JP3478293B2 - Communication control method and electronic device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication control method and an electronic device used in a system in which a plurality of electronic devices are connected by a bus in which control signals and information signals can be mixed and communication is performed between these electronic devices. The present invention relates to a device, and more specifically to a technique for effectively using a band, which is a shared resource of a bus.

[0002]

2. Description of the Related Art Conventionally, electronic devices such as a video tape recorder, a television receiver, a video tape recorder with a built-in camera, and a computer are connected by a bus capable of mixing control signals and information signals, and these electronic devices (hereinafter A communication system using a P1394 serial bus is considered as a communication system for transmitting and receiving control signals and information signals between "devices".

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 (for example, 125 μs). And isochronous (hereinafter abbreviated as "Iso") communication for continuously transmitting information signals such as digital audio / video signals,
Both Asynchronous (hereinafter abbreviated as “Async”) communication for transmitting control signals such as connection control commands irregularly as needed can be performed.

The management of the communication cycle in the bus is performed by the device which becomes the root of the communication system (hereinafter referred to as "root node").
Is started by sending a cycle start packet on the bus. The root node is automatically determined by the method specified in the IEEE-P1394 specification when the bus is reset.

FIG. 5 shows an example of the communication cycle. In this example, after the cycle start packet is sent to the bus,
This is the communication cycle as seen from the device that was able to send the Iso packet to the bus first. In this figure, the cycle start packet sent out on the bus by the root node reaches the device after the first propagation delay time pro1. Upon receiving the cycle start packet, the device that intends to transmit the 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 that uses the earliest bus use request to the bus. This is done at the arbitration time of FIG.

The device which has obtained the 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.

[0008] The equipment for which the permission to use the bus has not been obtained,
After the device that has obtained permission to use the bus sends the Iso packet, the reception is completed within the second propagation delay time pro2, and after waiting for a predetermined Iso gap from the completion of the data end, the bus is used again for the root node. Make a request. When permission to use the bus is obtained, an Iso packet (Iso-2 in this figure) is sent to the bus.

In this way, all the devices that try to send the Iso packet on the bus are arbitrated and I
After the transmission of the so packet is completed, 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. And this time configures the communication system,
When the bus is reset, IEEE-P139
Although it is possible to calculate with any device according to the procedure specified in the specification of No. 4, since it has a different value for each device, it is a heavy burden to have all the information. 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. Also, the arbitration time is determined according to the distance between each device and the root node,
Each device has its own value. The ISO gap, the data prefix, and the data end are IEEE-P1.
It is a fixed value specified in the specification of 394.

As shown in FIG. 5, the transmission of one Iso packet is at most I (by the time it travels between the most distant devices).
The time from the so gap to the second propagation delay time pro2 is required. Of this time, the rest of the Iso packets,
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 the overhead portion. From the above description of each time, it can be seen that this overhead amount changes depending on the connection configuration of the device.

The device that is going to send an Iso packet to the bus has a channel used and a band (time band) required for transmission.
Secure first. Therefore, the Iso resource manager, which is a device that centrally manages the bus channel and bandwidth,
Apply for channels and required bandwidth. The Iso resource manager includes a channel register indicating the usage status of each channel of the bus and a band register indicating the remaining capacity of the bus (hereinafter referred to as "remaining band"). Iso
The device that wants to send a packet writes a command (Compar) to these channels to write the channel and band that it wants to use using the Async packet.
e & Swap command). Then, if writing is successful, output to the bus becomes possible.

Connection control for performing Iso packet communication between devices is performed by using a plug control register provided in each device. By writing the information necessary for transmission management of the Iso packet and the information necessary for transmission of the Iso packet in the plug control register, it is possible to control the connection of the Iso packet both inside and outside the device.

FIG. 6 shows the output plug control register. Here, if you set Valid Flag to 1, Channe
The Iso packet is transmitted to the channel set to l at the transmission rate specified by Data Rate and using the band indicated by Bandwidth. When the Valid Flag is cleared to 0, the transmission is stopped. The Connection Counter indicates the number of devices that are inputting their own output. And Unowned Connecti
The on Counter becomes 1 when the output of the Iso packet is started by itself. Of the information explained above, Valid Flag, Un
The owned Connection Counter and Connection Counter are the information necessary for transmission management of Iso packets.
l, Data Rate, and Bandwidth are information necessary for transmission of Iso packet. The number above each field is the number of bits of data.

The input plug control register is also configured in the same manner, and when the Valid Flag is set to 1, the Chan
An Iso packet is received from the channel set in nel. When Valid Flag is cleared to 0, reception is stopped.

Next, in the communication system configured as shown in FIG. 7, the output of the device A is controlled by the device C to control the output of the device E.
A connection control procedure for inputting to 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 reproduction signal of the device A is recorded by the device E. In this communication system, the device B is Iso
Is a resource manager.

First, the device C checks the type of information signal output from the device A to the bus (procedure). In this case, the type of the information signal output by the device A is written in the device A, for example, by preparing a special register. Next, device A
The bandwidth required to output the so packet to the bus is written in the channel register of device B (procedure), and the bandwidth obtained by adding the overhead overhead bandwidth to the time bandwidth required for transmitting the Iso packet checked in the procedure Is subtracted from the remaining band indicated in the band register of device B (procedure). As a result, the device A is connected to the bus Iso
The channel and bandwidth required to output the packet are secured.

After the channels and bands are secured in this way, the information necessary for the transmission management of the Iso packet and the Iso packet described above are sent to the output plug control register of the device A and the input plug control register of the device E. Write the information required for transmission (procedure,). 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, let us consider a case in which the device A is being input to the device E and the device is inserted into or removed from the communication system. In this case, since the connection configuration of the device changes, the overhead part of the time band required for the device A to transmit the Iso packet changes.
Therefore, the device C adjusts the changed overhead band and subtracts the new transmission band from the remaining band indicated in the band register of the device B (procedure). Further, a new transmission band is written in the output plug control register of the device A (procedure).

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

In each of the procedures described above, I
Compare defined in the specifications of EEE-P1394
& Use a transaction consisting of Swap command and Response (however, the procedure may be Read command and Response).

[0022]

However, in the connection control procedure, the device C knows the bandwidth for the overhead determined by the structure of the bus and confirms the type of the information signal output by the device A by some control communication. It is necessary to know the bandwidth for data packets and specify the total of these.

At this time, if the structure of the communication system changes during the output, the bandwidth adjustment for the overhead can be changed only by the device C that knows the initial setting.

Further, when the type of the information signal changes during the output, only the device A can change the bandwidth adjustment for the data packet.

In any case, in order to allow another device to execute, the device A or C is used depending on the purpose.
Since it is necessary to perform communication of the control signal with the communication device, it takes time for the communication, and the communication of the information signal may be interrupted. In addition, the control procedure becomes complicated and it becomes difficult to develop an application using the plug control register.

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

[0027]

In order to solve the above problems, in the communication control method according to the present invention, a plurality of electronic devices are connected via a bus capable of transmitting control signals and information signals in a mixed manner. In a communication control method used in a communication system, when controlling input / output of the information signal between the electronic devices, a packet forming the information signal can take a band required for transmission of the information signal. A portion showing a maximum value and a portion showing a band for coping with a delay occurring when transmitting the packet are treated separately, and a portion showing a maximum value that a packet forming the information signal can take Max Payload Size And a part Ov indicating a band for coping with a delay that occurs when transmitting the packet.
The total bandwidth calculated by erhead ID and Overhea
It is characterized in that it is based on a value obtained by adding 32 times the d ID and the product of the coefficients determined by the Max Payload Size and the data rate.

The electronic equipment according to the present invention is an electronic equipment in a communication system in which a plurality of electronic equipments are connected via a bus capable of transmitting a control signal and an information signal in a mixed manner. A register that can read and write a control code for controlling input / output between devices also from other electronic devices in the communication system, and configures the information signal with a band necessary for transmission of the information signal in the register Part Max Payload Size that indicates the maximum value that the packet can take, and Part Overhead that indicates the bandwidth for coping with the delay that occurs when transmitting the packet.
A portion Max Payload Size, which is stored separately as an ID and indicates a maximum value that a packet forming the information signal can take,
The total bandwidth obtained by the partial overhead ID indicating the bandwidth for dealing with the delay occurring when the packet is transmitted is 32 times the overhead ID and Max Payload
It is characterized in that it is based on a value obtained by adding the product of the size and the coefficient determined by the data rate.

Here, the total bandwidth is: total bandwidth = (OverheadID) × 32 + (Max
PayloadSize) × k (k is a coefficient determined by the data rate) is satisfied, and the total bandwidth is: total bandwidth = (OverheadID) × 32 + (Max
PayloadSize + 3) × k (k is a coefficient determined by the data rate) is satisfied. Further, the coefficient k determined by the data rate has a transmission rate of 1600 MBPS.
It can be mentioned that it is a coefficient indicating how many times it takes compared to time.

In a communication system in which each device is provided with a register capable of reading and writing a control code for controlling the input / output of the information signal from other devices in the communication system, the band necessary for outputting the information signal is set. It is divided into a part that changes depending on the connection configuration of the device and a part that changes depending on the type of information signal, and the parts are stored separately in the register.

Further, regarding the portion that changes depending on the type of the information signal, the band determined by the type of the information signal that can be currently output even when the information signal is not output is stored in the register to indicate the band to be secured. To do so. As a result, another predetermined device that secures the band can secure the band by reading the band stored in the register without inquiring the device that is going to output the information signal about the type of the information signal. You can know the band to be used. Therefore, when securing the bandwidth by the Compare & Swap command specified in the IEEE-P1394 specification, no matter what register is Compare & Swap,
In most cases, the current state is read in the first time, and rewriting is successful in the second time. Therefore, the above procedure is a form in which the first procedure is omitted.

Further, when the connection configuration of the device changes during the output of the information signal, the band secured for outputting the information signal is adjusted and stored in the register. Rewrite the band that changes depending on the communication system. This band adjustment and rewrite command may be executed by any device in the communication system.

The equipment outputting the information signal is
When the type of the information signal changes during output, the band secured for outputting the information signal is adjusted, and the band stored in the register that changes according to the type of the information signal is rewritten.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the main parts of a device to which the present invention is applied.

As shown in this figure, an apparatus 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 a control unit. And a bus control block 3 for transmitting and receiving signals.

The information signal generating block 1 is a block for generating information signals such as digital audio / video signals, 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 information signal currently being generated.

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

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

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

The Overhead ID is an ID indicating a band corresponding to the overhead, and 32 times the ID number corresponds to the actual band value. As described above, this overhead component includes other components than the Iso packet component, that is, the Iso gap, the data prefix, the data end,
Arbitration time and second propagation delay time pro
It is the total of 2. Second propagation delay time pro2
Is determined by the time required for a packet to propagate from one device to the most distant device in the communication system. Use the time required between devices uniformly.

The Max Payload Size is the quadlet (4) which is the maximum value (that is, the maximum value that can be taken by the packet) of the Iso packets transmitted every cycle.
Indicated in bytes. Bandwidth unit is transmission speed S
Since it takes time to transmit 32 bits at 1600 (about 1600 MBPS), at the time of S1600
The Max Payload Size becomes the value of the bandwidth of the data packet as it is.

By these two, the total bandwidth is Overhead.
It is calculated based on the value obtained by adding 32 times the ID and the product of the coefficients determined by the Max Payload Size and the data rate. For example, total bandwidth = total bandwidth = (Overhead ID) x 32 + (Max Payload S
ize) × k. Here, k is a coefficient determined by the data rate, and indicates how many times as long as the time required in S1600, and therefore, for example, S100
Then k = 16.

Further, the total bandwidth is calculated as follows: total bandwidth = (Overhead ID) × 32 + (Max Payload S
Calculation by the formula of ize + 3) × k is also included. Where Max Pa
Addition of 3 quadlets to yload Size is for the header and CRC of the Iso packet.

Next, in the communication system configured as in FIG. 7, the output of the device A is controlled by the device C to control the output of the device E.
A connection control procedure for inputting to 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, the device C reads the value of Max Payload Size written in the output plug control register of the device A (procedure). Next, the channel required for the device A to output the Iso packet to the bus is written in the channel register of the device B (procedure), and further read in the procedure.
The bandwidth obtained by adding the overhead time bandwidth to the Max Payload Size value is subtracted from the remaining bandwidth indicated in the bandwidth register of the device B (procedure). As a result, the channel and band required for the device A to output the Iso packet to the bus are secured.

After the channels and bands are secured in this way, the information necessary for transmission management of the above-mentioned Iso packet and the Iso packet are stored in the output plug control register of the device A and the input plug control register of the device E. Write the information required for transmission (procedure,). 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, let us consider a case where the device A is input to the device E and the device is inserted into or removed from the communication system. In this case, since the connection configuration of the device changes, the overhead part of the time band required for the device A to transmit the Iso packet changes.
Therefore, the device A adjusts the changed overhead band and subtracts the new transmission band from the remaining band indicated in the band register of the device B (procedure). In addition, a new Ov is added to your output plug control register.
Write erhead ID (procedure).

Next, consider a case where the type of signal output by the device A changes while the output of the device A is being input to the device E. The case where the type of the information signal changes here means that the digital video signal changes from SD to HD.
, Or the transfer rate of a compressed video signal conforming to MPEG may change. In this case, the Iso packet portion changes in the time band required for the device A to transmit the Iso packet. Therefore, the device A adjusts the changed iso packet band and subtracts the new transmission band from the remaining band indicated in the band register of the device B (procedure). Furthermore, write a new Max Payload Size to my output plug control register (procedure).

In each of the procedures described above, Co specified in the IEEE-P1394 specification is also used, as in FIG.
Use a transaction consisting of mpare & Swap command and Response (however, the procedure may be Read command and Response).

As described above, in this embodiment, when the device connection configuration changes, the bus control block 3 detects this, and if the new configuration has insufficient bandwidth, the Iso resource manager adds it. If there is a surplus, it will be returned to the Iso resource manager, and its output plug control register 4
The Overhead ID shown in is also updated.

When the signal type in the information signal generating block 1 changes, the signal is notified to the bus control block 3, the band is adjusted in the same manner as the above method, and the result is shown in the own output plug control register 4. Ma
x Also update Payload Size.

After that, when the device C releases the transmission path (band and channel) of the information signal, the band corresponding to the output plug control register of the device A is returned to the Iso resource manager, and Bandwidth, which is a shared resource of the

Also, Max Payload Size is indicated according to the type of signal that can be currently output even when it is not output. Thus, when creating the signal path, the device C can know the band to be secured simply by reading MaxPayload Size of the output plug control register without knowing the type of information signal that the device A can output.

In the above embodiment, the device A that outputs the information signal when the connection configuration of the device changes.
Performs bandwidth adjustment for the overhead, but this bandwidth adjustment may be performed by any device in the communication system, such as devices C and B.

In the above embodiment, the device C secures the band, but the device A that outputs the information signal may secure the band.

Further, in the above embodiment, the data prefix, the data end, the arbitration time,
The total of the second propagation delay time pro2 and the Iso gap is used as the overhead, but since the data prefix and the data end are constant regardless of the device connection configuration, this part is included in the Iso packet and the arbitration time, The total of the two propagation delay times pro2 and the Iso gap may be used as the overhead.

According to the embodiment of the present invention described above, the band which is a shared resource of the communication system is divided into a part that changes depending on the connection configuration of the equipment and a part that changes depending on the type of the information signal, and distinguishes them. Since it is handled, it becomes easy to adjust the band when the connection configuration of the device changes, and the band can be effectively used.

Further, by applying to a system that manages the transmission path of the information signal using the plug control register, it is possible to immediately respond to the change of the information signal in the 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 device that creates the signal path can secure it by simply reading the plug control register without knowing the kind of information signal that the device that outputs the information signal can output. You can know the band to do.

[0061]

As described in detail above, according to the present invention, in a communication system in which a plurality of electronic devices are connected via a bus capable of transmitting control signals and information signals in a mixed manner, the information signals For controlling input / output between the electronic devices, a part Max Payload Size indicating a maximum value that a packet forming the information signal can take, and a delay occurring when transmitting the packet A part Ma indicating a maximum value that can be taken by a packet forming the information signal by treating it separately from a part indicating a band Overhead ID
x Payload Size and a part Overhead ID that indicates the bandwidth for coping with the delay that occurs when transmitting the packet
The total bandwidth obtained by and is 3 of Overhead ID.
Since it is based on the value obtained by adding 2 times and the product of the coefficient determined by the Max Payload Size and the data rate, it becomes easy to adjust the band when the connection configuration of the device changes, and the band becomes effective. Can be used.

Here, the total band is: total band = (OverheadID) × 32 + (Max
PayloadSize) × k (k is a coefficient determined by the data rate) is satisfied, and the total bandwidth is: total bandwidth = (OverheadID) × 32 + (Max
PayloadSize + 3) × k (k is a coefficient determined by the data rate) is satisfied.

Further, by applying to a system that manages the transmission path of the information signal using the plug control register, it is possible to immediately respond to the change of the information signal in the 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 device that creates the signal path can secure it by simply reading the plug control register without knowing the kind of information signal that the device that outputs the information signal can output. You can know the band to do.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main configuration of a device to which the present invention is applied.

FIG. 2 is a diagram showing an example of an output plug control register to which the present invention is applied.

FIG. 3 is a diagram showing an example of a connection control procedure using an output plug control register to which the present invention is applied.

FIG. 4 is a diagram showing an example of a configuration of a communication system using a P1394 serial bus.

FIG. 5 is a time chart showing an example of a communication cycle in a communication system using a P1394 serial bus.

FIG. 6 is a diagram showing an example of a conventional output plug control register.

FIG. 7 is a diagram showing an example of a communication system that controls connection of information signals using a conventional output plug control register.

FIG. 8 is a diagram showing an example of a connection control procedure using a 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

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Claims (8)

(57) [Claims] 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 control signal and an information signal in a mixed manner, wherein the information signal is input between the electronic devices. When controlling to output, in order to deal with the bandwidth required for the transmission of the information signal, the portion showing the maximum value that the packet forming the information signal can take and the delay that occurs when transmitting the packet The part MaxPayloadSize indicating the maximum value that the packet forming the information signal can take, and the part OverheadID indicating the band for coping with the delay occurring when transmitting the packet. The total bandwidth calculated by is 32 times of OverheadID and MaxPa
A communication control method, which is based on a value obtained by adding a product of a coefficient determined by yloadSize and a data rate. 2. The total bandwidth is the total bandwidth = (OverheadID) × 32 + (Max
The communication control method according to claim 1, wherein the PayloadSize) × k (k is a coefficient determined by a data rate) is satisfied. 3. The total bandwidth is total bandwidth = (OverheadID) × 32 + (Max
The communication control method according to claim 1, wherein PayloadSize + 3) × k (k is a coefficient determined by a data rate) is satisfied. 4. The coefficient determined by the data rate is a coefficient indicating how many times as long as a transmission speed is required at 1600 MBPS.
The described communication control method. 5. In an electronic device 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 information signal is controlled to be input and output between the electronic devices. A control code for reading and writing from other electronic devices in the communication system is provided, and the register indicates the maximum value that a packet forming the information signal can take a band required for transmission of the information signal. A portion MaxPayloadSize and a portion indicating a maximum value that can be taken by a packet forming the information signal are separately stored in a portion and a portion indicating a band for coping with a delay that occurs when the packet is transmitted. Total band obtained by the partial OverheadID indicating the band for coping with the delay that occurs when transmitting It is, and 32 times the OverheadID, MaxPa
An electronic device based on a value obtained by adding a product of a coefficient determined by yloadSize and a data rate. 6. The total bandwidth is the total bandwidth = (OverheadID) × 32 + (Max
The electronic device according to claim 5, wherein PayloadSize × k (k is a coefficient determined by a data rate) is satisfied. 7. The total bandwidth is total bandwidth = (OverheadID) × 32 + (Max
The electronic device according to claim 5, wherein PayloadSize + 3) × k (k is a coefficient determined by a data rate) is satisfied. 8. The coefficient determined by the data rate is a coefficient indicating how many times the transmission rate requires as compared with 1600 MBPS.
Electronic device described.