JP2824963B2 - 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 dedicated line terminals for transmitting and receiving mixed user data and control information on a dedicated line to realize communication between the terminal devices. In particular, the present invention relates to a method and apparatus for mutual synchronization between dedicated line terminals capable of reliably receiving user data.

[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, as one of the communication interfaces in ISDN, there is a method in which communication between subscriber terminals is realized using three channels called B1, B2, and D channels. By the way, this communication interface is called ISDN basic interface,
That channel is called 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. When such a dedicated line is used, since the communication partner is predetermined, dialing of the other party's telephone number or the like is unnecessary, and if mutual synchronization is established, data can be sent 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. 5 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. .

Incidentally, instead of raising an interrupt from the data receiving unit 6b (6a), the control unit 3b (3a) may be configured to take in data from the data receiving unit 6b (6a) by polling. Further, such data transmission / reception is performed by a data transfer unit 5b (5a) and a data reception unit 6b by DMA (direct memory access) transfer without using a CPU in the control unit 3b (3a).
This may be performed between (6a) and the RAM in the control unit 3b (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 inventors have devised a solution to the above-mentioned problem of the prior art, as will be described in detail later. That is, when transmitting control information between terminal devices, mutual synchronization is established between these terminal devices so that user data and control information are distinguished. Therefore, in mutual synchronization, one terminal device transmits a synchronization pattern for a synchronization request to the other terminal device, and the other terminal device compares the transmitted data with the above synchronization pattern. Then, a synchronization pattern is detected, and this is used to perform mutual synchronization.

By the way, as means for realizing mutual synchronization using such a synchronization pattern, the following configuration can be considered first. That is, a synchronization pattern detection unit for detecting a synchronization pattern from data received by the line interface units 7a and 7b shown in FIG. 5 and a synchronization pattern generation unit for generating a synchronization pattern are newly provided in each mutual synchronization device.
Here, since the data receiving units 6a and 6b are directly connected to the common bus, the control units 3a and 3b do not check the contents of the data, and the data strings received from the data receiving units 6a and 6b are directly stored in the built-in RAM. Take in.

In parallel with this, the synchronization pattern detector compares the received data with the synchronization pattern, and raises an interrupt to the controllers 3a and 3b when the synchronization pattern is detected. Thus, the control units 3a and 3b trace the received data fetched from the data receiving units 6a and 6b into the internal RAM, search for a synchronization pattern, and remove the synchronization pattern from the received data. By repeating such operations, only the user data is loaded into the built-in RAM while maintaining mutual synchronization.

As described above, whether data received from the dedicated line LC is a synchronization pattern is determined by comparing data of a predetermined length according to the length of the synchronization pattern. If there is, there is no problem at all. However, the processing in which the control units 3a and 3b remove the synchronization pattern from the received data is generally complicated,
If the control units 3a and 3b do not have a certain processing capability, there is a possibility that user data may be missed.
Further, if the detection time of the synchronization pattern becomes longer, the time required for completing the mutual synchronization operation becomes longer.

Furthermore, in order to strictly detect the synchronization pattern, it is conceivable to increase the bit length of the synchronization pattern or to make a plurality of synchronization patterns continuous. In such a case, the received data sequence to be captured becomes longer, so that the time required to search for and remove a portion that matches the synchronization pattern necessarily increases. Therefore, the above-described possibility of data loss is promoted.

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 capable of distinguishing user data and terminal control information which are mixedly transmitted using the same dedicated line. It is an object of the present invention to provide a method and apparatus for mutual synchronization between apparatuses, and in particular, to provide a method and apparatus for mutual synchronization between dedicated line terminal apparatuses that can reliably guarantee reception of user data even when a synchronization pattern is strictly detected. It is to provide a device.

[0021]

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 synchronizing dedicated line terminal devices for transmitting and receiving user data and control information over a line and realizing communication between these terminals, wherein the control information is transmitted and received between the first and second terminals. Before and after the transmission and reception of the synchronization pattern between these terminals to perform mutual synchronization, the first (or second) terminal side stores a first-in first-out buffer having at least a capacity capable of storing the synchronization pattern. , The second
The received data sent from the (or first) terminal is sequentially written, and it is determined whether or not the synchronization pattern is included in the reception data, and the synchronization pattern is included in the reception data. When it is detected that the synchronization pattern has been detected, the fixed area on the buffer including the synchronization pattern is cleared, and the reception data from which the synchronization pattern has been removed is transmitted to the first data via the buffer.
(Or a second) terminal.

[0022] The invention according to claim 2 is characterized in that:
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 synchronizer, comprising: transmitting and receiving the control information between the leased line terminals; and transmitting and receiving a synchronization pattern for obtaining mutual synchronization between the terminals. Pattern detection means for detecting from the inside, a first-in first-out buffer having at least a capacity capable of storing the synchronization pattern, buffer writing means for sequentially writing data received from the partner terminal side to the buffer, When the means detects the synchronization pattern, the fixed area on the buffer including the synchronization pattern is cleared to remove the synchronization pattern. It is characterized by comprising a control means for transmitting the received data to the dedicated line terminal from the buffer.

According to a third aspect of the present invention, in the second aspect, the buffer has at least a memory having the capacity, and a pointer for holding a read / write address of the memory. The control means reads out the contents of the memory indicated by the pointer and sends it to the dedicated line terminal, and the buffer writing means reads out the contents of the memory indicated by the pointer,
The reception data is written to an address of a memory indicated by the pointer.

[0024]

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, parts that are the same as those in FIG. 5 are given the same reference numerals, and descriptions thereof will be omitted. 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, a selector 11a, and a buffer 12a are added to the conventional configuration shown in FIG. First, the above-mentioned synchronization clock section 8a is modified so as to also supply a synchronization clock to the synchronization pattern detection section 10a and the buffer section 12a. 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 its generating polynomial is expressed as “X ¹⁰ +
X ⁹ +1 "(repetition cycle: 888).

To realize this, for example, as shown in FIG. 2A, ten D flip-flops are connected in cascade, 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. The buffer section 12a is buffer means for sequentially accumulating the received data string transmitted by the line interface section 7a in synchronization with the clock transmitted from the synchronization clock section 8a. Here, the capacity of the buffer unit 12a is set to be slightly larger than the bit length of the synchronization pattern (described above) detected by the synchronization pattern detection unit 10a.

This buffer section 12a is a kind of FIFO.
As described later, when a synchronous pattern is detected, it is necessary to search for a synchronous pattern portion from the buffer unit 12a and remove it.
Therefore, the buffer section 12a cannot have a general FIFO configuration. Therefore, in the present embodiment, the buffer unit 12a is realized by using a memory, and an area corresponding to the length of the FIFO is secured on the memory, and the FIFO unit 12a is used.
Function is realized.

Now, as an example, it is assumed that received data is handled in units of 1 byte, and that access to the memory is also performed in units of bytes. In such a case, the address for accessing the memory is circulated by the length of the FIFO, and a pointer for writing the received data is provided inside the buffer unit 12a. At the point of time when one byte worth of data is received from the line interface unit 7a, one byte of data is read from the address indicated by the pointer, and
Byte data is written to this same address. In this case, writing to the address indicated by the pointer corresponds to inputting data to the FIFO, and the read data becomes reception data written before by the length of the FIFO. The FIFO function is implemented in the same manner as when data is taken out from the beginning.

The buffer section 12a is controlled by the control section 3a via a common bus. That is, the buffer unit 12
As will be described in detail later, when a buffer clear instruction is sent from the control unit 3a, the synchronization pattern detection unit 10a
Search for and clear the portion where the same PN pattern as that detected by is stored. However, since the time from when the synchronous pattern detecting unit 10a detects the PN pattern to when the clear is instructed is always constant, actually, the PN pattern portion cleared on the buffer unit 12a always has the same area. become.

Further, the buffer unit 12a converts the serial data string sent from the line interface unit 7a into, for example, a byte unit in order to ensure data consistency between the line interface unit 7a and the data receiving unit 6a. And store it in the above memory. On the other hand, the buffer unit 12a converts, for example, byte data read from the memory into a serial data string and converts the data into a serial data string.
a.

On the other hand, the mutual synchronization device according to the present embodiment
The terminal device has a normal mode in which user data communicates with each other (hereinafter, referred to as a user data communication mode) and a special mode in which terminal control information is communicated (hereinafter, referred to as an information data communication mode). Therefore, the control units 3a,
3b has a status register inside, and always knows 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 buffer unit 12b. In parallel with this, the synchronization clock section 8b extracts a clock from the data received from the line interface section 7b,
b and the buffer section 12b.
It becomes possible to receive data synchronized with the leased line network. Also,
The synchronization clock unit 8b also supplies a clock to the data generation unit 5b, and realizes 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
Receive data from the buffer unit 1
2b is given to the data receiving section 6b after being delayed by the length of the FIFO described above.
The control unit 3b extracts the received data from the data receiving unit 6b after a delay time corresponding to the length of the FIFO. Thus, the control unit 3b takes in the received data into the built-in RAM at regular 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. While the user data is being received, the synchronization pattern detection unit 10b does not detect the PN pattern, so that the buffer unit 12b stores only the F
Functions as an IFO or buffer.

Next, the operation when the control information data is mutually transmitted and received between the terminal devices 2a and 2b will be described.
FIG. 3 is a diagram for explaining the operation in the information communication mode according to the present embodiment. In FIG. 3, 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, U
Points mean user points.

Now, as described above, the terminal devices 2a and 2
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 received data whose electric level has been converted by the line interface unit 7b is transmitted to the synchronization pattern detection unit 10b and the buffer unit 12b. The synchronization pattern detector 10b constantly monitors whether or not the bit string of the received data is a PN pattern in parallel with the reception of the data buffered by the buffer 12b by the data receiver 6b. At the time of detection, an interrupt is notified to the control unit 3b using an interrupt. Note that the synchronization pattern detection unit 10b
Performs such a detection process asynchronously with the data generation unit 5b.

Then, the control unit 3b instructs the buffer unit 12b to clear the buffer via the common bus. As a result, the buffer unit 12b clears the PN pattern portion in the memory of the buffer unit 12b. This will be described below with reference to FIG. In the drawing, data output from the left end of the buffer is sent to the data receiving unit side, and data received from the line interface unit is inserted from the right end of the buffer.

In FIG. 4, "DDDDDD" means data other than the PN pattern, and is data input to the buffer unit 12b before receiving the PN pattern. On the other hand, "PNPN ..." means a PN pattern, which corresponds to the PN pattern detected by the synchronization pattern detection unit 10b. Here, as described above, when the PN pattern is detected, the last data of the PN pattern is always at the end of the FIFO (the right end of the buffer). Is the area corresponding to the PN pattern length starting from the right end.

By clearing the PN pattern as described above, it is possible to prevent the PN pattern from being sent to the data receiving unit 6b, and only the user data is sent to the data receiving unit 6b. On the other hand, the control unit 3b enters the mode for receiving the mutual synchronization request by receiving the notification of the detection of the synchronization pattern, and activates the synchronization pattern generation unit 9b in response to the notification of the mutual synchronization request. The PN pattern is returned to the mutual synchronization device 1a in the same procedure as described above.

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 mutual synchronizing device 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.

After that, 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.

[0052]

As described above, according to the present invention,
When a dedicated line terminal transmits and receives a synchronization pattern to each other to achieve mutual synchronization, one terminal side sequentially writes data received from the other terminal into a first-in first-out buffer and checks whether the synchronization pattern is included. Since the fixed area on the buffer is cleared when the synchronization pattern is detected, the received data sequence is once taken into the storage device, and then the synchronization pattern is searched for and removed from the storage data sequence. There is no need to perform complicated processing such as retrieving only the data again, and it is possible to easily retrieve and receive only user data from the received data string in which user data and synchronization patterns are mixed, and therefore, strictly detect the synchronization pattern. Even in such a case, the effect of eliminating the risk of data loss is obtained. Also, since the complicated processing as described above is eliminated,
The process of mutual synchronization between leased line terminals is accelerated, and the line disconnection and connection in the information data communication mode can be accelerated
Various other processes can be executed, and there is an advantage that a multifunctional device can be constructed.

[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 is a diagram illustrating a synchronous pattern detection unit 1 according to the embodiment;
It is a figure showing a state of buffer part 12a (12b) at the time when 0a (10b) detects a PN pattern.

FIG. 5 shows a conventional mutual synchronizer 51a, 51.
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, 12a, 12b ... buffer part, LC ...
Dedicated line

Claims (3)

(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 before and after transmitting and receiving the control information between the first and second terminals, when mutually synchronizing by giving and receiving a synchronization pattern between these terminals, The first (or second) terminal sequentially writes the received data sent from the second (or first) terminal into a first-in first-out buffer having a capacity capable of storing at least the synchronization pattern. It is determined whether or not the synchronization pattern is included in the received data. When the synchronization pattern is detected to be included in the reception data, the synchronization pattern is included. A dedicated line terminal for transmitting received data from which the synchronization pattern has been removed to the first (or second) terminal via the buffer so as to clear a fixed area on the buffer. Mutual synchronization method between devices. 2. 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 synchronizer between dedicated line terminal devices for controlling synchronization, wherein a synchronization pattern transmitted and received for mutual synchronization between these dedicated line terminals before and after the control information is transmitted and received between the dedicated line terminals, Pattern detection means for detecting from among the received data sent from the side, a first-in first-out buffer having at least a capacity capable of storing the synchronization pattern, and sequentially writing the received data from the partner terminal into the buffer. When the buffer writing unit detects the synchronization pattern, the fixed region on the buffer including the synchronization pattern is cleared when the pattern detection unit detects the synchronization pattern. Te, mutual device between dedicated line terminal apparatus characterized by comprising a control means for transmitting the received data that has been removed of the synchronization pattern from said buffer to said private line terminal. 3. The buffer has at least a memory having the capacity, and a pointer for holding a read / write address of the memory. The control unit reads the contents of the memory indicated by the pointer to execute the exclusive operation. And sending the received data to the address of the memory indicated by the pointer after the control means reads the contents of the memory indicated by the pointer. Item 3. The mutual synchronization device between the leased line terminals according to Item 2.