JP2004007837A - Electronic apparatus and communication control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively utilize the band and channels in a communication system using a P1394 serial bus, even if the connection of the apparatuses changes while transmitting information signals. <P>SOLUTION: For controlling the input/output of information signals, a required band of a bus for transmitting the information signals is divided into a part changeable according to the connection structure of electronic apparatus and a part changeable according to the type of the information signals to handle both separately. In a shown output plug control register, the field of a transmission band is divided into an Overhead ID field changeable according to the connection structure of electronic apparatus and a Max Payload Size field changeable according to the type of the information signals. When the electronic apparatus stores a required band separated into a Payload and Overhead parts for communication, the electronic apparatus requests a manager apparatus to secure channels and a band at the start of communication, and transmits the information signals after a cycle start packet. <P>COPYRIGHT: (C)2004,JPO

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 a communication is performed between these electronic devices. The present invention relates to an electronic device and a communication control method that effectively use a band that is a shared resource of a bus.

2. Description of the Related Art 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”). A communication system using a P1394 serial bus has been considered as a communication system for transmitting and receiving control signals and information signals between them.

First, an example of such a communication system will be described with reference to FIG. This communication system includes devices AE. 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 a “bus”), communication is performed in a predetermined communication cycle (eg, 125 μs). Isochronous (hereinafter abbreviated as “Iso”) communication for continuously transmitting information signals such as digital audio / video signals, and Asynchronous (hereinafter “iso”) for transmitting control signals such as connection control commands irregularly as necessary. Abbreviated as “Async”).

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

5 shows an example of a communication cycle. This example is a communication cycle as seen from a device that can first transmit an Iso packet to the bus after a cycle start packet is transmitted to the bus. In this figure, the cycle start packet transmitted by the root node onto the bus arrives at the device after the first propagation delay time pro1. Upon receiving the cycle start packet, a device that intends to transmit 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 issued the bus use request earliest. This is performed at the arbitration time in FIG.

(4) A device that has been granted 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 added before and after the Iso packet, respectively.

The device for which the bus use permission has not been obtained may be received within the second propagation delay time pro2 after the device that has obtained the bus use permission transmits the Iso packet, and may have a predetermined Iso gap after the data end is completed. , And again sends a bus use request to the root node. When the permission to use the bus is obtained, an Iso packet (Iso-2 in this figure) is transmitted to the bus.

(4) In this way, after all devices that want to transmit the Iso packet on the bus end the arbitration and the transmission of the Iso packet, the period until the next cycle start packet is used for the communication of the Async packet.

Here, the second propagation delay time pro2 is determined according to the time required for a packet to propagate from a certain device to the farthest device in the communication system. This time constitutes the communication system, and when the bus is reset, any device can be calculated by the procedure specified in the IEEE-P1394 specification, but the value is different for each device. Therefore, having all the information is a heavy burden. Therefore, in order to simplify management calculations, it is practical to uniformly use the time required between the two farthest devices in the communication system. In addition, the arbitration time is determined according to the distance between each device and the root node, and therefore has a unique value for each device. The Iso gap, data prefix, and data end are fixed values defined in the IEEE-P1394 specification.

(5) As shown in FIG. 5, transmission of one Iso packet requires a maximum time (before transmission between the farthest devices) from the Iso gap to the second propagation delay time pro2. Of this time, the other of the Iso packets, that is, the total of the Iso gap, data prefix, data end, arbitration time, and second propagation delay time pro2 is called overhead. From the above description of each time, it is understood that the overhead changes depending on the connection configuration of the devices.

(4) A device that intends to transmit an Iso packet to the bus first secures a channel to be used and a band (time band) necessary for transmission. For this reason, a channel and a required band are applied to the Iso resource manager which is a device for centrally managing the bus channel and the band. The Iso resource manager has 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 transmit an Iso packet sends a write command (Compare & Swap command) for writing the channel and band that the user wants to use to these registers using an Async packet. Then, if the writing is successful, the output to the bus becomes possible.

(4) Connection control for communication of Iso packets between devices is performed using a plug control register provided in each device. By writing information required for transmission management of the Iso packet and information required for transmission of the Iso packet into the plug control register, connection control of the Iso packet can be performed both inside and outside the device.

Figure 6 shows the output plug control register. Here, when the Valid Flag is set to 1, an Iso packet is transmitted to the channel set in the Channel at the transmission rate specified by the Data Rate using the band indicated by the Bandwidth. When the Valid Flag is cleared to 0, transmission stops. Connection Counter indicates the number of devices that are inputting their output. The Unowned Connection Counter becomes 1 when it starts outputting the Iso packet by itself. Of 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 required for transmission of Iso packets. The number above each field is the number of data bits.

The input plug control register has the same configuration. When the Valid Flag is set to 1, an Iso packet is received from the channel set in Channel. When the 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 under the control of the device C in the communication system configured as shown in FIG. 7 will be described with reference to FIG. This is, for example, a case where the device C is an editing controller, the devices A and E are video tape recorders, and the device E records a reproduction signal of the device A. In this communication system, the device B is an Iso resource manager.

First, the device C checks the type of the information signal that the device A outputs to the bus (procedure (1)). In this case, for example, the device A prepares a special register and writes the type of the information signal output by the device A there. Next, the channel necessary for the device A to output the Iso packet to the bus is written into the channel register of the device B (procedure (2)), and further, the time band required for transmitting the Iso packet checked in the procedure (1). Then, the bandwidth obtained by adding the above-mentioned time bandwidth for the overhead 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 the band in this way, the information necessary for the transmission management of the Iso packet and the transmission of the Iso packet are transmitted to the output plug control register of the device A and the input plug control register of the device E. Information (steps (4) and (5)). Accordingly, 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, let us consider a case where a device is disconnected 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 device A to transmit the Iso packet changes. Therefore, the device C adjusts the bandwidth corresponding to the changed overhead and subtracts the new transmission band from the remaining bandwidth indicated in the bandwidth register of the device B (procedure (6)). Further, a new transmission band is written to the output plug control register of the device A (procedure (7)).

Next, consider a case where the type of signal output from the device A changes while the output of the device A is being input to the device E. In this case, the amount of Iso packets in the time band required for device A to transmit the Iso packets changes. Therefore, the device A adjusts the band for the changed Iso packet and subtracts the new transmission band from the remaining transmission band indicated in the band register of the device B (procedure (8)). Furthermore, write a new transmission band to its own output plug control register (step (9))

In each of the procedures described above, 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).
JP-A-8-340338

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

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

In any case, in order to be able to be executed by another device, it is necessary to communicate a control signal with the device A or C according to the purpose, so that it takes time. Therefore, communication of information signals may be interrupted. Further, the control procedure becomes complicated, and it becomes difficult to develop an application using the plug control register.

The present invention aims to provide an electronic device and a communication control method that can solve such a problem.

In order to solve the above problem, 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 in a mixed manner. Has a register that can be accessed from other electronic devices, and can control transmission of the information signal by reading or writing to the register, and the register has a band necessary for transmission of the information signal. A part indicating the maximum value that a packet constituting the information signal can take, and a part indicating a band for coping with a delay occurring when transmitting the packet are separately stored, and the information is stored. When securing a band and a channel necessary for signal transmission, a remaining band register and a channel, which are also included in the communication system and indicate the remaining band of the bus, Access to a manager device having a channel register indicating the usage status, updating the remaining bandwidth register to subtract the bandwidth required for the transmission from the remaining bandwidth, and updating the channel usage status to a channel used for the transmission. The channel register is updated so as to be changed accordingly, and the information signal is transmitted after a cycle start packet in each communication cycle.

Further, a 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 in a mixed manner. The device has a register accessible from other electronic devices, and can control transmission of the information signal by reading or writing to the register, and the register is necessary for transmission of the information signal. Bandwidth, a part indicating the maximum value that a packet constituting the information signal can take, and a part indicating a band for dealing with a delay occurring when transmitting the packet, so as to be stored separately. When securing the band and channel required for transmitting the information signal, the remaining band register is also included in the communication system and indicates the remaining band of the bus. Accessing a manager device having a channel register indicating a channel usage status, updating the remaining bandwidth register to subtract the bandwidth required for the transmission from the remaining bandwidth, and using the channel usage status for the channel used for the transmission. The channel register is updated so as to be changed in accordance with the above condition, and the information signal is transmitted after a cycle start packet in each communication cycle.

When the electronic device makes a bus use request to a root device similarly included in the communication system together with another electronic device, a bus use permission is issued when the electronic device makes a bus use request earliest. You may make it obtain.

There is a predetermined time interval between the information signals transmitted via the bus, where no signal is transmitted.

(4) When updating the remaining band register or the channel register, a Compare & Swap instruction may be used.

The register may further store information on a transmission rate, information on the number of other connected electronic devices, and information on a channel used to transmit the information signal. .

According to the present invention, the band, which 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 the information signal, and is treated separately, so that the connection configuration of the device has changed. Sometimes it is easy to adjust the band and the channel, and the band and the channel can be used effectively.

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

Furthermore, when the signal path is first created, the equipment that creates the signal path can read the plug control register without knowing the type of information signal that can be output by the information signal output apparatus. You 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 the figure, a device to which the present invention is applied includes an information signal generation block 1, a transmission block 2 for packetizing and transmitting source data of an information signal generated by the information signal generation block 1, and transmission and reception of a control signal. And a bus control block 3 for performing the following.

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

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

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. The bus control block 3 is provided with a plug control register for writing information required for transmission management of the Iso packet and information required for transmission of the Iso packet. 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 according to the present embodiment. Compared with 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 portions correspond to portions that are variable depending on the connection configuration of the electronic device and portions that change depending on the type of information signal.

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

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 many times as much time as required in S1600. For example, k = 16 in S100.

Next, a connection control procedure when the output of the device A is input to the device E under the control of the device C in the communication system configured 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 has the same configuration and includes a receiving block and an input plug control register.

First, the device C reads the value of Max Payload Size written in the output plug control register of the device A (procedure (1)). Next, the channel necessary for the device A to output the Iso packet to the bus is written into the channel register of the device B (procedure (2)), and the value of the Max Payload Size read in the procedure (1) is the time corresponding to the overhead. The band obtained by adding the band 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 the band in this way, the information necessary for the transmission management of the Iso packet and the transmission of the Iso packet are transmitted to the output plug control register of the device A and the input plug control register of the device E. Information (steps (4) and (5)). Accordingly, 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, let us consider a case where a device is disconnected 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 device A to transmit the Iso packet changes. Therefore, the device A adjusts the bandwidth corresponding to the changed overhead and subtracts the new transmission band from the remaining bandwidth indicated in the bandwidth register of the device B (procedure (6)). Further, a new Overhead ID is written to its own output plug control register (procedure (7)).

Next, consider a case where the type of signal output from the device A changes while 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 a case where the digital video signal changes from SD to HD, and a case where the transfer rate of the compressed video signal conforming to the MPEG changes. In this case, the amount of Iso packets in the time band required for device A to transmit the Iso packets changes. Therefore, the device A adjusts the band for the changed Iso packet and subtracts the new transmission band from the remaining band indicated in the band register of the device B (procedure (8)). Further, a new Max Payload Size is written to its own output plug control register (step (9)).

In each of the procedures described above, similarly to FIG. 8, 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).

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 new configuration has insufficient bandwidth, it is additionally acquired from the Iso resource manager, If a surplus has occurred, the excess is returned to the Iso resource manager, and the Overhead ID indicated in its own output plug control register 4 is also updated.

If the type of signal changes in the information signal generation block 1, the change is notified to the bus control block 3 and the bandwidth is adjusted in the same manner as described above. Also update.

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

Indicate the Max Payload Size according to the type of signal that can be output at present even when not outputting. Thus, when making 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-described embodiment, when the connection configuration of the devices changes, the device A that outputs the information signal adjusts the bandwidth for the overhead. Any device in the communication system may perform it.

Further, in the above-described embodiment, the device C executes the reservation of the band. However, the device A that outputs the information signal itself may execute the reservation of the band.
Further, in the above embodiment, the total of the data prefix, the data end, the arbitration time, the second propagation delay time pro2, and the Iso gap is used as the overhead, but the data prefix and the data end are used regardless of the connection configuration of the device. Therefore, this part 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 the overhead.

FIG. 2 is a block diagram illustrating a main configuration of a device to which the present invention is applied. FIG. 3 is a diagram illustrating an example of an output plug control register to which the present invention has been applied. FIG. 11 is a diagram illustrating an example of a connection control procedure using an output plug control register to which the present invention has been applied. FIG. 1 is a diagram illustrating an example of a configuration of a communication system using a P1394 serial bus. 6 is a time chart showing an example of a communication cycle in a communication system using a P1394 serial bus. FIG. 10 is a diagram illustrating an example of a conventional output plug control register. FIG. 11 is a diagram illustrating an example of a communication system that performs connection control of an information signal using a conventional output plug control register. FIG. 11 is a diagram illustrating an example of a connection control procedure using a conventional output plug control register.

Explanation of reference numerals

{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 that can transmit a control signal and an information signal in a mixed manner,
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 coping with a delay occurring when transmitting the packet. Without memorizing them separately
When securing the band and channel required for transmission of the information signal,
Similarly included in the communication system, accessing a manager device having a remaining band register indicating the remaining band of the bus and a channel register indicating a channel usage state,
Update the remaining band register to subtract the band required for the transmission from the remaining band,
Updating the channel register to change the channel use status according to the channel used for the transmission;
An electronic device 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 a root device similarly included in the communication system together with another electronic device, a bus use permission is issued when the electronic device makes a 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 a predetermined time interval in which no signal is transmitted exists between the plurality of information signals transmitted via the bus. 2. The electronic apparatus according to claim 1, wherein a compare & swap command is used when updating the remaining band register or the channel register. The register further stores information on a transmission speed, information on the number of other connected electronic devices, and information on a channel used to transmit 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 a control signal and an information signal,
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 coping with a delay occurring when transmitting the packet. Without memorizing them separately
When securing the band and channel required for transmission of the information signal,
Similarly included in the communication system, accessing a manager device having a remaining band register indicating the remaining band of the bus and a channel register indicating a channel usage state,
Update the remaining band register to subtract the band required for the transmission from the remaining band,
Updating the channel register to change the channel use status according to the channel used for the transmission;
A communication control method, wherein 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 similarly included in the communication system together with another electronic device, a bus use permission is issued when the electronic device makes a bus use request earliest. 7. The communication control method according to claim 6, wherein the communication control method is provided. 7. The communication control method according to claim 6, wherein a predetermined time interval in which no signal is transmitted exists between the plurality of information signals transmitted through the bus. 7. The communication control method according to claim 6, wherein when updating the remaining bandwidth register or the channel register, a Compare & Swap instruction is used. The register further stores information on a transmission speed, information on the number of other connected electronic devices, and information on a channel used to transmit the information signal. The communication control method according to claim 6.

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