JP3379522B2 - Data transmission device and 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 when transmitting data such as video signals and audio signals that require real-time processing between a plurality of devices.

[0002]

2. Description of the Related Art Development of devices for transmitting video signals and audio signals through digital transmission lines is in progress. In order to transmit a video signal or an audio signal as a digital signal, it is necessary to perform transmission / reception in synchronization with the processing speed of the equipment, and thus a transmission path capable of synchronous communication is required. Further, considering that the transmission signal from one device is received by a plurality of devices and is transmitted bidirectionally by one transmission path, it is considered that the bus connection is desirable.

Currently IEEE (THE INSTITUTE OF ELECTRI
CAL AND ELECTRINIC ENGINEERS, INC) P13
A next-generation high-speed serial bus called 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 / receiving a synchronous communication packet every 125 μsec (hereinafter referred to as a cycle).

Next, a method of managing the synchronous communication of P1394 will be briefly described. In P1394, the node identifier of each device is automatically assigned so that the user does not need to set the node identifier for each device with a switch or the like, and 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 the device (hereinafter referred to as a node) changes (for example, when the number of connected nodes changes due to the removal / insertion of a cable).

In P1394, a maximum of 3 in one cycle
Two synchronous communication packets can be sent. Therefore, in order to identify the synchronous communication packet, any channel number from 1 to 32 is added to each synchronous communication packet. In addition, in order to perform synchronous communication of multiple channels,
One of the nodes connected to the bus manages synchronous communication. This node will be referred to as CFM hereinafter. C
The FM manages the channel number used for synchronous communication and the remaining band that can be used for synchronous communication. In order to perform the synchronous communication, it is necessary to secure the channel number and the used band that the CFM wants to use. Note that 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
It is performed using the time during which synchronous communication is not performed within the cycle.

[0006]

First, the problem to be solved by the present invention will be described. In P1394, synchronous communication data of a plurality of channels can be output within one cycle. Therefore, the receiving node needs to specify the channel number of the synchronous communication data to be received.
As one of the methods for specifying the channel number of the synchronous communication data to be received by the receiving node, there is a method in which the user instructs the receiving node to receive the channel number. However, this method has a problem in that the user has to check the channel number of the synchronous communication data to be received and give an instruction to the receiving node, which imposes a heavy burden on the user.

[0007]

The present invention newly proposes the following method as means for solving the above problems. A data transmission method for transmitting the synchronous communication data by using a bus capable of transmitting the synchronous communication data of a plurality of channels by adding a channel number as a channel identifier to the data, the channel being used for transmitting the data. Unless a number is specified, the transmitting node acquires a predetermined default channel number and a use band necessary for transmitting the synchronous communication data, and uses the default channel number and the use band to perform the synchronous communication data. And the receiving node receives the synchronous communication data of the default channel number.

In the present invention, the channel number used by the audiovisual equipment is fixed, and unless the channel number is specified from the outside, the default channel number which is the fixed channel number is used for transmission and reception. In other words, the receiving node may always receive the synchronous communication data of the default channel number when not instructed from the outside. Therefore, according to the present invention, it is not necessary for the user to indicate the channel number of the reception channel to the reception node when performing synchronous communication.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to Examples. The present invention relates to a data transmission method for transmitting synchronous communication data such as audiovisual data using a protocol called P1394 currently under discussion in IEEE. FIG. 1 shows a connection example when a plurality of nodes are connected. FIG. 1 is an example in which four audiovisual devices are connected as a plurality of nodes. Audiovisual equipment 101, 102, 10
The cables 3 and 104 are connected by a cable 105. P13
The cable used in 94 is a cable having the shape described on pages 52 to 54 of the reference.

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

In P1394, when transmitting synchronous communication data, synchronous communication packets are used for transmission. FIG. 3 shows the format of the 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 / absence of a transmission error in the packet header 301, and a 4-byte header for checking the presence / absence of a transmission error in the data area 303 and the data area 303. It consists of a byte data CRC 304.
FIG. 4 shows the format of the packet header 301. The channel number 401 is included in the packet header 301. In P1394, nodes such as a plurality of audiovisual equipments can transmit a plurality of synchronous communication packets in a time division manner 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 the synchronous communication data, the control block 203 instructs the audiovisual signal processing block 202 to output the synchronous communication data such as the audiovisual data. The audiovisual signal processing block 202 outputs the 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 with information such as the channel number to be used. Interface block
In accordance with an instruction from the control block 203, the 201 packetizes the synchronous communication data from the audiovisual signal processing block 202 into the data area 303 of FIG. 3 in the packet format of FIG. The interface block 201 outputs the synchronous communication packet to another node (audiovisual device).

When receiving the 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 whether the packet is the synchronous communication packet of the channel number designated by the packet header of the synchronous communication packet. If the designated channel number, the data area 30 from the synchronous communication packet of FIG.
The synchronous communication data of 3 is output to the audiovisual signal processing block 202. The control block 203 is the audiovisual signal processing block 2
Instructs 02 to input synchronous communication data. The audiovisual signal processing block 202 inputs 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 a time division manner within the same cycle. That is, multiple nodes can apparently simultaneously perform multiple synchronous communications. Each synchronous communication must be performed by securing a band corresponding to the internal processing speed of each node. Since there is a limit to the bandwidth that can be transmitted, it is necessary to manage the bandwidth used by each node. Further, a channel number is added in the synchronous communication packet in order to identify each synchronous communication packet for performing synchronous communication of a plurality of channels. As the channel number, a natural number from 1 to 32 can be used in P1394. When a plurality of nodes output synchronous communication packets, it is necessary to manage the channel numbers used by the respective 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 entire configuration by CFM (C
onfiguration Manager) to centrally manage bandwidth and channel numbers. A node that performs synchronous communication such as an audiovisual device must acquire the band and channel number used by itself from the CFM before performing synchronous communication.

Communication other than synchronous communication, including communication for acquiring the band and channel number, is performed by asynchronous communication using asynchronous communication packets. Asynchronous communication is performed by using idle time in the cycle after synchronous communication is completed in one cycle. FIG. 5 shows the format of an asynchronous communication packet defined by P1394. The asynchronous communication packet includes a 16-byte packet header 501, a 4-byte header CRC 302 for checking whether or not there is a transmission error in the packet header 501, and a 4-byte for checking whether or not there is a transmission error between the asynchronous data 503 and the asynchronous data. Of the data CRC 504. Packet header 5
In 01, as shown in FIG. 6, a receiving node identifier 601 which is a node identifier of a destination node transmitting an asynchronous packet
And a transmission node identifier 602, which is its own node identifier, are added. Receiving node identifier in packet header 60
1 and the transmitting node identifier 602 are each represented by 2 bytes. The receiving node can specify the asynchronous packet that it should receive 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 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 an asynchronous communication packet, the control block 203 instructs the interface block 201 to perform asynchronous communication with the asynchronous communication data and the receiving node identifier which is the node identifier of the destination node. The interface block 201 creates an asynchronous packet from the asynchronous data input from the control block 203, the receiving node identifier, etc., and outputs it. Upon receiving the asynchronous packet, the interface block 201 outputs to the control block 203 the asynchronous data 503 and the transmitting node identifier 602 of the packet in which the receiving 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's 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, the command from the command analysis block 701 and the information necessary for communication management sent from other nodes by asynchronous communication are input, and the interface block 201 is input based on them.
And instructing the audiovisual signal processing block 202 to start and end synchronous communication, transmit and receive synchronous communication packets, and transmit and receive asynchronous packets. In addition, the information necessary for communication management of other nodes is treated as asynchronous data by the interface block 201.
And output the information at the same time by asynchronous communication.

An embodiment of the present invention will be described. In order to perform synchronous communication transmission using the P1394 protocol by the conventional method, the transmitting node selects a channel number that is not in use from 1 to 32 and adds the channel number to the packet header in the synchronous communication packet. And send. At the same time, the transmitting node needs to indicate to the user which channel number the channel is transmitting on. On the receiving side,
Since a plurality of synchronous communication packets may be output, the user needs to instruct the receiving node of the channel number of the synchronous communication packet to be received.
As described above, in order to transmit / receive the synchronous communication packet by the conventional technique, the user needs to perform an operation to match the channel numbers used by the transmitting node and the receiving node, which causes a problem that the burden on the user is heavy. . In the first aspect of the invention, unless a channel number to be used is designated by another node or a user, the default channel number which is a fixed channel number is used for transmission and reception.

A procedure for the transmitting node to start transmitting synchronous communication according to the present invention will be described. The user instructs the audiovisual device of the transmitting node to output audiovisual data. This instruction is input to the command analysis block 701 of the control block 203, the information that the output of synchronous communication data is started with the default channel number is extracted from the instruction, and these pieces of information are input to the communication management block 702. The communication management block 702 controls to start output of synchronous communication data with the default channel number.

The operation of the communication management block 702 of the transmitting node is shown in the flowchart of FIG. Command analysis block
When the 701 instructs to output the synchronous communication data with the default channel number, the communication management block 702 executes the step 8
Go to 01. Interface block 2 in step 801
Instruct 01 to obtain the default channel number and band to be used from CFM. The interface block 201 performs asynchronous communication with the CFM based on the instruction and acquires the band and the default channel number. The interface block 201 outputs to the communication management block 702 in the control block 203 whether the default channel number and the used band have been acquired. The communication management block 702 executes step 801 and then proceeds to step 802. Step 80
In step 2, it is judged from the information input from the interface block 201 whether or not the default channel number and used band have been acquired. If it can be acquired, the process proceeds to step 803. In step 803, the video signal processing block 202 is instructed to output synchronous communication data such as audiovisual data to the interface block 201. The audiovisual signal processing block 202 outputs the synchronous communication data to the interface block 201. Further, in step 803, the communication management block 702 instructs the interface block 201 to output the synchronous communication data input from the audiovisual signal processing block 202 in a synchronous communication packet using the default channel number. . The interface block 201 outputs the synchronous communication packet according to the instruction from the communication management block 702.

Next, a procedure for the receiving node to start receiving the synchronous communication according to the present invention will be described. The user instructs the audiovisual equipment of the receiving node to input audiovisual data. This instruction is input to the command analysis block 701 of the control block 203, and the information that the input of synchronous communication data is started with the default channel number is extracted from the instruction, and this information is input to the communication management block 702. The communication management block 702 performs control for starting the input of synchronous communication data with the default channel number.

The operation of the communication management block of the receiving node is shown in the flowchart of FIG. Command analysis block 701
When instructed to input the synchronous communication data with the default channel number, the communication management block 702 proceeds to step 901. In step 901, the communication management block 702
The interface block 201 is instructed to receive the synchronous communication packet of the default channel number. According to the instruction from the communication management block 702, the interface block 201 receives the synchronous communication packet to which the default channel number is added, and outputs the synchronous communication data to the audiovisual signal processing block 202. In step 901, the communication management block 702 inputs the synchronous communication data from the interface block 202 to the audiovisual signal processing block 202, and instructs the audiovisual signal processing block 202 to perform signal processing. The audiovisual signal processing block 202 inputs the synchronous communication data from the interface block 202 according to the instruction from the communication management block 702, and performs a predetermined signal processing.

As described above, according to the present invention, the user can perform the synchronous communication by only instructing the output and the input to the transmitting node and the receiving node, and the channel number used by the user can be set to the receiving node. You do n’t have to tell
This has the effect of reducing the burden on the user.

[0024]

According to the present invention, the transmitting node may always output the synchronous data with the fixed default channel number, and the receiving node may always receive the synchronous communication data with the default channel number. That is, there is no need to externally instruct the transmitting / receiving node about the channel number such as the user. Therefore, the first invention has the effect of reducing the burden on the user. Further, since communication relating to the channel number used between the transmitting node and the receiving node becomes unnecessary, there is an effect that the number of communications is reduced and the transmission / reception start procedure is simplified.

[Brief description of 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 equipment.

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 by 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 the operation of the communication management block when starting transmission according to the present invention.

FIG. 9 is a flowchart of the operation of the communication management block when starting reception according to the present invention.

[Explanation of symbols]

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

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor ▲ Hama ▼ Shinji I, 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-7-183933 (JP, A) Kaihei 7-222263 (JP, A) JP 2001-211187 (JP, A) Patent 3152055 (JP, B2) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04L 12/28-12 / 46

Claims (2)

(57) [Claims] 1. At least one data transmitter for transmitting the synchronous communication data using a bus capable of transmitting the synchronous communication data of a plurality of channels by adding a channel number as a channel identifier to the data, and data reception. A data transmission device in a data transmission system having a device, and obtains a predetermined default channel number and a band used for transmitting the synchronous communication data unless a channel number used for data transmission is specified. Acquiring means, and a transmitting means for transmitting the synchronous communication data by using the default channel number and the used band, wherein the data receiving device receives the synchronous communication data of the default channel number. A data transmission device characterized by: 2. At least one data transmitter for transmitting the synchronous communication data using a bus capable of transmitting the synchronous communication data of a plurality of channels by adding a channel number to the data as a channel identifier, and data reception. A data transmission method in a data transmission device in a data transmission system having a device, which is required to transmit a predetermined default channel number and the synchronous communication data unless a channel number used for data transmission is specified. An effective bandwidth is acquired, and the synchronous communication data is transmitted using the default channel number and the used band, the data receiving device receives the synchronous communication data having the default channel number. How to send data.