JP2001189728A - Device and method for data transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide data transmitting method and device which reduce the burden of a user by simplifying the procedures of transmission and reception. SOLUTION: In this data transmitting method that transmits and receives the synchronous communication of a plurality of channels among a plurality of devices by utilizing a fast serial bus, a node in the middle of outputting does not release a channel number and a band, a node outputting later does not have to acquire a channel number, either when an image and audio equipment transmits and receives synchronous communication data, and a node that does not have to newly insure a band is also provided when a band to be used is the same.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission apparatus and method for transmitting data requiring real-time processing, such as video signals and audio signals, between a plurality of devices.

[0002]

2. Description of the Related Art Devices for transmitting video signals and audio signals via digital transmission lines have been developed. In order to transmit a video signal or an audio signal as a digital signal, it is necessary to transmit and receive the digital signal in synchronization with the processing speed of the device. Also, considering that a transmission signal from one device is received by a plurality of devices and transmitted bidirectionally on one transmission line, a bus connection is considered to be desirable.

At present, IEEE (THE INSTITUTE OF ELECTRI)
CAL AND ELECTRINIC ENGINEERS, INC)
A next-generation high-speed serial bus 94 is under study. (Reference: High Performance Serial Bus P1
394 / Draft 6.6v0) In P1394, synchronous communication data such as video signals and audio signals can be transmitted by synchronous communication using synchronous communication packets. In P1394, synchronous communication is enabled by transmitting and receiving a synchronous communication packet every 125 μsec (hereinafter referred to as a cycle).

Next, a method of synchronous communication management of P1394 will be briefly described. In P1394, the user does not need to set a node identifier for each device with a switch or the like, and the node identifier of each device is automatically allocated so that the device can be used simply by connecting the device. This process occurs when the bus is initialized. The initialization of the bus is performed when the connection state of a device (hereinafter, referred to as a node) changes (for example, when the number of connected nodes changes due to disconnection or insertion of a cable or the like).

In P1394, a maximum of 3
Two synchronous communication packets can be transmitted. Therefore, any one of channel numbers from 1 to 32 is added to each synchronous communication packet to identify the synchronous communication packet. Also, in order to perform synchronous communication on multiple channels,
One of the nodes connected to the bus performs synchronous communication management. This node is hereinafter referred to as CFM. C
The FM manages the channel number used for synchronous communication and the remaining bandwidth available for synchronous communication. In order to perform synchronous communication, it is necessary to secure a channel number and a band to be used from the CFM. Communication required for synchronous communication management and information that does not require synchronous communication are performed by asynchronous communication using asynchronous communication packets. Asynchronous communication is
This is performed using the time during which the synchronous communication is not performed in the cycle.

[0006]

Problems to be solved by the present invention will be described. When the first node ends the output of the synchronous communication data while outputting the synchronous communication data, and the second node tries to output the synchronous communication data on behalf of the first node, the following processing is required. The user instructs the first node to stop outputting and release the band and channel number. The first node instructed to stop the output and release the band and the channel number stops the output and releases the used channel number and the band. The user instructs the second node to acquire a channel number and a band and start outputting. The node instructed to acquire the band and start the output starts the output after acquiring the band and the channel number. Therefore, when the transmitting node is switched to another node, such a method requires the release and acquisition of the channel and the band, so that the node that is outputting and the node that intends to output later are connected to the CFM. Communication has to be performed, and there is a problem that a response at the time of switching becomes slow. In addition, since the user needs to instruct both the node that is outputting and the node that outputs later, there is also a problem that the burden on the user is large.

[0007]

According to a first aspect of the present invention, a first aspect uses a bus capable of transmitting synchronous communication data of a plurality of channels by adding a channel number as a channel identifier to the data. A data transmission method for transmitting synchronous communication data, wherein a first node adds a node identifier for identifying a transmitting node to the synchronous communication data and outputs a channel number used by the first node during output. When the second node outputs the synchronous communication data using the same channel as the first node, the second node specifies the first node which is a transmission node by the node identifier, and the first node , And when the first node acknowledges the output stop request, the channel used by the first node is Which is a data transmission method characterized in that it performs the transmission of the synchronous communication data using.

The second invention newly proposes the following method as a means for solving the above-mentioned problem. By using a bus capable of transmitting a plurality of channels of synchronous communication data by adding a channel number to the data as a channel identifier, the first node is outputting the synchronous communication data while the second node is outputting the synchronous communication data. When outputting synchronous communication data, the first node determines whether an output stop request for stopping output of the synchronous communication data has been received or not received from the second node. A second determining step of determining whether the output of the synchronous communication data may be stopped or not to be stopped when it is determined in the first determining step that the output stop is received; and the second determining step. Transmitting an output stop rejection to the second node when it is determined that the second node does not stop; Third to determine not received or was received output stop command for stopping the output of the synchronous communication data
A step of stopping the output of the synchronous communication data when it is determined that the output stop command is received in the third determining step or when it is determined that the output may be stopped in the second determining step; First
Transmitting the used bandwidth used for outputting the synchronous communication data of the second node to the second node, wherein the second node transmits an output stop request to the first node And a fourth determining step of determining whether an output stop rejection has been received or not received from the first node; and determining that the first node has received the output stop rejection in the fourth determining step. A fifth determining step of determining whether to stop or not stop the output of the synchronous communication data; and, in the fifth determining step, determining that the forcible stop is performed. Transmitting to the first node the output stop instruction for forcibly stopping the output of the synchronous communication data of the first node; A sixth determining step of determining whether at least the use band has been received or not received from the first node when transmitting the output stop command or determining that the output stop command has not been received in the fourth determining step; If it is determined in the sixth determining step that the received bandwidth is received from the first node, whether the scheduled bandwidth required for the second node to output synchronous communication data is equal or not equal If it is determined in the seventh determination step that the determination is equal to the seventh determination step, the output of the synchronous communication data is started using the used bandwidth and the channel number used by the first node. Step 7;
If it is determined in the determining step that the bandwidths are not equal, the first node changes the used bandwidth used for outputting the synchronous communication data to the scheduled bandwidth of the second node; An eighth determining step of determining whether the change was successful or unsuccessful; and, if determining in the eighth determining step that the change was successful, using the channel number used by the first node and the scheduled bandwidth. And starting the output of the synchronous communication data.

In the first invention, when switching the transmitting node of the synchronous communication data, the second node that starts outputting later transmits an output stop request to the first node that is outputting. The first node that has received the stop request stops the output, and transmits the band used by the first node to the second node that has transmitted the output stop request. The second node that has received the used band compares its own planned band with the received used band and outputs the same if it is the same. Therefore, according to the present invention, when switching the transmitting node, the output node does not need to release the band and the channel in order to take over the used channel and the band to the next node as it is, and The output node does not need to acquire the channel and the band. Further, the user only needs to instruct the node that starts output later to start output, and does not need to instruct the node that is outputting to stop output.

[0010] In the second invention, in the first invention, when the first node receives the output stop request, the first node determines whether to stop the output, and sends a request to the second node. To send a rejection. When the second node receives the rejection, if it is necessary to forcibly stop the output of the first node, the second node transmits an output stop command for forcibly stopping the output to the first node. The first node that has received the output stop instruction stops the output unconditionally. According to the present invention, there is no need for the user to operate the first node to stop the output, and the user can stop the output of the first node by operating only the second node.

[0011]

Embodiments of the present invention will be described below. The present invention relates to a data transmission method for transmitting synchronous communication data such as video and audio data using a protocol called P1394, which is currently being discussed in IEEE. FIG. 1 shows a connection example when a plurality of nodes are connected. FIG. 1 shows an example in which four audiovisual devices are connected as a plurality of nodes. Audiovisual equipment 101, 102, 10
3 and 104 are connected by a cable 105. P13
As the cable used in 94, a cable having a shape described on pages 52 to 54 of the reference is used.

FIG. 2 shows a block diagram of a video and audio device using the video and audio device 102 as an example. The audiovisual device includes an interface block 201 and an audiovisual signal processing block 202.
And a control block 203. A signal input from another node, for example, the audiovisual device 102 from the audiovisual device 101 is input to the interface block 201. The interface block 201 shapes the waveform of the input signal and outputs it to the audiovisual device 103. In P1394, the connection form as shown in FIG. 1 is adopted, but an output signal from a certain node (video and audio equipment) can be transmitted to all nodes (video and audio equipment).

In P1394, synchronous communication data is transmitted using a synchronous communication packet. FIG. 3 shows a format of a synchronous communication packet defined by P1394. The synchronous communication packet includes a 4-byte packet header 301, a 4-byte header CRC 302 for checking the presence or absence of a transmission error in the packet header 301, and a 4-byte CRC for checking the presence or absence of a transmission error in the data area 303 and the data area 303. It comprises a CRC 304 for byte data.
FIG. 4 shows the format of the packet header 301. The packet header 301 includes a channel number 401. In P1394, a node such as a plurality of audiovisual devices can transmit a plurality of synchronous communication packets in a time-division manner about every 125 μsec (hereinafter referred to as a cycle). A channel number 401 is added to the synchronous communication packet to identify each packet in the same cycle.

When transmitting synchronous communication data, the control block 203 instructs the video and audio signal processing block 202 to output synchronous communication data such as video and audio data. The video / audio signal processing block 202 outputs synchronous communication data to the interface block 201 according to the instruction of the control block 203. The control block 203 instructs the interface block 201 to output a synchronous communication packet along with information such as a channel number to be used. Interface block
In accordance with the instruction from the control block 203, the synchronous communication data 201 from the video / audio signal processing block 202 is packetized in the packet format of FIG. 3 as the data area 303 of FIG. The interface block 201 outputs the synchronous communication packet to another node (video / audio equipment).

When receiving synchronous communication data, the control block 203 indicates to the interface block 201 the channel number of the synchronous communication packet to be received. The interface block 201 determines from the packet header of the synchronous communication packet whether the packet is a synchronous communication packet of the designated channel number. If it is the designated channel number, the data area 30 from the synchronous communication packet of FIG.
The synchronous communication data of No. 3 is output to the video and audio signal processing block 202. The control block 203 is an audiovisual signal processing block 2
Instruct 02 to input synchronous communication data. The video / audio signal processing block 202 receives the synchronous communication data and performs signal processing.

As described above, in P1394, a plurality of nodes can transmit a plurality of synchronous communication packets in the same cycle in a time-division manner. That is, a plurality of nodes can apparently simultaneously perform a plurality of synchronous communications. Each synchronous communication must be performed while securing a band corresponding to the processing speed inside each node. Since the band that can be transmitted is limited, it is necessary to manage the band used by each node. Further, a channel number is added to the synchronous communication packet in order to identify each synchronous communication packet for performing synchronous communication on a plurality of channels. In P1394, a natural number from 1 to 32 can be used for this channel number. When a plurality of nodes output synchronous communication packets, it is necessary to manage the channel numbers used by the nodes so that the channel numbers of the synchronous communication packets do not overlap. In order to perform synchronous communication in P1394, one node manages the CFM (C
onfiguration Manager) to centrally manage bandwidth and channel numbers. A node that performs synchronous communication, such as an audiovisual device, needs to perform synchronous communication after acquiring its own band and channel number from the CFM.

Communication other than synchronous communication including communication for obtaining such a band and a channel number is performed by asynchronous communication using asynchronous communication packets. Asynchronous communication is performed using idle time in a cycle after synchronous communication is completed in one cycle. FIG. 5 shows a format of an asynchronous communication packet defined by P1394. The asynchronous communication packet is a 16-byte packet header 501, a 4-byte header CRC 302 for checking the presence or absence of a transmission error of the packet header 501, and a 4-byte for checking whether or not the asynchronous data 503 and the asynchronous data transmission error exist. And a data CRC 504. Packet header 5
As shown in FIG. 6, a receiving node identifier 601 which is a node identifier of a destination node to which an asynchronous packet is transmitted is shown in FIG.
And a transmission node identifier 602 which is its own node identifier. Receiver node identifier 60 in the packet header
1 and the transmission node identifier 602 are each represented by 2 bytes. The receiving node can specify the asynchronous packet to be received by receiving the asynchronous packet whose receiving node identifier 601 is equal to its own node identifier. Further, the receiving node can recognize which node has transmitted the asynchronous packet from the transmitting node identifier 602 of the received asynchronous packet.

Next, a procedure for performing asynchronous communication will be described. When transmitting the asynchronous communication packet, the control block 203 instructs the interface block 201 to perform the asynchronous communication by adding the asynchronous communication data and the receiving node identifier which is the node identifier of the destination node. The interface block 201 creates and outputs an asynchronous packet based on the asynchronous data input from the control block 203, the receiving node identifier, and the like. Upon receiving the asynchronous packet, the interface block 201 outputs to the control block 203 the asynchronous data 503 and the transmission node identifier 602 of the packet whose reception node identifier 601 in the packet header 501 is equal to its own node identifier. The control block 203 performs necessary processing based on the input asynchronous data.

FIG. 7 is a block diagram of the control block 203. The command analysis block 701 interprets an operation command or the like sent from another node by a user operation or asynchronous communication, and instructs the communication management block 702 to start and end synchronous communication and asynchronous communication. In the communication management block 702, an instruction from the command analysis block 701 and information necessary for communication management sent from another node by asynchronous communication are input, and based on them, the interface block 201 is input.
And the video and audio signal processing block 202 to instruct the start and end of synchronous communication, transmission and reception of synchronous communication packets, and transmission and reception of asynchronous packets. Also, information necessary for communication management of other nodes is used as asynchronous data in the interface block 201.
At the same time, and at the same time, instruct to output the information by asynchronous communication.

The first invention will be described. The first invention relates to a procedure for starting and ending synchronous communication in the nodes A and B when the node B transmits synchronous communication on behalf of the node A when the node A transmits synchronous communication. . Switching of the transmission node using the conventional technique is performed in the following procedure. In order to stop the transmission of the node A while the node A is transmitting by the synchronous communication, the user operates the node A, and the user instructs the node A to stop the output. Upon receiving an instruction to stop the output from the user, the node A stops outputting the synchronous communication packet and outputs the CFM.
Release the channel number and bandwidth used for Next, the user instructs the node B to output with the channel number to be used. The node B acquires the designated channel number and its own band from the CFM, and starts transmission of synchronous communication. Thus, the user needs to operate both the node A and the node B. Also,
Both the node A and the node B need to perform asynchronous communication with the CFM, and the number of times of communication increases.

An embodiment of the first invention will be described. In this embodiment, when node A is transmitting synchronous communication using a default channel number which is a fixed channel number, node B transmits synchronous communication using the default channel number instead of node A. This is the case when starting. In this embodiment, the synchronous communication packet is output by adding the node identifier of the transmitting node to the synchronous communication packet so that the transmitting node of the synchronous communication packet can be specified only by receiving the synchronous communication packet. FIG. 8 shows an example of the format of the data area 303 in the synchronous communication packet of this embodiment. A transmission node identifier 1001 that is a node identifier of the transmission node is added to the data area 303. In this example, the synchronous communication data 1002 is added after the transmission node identifier 1001. This synchronous communication data 1002 is synchronous communication data input from the video / audio signal processing block 202 and output to the video / audio signal processing block 202.

A procedure for starting transmission of synchronous communication by the node B in this embodiment will be described.

The operation of the communication management block 702 in the control block 203 of the node B is shown in the flowchart of FIG. When the user instructs the node B to start transmission of synchronous communication by operating the node B or another node, the command is transmitted to the communication management block 702 through the command analysis block 701 in the control block 203 of the node B. The person's instructions are transmitted. When the communication management block 702 receives the user's instruction, in step 1101, it instructs the interface block 201 to receive a synchronization packet of the default channel number. Interface block
Upon receiving the synchronous communication packet of the default channel number, 201 detects the transmission node identifier 1001 added in the packet and notifies the communication management block 702 of the node identifier as a control block. Communication management block 702
Proceeds to step 1102 after executing step 1101. In step 1102, the transmission node identifier of the default channel number is input from the interface block 201, and it is recognized that the node A is transmitting synchronous communication with the default channel number, and the process proceeds to step 1103. In step 1103, the node A is sent to the interface block 201.
Is instructed to transmit an output stop request. The interface block 201 outputs an output stop request to the node A using an asynchronous communication packet in accordance with an instruction from the communication management block 702. The communication management block 702 proceeds to step 1104, and determines whether the band used by the node A has been received or an output stop rejection has been received. When the node A stops the output, the node A notifies the node B of the bandwidth used by the node A using the asynchronous communication, and when not stopping the output, notifies the stop rejection. When the interface block 201 of the node B receives the asynchronous packet including the information of the used band or the output stop rejection from the node A, the interface block 201 notifies the communication management block 702 of the information.

When the communication management block 702 of the node B is notified of the used band from the interface block 201, the process proceeds to step 1105. In step 1105, it is determined whether or not the notified band used by node A is equal to the band to be used by itself. If they are equal, the process proceeds to step 1106. In step 1106, the video and audio signal processing block 202 and the interface block 201 are instructed to output the synchronous communication data as a synchronous communication packet of the default channel number. In accordance with an instruction from the communication management block 702, the video signal processing block 202 outputs synchronous communication data to the interface block 201. Further, the interface block 201 outputs a synchronous communication packet in accordance with an instruction from the communication management block 702.

If the communication management block 702 determines in step 1105 that they are not equal, the process proceeds to step 1107, and the CFM
To the interface block 201 to request the interface block 201 to change the band used. The interface block 201 performs asynchronous communication with the CFM to change the band used. The interface block 201 reports to the communication management block 702 whether the used bandwidth has been changed. The communication management block 702 proceeds to step 1108, and determines whether the used bandwidth has been changed. If it cannot be changed, go to step 1110 and block the interface.
201 is instructed to release the default channel number and the band used by the node A to the CFM.
The interface block 201 sets the CF according to the instruction.
The default channel number and the band used by node A are released by performing asynchronous communication with M. If it is determined in step 1108 that the bandwidth has been changed, the flow advances to step 1109 to instruct the video / audio signal processing block 202 and the interface block 201 to output the synchronous communication data as a synchronous communication packet of the default channel number. In accordance with an instruction from the communication management block 702, the video signal processing block 202 outputs synchronous communication data to the interface block 201. Also, interface block 201
Outputs a synchronous communication packet in accordance with an instruction from the communication management block 702. Next, a procedure for terminating the transmission of the synchronous communication by the node A will be described. The operation of the communication management block 702 in the control block 203 of the node B is shown in FIG.
0 is shown in the flowchart. When the node A is transmitting synchronous communication, the communication management block 702 in the control block 203 of the node A monitors in step 1201 whether an output stop request has been received from another node. Upon receiving the asynchronous packet including the output stop request from the node B by asynchronous communication, the interface block 201 notifies the communication management block 702 that the output stop request has been received from the node B.

If the communication management block 702 determines in step 1201 that it has received the output stop request, it proceeds to step 1202 and determines whether output can be stopped.
Although this determination may be entrusted to the user, the determination may be made based on the presence or absence of a device that is inputting the audiovisual data output from the normal node A. For this purpose, a node that is inputting audiovisual data from another node needs to request the node that is outputting audiovisual data not to stop the output.

If it is determined in step 1202 that the output is not to be stopped, the flow advances to step 1205 to instruct the interface block 201 to notify the node B of the rejection of the output stop. According to the instruction of the communication management block 702, the interface block 201 notifies the node B of the output stop rejection using the asynchronous communication. In this case, the node A does not stop the output. If it is determined in step 1202 that the operation can be stopped, the process proceeds to step 1203, where the interface block 201 and the video / audio signal processing block 202
To end the synchronous communication. The interface block 201 stops outputting the synchronous communication packet according to the instruction of the communication management block 702. The video / audio signal processing block 202 transmits the synchronous communication data to the interface block 201 according to the instruction of the communication management block 702.
Terminate output to. Communication management block 702 is step 1
In step 204, the interface block 201 is instructed to notify the node B of the band used by the node A. The interface block 201 notifies the node B of the used bandwidth by asynchronous communication according to the instruction.

As described above, according to the present embodiment, the user operates the node B only to switch from the node A to the node B.
The transmission nodes can be switched to each other. If the bandwidths used by the nodes A and B are equal, the nodes A and B
There is no need to communicate with the FM and the number of communications can be reduced.

Further, in this embodiment, the node B needs to specify the transmitting node of the default channel number, but the node B receives the synchronous communication packet of the default channel number, and the transmitting node identifier 1001 in the synchronous communication packet. Is detected, the transmitting node can be specified. That is, there is no need for the user to check the channel number to identify the transmitting node and notify the node B of the channel number.

Next, in the second invention, the node A
To switch the transmission node of the synchronous communication. In the first invention, when the node B transmits synchronous communication on behalf of the node A, the node B transmits an output stop request to the node A. If the node A determines that the output is not stopped, the node A notifies the node B of the refusal to stop the output and continues the output. In such a case, according to the first invention, if the user forcibly switches the transmission node from the node A to the node B, the user forcibly stops the output of the node A, To output. When the user instructs the output stop, the node A outputs CF.
M must be asynchronously communicated to release the default channel number and used bandwidth. Also, the node B needs to perform asynchronous communication with the CFM in accordance with a user's instruction to acquire a default channel number and a band used by the node B. When the node A notifies the node B of the refusal to stop the output, the user must operate both the node A and the node B, and both the nodes A and B are asynchronous with the CFM. Communication was needed.

An embodiment of the second invention will be described. A procedure for starting transmission of synchronous communication by the node B in this embodiment will be described. The operation of the communication management block 702 in the control block 203 of the node B is shown in the flowchart of FIG. This embodiment is different from the first invention in step 1104.
Is an operation when it is determined that the output stop rejection has been received from the node A. In the present embodiment, the communication management block 70
When it is determined in step 1104 that the output stop rejection has been received, the process proceeds to step 1301. In step 1301, it is determined whether the output of the node A is forcibly stopped. This determination is made by the user, and the command analysis block 70
The communication management block 702 is notified through 1.

If it is determined in step 1301 that the termination is not forcibly terminated, the output using the default channel number of the node B is not performed. If it is determined in step 1301 that the communication is to be forcibly terminated, the communication management block 702 proceeds to step 1302. In step 1302,
The communication management block 702 instructs the interface block 201 to transmit an output stop command to the node A. The interface block 201 is a communication management block 7
According to the instruction of 02, an output stop command is transmitted to the node A by asynchronous communication. The output stop command must be transmitted within a predetermined time after receiving the output stop rejection.
When receiving the output stop command, the node A stops the output and notifies the node B of the band used by the node A. The interface block 201 of the node B receives the asynchronous packet including the used band from the node A, and notifies the communication management block 702 of the node B of the used band. After performing Step 1302, the communication management block 702 proceeds to Step 1104. In step 1104, since the used band has been received from the node A, the process proceeds to step 1105, where the same operation as in the first invention is performed.

Next, a procedure for terminating the transmission of the synchronous communication by the node A in the embodiment of the second invention will be described.
The operation of the communication management block 702 of the node A is shown in the flowchart of FIG. This embodiment is different from the first invention in the operation after executing step 1205 in the first invention. In step 1205, the communication management block 702 of the node A instructs the interface block 201 to notify the node B of the rejection of the output. According to the instruction of the communication management block 702, the interface block 201 notifies the node B of the rejection of the output stop using asynchronous communication. The communication management block 702 includes a step 1401
To monitor for a predetermined time whether an output stop command has been received from the node B.

If the node B receives the output stop rejection from the node A and determines that the output of the node A is to be forcibly stopped, the output to the node A is performed within a predetermined time after receiving the output stop rejection. Send a stop command. The interface block 201 of the node A receives the asynchronous packet including the output stop command from the node B, and notifies the communication management block 702 that the communication stop command has been received from the node B. The communication management block 702 determines in step 1401 that an output stop command has been received, and proceeds to step 1203.
The operation after step 1203 is the same as in the first invention. When the node B determines that the output of the node A is not stopped, the node B does not receive the output stop command within a predetermined time.
The communication management block 702 determines that the output stop command has not been received in step 1401, and the transmission of the synchronous communication of the node A continues.

As described above, according to the second aspect, the node A
When switching the synchronous communication transmitting node from the to the node B,
Even when the node A rejects the node B output stop request, the user can stop the node A output only by operating the node B without operating the node A.

[0036]

According to the first aspect of the present invention, the outputting node does not release the channel number and the band, the node outputting later does not need to acquire the channel number, and if the used band is the same, the band is renewed. There is no need to secure. As described above, the first invention has an effect that the procedure for switching the transmission node is very simple.

Further, in the second invention, even if the output node in the first invention does not stop the output in spite of receiving the output stop request, only the node that outputs later is used. Is operated by the user, the output of the node being output can be stopped, and the transmission node can be switched, which has the effect of reducing the burden on the user.

[Brief description of the drawings]

FIG. 1 is a diagram showing a connection example when a plurality of audiovisual devices are connected using P1394.

FIG. 2 is a block diagram of the inside of the audiovisual apparatus.

FIG. 3 is a format diagram of a synchronous communication packet defined in P1394.

FIG. 4 is a format diagram of a packet header of a synchronous communication packet specified in P1394.

FIG. 5 is a format diagram of an asynchronous communication packet specified in P1394.

FIG. 6 is a format diagram of a packet header of an asynchronous communication packet specified in P1394.

FIG. 7 is a block diagram of a control block according to the present invention.

FIG. 8 is a format diagram of a data area in a synchronous communication packet according to the first invention and the second invention;

FIG. 9 is a flowchart of an operation of a communication management block when starting transmission according to the first invention;

FIG. 10 is a flowchart of the operation of the communication management block when ending transmission according to the first invention;

FIG. 11 is a flowchart of an operation of a communication management block when starting transmission according to the second invention;

FIG. 12 is a flowchart of the operation of the communication management block when ending transmission according to the second invention;

[Explanation of symbols]

101 Video and audio equipment 105 Cable used in P1394 201 Interface block in the present invention 202 Video signal processing block in the present invention 203 Control block in the present invention 301 Packet header of synchronous communication packet in P1394 302 Header C of synchronous communication packet in P1394
RC 303 Data area of synchronous communication packet in P1394 304 CRC for data data of synchronous communication packet in P1394 401 Channel number added to synchronous communication packet in P1394 501 Packet header of asynchronous communication packet in P1394 502 Header of asynchronous communication packet in P1394 CRC 503 Data area of asynchronous communication packet in P1394 504 CRC for data data of asynchronous communication packet in P1394 601 Receiving node identifier added to asynchronous communication packet in P1394 602 Transmission node identifier added to asynchronous communication packet in P1394 701 Command management block according to the present invention 702 Communication management block according to the present invention

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takuya Nishimura 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. Inside the corporation

Claims (2)

[Claims] At least a first data transmission device for transmitting synchronous communication data using a bus capable of transmitting synchronous communication data of a plurality of channels by adding a channel number to the data as a channel identifier, and a second data transmission device. A second data transmission device in a data transmission system having the data transmission device, wherein the first data transmission device that is a transmission node is identified by a node identifier that identifies the transmission node; Means for transmitting an output stop request to the transmission device; means for transmitting synchronous communication data using the channel used by the first data transmission device; and the first data transmission device Adds the node identifier to the synchronous communication data and outputs the same while using the channel used by the first data transmission device. When the second data transmission device outputs synchronous communication data using the same channel as the number, the second data transmission device specifies the first data transmission device that is a transmission node by the node identifier. And transmitting an output stop request to the first data transmission device, and when the first data transmission device acknowledges the output stop request, the first data transmission device is using the output stop request. A data transmission device for transmitting synchronous communication data using a channel as it is. 2. At least a first data transmission device for transmitting synchronous communication data using a bus capable of transmitting synchronous communication data of a plurality of channels by adding a channel number to the data as a channel identifier, and a second data transmission device. A data transmission method performed in a second data transmission device in a data transmission system having a data transmission device, wherein the first data transmission device adds the node identifier to synchronous communication data and outputs the data. When the second data transmission device outputs the synchronous communication data using the same channel number as the channel number used by the first data transmission device, the second data transmission device transmits the synchronous communication data using the node identifier. The first data transmission device, which is a node, is specified and output to the first data transmission device. Transmitting a stop request, and transmitting the synchronous communication data using the channel used by the first data transmission device as it is when the first data transmission device acknowledges the output stop request. A data transmission method characterized by the above-mentioned.