JPH0870486A - Communication controlling system and electronic equipment - Google Patents

Abstract

PURPOSE: To connect plural electronic equipments by a communication control bus, and to make a command transmitted precedently to be executed surely in a communication system among these electronic equipments, and simultaneously, to confirm the success/failure of the command. CONSTITUTION: A write-in side sends a write instruction in which information αread out of a register and the information βdesired to write newly in the register are made a set to the register. The register rewrites the information of the register to P only in the case that the information α sent from the write-in side matches with the information α' written in presently in the register, and further, it transmits the information α' to the write-in side. The write-in side can confirm the success/failure of write-in by comparing α with α'.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system in which a plurality of electronic devices are connected by a communication control bus capable of mixing control signals and data and data is communicated between these electronic devices. The present invention relates to a technique for successfully executing the earliest transmitted command when a plurality of devices transmit commands to the devices at substantially the same time.

[0002]

2. Description of the Related Art Conventionally, electronic devices such as a video tape recorder (hereinafter referred to as "VTR"), a television receiver (hereinafter referred to as "TV"), a camera-integrated VTR (hereinafter referred to as "CAM"), a computer, etc. A communication system using a P1394 serial bus is considered as a communication system that connects with a communication control bus capable of mixing control signals and data and transmits and receives control signals and data between these electronic devices.

First, an example of such a communication system will be described with reference to FIG. This communication system includes VTR-A, VTR-B, VTR-C, and an editor as electronic devices. And between VTR-A and the editor,
Between editor and VTR-B, and between VTR-B and VTR-C
During this period, control signals and data can be mixed and transmitted.
It is connected by a 1394 serial bus. Since each electronic device has a function of relaying control signals and data on the P1394 serial bus, this system is equivalent to a communication system in which each electronic device is connected to the common P1394 serial bus.

In the communication system of FIG. 5, as shown in FIG. 6, communication is performed in a predetermined communication cycle (for example, 125 μs). Then, synchronization (I) for continuously transmitting data such as a digital AV signal at a constant data rate.
communication and asynchronous (A) that transmits control signals such as connection control commands irregularly as needed.
Both synchronous communication can be performed.

There is a cycle start packet CSP at the beginning of the communication cycle, and a period for transmitting the synchronous communication packet is set following the cycle start packet CSP. It is possible to perform a plurality of synchronous communications by assigning channel numbers 1, 2, 3, ... N to the respective synchronous communication packets. Then, after the transmission of the synchronous communication packets of all the channels to be transmitted is completed, the next cycle start packet CS
The period up to P is used for communication of asynchronous communication packets.

A device that intends to send a synchronous communication packet to the bus first secures a used channel and a band required for data transmission. Therefore, the channel and required bandwidth are applied to a bus manager (hereinafter referred to as "BM"), which is a device that manages the channel and bandwidth of the bus.
As shown in FIG. 7, the BM includes a register REG1 indicating the usage state of each channel of the bus and a register REG2 indicating the remaining capacity of the bus. The device that intends to send the synchronous communication packet receives these registers REG1,
2, a read command is sent using an asynchronous communication packet to read the contents of REG1 and REG2. Then, if there is a free channel and free space, the channel and band that one wants to use is set to REG1, using the asynchronous communication packet.
2. Send write command to BM to write to 2. If writing to the registers REG1 and REG2 succeeds, output to the bus becomes possible. In addition, BM is a multiple device P139
When connecting to the serial bus and configuring the communication system,
It is automatically determined by the method specified in IEEE-P1394.

Connection control of data communication in a communication system in which a plurality of electronic devices are connected by a P1394 serial bus is performed using a virtual digital plug provided in each electronic device. FIG. 8 shows an example of virtual digital input plugs and output plugs. Each of these digital plugs is a 4-byte register provided in the communication control microcomputer of the electronic device.

When the plug-enable is set to 1 in the digital input plug shown in FIG. 8A, the synchronous communication packet is received from the channel set to the channel number. When the plug-enable of the input plug is cleared to 0, the reception is stopped. At that time, the other fields of the plug are also cleared to zero. Input plug PC (Prote
ct Counter) sets the LSB to 1 when protecting the signal connection with the transmitting device, and clears it to 0 when unprotecting.

Further, in the digital output plug shown in FIG. 8B, when the plug-enable is set to 1,
DR (D
Bandwidth at the transmission rate specified by
The synchronous communication packet is transmitted using the band indicated by the width. When the plug-enable of the output plug is cleared to 0, the transmission is stopped. At that time, the other fields of the plug are also cleared to zero. The PC of the output plug is incremented by 1 when the signal connection with the receiving device is protected and is decremented by 1 when the signal connection with the receiving device is unprotected, and the devices that have requested protection are counted.

These plugs can be rewritten by themselves or from other devices by the transaction of P1394. However, to protect the connection, the PC is 0
Rewrite only when is. Note that "-", "---", "---" in each plug are reserved bits.

In the communication system configured as described above, when the synchronous communication is not performed between the respective devices, for example, the VTR-B and VTR-C request the VTR-A to output the synchronous communication packet almost at the same time. When a command is transmitted, each device performs a P1394 read transaction (write transaction) and a write transaction (write transaction) in order to perform a process for successfully executing the previously arrived command.
Ion) to communicate with the VTR-A digital plug.

At this time, as shown in FIG. 9, if the VTR-B sends a command slightly earlier, first, the VTR
When -B reads the contents of the digital output plug of the VTR-A, the response from the VTR-A is the information .alpha. Of the output plug indicating whether it has already been output or is protected. When the VTR-B sees the read information α and finds that the VTR-A does not output and is not protected, it writes the information β such as the output channel number to the digital output plug of the VTR-A and outputs it. Complete the setting of. After that, if the VTR-C sends the same command to VTR-A with a slight delay, VTR-C
When reading the contents of the digital output plug of VTR-A, a reply β including information indicating that VTR-A is already outputting is returned, so it is understood that the command execution failed, and writing The process ends without performing.

[0013]

However, in order to execute the command arriving earlier in this way, P139
When the process using the read transaction and the write transaction of 4 is performed, the communication between the read and the write is not protected,
Other devices can interrupt and perform communication between the time of reading and the time of writing.

For example, as shown in FIG. 10, VTR-B is V
Read the contents of the digital output plug of TR-A and VT
After receiving the reply α from RA, VTR-C sends VT
Read the contents of the digital output plug of RA and reply α
When it is determined that the data is not protected, the information γ can be written. In this case, as shown in the figure,
When the writing by the RC is faster than the writing by the VTR-B, the VTR-C first completes the output setting to the VTR-A. Since the VTR-B does not know that it has been interrupted, the information β is overwritten on the digital output plug of the VTR-A to complete the output setting of the VTR-A.

In this case, the VTR-B that later sent the write transaction succeeded in executing the command, and the VTR-C that sent the write transaction first failed, but VTR-B and VTR-C. I think that both are successful. Here, VTR-B, VT
If the R-Cs make output requests to different channels, the VTR-C that has failed to execute the command may not receive anything from the receiving channel, or may receive the transmission data of another device. is there.

Similarly in the case of FIG. 11, VTR-B is VT.
Read the contents of the digital output plug of RA and reply α
After receiving, the VTR-C reads the contents of the VTR-A digital output plug. After that, as a result of reading the VTR-B, it was found that the VTR-B was not protected, so the information β is written. Further, since the VTR-C was not protected when it was read, the information γ is written. As a result, in the digital output plug of VTR-A, after VTR-B writes and completes the output setting, VTR-C overwrites and completes the output setting.

In this case as well, the VTR-C which later sent the write transaction succeeded in executing the command,
The VTR-B that sent the write transaction first fails, but I think that both VTR-B and VTR-C have succeeded. Therefore, here, V
If TR-B and VTR-C are requesting output to different channels, V
TR-B may not flow anything from the reception channel or may receive the transmission data of another device.

The present invention has been made in order to solve such a problem, and ensures that the previously transmitted command is executed and confirms the success / failure of command execution. It is an object of the present invention to provide a communication control method and electronic device as described above.

[0019]

In order to solve the above-mentioned problems, the present invention relates to a communication system in which a plurality of electronic devices are connected by a communication control bus and data communication is performed between these child devices. The device is a communication control method for executing the connection control command by writing the connection control information to a predetermined storage means included in itself or another electronic device when performing the connection control. The electronic device that writes the connection control information transmits a write command to a predetermined storage unit, and the storage unit that receives the write command executes only the earliest write command and a response indicating success / failure of the execution of the write command. Is transmitted.

For example, the electronic device for writing the connection control information transmits a write command including the first information and the second information to be written, and the storage means stores the stored third information. And the first information, the third information is rewritten to the first information and the third information is transmitted. Here, the first information is preferably information read from the storage means.

Further, the present invention is an electronic device used in a communication system in which a plurality of electronic devices are connected by a communication control bus and data is communicated between these electronic devices, in order to execute a connection control command. And a storage unit for writing the connection control information of the first write command, and the storage unit sends a response indicating success / failure of execution of the write command. Is.

[0022]

According to the present invention, only the connection control information by the earliest write command is stored in the storage means. Then, a response indicating whether the execution of the write command has succeeded or failed is transmitted. Therefore, the command that arrives earliest in the predetermined storage means of the electronic device is surely executed, and
You can check the success / failure of command execution.

[0023]

Embodiments of the present invention will now be described in detail with reference to the drawings. In this embodiment, it is assumed that inter-device connection processing is performed in the communication system of FIG. As described above, in order to perform the device-to-device connection process, it is necessary to write the device-to-device connection information into the digital plug. In this embodiment, in order to write the connection information between devices, the lock transaction (lock transaction) of P1394 is used.
Compare & Swap (hereinafter abbreviated as "C &S") transaction, which is one of the (ion).

The C & S transaction is to send a write command in which the first data read from the register and the second data to be newly written in the register are sent, and the third data currently written in the register is sent. The data is compared with the first data, and the third data is rewritten to the second data only when they match. Then, the third data is transmitted to the device that has transmitted the write command.

Explaining with reference to FIG. 1, first, when the write side reads the contents of the register (read), the contents information α of the register is returned from the register as a reply (read response). The procedure up to this point is the same as the conventional processing procedure. Next, the writing side sends to the register a write command (lock request) in which the content information α and the information β to be newly written in the register are set. The register rewrites the content information of the register into β and transmits the content information α ′ to the writing side only when the content information α sent from the writing side matches the content information α ′ currently written in the register. (Lo
ck response). Reply from register (re
α = α ', except when the write command of another device succeeds between the ad response) and the write command.
Therefore, it can be confirmed that the writing was successful and the writing side was successful.

The same case as in FIGS. 10 and 11 of the related art is shown in FIGS. In FIG. 2, when the VTR-C first transmits the write command, the VTR-A rewrites the information of the digital output plug into γ, and transmits the information α of the digital output plug before rewriting to the VTR-C. This confirms that the VTR-C has been successfully written. However, when the VTR-B sends a write command, the content of the digital output plug is γ, and it does not match the read information α, so rewriting is not performed.
Then, γ which is the content of the digital output plug is transmitted to the VTR-B. Since VTR-B is γ ≠ α, it can be confirmed that writing has failed. Similarly, in the case of FIG. 3 as well, the VTR-B that has sent the write command first succeeded in writing, and the VTR-C that has sent the write command later.
Has failed.

As described above, in this embodiment, the device which has transmitted the write command first succeeds in writing. Then, both the device that has succeeded in writing and the device that has failed in writing can confirm whether the writing has succeeded or failed.

Next, as an example of connection control, a case where the VTR-A performs broadcast output will be described with reference to the flowchart of FIG. First, in S1, a process of acquiring a broadcast channel is performed. And
If the acquisition is successful, the process proceeds to S2, and if the acquisition is unsuccessful, the process ends (FAIL). In S2, a process for acquiring a band for broadcasting is performed. If the acquisition is successful, the process proceeds to S3, and if the acquisition is unsuccessful, the process proceeds to S5.

Now, a method of acquiring a band and a channel according to the present invention will be specifically described. As described above, in the communication system using the P1394 serial bus, the device that intends to send the synchronous communication packet to the bus needs to write the used channel and the necessary band in the registers REG1 and REG2 of the BM. If the writing is successful, the synchronous communication packet can be transmitted. Then, in the present invention, the used channel and band are written using the C & S transaction of P1394.

That is, in S1, the REG of the BM is registered.
A transaction (read) for reading 1 is transmitted, and an empty channel is checked from the reply (read response). If the broadcast channel (a predetermined channel that is defined to be used for broadcasting by default) is in use, it means that acquisition of the channel has failed.

On the other hand, when the broadcast channel is idle, the read register REG1
Write command (lock) with the value corresponding to the broadcast channel set to 0
request) is transmitted. As a result, if the value of the register REG1 included in the write command is returned as a response from the BM (lock response), it means that the acquisition of the broadcast channel has been successful.
Here, if any other value is returned, it means that the acquisition of the channel has failed. Therefore, the process is repeated from the process of checking whether the broadcast channel is in use by looking at the returned value.

Similarly, in S2, the register REG2 of the BM is
Then, the process for bandwidth acquisition is performed. That is, BM
Send a transaction to read the register REG2 of the device (read), and reply (read resp)
onse) to check the remaining bandwidth. And
If the remaining bandwidth is less than the bandwidth required for data output, it is a failure. On the other hand, if the remaining bandwidth is larger than the bandwidth required to output the data, the write command (lock
request) is sent. In this write command, the value read from the register REG2 and the value obtained by subtracting the band required for data output from that value are entered as a set.
As a result, REG2 set to write command from BM
If the same value is returned as (lock response
se), acquisition of the band is successful. If any other value is returned, the process fails, and the process returns from the process of checking the returned value and checking the magnitude relationship between the band currently remaining and the band required for data output.

Next, in S3, the digital output plug 0 of its own is set to the ON state. Here, digital output plug 0
Is the default for broadcast output. Then, if the setting is successful, the process ends (success), and if the setting fails, the process proceeds to S4. Specifically, first, the content of the digital output plug 0 is read (re
It is a failure if it turns out that it is protected from the read response. Also,
If not protected, a C & S transaction turns the plug on. That is, as a write command (lock request), a reply value obtained by reading the digital output plug and a plug enable of the digital output plug = 1 / BCN (broadcast channel number) / DR / BW are set, and the reply (lock response) is sent. If the value of the digital output plug 0 entered in the write command is returned, it is successful. If any other value is returned, it will fail,
Start again from the process of checking the value returned to see if it is protected.

Next, in S4, the band acquired in S2 is released, and in S5, the broadcast channel acquired in S3 is released. The C & S transaction is also used in these release processes. That is, in S4, first, the contents of the register REG2 of the BM are read, and a write command in which the read value and the value obtained by adding the band acquired in S2 are set is sent, and the response from the BM is the REG2 of the write command. If the value is the same, the channel release is completed. When any other value is returned, the process is repeated from the process of sending the write command in which the value obtained by adding the returned value and the bandwidth acquired in S2 is set. The same applies to S5.

The present invention is not limited to the above embodiments, but various modifications can be made based on the spirit of the present invention. For example, the write command (resd) in FIG.
It is also possible to omit the exchange of the read response and the response and to use only the C & S transaction. This can reduce the number of communications. This is effective when the information in the register can be estimated, such as in the initial state.

Further, although the P1394 serial bus is used as the communication control bus in the above-mentioned embodiment, the present invention can use another bus as long as it is a communication control bus capable of transmitting mixed control signals and data.

[0037]

As described above in detail, according to the present invention, the connection control command can be executed simply and surely on a first-come-first-served basis, and the success / failure of command execution can be confirmed. For this reason, the inter-device connection processing unit can be easily implemented as hardware, so that high-speed processing and low cost of the processing unit can be achieved.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a command processing procedure of the present invention.

FIG. 2 is a diagram showing an example of a processing procedure in the case where a plurality of devices transmit commands almost simultaneously in the present invention.

FIG. 3 is a diagram showing another example of a processing procedure in the case where a plurality of devices send commands almost simultaneously in the present invention.

FIG. 4 is a diagram showing a processing flow when the VTR-A performs broadcast output in the present invention.

FIG. 5 is a diagram showing an example of a communication system in which a plurality of devices are connected by a P1394 serial bus.

FIG. 6 is a diagram showing an example of a communication cycle in a communication system in which a plurality of devices are connected by a P1394 serial bus.

FIG. 7 is a diagram illustrating an operation for acquiring a band and a channel.

FIG. 8 is a diagram showing an example of a digital plug.

FIG. 9 is a diagram showing an example of a conventional command processing procedure.

FIG. 10 is a diagram showing an example of a conventional command processing procedure in the case where a plurality of devices transmit commands almost simultaneously.

FIG. 11 is a diagram showing another example of a conventional command processing procedure when a plurality of devices transmit commands almost simultaneously.

[Explanation of symbols]

BM ... bus manager, REG1 ... used channel register, REG2 ... bus capacity register, PSR ... plug status register

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication H04N 5/44 A (72) Inventor Makoto Sato 6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni -Inside the corporation

Claims (4)

[Claims] 1. In a communication system in which a plurality of electronic devices are connected by a communication control bus and data is communicated between the electronic devices, each electronic device has its own or another electronic device when performing connection control. The communication control method is such that the connection control command is executed by writing the connection control information to a predetermined storage means, and the electronic device that writes the connection control information is written to the storage means. A communication control system characterized by transmitting a command, and receiving the write command, the storage means executes only the earliest write command and transmits a response indicating success / failure of execution of the write command. 2. The electronic device for writing the connection control information transmits a write command including the first information and the second information to be written, and the storage means stores the stored third information. 2. The communication control method according to claim 1, wherein the third information is rewritten to the first information and the third information is transmitted only when the first information and the first information match. 3. The communication control system according to claim 2, wherein the first information is information read from the storage means. 4. An electronic device used in a communication system for connecting a plurality of electronic devices via a communication control bus and performing data communication between the electronic devices, the connection control information for executing a connection control command. An electronic device, comprising: a storage unit for writing, storing only the connection control information by the earliest write command, and transmitting a response indicating success / failure of execution of the write command.