JP3678244B2 - Electronic device and communication control method - Google Patents

Description

  The present invention relates to an electronic device and a communication control method used in a system in which a plurality of electronic devices are connected by a bus capable of mixing control signals and information signals and communication is performed between these electronic devices. The present invention relates to an electronic device and a communication control method that effectively use a bandwidth that is a shared resource of a bus.

  Conventionally, electronic devices such as a video tape recorder, a television receiver, a camera-integrated video tape recorder, and a computer are connected by a bus capable of mixing control signals and information signals, and these electronic devices (hereinafter referred to as “devices”). As a communication system that transmits and receives control signals and information signals between them, a communication system using a P1394 serial bus is considered.

  First, an example of such a communication system will be described with reference to FIG. This communication system includes devices A to E. The devices A and B, the devices B and C, the devices C and D, and the devices C and E are connected by a P1394 serial bus.

  In a communication system using a P1394 serial bus (hereinafter referred to as “bus”), communication is performed in a predetermined communication cycle (eg, 125 μs). And isochronous (hereinafter abbreviated as “Iso”) communication that continuously transmits information signals such as digital audio / video signals and asynchronous transmission (hereinafter referred to as control signals such as connection control commands) as required. Both communication can be performed.

  Management of the communication cycle in the bus is started when a device (hereinafter referred to as a “root node”) that is the root of the communication system sends a cycle start packet onto the bus. The root node is automatically determined by a method defined in the IEEE-P1394 specification when the bus is reset.

  FIG. 5 shows an example of a communication cycle. This example is a communication cycle viewed from a device that can first send an Iso packet to the bus after the cycle start packet is sent to the bus. In this figure, the cycle start packet sent by the root node onto the bus reaches the device after the first propagation delay time pro1. Upon receiving a cycle start packet, a device that intends to send an Iso packet on the bus waits for a predetermined time (Iso gap) and then requests the root node to use the bus. When a plurality of devices make a bus use request, the root node grants the bus use to the device that has requested the bus use the earliest. This is performed at the arbitration time of FIG.

  The device that has obtained permission to use the bus from the root node sends an Iso packet (Iso-1 in this figure) to the bus. At this time, a data prefix and a data end are respectively added before and after the Iso packet.

  A device that has not been granted permission to use the bus has completed reception within the second propagation delay time pro2 after the device that has received permission to use the bus has transmitted the Iso packet, and has received a predetermined Iso gap from the completion of the data end. Then, the bus request is again made to the root node. When permission to use the bus is obtained, an Iso packet (Iso-2 in this figure) is sent to the bus.

  In this way, the period from the completion of the arbitration and the transmission of the Iso packet to all the devices that intend to transmit the Iso packet on the bus is used for the communication of the Async packet.

  Here, the second propagation delay time pro2 is determined according to the time required for the packet to propagate from a certain device to the farthest device in the communication system. This time can be calculated by any device according to the procedure defined in the IEEE-P1394 specification when the communication system is configured and the bus is reset. However, this time varies depending on the device. So having all the information is a heavy burden. Therefore, in order to simplify the management calculation, it is practical to uniformly use the time required between the two most distant devices in the communication system. Further, since the arbitration time is determined according to the distance between each device and the root node, it is a unique value for each device. The Iso gap, data prefix, and data end are fixed values defined in the IEEE-P1394 specification.

  As shown in FIG. 5, the transmission of one Iso packet requires a maximum time from the Iso gap to the second propagation delay time pro2 (until it is transmitted between the most distant devices). Of this time, the other part of the Iso packet, that is, the total of the Iso gap, the data prefix, the data end, the arbitration time, and the second propagation delay time pro2 is called an overhead part. From the description of each time described above, it can be seen that this overhead varies depending on the connection configuration of the devices.

  A device that intends to send an Iso packet to the bus first secures a use channel and a band (time band) necessary for transmission. Therefore, an application is made to the Iso resource manager, which is a device that centrally manages the bus channel and bandwidth, for the channel and the required bandwidth. The Iso resource manager includes a channel register indicating the use state of each channel of the bus and a band register indicating the remaining capacity of the bus (hereinafter referred to as “remaining band”). A device that intends to send an Iso packet sends a write command (Compare & Swap command) for writing a channel and a band that it wants to use to these registers using an Async packet. If writing is successful, output to the bus is possible.

  Connection control for communicating Iso packets between devices is performed using a plug control register provided in each device. By writing information necessary for the transmission management of the Iso packet and information necessary for the transmission of the Iso packet in the plug control register, the connection control of the Iso packet can be performed from inside or outside the device.

  FIG. 6 shows the output plug control register. Here, when Valid Flag is set to 1, an Iso packet is transmitted to the channel set in Channel using the band indicated by Bandwidth at the transmission rate specified by Data Rate. When Valid Flag is cleared to 0, transmission stops. Connection Counter indicates the number of devices that input their output. The Unowned Connection Counter becomes 1 when the output of the Iso packet is started by itself. Among the information described above, Valid Flag, Unowned Connection Counter, and Connection Counter are information necessary for transmission management of Iso packets, and Channel, Data Rate, and Bandwidth are information necessary for transmission of Iso packets. The numbers given above each field are the number of bits of data.

  The input plug control register is configured in the same manner. When Valid Flag is set to 1, an Iso packet is received from the channel set in Channel. When Valid Flag is cleared to 0, reception stops.

  Next, a connection control procedure when the output of the device A is input to the device E by the control of the device C in the communication system configured as shown in FIG. 7 will be described with reference to FIG. In this case, for example, the device C is an editing controller, the devices A and E are video tape recorders, and the playback signal of the device A is recorded by the device E. In this communication system, the device B is an Iso resource manager.

  First, device C checks the type of information signal that device A outputs to the bus (procedure (1)). In this case, the type of information signal output by the device A is prepared by, for example, preparing a special register for the device A. Next, the channel necessary for the device A to output the Iso packet to the bus is written in the channel register of the device B (procedure (2)), and the time band necessary for the transmission of the Iso packet checked in the procedure (1). Is subtracted from the remaining bandwidth indicated in the bandwidth register of the device B (procedure (8)). As a result, a channel and a band necessary for the device A to output the Iso packet to the bus are secured.

  After securing the channel and bandwidth in this way, the information necessary for the above-described transmission management of the Iso packet and the transmission of the Iso packet to the output plug control register of the device A and the input plug control register of the device E are required. Write appropriate information (procedures (4) and (5)). As a result, the Iso packet output from the device A to the bus passes through the devices B and C and is input to the device E.

  Next, consider the case where the device is inserted into and removed from the communication system while the output of the device A is being input to the device E. In this case, since the connection configuration of the device changes, the overhead portion of the time band required for the device A to transmit the Iso packet changes. Therefore, device C adjusts the bandwidth for the changed overhead and subtracts a new transmission bandwidth from the remaining bandwidth indicated in the bandwidth register of device B (procedure (6)). Further, a new transmission band is written in the output plug control register of the device A (procedure (7)).

  Next, let us consider a case where the type of signal output by the device A changes in a state where the output of the device A is being input to the device E. In this case, the portion of the Iso packet in the time band necessary for the device A to transmit the Iso packet changes. Therefore, device A adjusts the bandwidth of the changed Iso packet and subtracts a new transmission bandwidth from the remaining transmission bandwidth indicated in the bandwidth register of device B (procedure (8)). In addition, write a new transmission band to your output plug control register (Procedure (9)).

In each procedure described above, a transaction composed of a Compare & Swap instruction and a Response defined in the IEEE-P1394 specification is used (however, the procedure (1) may be a Read instruction and a Response).
JP-A-8-340338

  However, in the connection control procedure, the device C knows the bandwidth for the overhead determined by the structure of the bus, confirms the type of information signal output from the device A by some control communication, knows the bandwidth for the data packet, You need to specify the sum of these.

At this time, if the structure of the communication system changes during output, the bandwidth adjustment for the overhead can be changed only by the device C that knows the initial setting.
When the type of information signal changes during output, only the device A can change the bandwidth adjustment for the data packet.

  In either case, in order to be able to be executed by another device, it is necessary to communicate control signals with the device A or C according to the purpose, which takes time. The information signal communication may be interrupted. In addition, the control procedure becomes complicated, making it difficult to develop an application using a plug control register.

  An object of this invention is to provide the electronic device and communication control method which can solve such a problem.

  In order to solve the above problems, an electronic device according to the present invention is an electronic device included in a communication system in which a plurality of electronic devices are connected via a bus capable of transmitting a control signal and an information signal mixedly. A register accessible from other electronic devices, and can be controlled to transmit the information signal by reading or writing to the register, and the register has a bandwidth required for transmitting the information signal. Are stored separately in a portion indicating a maximum value that can be taken by a packet constituting the information signal and a portion indicating a band for dealing with a delay generated when the packet is transmitted, and the information is stored. When releasing the band and channel necessary for signal transmission, the remaining band register and channel usage indicating the remaining band of the bus are also included in the communication system. A manager device having a channel register indicating the status, and updating the remaining bandwidth register so as to add the bandwidth necessary for the transmission from the remaining bandwidth, and the channel usage status according to the channel used for the transmission The channel register is updated so as to be changed, and the information signal is transmitted after a cycle start packet in each communication cycle.

  The communication control method according to the present invention is a communication control method used in a communication system in which a plurality of electronic devices are connected via a bus capable of transmitting a control signal and an information signal mixedly. The device has a register that can be accessed from other electronic devices, and can be controlled to transmit the information signal by reading or writing to the register, and the register is necessary for transmitting the information signal. A band indicating a maximum value that can be taken by a packet constituting the information signal and a part indicating a band for dealing with a delay that occurs when the packet is transmitted, When releasing the band and channel necessary for the transmission of the information signal, the remaining band register that is also included in the communication system and indicates the remaining band of the bus; A channel register that uses a channel register that indicates the channel usage status, updates the remaining bandwidth register so as to add the bandwidth required for the transmission from the remaining bandwidth, and uses the channel usage status for the transmission channel. The channel register is updated so as to change in accordance with the information, and in each communication cycle, the information signal is transmitted after a cycle start packet.

  When the electronic device makes a bus use request to a root device that is also included in the communication system, together with other electronic devices, the bus use permission is granted when the electronic device makes the bus use request earliest. You may make it obtain.

  There is a predetermined time interval in which no signal is transmitted between the plurality of information signals transmitted through the bus.

  When updating the remaining bandwidth register or the channel register, a Compare & Swap command may be used.

  The register may further store information regarding a transmission speed, information regarding the number of other electronic devices connected, and information regarding a channel used for transmitting the information signal. .

  According to the present invention, the bandwidth that is a shared resource of the communication system is divided into a portion that changes depending on the connection configuration of the device and a portion that changes depending on the type of information signal, and is handled separately. Sometimes it becomes easy to adjust the band and channel, and the band and channel can be used effectively.

  Further, by applying the present invention to a system that manages the transmission path of an information signal using a plug control register, it is possible to immediately cope with a change in the information signal in the output device. Therefore, there is no possibility that communication of information signals is interrupted.

  In addition, when creating a signal path for the first time, the device that creates the signal path does not need to know the type of information signal that can be output by the device that outputs the information signal. Can know.

Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.
FIG. 1 is a block diagram showing a main configuration of a device to which the present invention is applied.
As shown in this figure, a device to which the present invention is applied includes an information signal generation block 1, a transmission block 2 that packetizes and transmits source data of an information signal generated by the information signal generation block 1, and transmission and reception of control signals. And a bus control block 3 for performing

  The information signal generation block 1 is a block for generating an information signal such as a digital audio / video signal. If the device is a digital VTR, it corresponds to a deck unit. The information signal generation block 1 notifies the bus control block 3 of the type of information signal currently being generated.

  The transmission block 2 converts the source data sent from the information signal generation block 1 into an Iso packet and sends it to the bus. At this time, the bus control block 3 performs on / off control of packet transmission.

  The bus control block 3 analyzes the structure of the communication system, analyzes the type of information signal sent from the information signal generation block 1, acquires the transmission band, sets the plug control register, and turns on the transmission operation in the transmission block 2. / Off control etc. The bus control block 3 is provided with a plug control register for writing information necessary for transmission management of Iso packets and information necessary for transmission of Iso packets. Here, since transmission of an Iso packet is considered, only the output plug control register 4 is illustrated.

  FIG. 2 shows an output plug control register in this embodiment. Compared to the conventional output plug control register shown in FIG. 6, the field used for Bandwidth is divided into two fields of Overhead ID and Max Payload Size. These two correspond to a variable portion depending on the connection configuration of the electronic device and a portion that varies depending on the type of information signal.

Overhead ID is an ID indicating a bandwidth corresponding to the overhead, and 32 times the ID number corresponds to an actual bandwidth value.
Max Payload Size indicates a value at the time of the maximum size of an Iso packet transmitted every cycle (that is, the maximum value that the packet can take) in units of quadlets (4 bytes). Since the unit of the band is the time required to transmit 32 bits when the transmission speed is S1600 (about 1600 MBPS), Max Payload Size is the value of the band for the data packet as it is at S1600.

With these two, the total bandwidth is calculated as follows.
Total bandwidth = (Overhead ID) x 32 + (Max Payload Size) x k

  Here, k is a coefficient determined by the data rate and indicates how much time is required as compared with S1600. For example, when S100, k = 16.

  Next, a connection control procedure when the output of the device A is input to the device E by the control of the device C in the communication system configured in the same manner as in FIG. 7 will be described with reference to FIG. However, in this case, the device A is configured as shown in FIG. 1 and includes the output plug control register shown in FIG. The device E is similarly configured and includes a reception block and an input plug control register.

  First, device C reads the value of Max Payload Size written in the output plug control register of device A (procedure (1)). Next, the channel necessary for device A to output the Iso packet to the bus is written to the channel register of device B (procedure (2)), and the time for overhead is added to the value of Max Payload Size read in step (1). The band obtained by adding the bands is subtracted from the remaining band indicated in the band register of the device B (procedure (8)). As a result, a channel and a band necessary for the device A to output the Iso packet to the bus are secured.

  After securing the channel and bandwidth in this way, the information necessary for the above-described transmission management of the Iso packet and the transmission of the Iso packet to the output plug control register of the device A and the input plug control register of the device E are required. Write appropriate information (procedures (4) and (5)). As a result, the Iso packet output from the device A to the bus passes through the devices B and C and is input to the device E.

  Next, consider the case where the device is inserted into and removed from the communication system while the output of the device A is being input to the device E. In this case, since the connection configuration of the device changes, the overhead portion of the time band required for the device A to transmit the Iso packet changes. Therefore, the device A adjusts the bandwidth for the changed overhead and subtracts a new transmission bandwidth from the remaining bandwidth indicated in the bandwidth register of the device B (procedure (6)). Further, a new Overhead ID is written into its own output plug control register (step (7)).

  Next, let us consider a case where the type of signal output by the device A changes in a state where the output of the device A is being input to the device E. Here, the case where the type of the information signal changes includes the case where the digital video signal changes from SD to HD, the case where the transfer rate of the compressed video signal compliant with MPEG changes, and the like. In this case, the portion of the Iso packet in the time band necessary for the device A to transmit the Iso packet changes. Therefore, device A adjusts the bandwidth for the changed Iso packet and subtracts a new transmission bandwidth from the remaining bandwidth indicated in the bandwidth register of device B (procedure (8)). In addition, a new Max Payload Size is written to its own output plug control register (step (9)).

  In each of the procedures described above, as in FIG. 8, a transaction including a Compare & Swap instruction and a Response defined in the IEEE-P1394 specification is used (however, the procedure (1) may be a Read instruction and a Response).

  As described above, in the present embodiment, when the connection configuration of the device changes, the bus control block 3 detects this, and if the bandwidth is insufficient for the new configuration, additionally acquires from the Iso resource manager, If there is a surplus, the surplus is returned to the Iso resource manager, and the Overhead ID shown in its own output plug control register 4 is also updated.

  Also, if the signal type changes in the information signal generation block 1, this is notified to the bus control block 3, the band is adjusted in the same manner as described above, and the Max Payload Size shown in its own output plug control register 4 is displayed. Also update.

  Thereafter, when the device C releases the information signal transmission path (band and channel), the bandwidth indicated in the output plug control register of the device A is returned to the Iso resource manager, thereby sharing the bus resources. Can be managed without contradiction.

  In addition, the maximum payload size is indicated according to the signal type that can be output even when it is not output. As a result, when creating a signal path, the device C can know the band to be secured only by reading the Max Payload Size of the output plug control register without knowing the type of information signal that the device A can output. .

  In the above embodiment, when the connection configuration of the devices changes, the device A outputting the information signal performs the bandwidth adjustment for the overhead, but this bandwidth adjustment is performed by the devices C, B, etc. Any device in the communication system may do this.

In the above-described embodiment, the device C executes the band securing. However, the device A itself that intends to output the information signal may perform the band securing.
Furthermore, in the above-described embodiment, the total of the data prefix, data end, arbitration time, second propagation delay time pro2, and Iso gap is used as overhead, but the data prefix and data end depend on the connection configuration of the devices. Since this portion is constant, this portion may be included in the Iso packet, and the total of the arbitration time, the second propagation delay time pro2, and the Iso gap may be used as an overhead portion.

It is a block diagram which shows the principal part structure of the apparatus to which this invention is applied. It is a figure which shows an example of the output plug control register to which this invention is applied. It is a figure which shows an example of the connection control procedure using the output plug control register to which this invention is applied. It is a figure which shows an example of a structure of the communication system using a P1394 serial bus. It is a time chart which shows an example of the communication cycle in the communication system using a P1394 serial bus. It is a figure which shows an example of the conventional output plug control register. It is a figure which shows an example of the communication system which performs connection control of an information signal using the conventional output plug control register. It is a figure which shows an example of the connection control procedure using the conventional output plug control register.

Explanation of symbols

  1 Information signal generation block, 2 transmission block, 3 bus control block, 4 output plug control register

Claims (10)

An electronic device included in a communication system in which a plurality of electronic devices are connected via a bus capable of transmitting a mixture of control signals and information signals,
It has a register that can be accessed from other electronic devices,
The information signal can be controlled to be transmitted by reading or writing to the register,
The register indicates a band necessary for transmission of the information signal, a portion indicating a maximum value that can be taken by a packet constituting the information signal, and a band for dealing with a delay generated when the packet is transmitted. So that it is memorized separately from the parts,
When releasing the band and channel necessary for transmission of the information signal,
Access to a manager device that is also included in the communication system and has a remaining bandwidth register that indicates the remaining bandwidth of the bus and a channel register that indicates a channel usage status;
Updating the remaining bandwidth register to add the bandwidth required for the transmission from the remaining bandwidth;
Updating the channel register to change the channel usage according to the channel used for the transmission;
An electronic apparatus, wherein the information signal is transmitted after a cycle start packet in each communication cycle. When the electronic device makes a bus use request to the root device included in the communication system together with other electronic devices, the bus use permission is granted when the electronic device makes the bus use request earliest. The electronic device according to claim 1, wherein the electronic device is obtained. 2. The electronic apparatus according to claim 1, wherein there is a predetermined time interval in which no signal is transmitted between the plurality of information signals transmitted through the bus. 2. The electronic apparatus according to claim 1, wherein when the remaining band register or the channel register is updated, a Compare & Swap instruction is used. The register further stores information regarding a transmission speed, information regarding the number of other electronic devices connected, and information regarding a channel used for transmitting the information signal. The electronic device according to claim 1. A communication control method used in a communication system in which a plurality of electronic devices are connected via a bus capable of transmitting a mixture of control signals and information signals,
The electronic device has a register accessible from other electronic devices,
The information signal can be controlled to be transmitted by reading or writing to the register,
The register indicates a band necessary for transmission of the information signal, a portion indicating a maximum value that can be taken by a packet constituting the information signal, and a band for dealing with a delay generated when the packet is transmitted. So that it is memorized separately from the parts,
When releasing the band and channel necessary for transmission of the information signal,
Access to a manager device that is also included in the communication system and has a remaining bandwidth register that indicates the remaining bandwidth of the bus and a channel register that indicates a channel usage status;
Updating the remaining bandwidth register to add the bandwidth required for the transmission from the remaining bandwidth;
Updating the channel register to change the channel usage according to the channel used for the transmission;
In each communication cycle, the information signal is transmitted after a cycle start packet. When the electronic device makes a bus use request to the root device included in the communication system together with other electronic devices, the bus use permission is granted when the electronic device makes the bus use request earliest. The communication control method according to claim 6, wherein the communication control method is obtained. 7. The communication control method according to claim 6, wherein there is a predetermined time interval in which no signal is transmitted between the plurality of information signals transmitted through the bus. 7. The communication control method according to claim 6, wherein when the remaining bandwidth register or the channel register is updated, a Compare & Swap command is used. The register further stores information regarding a transmission speed, information regarding the number of other electronic devices connected, and information regarding a channel used for transmitting the information signal. The communication control method according to claim 6.

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