JP3690409B2 - Communication system and communication control method - Google Patents

Description

The present invention relates to a communication system in which a plurality of electronic devices are connected via a bus in which information signals and control signals are mixed and can be communicated in packets, and a communication control method used in the communication system .

  Conventionally, for example, D2B (Domestic Digital) is a communication system in which AV equipment such as a video tape recorder (hereinafter referred to as VTR) and a television receiver (hereinafter referred to as TV) is connected by a digital communication line and AV signals are transmitted in packets. A communication system using Bus) has been considered.

  First, an example of such a communication system will be described with reference to FIG. This communication system includes a TV, a video camera (hereinafter referred to as CAM), a VTR-A, and a VTR-B as AV devices. The AV signal is connected between the CAM output plug P3 and the TV input plug P1, the VTR-A output plug P3 and the VTR-B input plug P1, and the TV output plug P3 and the VTR-A input plug P1. They are connected by AV signal lines L1, L2, L3 that can be transmitted only in the direction. The CAM and VTR-A, VTR-A and VTR-B, and TV and VTR-A are connected by control signal lines (buses) D1, D2, and D3 capable of transmitting control signals in both directions. Since each AV device has an input / output function for control signals and AV signals, for example, bi-directional transmission of control signals can be performed between the CAM and the TV or VTR-B, and from the CAM to the VTR-A or VTR-B. AV signals can be transmitted to

  FIG. 20 shows a main configuration of each AV device in the communication system of FIG. AV signal input / output plugs of each AV device are indicated by only numbers P1, P2, and P3 so as to be directly exposed to the outside from a functional unit called a switch box (SWBox), and other AV devices are connected by AV signal lines. Connected to the input / output plug. Further, the control signal line is bus-connected separately from the AV signal line from other AV devices, and commands such as connection control are transmitted and received. Furthermore, each AV device has a function unit that it originally has, for example, a VCR, a recording / playback deck and a tuner for selecting a received signal, and a TV, a monitor and an amplifier. Further, although not shown, an AVC (AV controller) that controls the operation of the entire AV device is provided. Hereinafter, these functional units are referred to as sub-devices in this specification.

  In the communication system configured as described above, two types of methods for performing control connection are considered. Hereinafter, these will be referred to as connection control method 1 and connection control method 2, and will be described in order.

  In connection control method 1, each AV device holds connection configuration information indicating in which direction of input / output to which plug of which partner AV device is connected for each plug by setting in advance by the user. Yes. As a result, when a connection control command is received, a sub-device that is the source of the AV signal is connected to an output plug that is likely to reach the destination, or an input plug with a specified number is appropriately selected. A suitable output plug is connected and passed through the AV device, and the command is transmitted to the AV device connected to the tip of the output plug. The purpose is achieved when the command reaches the sub-device in the specific AV device designated as the destination.

  At this time, since the command cannot be propagated to the non-bus compatible AV device via the control signal line, the plug number of the AV device connected thereto is directly designated. For example, when a non-bus compatible AV device is connected to the plug P2 of the VTR device B in FIG. 20, connection control to the non-bus compatible AV device is performed by designating the plug P2 of the VTR device B.

  Next, in connection control method 2, a central AV device (hereinafter referred to as an AV center) is connected to any numbered port of any partner AV device in each direction (In / Out) for each AV device plug. ) To manage all connection information. When receiving a command requesting AV signal connection via the control signal line, the command is transmitted to the target AV device via the control signal line. The target AV device receives this command and switches the input.

  At this time, it is possible to specify a sub-device by category (BS tuner, Hi8 deck, etc.) in the first connection request from the command master. However, the plug designation at the time of the connection request can be made only for the plug within the user who knows the structure.

  In the connection control method 1, the control signal line is congested by sequentially propagating commands to adjacent AV devices. In addition, there is a possibility of an infinite loop depending on the setting of the AV device intervening. Furthermore, in order to directly specify the plug number, it is necessary for the command master to know the configuration of the AV device that the command master wants to control and the connection configuration of the AV device of the entire system.

  Also, with the connection control method 2, even a simple connection with a partner connected to the end of its own plug cannot be realized without always requesting it from the AV center. In addition, although it can be specified by the category of the sub device at the time of the connection request, the plug specification can be performed only for the plug within one's own who knows the structure.

  Further, in either connection control method, when there is another AV device between the AV device that has requested connection and the target AV device, the AV is transmitted via all the AV devices existing between them. It is necessary to set signal input and output. Therefore, as the number of AV devices constituting the system increases, the number of AV devices that need to be set for input / output increases and the control becomes more complicated. For this reason, measures such as limiting the system configuration are required. Further, since the AV signal line can transmit a signal only when the power of the AV device is ON, it is necessary that the power of all the AV devices that pass through the AV signal line is ON.

An object of this invention is to provide the communication system which can solve the trouble which the prior arts as mentioned above have, and the communication control method utilized in this communication system .

In the present invention proposed to achieve the above-described object, a plurality of electronic devices to which a predetermined digital bus is connected perform bi-directional digital communication in a predetermined communication cycle. There is a start packet, a period for transmitting the synchronous communication packet is set following the cycle start packet, and after the transmission of the synchronous communication packet is completed, the period until the next cycle start packet is used for the transmission of the asynchronous communication packet. An information signal is transmitted as data of the synchronous communication packet, the synchronous communication packet includes channel number information regarding a channel transmitting the information signal, and enables transmission of a plurality of the synchronous communication packets in the communication cycle, A control signal is transmitted as data of an asynchronous communication packet, and the asynchronous communication packet is transmitted. In the communication system signal packet containing the address of the electronic apparatus of the transmission source and transmission destination of the control signal, the electronic device is a transmitting device that transmits the information signal on the digital bus, the channel number information to the information signal The information signal to which the channel number information is added is transmitted on the digital bus in the synchronous communication packet, and an arbitrary electronic device connected to the digital bus is set as the transmission source and the transmission device is set as a transmission destination. When the control signal requesting the output of the information signal is transmitted by the asynchronous communication packet, the information signal is transmitted by the synchronous communication packet, and the channel number added to the synchronous communication packet and the information A counter that represents the number of electronic devices that have requested output of signals is managed in association with information on the digital bus. A receiving device, which is an electronic device that receives a signal, receives the information signal by capturing the synchronous communication packet to which predetermined channel number information is added on the digital bus, and receives an arbitrary signal connected to the digital bus. When the electronic device requests the output of the information signal, the count value of the counter increases, and the electronic device that has requested the output of the information signal requests the output stop of the information signal requested by the electronic device. In this case, when the count value of the counter decreases and the count value of the counter becomes 0, the transmitting device stops outputting the information signal managed by the counter to the digital bus. is there.

Further, according to the present invention, a plurality of electronic devices to which a predetermined digital bus is connected perform bidirectional digital communication in a predetermined communication cycle. A cycle start packet is provided at the beginning of the communication cycle, and the cycle start packet is followed. A period for transmitting the synchronous communication packet is set, and after the transmission of the synchronous communication packet is completed, a period until the next cycle start packet is used for transmission of the asynchronous communication packet, and an information signal is used as data of the synchronous communication packet. The synchronous communication packet includes channel number information related to a channel transmitting the information signal, enables transmission of a plurality of the synchronous communication packets in the communication cycle, and transmits a control signal as data of the asynchronous communication packet. the asynchronous communication packet transmission source of the control signal and In the communication control method including the address of the electronic device of the signal destination, an electronic apparatus in which the transmitting device for transmitting information signals on the digital bus, and adds the channel number information to the information signal, adding the channel number information The information signal is transmitted on the digital bus by the synchronous communication packet, and the information is transmitted by the asynchronous communication packet having an arbitrary electronic device connected to the digital bus as the transmission source and the transmission device as a transmission destination. When a control signal requesting output of a signal is transmitted, the information signal is transmitted in the synchronous communication packet, and the channel number added to the synchronous communication packet and the electronic device requesting the output of the information signal Receiving device which is an electronic device that manages a counter representing a number in association with each other and receives an information signal on the digital bus The information signal is received by capturing the synchronous communication packet to which the predetermined channel number information is added on the digital bus, and an arbitrary electronic device connected to the digital bus requests the output of the information signal In this case, the count value of the counter is increased, and the electronic device that has requested the output of the information signal decreases the count value of the counter when the electronic device requested to stop the output of the information signal requested by the electronic device. When the count value of the counter reaches 0, the transmitting device stops outputting the information signal managed by the counter to the digital bus.

In the present invention , a receiving device, which is an electronic device that receives an information signal on a digital bus, receives an information signal by fetching a synchronous communication packet to which predetermined channel number information is added on the digital bus, and connects to the digital bus. When the requested electronic device requests the output of the information signal, the count value of the counter is increased, and the electronic device that requested the output of the information signal requests the output stop of the information signal requested by the electronic device. Is not used because the transmission device stops the output of the information signal managed by the counter to the digital bus when the count value of the counter is reduced to 0. You don't waste information signals on the bus. Therefore, the bus can be effectively used within a limited number of channels.

  [1] Communication system to which the present invention is applied [2] Signal input switching concept [3] Specific example [4] Signal input / output management concept [5] Specific This will be described in detail in the order of examples.

[1] Communication System to which the Present Invention is Applied FIG. 1 is a system configuration diagram showing an example of a configuration of a communication system to which the present invention is applied. This communication system includes CAM1, TV1, VTR1 to 4, and an editing machine (editing controller) as AV equipment. The CAM1 and the TV1, the TV1 and the VTR3, the VTR3 and the VTR1 and the editing machine, the VTR1 and the VTR2, and the editing machine and the VTR4 are connected by a P1394 serial bus. The P1394 serial bus can mix and transmit control signals and AV signals in both directions. Each device has a function of relaying control signals and AV signals on the P1394 serial bus.

  FIG. 2 is a block diagram showing a basic configuration of a VTR which is an example of an AV device in the communication system of FIG. In addition to the deck subdevice 1 and tuner subdevice 2, which are the basic blocks of the VTR, the operation unit 3 and display unit 4 which are user interfaces, and the microcomputer 5 which controls the overall operation of the VTR, this VTR also supports the P1394 serial bus A digital interface (hereinafter referred to as a digital I / F) 6 and a switch box sub device 7 for switching signals between a deck sub device 1-a tuner sub device 2-a digital I / F 6 are provided. When the AV device is a TV, a monitor subdevice and an amplifier subdevice are provided instead of the deck subdevice 1, and when the AV device is a CAM, a camera subdevice is provided instead of the tuner subdevice 2.

  For example, as shown in FIG. 3, the display unit 4 of each AV device is configured such that the names of all devices on the communication system are displayed as fluorescent tubes. By operating the key 3a of the operation unit 3, the AV unit is operated. The other party to send or receive the signal can be selected. Note that all devices on the communication system may be displayed simultaneously or sequentially. Also, only devices other than the user may be displayed. Furthermore, these operations can be performed using an infrared remote controller or a mouse. When the device is a TV, it can be displayed on the monitor subdevice. In addition, pictograms (icons) can be displayed instead of device names.

  In the communication system of FIG. 1, communication is performed in a predetermined communication cycle (for example, 125 μs) as shown in FIG. Then, both synchronous communication that performs continuous communication at a constant data rate, such as a digital video signal, and asynchronous communication that transmits connection control commands and the like irregularly as necessary can be performed.

  There is a cycle start packet CSP at the beginning of the communication cycle, followed by a period for transmitting a packet for synchronous communication. By assigning channel numbers 1, 2, 3,... N to each packet for synchronous communication, a plurality of synchronous communications can be performed. For example, if channel 1 is assigned to communication from CAM1 to VTR1, CAM1 transmits a synchronous communication packet with channel number 1 immediately after the cycle start packet CSP, VTR1 monitors the bus, and channel number 1 Communication is performed by fetching synchronous communication packets marked with. Furthermore, if channel 2 is assigned to communication from VTR3 to VTR4, communication from CAM1 to VTR1 and communication from VTR3 to VTR4 can be performed in parallel.

  Then, after the transmission of synchronous communication packets for all channels is completed, a period until the next cycle start packet CSP is used for asynchronous communication. Asynchronous communication packets (packets A and B in FIG. 4) have the physical and logical addresses of the transmitting device and the receiving device, and each node captures a packet with its own address.

[2] Concept of signal input switching FIG. 5 shows an example of a main configuration of an asynchronous communication packet used in a communication system to which the present invention is applied. In this figure, the master address is the logical address of the packet source, the slave address is the logical address of the destination, the frame type is the type of packet (command, response, inquiry, etc.), and SSSA / DADA is the subdevice address of the source or destination , OPC (opcode) and OPR (operand) are the contents of the command.

  Hereinafter, an example in which a playback image of CAM1 is recorded by VTR1 will be described with reference to FIG. 6 showing an input switching procedure and FIG. 7 showing a packet used in each procedure.

  First, the command master requests CAM1 “output to CH?” (A1). In response to this, CAM1 responds to the command master (output OK. Output to CH1) (A2). Next, the command master requests VTR1 to input “CH1”. (A3) Then, VTR1 responds to the command master as “CH1 input OK.” (A4) This completes the input switching process.

  Here, the command master is an AV device that first outputs a command, and becomes a command master depending on whether or not it has a function as a command master in advance and which AV device is used to select a communication partner. AV equipment changes (see specific examples below). The SW BOX (switch box) in the SSDA / DSDA of the packet means that the purpose of the command is input / output switching. Further, the input switching command in P1394 is temporarily called P1394 input switching. Further, Deck (deck) in the destination of the AV signal means a deck subdevice of CAM1.

[3] Specific Example (1) When CAM1 Playback Images are Recorded by VTR1 and VTR2 As described above, the display units of VTR1 and VTR2 are configured so that AV equipment on the communication system is displayed as a fluorescent tube. Therefore, the user can select the target CAM 1 as a communication partner (input partner) while watching this. In this way, when the user sets an operation mode using VTR1 and VTR2, VTR1 and VTR2 become command masters. The operation will be described below with reference to FIG. 8 showing the input switching procedure and FIG. 9 showing an example of the packet structure of the command used in each.

  First, the VTR 1 requests the CAM 1 “output to CH?” (B1). Next, CAM1 responds to VTR1 with “Output OK. Output to CH1” (B2). VTR1 inputs CH1 and starts recording.

  Next, similarly to the processing of VTR1, VTR2 requests CAM1 to “output to CH?” (B3). Next, in response to this, CAM1 answers to VTR2 “Output OK. Outputting to CH1” (B4). VTR2 also inputs CH1 and starts recording.

  Here, it has been described that VTR 1 first sends a command to CAM 1, and then VTR 2 sends a command to CAM 1, but actually these operations are performed independently.

(2) When recording the playback image of the VTR 3 with the VTR 4 using the editing machine In this case, the VTR 3 is selected as the output AV device using the display unit of the editing machine, and the VTR 4 is selected as the input AV device. In this case, the editing machine becomes the command master. The input switching procedure will be described below with reference to FIGS.

  First, the editing machine that is the command master requests the VTR 3 to “output to CH?” (C1). Next, in response to this, VTR3 outputs to CH2 because CH1 has already been used, and responds to the editing machine “output OK. Output to CH2” (C2). Next, the editing machine requests the VTR 4 to “input CH2” (C3). In response to this, the VTR 4 answers “CH2 input OK” to the editing machine (C4). The VTR 4 inputs CH2 and starts recording.

[4] Concept of signal input / output management Hereinafter, referring to FIG. 12 showing the input / output management procedure and FIG. 13 showing the packet used in each procedure, the playback image of CAM1 is recorded by VTR1, and then VTR1 interrupts the recording. An example of the case will be described.

  First, the command master requests CAM1 to “output to CH?” And holds the address of CAM1 (D1). Here, as the address, a product category-specific address (device logical address) is used instead of a node ID (device physical address) unique to the P1394 serial bus. This is because, for example, if another AV device unrelated to the dubbing is performed between predetermined AV devices, the bus is reset. At this time, since the system configuration changes, the node ID after reset also changes, but the product category address is held in the register of the AV device, so that the recording state can be protected.

  Next, CAM1 responds to the command master (output OK. Output to CH1), and adds 1 to the count value of the input device (D2). However, it is not necessary to hold the address of the command master that requested the output, and conversely, since there may be a plurality of input AV devices, it is difficult to retain all the addresses of the devices that requested the output. Thus, the command master holds information that CAM1 is outputting to CH1.

  Next, in response to this, the command master requests VTR1 “Input CH1” (D3). In this case as well, it is not necessary to hold the address, but since it is necessary to manage the number of counterpart devices requested to be input responsibly, the count value of the requested device is increased by one. However, when an input is requested, it is considered as a semi-output machine, and when an output is requested, it is considered as an output machine. Both the input request and output request count the input devices, but both can be made with a common structure.

  Next, the VTR 1 replies “CH 1 input OK” to the command master, and holds the address of the command master (D 4). Up to this point, the input / output setting is completed, and VTR1 starts recording the output of CAM1.

  Next, a case where the video recording is interrupted by the VTR 1 after a while will be described. First, VTR1 informs the command master that “CH1 input has been interrupted”. Then, the input is interrupted and the held address of the command master is cleared (D5). Here, Dummy (dummy) of the packet means interruption of the source CH1.

  Next, in response to this, the command master returns “CH1 input interruption OK” to the VTR 1 and decrements the counter number of the input device by 1 (D6). Therefore, the sum of the counters becomes 0, and it can be determined that there is no input device.

  Next, since it is understood from the address information stored in D1 and D2 that it is CAM1 that is outputting to CH1, it is informed to CAM1 that “CH1 input has been interrupted”. Further, since all the input devices that the user counts no longer exist, the address is cleared (D7).

  In response to this, CAM1 returns a “CH1 input interruption OK” response to the command master and decrements the count value of the input device by one. Here, since the count value is 1, the current count value is 0, and it is determined that there is no input device, and the AV signal is suspended from being placed on the bus (D8).

  Note that if the device that outputs the AV signal, instead of the input device, interrupts the signal output for some reason, the AV is read from the input side to the position (channel) where the packet is read out. Since it can be determined that the signal is not included, the input of the signal is voluntarily interrupted at that time.

  FIG. 14 shows the correspondence relationship regarding whether or not the address needs to be held when switching the input / output of signals in the command master and the slave device (AV device other than the command master).

  In this way, the present invention performs input / output management so that unused AV signals can be prevented from flowing unnecessarily to the bus and more AV signal processing can be performed within a limited number of channels. .

[5] Specific example (1) When recording the playback image of CAM1 with VTR1 and VTR2 and interrupting the input in the order of VTR1 and VTR2 In this case, as with [3] (1), both VTR1 and VTR2 Become a command master. The operation will be described below with reference to FIG. 15 showing the input / output management procedure and FIG. 16 showing an example of the packet structure of the command used in each.

  First, the VTR 1 requests the CAM 1 “output to CH?”. At the same time, the address of CAM1 is held (E1). Next, CAM1 responds to VTR1 “output OK. Output to CH1” and increments the count value of the number of input devices by 1 (E2). Therefore, VTR1 inputs CH1 and starts recording. Here, VTR1 also holds information that CAM1 is outputting to CH1.

  Next, similarly to the processing of VTR1, VTR2 requests CAM1 to “output to CH?” And holds the address of CAM1 (E3). Next, in response to this, CAM1 replies “Output OK. Outputting to CH1” to VTR2, and further increases the count value of the number of input devices by 1 (E4). As a result, the total number of input devices is 2. Here, VTR2 also holds information that CAM1 is outputting to CH1.

  Further, after a while, the VTR 1 informs the CAM 1 holding the address at E 1 that “CH 1 input has been interrupted”. Then, the held address of CAM1 and CH1 are cleared (E5). Next, in response to this, CAM1 replies “CH1 input interruption OK” to VTR1 and decrements the count value of the input device by 1 (E6). Although the total number of input devices is reduced to 1, CAM1 continues to output AV signals to CH1 because there is still one input device.

  Next, VTR2 also informs CAM1 who has remembered the address at E4 that "CH1 input has been interrupted". Here, the address of CAM1 and CH1 are cleared (E7). Next, in response to this, CAM1 responds to the VTR2 “CH1 input interruption OK”, and further decreases the count value of the input device by one. As a result, the number of counters of the input device becomes 0. Therefore, it is determined that all the input devices are gone, and the CAM 1 interrupts the flow of the AV signal to the bus (E8).

  When CAM1 interrupts the output of the AV signal for some reason, VTR1 and VTR2 determine that the AV signal is not output to CH1, and the input is interrupted by a timeout process.

(2) When a VTR3 playback image is monitored on the TV1 using an editing machine, and recorded on the VTR4, and then the input is interrupted in the order of VTR4 and TV1. In this case, the editing machine is the same as [3] (2) above Becomes the command master. Therefore, since it is known that data is exchanged between the VTR 3 and the VTR 4 and the TV 1, it is not necessary to select an input target device on the fluorescent tube display of the VTR or TV. The procedure will be described below with reference to FIGS.

  First, the editing machine that is the command master requests the VTR 3 to “output to CH?” And holds the address of the VTR 3 (F1). Next, in response to this, VTR 3 outputs CH 2 because CH 1 has already been used, and responds to the editing machine “output OK. Output to CH 2”, and increments the count value of the input device by one. The editing machine also holds information that the VTR 3 is outputting to CH2 (F2).

  Next, the editing machine requests TV 1 to “input CH2”, and increments the count value of the device that has requested input (F3). On the other hand, TV1 answers “CH2 input OK” to the editing machine and holds the address of the editing machine (F4). Next, the editing machine requests the VTR 4 to “input CH2”, and further increments the count value of the device that requested the input (F5). Therefore, the total number of input devices managed by the editing machine is two. On the other hand, the VTR 4 answers “CH2 input OK” to the editing machine and holds the address of the editing machine (F6).

  Thereafter, the VTR 4 informs the editing machine that has remembered the address at F6 that “CH2 input has been interrupted” and clears the address of the editing machine (F7). In response to this, the editing machine replies “CH2 input interruption OK” to the VTR 4 and decrements the count value of the device that requested the input by one. Accordingly, the total number of input requested devices managed by the editing machine is one. Since there is still one input device, the address of the VTR 3 is held as it is (F8).

  Next, TV 1 informs the editing machine that “CH2 input has been interrupted” (F9). The editing machine decrements the count value of the device that requested the input and the total becomes 0. Therefore, the editing machine determines that all the input devices managed by the editing machine no longer exist, and responds to TV 1 with “CH2 input interrupt OK” (F10). ) Informs the VTR 3 that holds the address that “CH2 input has been interrupted” and clears the address and CH2 (F11). On the other hand, the VTR 3 responds to the editing machine with “CH2 input interrupt OK” and decrements by 1 from the count value of the input device counted by the VTR 3. As a result, the sum of the count values becomes 0, and it can be determined that all the input devices are gone, so the VTR 3 interrupts the output of the AV signal to CH2 (F12).

  When VTR 3 interrupts output to CH 2 for some reason, VTR 4 can determine that an AV signal is not output on CH 2, and therefore interrupts input in a timeout process.

  Further, for example, even when VTR 3 starts outputting and requests TV 1 to “input CH 2”, and when V TR 4 requests “output” to VTR 3, in both cases the meaning of counting Therefore, the total number of input devices managed by VTR3 is 2, and when both TV1 and VTR4 are informed that “CH2 input has been interrupted.” The AV signal output to CH2 is interrupted.

  Although the P1394 serial bus is used here, any other bus can be used as long as it is a digital bus on which control lines and signal lines can be mixed. Further, in selecting an input target device, it is conceivable to display an OSD display such as a TV as well as a fluorescent tube display. Furthermore, the present invention can be applied not only to a system connected to an AV device but also to a system that communicates data by connecting a computer.

1 is a system configuration diagram showing an example of a configuration of a communication system to which the present invention is applied. FIG. 2 is a block diagram illustrating a basic configuration of a VTR that is an example of an AV device in the communication system of FIG. 1. It is a figure which shows an example of the display part of AV apparatus in the communication system of FIG. It is a figure which shows an example of the communication cycle in a P1394 serial bus. It is a figure which shows one example of the principal part structure of the asynchronous communication packet used with the communication system to which this invention is applied. It is a figure which shows the input switching procedure in the case of recording the reproduction image of CAM1 by VTR1. It is a figure which shows the structure of the packet used in the procedure of FIG. It is a figure which shows the input switching procedure in the case of recording the output of CAM1 by VTR1 and VTR2. It is a figure which shows the structure of the packet used in the procedure of FIG. It is a figure which shows the input switching procedure in the case of recording the output of VTR3 by VTR4 using an editing machine. It is a figure which shows the structure of the packet used in the procedure of FIG. It is a figure which shows the input / output management procedure in the case of recording the reproduction image of CAM1 by VTR1. It is a figure which shows an example of the packet structure used in the procedure of FIG. It is a figure which shows the correspondence regarding the presence or absence of the address holding at the time of the input / output of a command master and a slave apparatus. It is a figure which shows the input / output management procedure in the case of recording the reproduction image of CAM1 by VTR1 and VTR2, and VTR1 and VTR2 interrupting input after that. It is a figure which shows an example of the structure of the packet used in the procedure of FIG. It is a figure which shows the input / output management procedure in the case of recording the reproduction | regeneration image of VTR3 by VTR4 using an editing machine, and VTR4 interrupting input after that. It is a figure which shows an example of the structure of the packet used in the procedure of FIG. It is a figure which shows one example of a structure of the communication system which connects the conventional AV apparatus with a digital communication line, and transmits AV signal with a packet. It is a figure which shows the principal part structure of each AV apparatus in the communication system of FIG.

Explanation of symbols

  VTR1 to 4 Video tape recorder, TV1 Television receiver, CAM video camera, 1 deck subdevice, 2 tuner subdevice, 3 operation unit, 4 display unit, 5 microcomputer, 6 digital I / F, 7 switch box subdevice

Claims (2)

A plurality of electronic devices connected to a predetermined digital bus perform bi-directional digital communication in a predetermined communication cycle. A cycle start packet is present at the beginning of the communication cycle, and a synchronous communication packet is transmitted following the cycle start packet. After a period is set and the transmission of the synchronous communication packet is completed, a period until the next cycle start packet is used for transmission of an asynchronous communication packet, an information signal is transmitted as data of the synchronous communication packet, and the synchronous communication The packet includes channel number information related to a channel for transmitting the information signal, enables transmission of a plurality of the synchronous communication packets in the communication cycle, a control signal is transmitted as data of the asynchronous communication packet, and the asynchronous communication packet is source and destination of the electronic device of said control signal In a communication system including an address,
A transmitting device that is an electronic device that transmits an information signal on the digital bus adds the channel number information to the information signal, and the information signal to which the channel number information is added is transmitted on the digital bus in the synchronous communication packet. When a control signal for requesting output of the information signal is transmitted by the asynchronous communication packet having the transmission source as an arbitrary electronic device connected to the digital bus and the transmission device as a transmission destination The information signal is transmitted in the synchronous communication packet, and the channel number added to the synchronous communication packet is managed in association with a counter indicating the number of electronic devices that have requested the output of the information signal.
A receiving device that is an electronic device that receives an information signal on the digital bus receives the information signal by capturing the synchronous communication packet to which predetermined channel number information is added on the digital bus,
When any electronic device connected to the digital bus requests the output of the information signal, the count value of the counter increases,
When the electronic device requesting the output of the information signal requests the output stop of the information signal requested by the electronic device, the count value of the counter is decreased.
When the count value of the counter reaches 0, the transmitting device stops outputting the information signal managed by the counter to the digital bus.
A communication system characterized by the above. A plurality of electronic devices connected to a predetermined digital bus perform bi-directional digital communication in a predetermined communication cycle. A cycle start packet is present at the beginning of the communication cycle, and a synchronous communication packet is transmitted following the cycle start packet. After a period is set and the transmission of the synchronous communication packet is completed, a period until the next cycle start packet is used for transmission of an asynchronous communication packet, an information signal is transmitted as data of the synchronous communication packet, and the synchronous communication The packet includes channel number information related to a channel for transmitting the information signal, enables transmission of a plurality of the synchronous communication packets in the communication cycle, a control signal is transmitted as data of the asynchronous communication packet, and the asynchronous communication packet is source and destination of the electronic device of said control signal In the communication control method including the address,
A transmitting device that is an electronic device that transmits an information signal on the digital bus adds the channel number information to the information signal, and the information signal to which the channel number information is added is transmitted on the digital bus in the synchronous communication packet. When a control signal for requesting output of the information signal is transmitted by the asynchronous communication packet having the transmission source as an arbitrary electronic device connected to the digital bus and the transmission device as a transmission destination The information signal is transmitted in the synchronous communication packet, and the channel number added to the synchronous communication packet is managed in association with a counter indicating the number of electronic devices that have requested the output of the information signal.
A receiving device that is an electronic device that receives an information signal on the digital bus receives the information signal by capturing the synchronous communication packet to which predetermined channel number information is added on the digital bus,
When any electronic device connected to the digital bus requests the output of the information signal, the count value of the counter increases,
When the electronic device requesting the output of the information signal requests the output stop of the information signal requested by the electronic device, the count value of the counter is decreased.
When the count value of the counter reaches 0, the transmitting device stops outputting the information signal managed by the counter to the digital bus.
A communication control method characterized by the above .

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