting the communication system and display information indicating the flow of Isochronous data are displayed. By doing
The user can easily recognize the flow of the transfer data between the nodes and the connection state.

Further, by operating the display information of each node and the display information indicating the flow of data, the communication destination of the data can be easily changed.

Further, by manipulating the display information indicating the flow of the isochronous data, the contents of the data can be displayed.

It should be noted that the present invention can be embodied in various other forms without departing from its spirit or main characteristics.

For example, in this embodiment, a communication system constituted by a data communication device having a 1394 interface conforming to the IEEE 1394-1995 standard has been described. However, the present invention is not limited to this. The present invention can be applied to any communication system as long as it has a function of automatically setting and recognizing ID information set for each device on the network according to a change in the configuration.

In this embodiment, the IEEE1394 is used as a communication interface of each node constituting the network.
The digital interface conforming to the -1995 standard was used, but it is not limited to this, and one communication cycle period (12
Any interface can be used as long as it has a transfer mode that guarantees transmission and reception of a fixed amount of packets every 5 μs) and a transfer mode that asynchronously transmits and receives control commands and files as needed. Good.

Therefore, the above-described embodiments are merely examples in every aspect, and should not be interpreted in a limited manner.

[0073]

As described above, according to the present invention,
By displaying display information (consisting of icons and character information) indicating device information and operation status of each device constituting the communication system and display information indicating a flow of an information signal on the network, the user can operate each node. The flow of information signals and the connection state between them can be easily recognized.

Further, according to the present invention, the communication destination of the information signal can be easily changed by operating the display information of each node or the display information indicating the flow of the information signal.

Further, according to the present invention, by operating display information indicating the flow of an information signal, the content of the information signal can be displayed together with the flow of the information signal.

[Brief description of the drawings]

FIG. 1 is a diagram showing a digital communication system configured using a plurality of electronic devices having a 1394 interface.

FIG. 2 is a diagram illustrating a configuration example of an asynchronous transfer packet.

FIG. 3 is a diagram showing a configuration example of a packet for isochronous transfer.

FIG. 4 is a diagram showing a configuration of a communication system according to the embodiment.

FIG. 5 shows a transmission connection register 505 and a reception connection register 5
The figure which shows the structure of 06.

FIG. 6 is a block diagram illustrating the configuration of a monitor 406 according to the present embodiment in detail.

FIG. 7 is a diagram showing the contents of a management table for managing information on each node.

FIG. 8 is a view showing an example of a screen displayed on a monitor unit 603.

FIG. 9 is a view showing another example of a screen displayed on the monitor unit 603.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04L 12/26

Claims (16)

[Claims] 1. A display unit for displaying a flow of an information signal between a plurality of devices, a selection unit for selecting at least one of the flow of an information signal displayed by the display unit, and a selection unit selected by the selection unit. A data communication device comprising: control means for controlling display of the content of the information signal indicated by the flow. 2. The data communication device according to claim 1, wherein said display means can also display device information of said plurality of devices. 3. The data communication device according to claim 2, wherein the display means can also display device information of a device that is not performing communication. 4. The data communication apparatus according to claim 2, wherein said selecting means can also select said device information. 5. The data communication apparatus according to claim 4, wherein the control unit controls to set a device indicated by the device information selected by the selection unit as a communication destination of the information signal. . 6. The data communication apparatus according to claim 1, wherein the information signal is an information signal flowing on a network capable of automatically recognizing a connection relationship between the plurality of devices. . 7. The data communication device according to claim 1, wherein the display means can also display the operation states of the plurality of devices. 8. The data communication device according to claim 1, wherein the information signal is transmitted as a predetermined amount of data in each communication cycle. 9. The data communication device according to claim 1, wherein the information signal is an image signal or an audio signal. 10. The data communication device according to claim 9, wherein the content of the information signal is an image or a sound. 11. A data communication apparatus according to claim 10, wherein said control means controls the display means to display the content of said information signal together with the flow of said information signal. 12. A display unit for displaying a flow of an image signal between a plurality of devices, and a control unit for controlling a content of the image information to be displayed together with the flow of the image signal displayed on the display unit. A data communication device, comprising: 13. The data communication apparatus according to claim 12, wherein the control means controls the contents of the image signal and the flow of the image signal to be displayed on the same screen. 14. A display step of displaying a flow of an information signal between a plurality of devices; a selection step of selecting at least one of the flow of the information signal displayed in the display step; and a selection step of the selection step. And a control step of controlling to display the content of the information signal indicated by the performed flow. 15. A display unit for displaying a flow of an information signal between a plurality of devices, a selection unit for selecting at least one of the flow of an information signal displayed by the display unit, and a selection unit selected by the selection unit. Control means for controlling display of the content of the information signal indicated by the flow. 16. A display apparatus comprising: a display step of displaying a flow of an image signal between a plurality of devices; and a control step of controlling to display the contents of the image information together with the flow of the image signal. Data communication method.