JP2828039B2 - Mutual synchronization method and apparatus between leased line terminals - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for mutually synchronizing between dedicated line terminals for transmitting and receiving user data and control information mixedly on a dedicated line to realize communication between the terminals. It is.

[0002]

2. Description of the Related Art A network called ISDN is conventionally known as a digital network for transmitting various media such as facsimile, still image and moving image in addition to voice at high speed. The ISDN realizes a many-to-many line connection between a large number of subscribers by circuit switching, and each subscriber performs a line connection and performs communication only when communication is required. Here, in the basic interface service of ISDN, communication between subscriber terminals is realized using three channels called B1, B2, and D channels. By the way, this communication channel is 2B
+ D.

[0003] Of these channels, both the B1 channel and the B2 channel are information channels for transmitting voice and various data, and both have a channel speed of 64k.
bps (kilobits per second). In contrast,
The D channel is a signal channel used for line control at the time of transmission and reception for communication performed on the B1 and B2 channels, and the channel speed is set to 16 kbps. A terminal suitable for such an interface is called an ISDN terminal.

On the other hand, apart from ISDN, 128 kbps
There is a communication form called "dedicated line" such as super digital having a line speed of. In this embodiment, the leased line presupposes one-to-one communication, and is used, for example, for an extension telephone between a head office and a branch of a company. In the case of using such a dedicated line, since the communication partner is predetermined, it is not necessary to dial the telephone number of the other party, and if the mutual connection is established, the data can be drained out. Therefore, in the communication using the dedicated line, the control channel existing in the ISDN is unnecessary, and the communication between the terminals is realized using only the information channel. As can be seen from the above, the terminal connected to the dedicated line communicates only with the information channel, and a dedicated line terminal different from the ISDN terminal is used.

Here, the following are conceivable advantages of using the dedicated line. In other words, ISDN and the like generally adopt a pay-as-you-go system in which a fee is charged in proportion to the usage time of the line. In applications where the line is occupied for a long time, the line usage fee becomes enormous. There is also a possibility. On the other hand, the dedicated line has the restriction that the communication partner is fixed, but it is only necessary to pay a fixed usage fee that does not depend on the line usage time, and always connect the line without worrying about the connection time Can be. Therefore, when a line is expected to be used for a predetermined time or more, it can be said that it is advisable to use a dedicated line instead of the ISDN.

Meanwhile, communication using a dedicated line has conventionally been
This is realized by connecting a device configured as shown in FIG. 4 to each terminal device. That is, as shown in FIG.
a and 51b are disposed opposite each other via a dedicated line LC, and the mutual synchronizers 51a and 51b are respectively connected to the terminal devices 2a and 2b.
b is connected. Here, as is clear from the figure, the mutual synchronizers 51a and 51b have exactly the same configuration. Therefore, hereinafter, the mutual synchronizer 51a will be representatively described.
Only the configuration will be described.

In the mutual synchronization device 51a, the control unit 3a
Is a control circuit that controls each unit in the device via a common bus, and mainly controls data generation and reception,
Input / output control with the terminal device 2a is performed. As an example,
The control unit 3a includes a CPU (central processing unit), a ROM (read only memory), and a RAM (random access memory).

[0008] A terminal interface (in the figure, "I /
F ") section 4a is an interface circuit for connecting the terminal device 2a to a common bus. Data generator 5a
Converts the transmission data sent from the terminal device 2a via the control unit 3a, generates a transmission data pattern, and sends it to the transmission end T of the line interface unit 7a described later. The data sent from the controller 3a to the data generator 5a via the common bus is transferred, for example, in units of 8 bits.

The data receiving unit 6a receives a serial data string received by the line interface unit 7a via the dedicated line LC from the receiving end R of the line interface unit 7a, and converts it into a format handled by the control unit 3a. Output to the common bus. The line interface unit 7a
By performing electrical level conversion at the time of data transmission or reception, serial data received from the dedicated line LC is transmitted to the data receiving unit 6a and the synchronization clock unit 8a. Further, the line interface unit 7a converts the transmission data sent from the data generation unit 5a to an electric level,
This is sent to the dedicated line LC.

The synchronization clock section 8a extracts a synchronization clock for operating the data generation section 5a and the data reception section 6a from the received data sent from the line interface section 7a. Next, such a mutual synchronization device 51
Communication between the terminal devices 2a and 2b using the terminals a and 51b is performed as follows. First, in the mutual synchronization device 51a, the control unit 3a sequentially writes transmission data from the terminal device 2a to the data generation unit 5a. The data generator 5a sends out transmission data to the dedicated line LC through the line interface 7a in synchronization with the clock from the synchronization clock 8a.

Then, in the mutual synchronizer 51b, the synchronization clock section 8b extracts a synchronization clock from the data received from the mutual synchronizer 51a through the dedicated line LC and the line interface 7b. Data received from the line interface unit 7b is input to the data receiving unit 6b in synchronization with this clock. Then, the control unit 3
b reads the data received by the data receiving unit 6b into the internal RAM at regular time intervals. Here, the data receiving unit 6b (6a) sends an interrupt signal to the control unit 3b (3a) every time it receives data of 8 bits, and the control unit 3b (3a) sequentially reads the interrupt signal. .

The transmission / reception of such data is performed by DMA (Direct Memory Access) transfer without the intervention of the CPU in the control unit 3b (3a).
b (5a), data receiving unit 6b (6a) and control unit 3b
There is also a case where data is exchanged between the RAMs in (3a).

[0013]

In the terminal devices connected to the dedicated line as described above, the terminal devices communicate with each other by flowing user data to the dedicated line. On the other hand, in such a terminal device, in addition to user data, it is necessary to transmit status information and various control information relating to the terminal device to a terminal device of a communication partner. In order to realize such transmission of control information, it is conceivable to provide an independent communication line for control information separately from a communication line for transmitting user data. However, such a configuration doubles the cost of the line usage fee, and the relationship between the communication line carrying the user data and the communication line carrying the control information becomes asynchronous. It cannot be said that.

Therefore, it is inevitable to adopt a configuration for transmitting user data and control information through the same communication line. A problem with such a method is that, for user data and control information transmitted in a mixed manner over a communication line, there is a possibility that these data patterns will match and malfunction. That said, in practice it is very difficult to distinguish them completely. The present invention has been made in view of the above points, and an object of the present invention is to provide a dedicated line terminal device capable of distinguishing user data and terminal control information transmitted in a mixed manner using the same dedicated line. An object of the present invention is to provide a mutual synchronization method and apparatus.

[0015]

In order to solve the above-mentioned problems, the invention according to claim 1 provides a dedicated terminal between a first terminal and a second terminal which is a communication partner of the first terminal. A method for mutually transmitting and receiving user data and control information via a line, and a mutual synchronization method between dedicated line terminal devices for realizing communication between these terminals, wherein in the user data communication mode, the first and second communication modes are performed. When transmitting and receiving the control information between terminals, the first and second terminals are synchronized, and after the synchronization is established, in the first terminal and the second terminal, Set the communication mode of the control information,
When the setting of the communication mode of the control information is completed, the first terminal and the second terminal transmit and receive the control information to and from each other, and when the transmission and reception of the control information are completed, 2, and after the synchronization is established, the first terminal and the second terminal respectively release the communication mode of the control information and return to the communication mode of the user data. It is characterized by doing.

According to a second aspect of the present invention, in the first aspect of the present invention, the synchronization between the first and second terminals is
From the first (or second) terminal to the second (or first)
The second (or first) terminal that has detected the synchronization pattern returns the synchronization pattern to the first (or second) terminal, and transmits the first (or second) The terminal of (2) performs the detection by detecting the returned synchronization pattern, and setting or canceling of the communication mode of the control information is performed by the first (or second) terminal stopping transmission of the synchronization pattern, Stopping the transmission of the synchronization pattern is performed by the second
(Or the first) terminal detects and stops the transmission of the synchronization pattern in the second (or first) terminal.
The transmission stop of the synchronization pattern in the (or first) terminal is performed by detecting the first (or second) terminal.

Further, the invention according to claim 3 provides a dedicated line,
The dedicated line terminal is arranged between a dedicated line terminal that transmits and receives user data and control information to and from each other using the dedicated line, and performs mutual synchronization between the dedicated line terminal and its partner terminal. A mutual synchronizing apparatus, comprising: a pattern generating means for generating a synchronization pattern for the mutual synchronization and transmitting the synchronization pattern to the partner terminal via the dedicated line; and Pattern receiving means for detecting the synchronization pattern from the received data transmitted via the communication terminal, and transmitting and receiving the synchronization pattern to and from the partner terminal using the pattern generation means and the pattern detection means. When the synchronization is established,
The communication mode of the control information is set or released according to whether the current communication mode is the communication mode of the user data or the communication mode of the control information. Control means for transmitting and receiving the user data to and from the partner terminal. Further, the invention according to claim 4 is characterized in that the synchronization pattern described in claim 2 or 3 comprises at least one or more pseudo-random patterns.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a connection configuration of the mutual synchronizers 1a and 1b according to the embodiment and terminal devices 2a and 2b connected thereto. In this figure, the same parts as those in FIG. Further, since the configurations of the mutual synchronizers 1a and 1b are the same, the mutual synchronizer 1a will be described below as a representative thereof.

In this embodiment, a synchronization pattern generator 9a, a synchronization pattern detector 10a, and a selector 11a are added to the conventional configuration shown in FIG. First, the synchronization clock section 8a described above is connected to the synchronization pattern detection section 10
It has been changed so that a clock for synchronization is also supplied to a. Next, the synchronization pattern generation unit 9a is a means for generating a pattern for realizing mutual synchronization between terminal devices, and a pattern to be used is preferably, for example, a cyclic code. In the present embodiment, a 10-stage PN pattern (pseudo random pattern) is used, and the generator polynomial is “X ¹⁰ + X ⁹ +1” (repetition period: 888).

To realize this, for example, as shown in FIG. 2A, ten D flip-flops are cascaded, and the outputs of the ninth and tenth (final) D flip-flops are output. The exclusive-OR (XOR) of the first stage D flip-flop may be returned to the input of the first stage D flip-flop. In the figure, clocks for driving the D flip-flops are not shown, but these D flip-flops all operate in synchronization with the same clock.

Referring again to FIG. 1, the synchronization pattern detector 1
Reference numeral 0a denotes a unit for detecting, from the received data extracted by the line interface unit 7a, the same synchronization pattern as that generated by the synchronization pattern generation unit 9a. Here, as an example of the configuration of the synchronization pattern detection unit 10a, the configuration shown in FIG. As shown in this figure, ten D
The flip-flops are connected in cascade, and the data received from the line interface unit 7a is input to the first-stage D flip-flop, and the output of the ninth and tenth (final) D flip-flops and the received data are connected. An exclusive OR is used to generate an error detection signal.

Then, for the received data, five consecutive
If no error signal is detected in 6 bits, it is assumed that the PN pattern has been detected (synchronization has been established). Now, assuming that the pattern of the received data is random, the probability of erroneously detecting the PN pattern (synchronization) is 2 ⁻⁵⁶ (1.3 × 10
^-17 ). Therefore, for example, if the data communication speed is 6
If it is 4 kbps, false detection will be once every 35702. Actually, when such a synchronization pattern is sent three times in a row, it is assumed that synchronization has been performed for the first time, thereby improving reliability.

On the other hand, the selector 11a in FIG. 1 selects the output of the data generator 5a and the output of the synchronization pattern generator 9a under the control of the controller 3a via the common bus, and transmits the output of the line interface 7a. Send to end T. On the other hand, the mutual synchronization device according to the present embodiment includes a normal mode in which the terminal device mutually communicates user data (hereinafter, referred to as user data communication mode) and a special mode in which terminal control information is communicated (hereinafter, information mode). Data communication mode). For this purpose, each of the control units 3a and 3b has a status register therein so as to keep track of which mode it is in.

Next, the operation of the mutual synchronizer having the above configuration will be described. First, the operation in the user data communication mode will be described. In the following, it is assumed that user data is transmitted from the terminal device 2a to the terminal device 2b. Now, when the terminal device 2a transmits data, the control unit 3a
Temporarily captures user data to be transmitted from the terminal interface unit 4a to the built-in RAM.

Then, the control section 3a writes the user data on the RAM into the data generation section 5a. that time,
The control unit 3a controls the selector 11a so that the selector 11a selects the output of the data generation unit 5a. The transmission data written in the data generation unit 5a is converted into a serial pattern sequence by the data generation unit 5a, passes through the selector 11a, and passes through the line interface unit 7a.
The signal is converted into the electric level of the dedicated line LC at a and transmitted to the mutual synchronizer 1b.

In the mutual synchronizer 1b, in order to receive the transmitted data, the data on the dedicated line LC is converted into an electric level by the line interface unit 7b, and the obtained received data is sent to the data receiving unit 6b. In parallel with this, the synchronization clock section 8b extracts a clock from the data received from the line interface section 7b,
b, thereby receiving data synchronized with the leased line network. In addition, the synchronization clock section 8b
Also supplies a clock to the data generating unit 5b, and achieves synchronization of transmission data to be transmitted to the dedicated line LC with the dedicated line network.

Thereafter, the control unit 3b sets the data receiving unit 6b
Fetches the received data into the built-in RAM at fixed time intervals, and sends it to the terminal device 2b via the terminal interface unit 4b. Thus, the transmission process of the user data from the terminal device 2a to the terminal device 2b is completed. Next, an operation when control information data is mutually transmitted and received between the terminal devices 2a and 2b will be described. FIG.
Is a diagram for explaining the operation in the information communication mode in the present embodiment, in which time flows from top to bottom. Therefore, in the following description, the description will be made in the order of arrangement from the top to the bottom of FIG. In the figure, point U means a user point.

Now, as described above, the terminal devices 2a, 2a
It is assumed that the communication of the user data is performed mutually between the terminals b and the terminal control information is transmitted from the terminal device 2a to the terminal device 2b in this state. First, on the side of the mutual synchronizer 1a, the control unit 3a controls the selector 11a so that the selector 11a selects the output of the synchronization pattern generation unit 9a. At this time, the control unit 3a controls the data generation unit 5a so as to temporarily suspend the transmission of the user data from the data generation unit 5a.

Next, when the control unit 3a instructs the synchronous pattern generation unit 9a to generate a PN pattern, the PN pattern generated by the control unit 3a is transmitted to the dedicated line LC through the selector 11a and the line interface unit 7a. You. As a result, a control information transmission request ("mutual synchronization request notification" on the right side of FIG. 3) is notified to the opposing mutual synchronization device 1b. Here, the control unit 3a (3b) manages the idle state of the information channel transmitted on the dedicated line LC. For example, when transmitting a PN pattern, the control unit 3a (3b) transmits data by selecting an empty channel from these channels and placing the PN pattern in a time slot corresponding to the channel.

On the other hand, in the mutual synchronizer 1b, the reception data whose electric level has been converted by the line interface unit 7b is transmitted to the data reception unit 6b and the synchronization pattern detection unit 10b. The synchronization pattern detector 10b constantly monitors whether the bit string of the received data is a PN pattern in parallel with the reception of the data by the data receiver 6b, and uses an interrupt when the PN pattern is detected. Then, the control unit 3b is notified that the PN pattern has been detected. Note that the synchronous pattern detection unit 10b performs such detection processing asynchronously with the data generation unit 5b. And the control unit 3b
Receives the notification, enters the mode for receiving the mutual synchronization request, activates the synchronization pattern generating unit 9b in response to the mutual synchronization request notification, and executes the PN in the same procedure as in the above-described mutual synchronization device 1a. The pattern is returned to the mutual synchronization device 1a.

Then, in the mutual synchronization device 1a, the synchronization pattern detection unit 10a detects the transmitted PN pattern and notifies the control unit 3a of the PN pattern detection. Based on this notification, the control unit 3a determines that the mutual synchronization device 1b is ready to receive a mutual synchronization request (“mutual synchronization request reception notification” on the left side of FIG. 3), and sends a PN to the synchronization pattern generation unit 9a. Instruct to stop sending patterns,
At the same time, the selector 11a is controlled to
Switching is performed so that a selects the output of the data generation unit 5a.

Thereafter, on the side of the mutual synchronizer 1b, the synchronous pattern detector 10b detects the loss of synchronization due to the stop of the transmission of the PN pattern from the mutual synchronizer 1a and notifies the controller 3b. Here, when the transmission of the PN pattern is stopped, NULL (continuation of “0” bits) is transmitted, and the synchronization pattern detecting unit 10b detects the loss of synchronization by detecting the NULL pattern. Detected.

When the out-of-synchronization is detected, the control unit 3b enters a mode for receiving a mutual synchronization request, and stops transmission of the PN pattern to the synchronization pattern generation unit 9b (see "Information" on the right side of FIG. 3). Data communication mode ON notification ”), and the selector 11b selects the output of the data generator 5b.
control b.

Next, in the mutual synchronization device 1a, the synchronization pattern detection unit 10a detects the loss of synchronization due to the stop of the transmission of the PN pattern from the mutual synchronization device 1b, and notifies the control unit 1a of this. As described above, the mutual synchronization devices 1a,
1b is established, and the mutual synchronization device 1
The a side also enters the information data communication mode to perform communication of terminal control information (“information data communication mode ON notification” on the left side of FIG. 3).

Next, in the information data communication mode, the control units 3a and 3b in each of the mutual synchronizers are controlled by the data generation units 5a and 5a.
5b to transmit terminal control information to the partner terminal side, and to control the data receiving units 6a and 6b from the partner terminal side.
Receiving the information data sent via the. Thus, communication of the terminal control information is performed between the terminal devices 2a and 2b.

Thereafter, when the communication of the terminal control information is completed, the mutual synchronization device 1a sets "information data communication mode ON".
The PN pattern is transmitted to the mutual synchronization device 1b in the same procedure as that performed at the time of "notification". As a result, the return of the PN pattern from the mutual synchronizer 1b, the stop of the transmission of the PN pattern by the mutual synchronizer 1a, and the stop of the transmission of the PN pattern by the mutual synchronizer 1b are sequentially performed. The communication mode is released (“information data communication mode OFF notification” in FIG. 3). Thereafter, as in the above description, communication of user data or communication of terminal control information is appropriately performed while switching modes.

[0037]

As described above, according to the present invention,
A mode for communicating control information and a mode for communicating user data are provided, and after synchronizing between dedicated line terminals, control information or user data is transmitted and received after setting or canceling the communication mode of control information, respectively. Therefore, not only normal user data exchanged between the dedicated line terminal devices but also various control information such as terminal control information data can be communicated with each other while synchronizing with each other. There is an advantage that it is not necessary to newly install another line or use an ISDN line having a separate control channel.

According to the second aspect of the present invention, the first
The synchronization pattern sent from the (or second) terminal is
(Or first) terminal, and the synchronization pattern is returned from the second (or first) terminal to the first (or second) terminal, and the first (or second) terminal detects the synchronization pattern. Since the synchronization pattern is detected, the effect that the mutual synchronization between the dedicated line terminals can be further ensured can be obtained.
According to the fourth aspect of the present invention, since a pseudo-random pattern is used as the synchronization pattern, the effect that the probability that the synchronization pattern matches the line data flowing through the dedicated line can be completely eliminated can be obtained. Further, if a plurality of pseudo-random patterns are used as the synchronization pattern, the effect of further improving the reliability of mutual synchronization between the leased line terminals can be obtained.

[Brief description of the drawings]

FIG. 1 shows a mutual synchronization device 1 according to an embodiment of the present invention.
a, 1b, the device and the terminal devices 2a, 2b
FIG. 4 is a block diagram illustrating a connection form of FIG.

2A and 2B are diagrams illustrating the principle of generation and detection of a PN pattern according to the embodiment, wherein FIG. 2A illustrates the principle of generation of a synchronization pattern in synchronization pattern generation units 9a and 9b;
(B) is a principle diagram of synchronous pattern detection in the synchronous pattern detection units 10a and 10b.

FIG. 3 is a diagram illustrating a mutual synchronization method between the terminal devices 2a and 2b according to the embodiment.

FIG. 4 shows a mutual synchronization device 51a, 51 according to the prior art.
3b is a block diagram illustrating a configuration of the terminal device b and a connection form between the device and the terminal devices 2a and 2b.

[Explanation of symbols]

1a, 1b ... mutual synchronization device, 2a, 2b ... terminal device, 3
a, 3b control section, 4a, 4b terminal interface section, 5a, 5b data generation section, 6a, 6b data reception section, 7a, 7b line interface section, 8a, 8
b: synchronization clock section, 9a, 9b: synchronization pattern generation section, 10a, 10b: synchronization pattern detection section, 11a, 1
1b ... Selector, LC ... Dedicated line

Claims (4)

(57) [Claims] An apparatus for transmitting and receiving user data and control information over a dedicated line between a first terminal and a second terminal that is a communication partner of the first terminal to realize communication between these terminals. A method for mutual synchronization between dedicated line terminal devices, wherein in the user data communication mode, when the control information is transmitted and received between the first and second terminals, After the synchronization is established, the first terminal and the second terminal
Each of the terminals sets the communication mode of the control information, and when the setting of the communication mode of the control information is completed, the first terminal and the second terminal transmit and receive the control information to and from each other, When the transmission and reception of the control information is completed, the first and second
After the synchronization is established, the first terminal and the second terminal are synchronized.
Wherein each terminal releases the communication mode of the control information and returns to the communication mode of the user data. 2. The synchronization between the first and second terminals is performed by transmitting a synchronization pattern from the first (or second) terminal to the second (or first) terminal. The detected second (or first) terminal returns the synchronization pattern to the first (or second) terminal, and the first (or second) terminal detects the returned synchronization pattern. The setting or release of the communication mode of the control information is performed by the first (or second) terminal stopping the transmission of the synchronization pattern and stopping the transmission of the synchronization pattern by the second (or second communication terminal). 1)
Of the second (or first) terminal stops the transmission of the synchronization pattern in the second (or first) terminal and detects the second (or first) terminal.
Stop transmission of the synchronization pattern in the first terminal.
2. The mutual synchronization method between leased line terminals according to claim 1, wherein the method is performed by detection of a (or second) terminal. 3. An exclusive line between a dedicated line and a dedicated line terminal for transmitting and receiving user data and control information to and from each other by using the dedicated line and communicating between the dedicated line terminal and its partner terminal. A mutual synchronizing device between dedicated line terminal devices for controlling synchronization, a pattern generating means for generating a synchronization pattern for the mutual synchronization, and transmitting the synchronization pattern to the partner terminal side via the dedicated line, A pattern detection unit for detecting the synchronization pattern from the reception data transmitted from the partner terminal via the dedicated line, and a pattern generator and the pattern detector using the pattern detection unit to communicate with the partner terminal. The synchronization is performed by transmitting and receiving the synchronization pattern, and when the synchronization is established, the current communication mode is set according to whether the current communication mode is the communication mode of the user data or the communication mode of the control information. Control means for setting or canceling the communication mode of the control information, and transmitting and receiving the control information or the user data to and from the partner terminal according to the communication mode after the setting or the cancellation. Mutual synchronization device between dedicated line terminals. 4. The synchronization pattern according to claim 2, wherein the synchronization pattern comprises at least one or more pseudo-random patterns.