JP3152233B2 - Data transmission method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission method used for transmitting data requiring real-time processing, such as a video signal and an audio signal, 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. Therefore, a transmission path capable of synchronous communication is required. 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 for identification of the synchronous communication packet. Also, in order to perform synchronous communication on multiple channels,
One of the nodes connected to the bus manages synchronous communication. 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. 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 node A designates a channel number to another node B to output synchronous communication data, the node A sends an output request to the node B with an output channel number. Upon receiving the output request, the node B acquires the designated channel number and band and outputs the acquired channel number and band. However, if the node B cannot acquire the channel number or the band,
Is notified that the band or channel number could not be obtained. The node A sends an output request to the node B by designating another channel number. As described above, when the node B cannot acquire the channel number or the band, the node A and the node B have a problem that the number of communications increases and the processing becomes complicated.

[0007]

The present invention newly proposes the following method as means for solving the above-mentioned problems. Channel number as data for channel identifier
Synchronous communication data of multiple channels by adding
The synchronous communication data using a bus capable of transmitting
A data transmission method for transmitting data, comprising: a first node;
Commands the second node to output synchronous data.
The first node uses the second node.
Get the channel number and bandwidth to use and output at least
Send the command and the channel number to use, and
The second node uses the received channel number
Data transmission characterized by starting transmission of synchronous data
It is a sending method. In the present invention, a node that instructs output acquires a channel and a band for a node that actually outputs, and then transmits an output request to the node that actually outputs. Therefore, according to the present invention, since the node that actually outputs does not obtain the channel and the band, the node between the node that instructs the output and the node that actually outputs the signal for the case where the channel or the band cannot be obtained. No communication occurs.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. 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 / audio device, taking the video / 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 / audio signal processing block 202 to output synchronous communication data such as video / 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.

The communication other than the synchronous communication including the communication for obtaining the band and the channel number is performed by the asynchronous communication using the asynchronous communication packet. 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 shows 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 present invention will be specifically described. The present embodiment relates to a case where the node A instructs the node B to transmit a synchronous communication by designating a channel number to be used. When the node A designates the channel number to be used and instructs the node B to transmit synchronous communication, the node B
Performs asynchronous communication with the CFM to obtain the specified channel number and the band to be used. When the node B can acquire the band and the channel number, the node B starts the output as it is. For example, when the node B cannot acquire the channel number specified by the node A, Must be requested from the node A, and the number of communications between the node A and the node B increases.

A procedure when the node A in this embodiment designates a channel number and issues an output command to the node B will be described. By operating the node A, the user instructs the node A to issue an output command to the node B. The user's instruction is transmitted to the communication management block 702 via the command analysis block 701. Node A is Node B
FIG. 8 is a flowchart showing the operation of the communication management block 702 of the node A when a channel number is designated for the node A.

In step 1501, the communication management block 702 instructs the interface block 201 to acquire a channel number other than the default channel number, which is a fixed channel number, and a band to be used.
Proceed to step 1502. Interface block 201
Performs asynchronous communication with the CFM according to the instruction of the communication management block 702, and obtains one of unused channel numbers other than the default channel number and a band to be used.
The interface block 201 reports the acquired channel number to the communication management block 702. The communication management block 702 determines in step 1502 whether the channel number and the band have been acquired. If it is determined in step 1502 that the channel number and the band have been acquired, the process proceeds to step 1503. In step 1503, the communication management block 702 transmits an output command so that the node B starts output with the acquired channel number,
An instruction is given to the interface block 201. The interface block 201 transmits an output command and a channel number to be used to the node B using asynchronous communication according to the instruction of the communication management block 702.

Next, in the present embodiment, the node B is the node A
A procedure for starting transmission of synchronous communication by specifying a channel number will be described. The interface block 201 of the node B receives the output command and the asynchronous packet including the channel number to be used from the node B. The presence or absence of the output command and the channel number to be used are transmitted to the communication management block 702 of the node B.

FIG . 9 is a flowchart illustrating the operation of the communication management block 702 of the node B. Communication management block 70
2 monitors the presence or absence of an output instruction in step 1601,
When notified that the output stop command has been received from the interface block 201, the process proceeds to step 1602. In step 1602, the communication management block 702 instructs the video / audio signal processing block 202 to output synchronous communication data to the interface block 201. Further, the communication management block 702 instructs the interface block 201 to transmit synchronous communication using the channel number specified by the node A. Video signal processing block 20
2 outputs synchronous communication data to the interface block 201 in accordance with an instruction from the communication management block 702. The interface block 201 transmits the synchronous communication data input from the video signal processing block 202 using the synchronous communication packet of the channel number designated by the node A according to the instruction from the communication management block 702.

As described above, according to the present embodiment, the node that issues the output command (the node A in the present embodiment) acquires the band and the channel number to be used, and attaches the acquired channel number to the node B. Issue an output instruction. Therefore, when the channel number and the bandwidth cannot be acquired, the asynchronous communication between the nodes A and B does not occur.

In this embodiment, when a channel number is specified for another node, a number other than the default channel number is obtained. Thereby, nodes other than the node A and the node B can perform synchronous communication using the default channel number.

[0024]

According to the present invention, the person who issues an output command issues an output command by designating the acquired channel number to another node after obtaining the channel number and bandwidth. That is, if the channel number and the bandwidth cannot be obtained, no communication occurs between the node that issues the output command and the node that receives the command. Therefore, the present invention has the effect of simplifying the procedure for instructing another node to output.

[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 flowchart of an operation of a communication management block when instructing another node to transmit synchronous communication according to the present invention;

FIG. 9 is a flowchart of an operation of a communication management block when another node instructs transmission of synchronous communication according to the present 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 701 702 Command analysis block according to the present invention

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor ▲ Hama ▼ Shinji I. 1006 Kazuma, Kazuma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (56) References JP-A-63-107239 (JP, A) Kaihei 7-222263 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H04L 12/28 JICST file (JOIS)

Claims (1)

(57) [Claims] 1. A channel number as a channel identifier.
Multi-channel synchronization by appending
Using a bus capable of transmitting communication data.
Data transmission method for transmitting initial communication data, wherein a first node transmits synchronous data to a second node.
In commanding the output, the first node uses the channel used by the second node.
Get channel number and bandwidth, and use at least output command
And the second node uses the received channel number.
Characterized by starting transmission of synchronous data by
Transmission method.