JPH0237857A - Communication channel connection system - Google Patents

Abstract

PURPOSE:To prevent a terminal equipment from receiving data including a noise component by monitoring the timing signal of a channel termination equipment by a signal repeater and interrupting a data transmission line when the timing signal is out of the specified range. CONSTITUTION:A signal repeater 11 is inserted and arranged between a channel termination equipment 2 and a terminal equipment 3 connected to a line exchange network 1 and an interrupting circuit 14 inserted into a data transmission line 4 and a phase synchronizing circuit 15 inserted into a transmission line 5 of a timing signal are provided. A prescribed timing pulse is outputted always to the terminal equipment 3 by the phase synchronizing circuit 15, a timing signal inputted from the line termination equipment 2 is monitored, it is decided whether or not the repeating period of the timing signal is in the specified range, and when it is decided that it is out of the specified range, the data transmission line 4 is interrupted. Thus, the terminal equipment 3 does not receive the data including the noise component.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a line terminating device provided at the end of a communication line such as a circuit switching network or a dedicated line, and a terminal device connected to this line terminating device. The present invention relates to a communication line connection system including a signal relay device inserted between the communication line and the signal relay device.

(Prior Art) In recent years, with the development of computers and public communication networks, various data communication systems have been put into practical use. These data communication systems include a computer center that processes input and output information, and a terminal device that transmits and receives input and output information. The computer center and the terminal devices are connected via communication lines consisting of circuit switching networks, dedicated lines, and the like.

A line termination device, a signal relay device, or the like is inserted between the communication line and the terminal device. These arrangements will be referred to herein as communication line connection systems.

FIG. 2 shows a configuration diagram of the main parts of a conventional communication line connection system.

Here, an example of a communication line will be explained using a circuit switching network 1.

In the figure, a line termination equipment 2 (DCE) is connected to a line switching network 1 connected to a computer center (not shown). The line termination device 2 includes a terminal device 3 (DT
E) is connected. The line switching network 1 is a network that multiplexes and stores information in order to smoothly transmit and receive information between the computer center and the terminal devices 3. The line termination device 2 is a device that matches signals of different formats between the line switching network 1 and the terminal device 3. The terminal device 3 is a device that inputs and outputs various information.

Between the line termination device 2 and the terminal device 3, the line termination device 2
The R line 4 is a data transmission path from the terminal device 3 to the terminal device 3, the S line 5 is used to transmit timing signals that control the operation timing of the terminal device 3, and signal lines such as T, C, and I lines (not shown) are used. It is connected. The terminal device 3 is provided with two receivers 6.7 and a communication LSI 8. The R line 4 is connected to the receiving terminal R of the communication LSI 8 via the receiver 6 . Further, the S line 5 is connected to the transmission control terminal TX and reception control terminal RX of the communication LSI 8 via the receiver 7.

The communication LSI 8 samples the serial data input to the reception terminal R in synchronization with the timing signal input to the reception control terminal RX, and outputs parallel data consisting of predetermined bits to the data bus.

FIG. 3 shows a timing chart showing the operation of the conventional communication LSI 8.

FIG. 3(a) shows data manually input to the reception terminal R of the communication LSI 8, and FIG. 3(b) shows timing pulses input to the reception control terminal RX.

First, as shown in FIG. 3(a), binary data consisting of marks and spaces is input to the receiving terminal R of the communication LSI 8 (FIG. 2) through the R line 4. Furthermore, as shown in FIG. 3(b), a timing signal with a predetermined repetition period is input to the reception control terminal RX of the communication LSI 8.

At the rising edge of this timing signal, as shown in Figure 3(a)
Sample the data shown in . When jitter occurs in the data shown in Figure 3 (a), the timing signal shown in Figure 3 (b) also follows the jitter and its phase is finely adjusted, so that the data and sampling signal are always in synchronization. is maintained.

(Problem to be Solved by the Invention) By the way, when the power to the line terminating equipment 2 (DCE) is turned on and off for maintenance, or when the power is momentarily cut off due to a power outage, etc., the line terminating equipment 2 and the terminal device 3 (D
Normal operation timing with TE) cannot be guaranteed. That is, the line termination device 2 transmits noise to the terminal device 3 through the S line 5 until its operation becomes stable after the power is restored. Therefore, in the terminal device 3, a timing signal containing a noise component is input to the transmission control terminal TX and the reception control terminal RX of the communication LSI 8. For this reason, the communication LSI 8 may malfunction internally due to the input of non-standard noise pulses.
Even after the input signal returned to normal, subsequent operations were no longer performed normally, resulting in a hang-up condition in which data transmission and reception processing was stopped. Therefore, the terminal device 3
Even if there is no failure in anything other than the communication LSI 8, its operation stops, resulting in a deadlock state in which data transmission/reception and input/output processing of the terminal device 3 cannot be performed.

In such a case, to return the terminal device 3 to a normal state,
The system had to be reset, that is, started up manually. Further, in the case of an unmanned terminal device 3 that operates all day long, a staff member is dispatched to the terminal device 3 side to reset the system. In this case, it is difficult to take prompt action, and if the deadlock state of the terminal device 3 affects the line termination device 2 or the like, there is a risk that the system will go down. Furthermore, when resetting the system, various initializations, loading of programs, etc. must be performed, which requires a great deal of time.

By the way, the transmission control terminal TX of the communication LSI 8
A conceivable method is to insert a capacitor into the S line 5 to prevent noise from entering the control terminal RX and the reception control terminal RX. There was a risk that noise components would be sampled.

The present invention has been made with attention to the above points, and when the circuit terminating equipment 2 (DCE) generates noise, this noise is manually applied to the terminal equipment 3 (DTE) to prevent a deadlock state. However, it is an object of the present invention to provide a communication line connection method that eliminates the need for processing such as system reset and can sufficiently withstand unattended operation all day long.

(Means for Solving the Problems) The communication line connection system of the present invention is arranged between a line termination device used for connection of a communication line and a terminal device connected to this line termination device, and A cutoff circuit inserted in a data transmission path connecting the line termination device and the terminal device; and a phase synchronization circuit inserted in the timing signal transmission path connecting the line termination device and the terminal device. circuit, the phase synchronized circuit outputs a predetermined timing pulse toward the terminal device, and determines whether the repetition period of the timing signal is within a specified range; As a result, when it is determined that the data transmission path is outside the specified range, a cutoff setting means is installed in the cutoff circuit to cut off the data transmission path.

(Operation) The above device always outputs a predetermined timing pulse toward the terminal device using the phase synchronization circuit. Then, the timing signal input from the line terminating device is monitored, and it is determined whether the repetition period of this timing signal is within a specified range. and the terminal device. The terminal device always maintains its normal operating timing by means of timing pulses. Furthermore, data containing noise components input from the line termination device is not received due to the interruption of the data transmission path.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of the communication line connection system of the present invention. Here, an example of a communication line will be explained using a circuit switching network 1.

In the figure, the communication line connection system according to the present invention allows a signal to be transmitted between a line termination equipment 2 (DCE) and a terminal device 3 connected to the line switching network l of the conventional communication line connection system shown in FIG. A relay device 11 is inserted and arranged. The signal relay device 11 includes a receiver 12.13, a cutoff circuit 14, a phase synchronization circuit 15, a driver 18.19, and a clock circuit 2o. The phase synchronization circuit 15 includes a determining means 16 and a cutoff setting means 17. The input of the receiver 12 is connected to the R line 4 of the line termination device 2.

The output of the receiver 12 is connected to the input of a driver 18 via a cutoff circuit 14 . The output of the driver 18 is
The R line 4a of the terminal device 3 is connected. Receiver 13
The input of is connected to the S line 5 of the line termination device 2.

The output of the receiver 13 is connected to the input of the driver 19 via the phase synchronization circuit 15. The output of the driver 19 is connected to the S line 5a of the terminal device 3. Note that the R line 4a and S line 5a of the terminal device 3 are L for communication, respectively.
It is connected to the reception terminal R, transmission control terminal TX, and reception control terminal RX of SI8. Further, the phase synchronization circuit 15 and the cutoff circuit 14 are also connected,
A clock circuit 20 that generates a clock at a predetermined timing is connected to the phase synchronization circuit 15.

When the line termination device 2 is operating normally, the cutoff circuit 14 sets the data transmission path between the R line 4 and the R line 4a in a connected state. At this time, the phase synchronization circuit 15 outputs a timing pulse synchronized with the timing signal transmitted from the S line 5 to the communication LSI 8 of the terminal device 3 via the S line 5a. As a result, the terminal device 3 samples the data input to the reception terminal R of the communication LSI 8 via the R line 4a using the timing pulse input to the reception control terminal RX, converts it into predetermined parallel data, and outputs it to the data bus. do.

Here, the signal relay device 11 will be explained in detail using FIG. 4.

FIG. 4 is a detailed configuration diagram of the signal relay device 11 according to the present invention.

In the figure, the cutoff circuit 14 is composed of an AND gate 30, and the phase locked circuit 15 is composed of a differentiating circuit 31. Counter 32. It is composed of a ROM 33.

The ROM 33 is equipped with a determining means 16 and a cutoff setting means 17.

The R line 4 of the line termination device 2 (FIG. 1) is connected to the input of the receiver 12. The output of receiver 12 is connected to one of the inputs of AND gate 30. The output of the AND gate 30 is connected to the human power of the driver 19. The output of the driver 19 is the R line 4 of the terminal device 3 (Fig. 1).
connected to a. The S line 5 of the line termination device 2 is connected to the receiver 13 . The output of the receiver 13 is connected to the input of the differentiating circuit 31. Differential circuit 3
The output of 1 is connected to the counter 32 and ROM 33. The counter 32 and the ROM 33 are connected by a plurality of address lines AD. The counter 32 is provided with a pulse terminal 34 . Furthermore, a clock circuit 2o is connected to the counter 32. Pulse terminal 3
4 is connected to the input of the driver 19. Driver 1
The output of 9 is connected to the S line 5a of the terminal device 3. R
The OM 33 is provided with a determining means 16 and a cutoff setting means 17, and is further provided with a cutoff terminal 35. The cutoff terminal 35 is connected to the other input of the AND gate 30.

The AND gate 30 is a circuit that connects and disconnects the data transmission path between the R line 4 and the R line 4a. The differentiation circuit 31 is
This circuit differentiates the timing signal input from the S line 5 and outputs a differentiated pulse.

The counter 32 is a circuit that performs a predetermined count at the timing of the clock output from the clock circuit 20 and outputs a predetermined timing pulse to the pulse terminal 34. The start and end of this counting is controlled by a differential pulse input from a differentiating circuit. The ROM 33 automatically applies a predetermined correction value to the counter 32 according to the counting result of the counter 32.
This is a circuit configured to input to the Also ROM3
The determining means 16 provided in the differential circuit 3 determines whether the repetition period of the timing signal of the S line 5 is within a specified range based on the pulse inputted from the differentiating circuit 31. In the cutoff setting means 17, when the judgment means 16 makes a judgment outside the specified range,
A cutoff signal is output to the cutoff terminal 35.

In the signal relay device 11 having the above configuration, a regular timing signal is generated on the S line 5 when the line termination device 2 (FIG. 1) is operating normally. When this timing signal is differentiated by a differentiating circuit 31, differential pulses are input to the counter 32 and ROM 33 at a constant period. counter 3
2, a predetermined count can always be performed and a predetermined timing pulse can be outputted to the pulse terminal 34 accordingly. In this case, the timing pulse and the timing signal are in a synchronized state, that is, the repetition period of the timing pulse and the timing signal are the same. At this time, a mark state (high level) cutoff signal is set at the cutoff terminal 35, the AND gate 30 is kept open, and the data transmission path is in the connected state. As a result, data input via the R line 4 and receiver 12 is output as is to the driver 18 and R line 4a.

Further, if jitter or the like occurs in the timing signal of the S line 5, the determining means 16 of the ROM 33 determines whether the jitter is within the allowable range, and if it is within the allowable range, a predetermined correction value is sent to the counter is set so that the repetition period of the timing pulse outputted from the pulse terminal 34 of the counter 32 is kept constant. At this time as well, as described above, the cutoff terminal 35 of the ROM 33 is kept in the marked state, and the AND gate 3o is kept open, which is what is called the connected state of the transmission line.

Now, when the power to the line termination device 2 (Fig. 1) is turned on and off, or when there is a momentary power cut, etc., the S line 5,
Noise is input to the differentiating circuit 31 via the receiver 13 . The differentiating circuit 31 also differentiates this noise component and outputs a differentiated pulse.

Due to this differential pulse containing noise, a differential pulse having a repetition period shorter than that of the regular timing signal is input to the counter 32 and the ROM 33.

The counter 32 and ROM 33 are unable to follow this differential pulse, and the counter 32 does not count sufficiently. In this case, the ROM 33 performs a slight correction and sets a correction value in the counter 32. The counter 32 performs counting based on this correction value, and the pulse terminal 34
continues to output a predetermined timing pulse.

On the other hand, the determining means 16 determines that the timing signal has a repetition period outside the specified range, and operates the cutoff setting means 17. The cutoff setting means 17 sets a cutoff signal in a space state (low level) to the cutoff terminal 35. As a result, the AND gate 30 closes, cutting off the data transmission path, and R
line 4, interrupting data input via receiver 12.

Furthermore, if the timing signal on the S line 5 stops, the counter 32 continues to count based on the pulses from the clock circuit 20, so that the timing signal is always output from the pulse terminal 34. Therefore, the terminal device 3
(FIG. 1) will not lose its operating timing. Further, since the terminal device 3 does not receive unnecessary data containing noise, it is prevented from performing erroneous data processing.

When the timing signal on the S line 5 returns to its normal state, the counter 32 again outputs a timing pulse synchronized with the timing signal. Further, the cutoff setting means 17 sets the cutoff signal to a mark state (high level). This opens the AND gate 30, and the data transmission path between the R line 4 and the R line 4a becomes connected.

The communication line connection system of the present invention is not limited to the above embodiments. In the embodiment, the circuit switching network 1 is used as an example of a communication line, but the communication line may be, for example, a dedicated line connecting specific networks. Furthermore, although the signal relay device 11 has been described as a single unit, it may be built into the line termination device 2 or the terminal device 3. Furthermore, the cutoff circuit 14 is connected to the AND gate 3.
0, but after accepting the cutoff signal, R line 4 and R line 4a
It is also possible to use an equivalent circuit, such as a flip-flop, which can connect and disconnect the data transmission path between the two.

(Effects of the Invention) The communication line connection system of the present invention configured as described above monitors the timing signal from the S line of the line termination device using the signal relay device, and when the repetition period of this timing signal is within a specified range, outputs a timing pulse based on this timing signal to the terminal device. Furthermore, if the timing signal is outside the specified range, a unique timing pulse is output without depending on the timing signal. Further, the data transmission path between the R line 4 and the R line 4a is cut off. As a result, the terminal device 3 does not lose its operating timing, and at the same time does not receive data on the R line 4 containing noise components.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the communication line connection method of the present invention, FIG. 2 is a block diagram of the main parts of a conventional communication line connection method,
FIG. 3 is a timing chart showing the operation of a conventional communication LSI, and FIG. 4 is a detailed configuration diagram of a signal relay device according to the present invention. l...Line switching network, 2...Line termination device, 3...
Terminal device, 11... Signal relay device, 14... Cutoff circuit, 15... Phase synchronized circuit, 16... Determination means, 1
7... Cutoff setting means, 20... Clock circuit, 3o
...And gate, 31...Differential circuit, 32...
Counter, 33...ROM, 34...Pulse terminal,
35... Cutoff terminal.

Claims (1)

[Scope of Claims] A signal relay device inserted between a line terminating device used to connect a communication line and a terminal device connected to the line terminating device, comprising: the line terminating device and the terminal device; and a phase synchronization circuit inserted into a timing signal transmission path between the line termination device and the terminal device, The phase synchronized circuit outputs a timing pulse toward the terminal device, and includes a determining means for determining whether or not a repetition period of the timing signal is within a specified range; A communication line connection system characterized in that the communication line connection method further comprises a cutoff setting means that is controlled by the cutoff circuit and cuts off the data transmission path.