JPH0561823B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] Regarding a multi-drop communication system using a digital leased line branch network, a time division multiplexing device is connected to a master station and each slave station of the digital leased line branch network, and these In order to enable multi-drop communication via is controlled to all 1, and when the control signal is on, a frame format signal is transmitted in synchronization with the frame bit, and the signal is called by a polling method from the desired channel of the master station via the time division multiplexing device. When the control signal is turned on at the terminal interface section of the called channel, the slave station transmits a response signal in synchronization with the frame bit, and the control signal is turned on at the terminal interface section of the corresponding channel of the slave station that is not called. Configure it to transmit an all-1 signal when it is off.

[Industrial application field]

The present invention relates to a multi-drop communication system that uses a digital leased line branch network, connects a time division multiplexing device to a master station and each slave station, and enables multi-drop communications via these devices.

Recently, a digital dedicated line branch network service has begun, in which the transmitting line from the master station is branched at each slave station, and the receiving line is capable of inserting data via an AND circuit at each slave station. Ta.

Accordingly, it is desired to provide a multi-drop communication system in which a time division multiplexing device is connected to a master station and each slave station, thereby enabling multi-drop communication.

[Conventional technology]

A conventional example will be explained below using figures.

FIG. 6 is a block diagram of a conventional time division multiplexing device, and FIG. 7 is a time chart of signals at each part in the case of FIG. 6. A to E correspond to points a to e in FIG. 6. D-1 is an enlarged view of D.

Terminals 1, 1-1, . . . of multiple channels (hereinafter referred to as CH) are generally connected to the time division multiplexing device 30, and data from these terminals is transmitted to the terminal interface unit 60. , 61, .

So, to explain the flow of data, for example,
When transmitting 6-bit transmission data SD from terminal 1 as shown in Figure 6B, to indicate that transmission is in progress,
The control signal RS is input to the terminal interface 60 as 1 level as shown in A, and the terminal interface section 60 compresses 6-bit data SD between frame bits F of the system clock shown in C.
The control signal RS is inserted together with the sampled control bits S, and is output as one frame of 8-bit data as shown in D.

When expanded, this 8-bit data is as shown in D-1, and the multiplexing unit 20 receives terminal data for 8 CHs as shown in D-1, which is time-division multiplexed as shown in E. It is output via the line termination device 36.

In this case, in order to achieve synchronization, the output from the terminal interface sections 60, 61, ... is the transmission data.
Regardless of the presence or absence of SD, it is transmitted as an 8-bit frame format signal including frame bit F and control bit S.

Therefore, when this time division multiplexing device 30 is used, one line is always required for each terminal, and only point-to-point communication is possible.

[Problem that the invention seeks to solve]

That is, when the above-mentioned time division multiplexing device is connected to the master station and slave stations of the digital leased line branch network and an attempt is made to perform multi-drop communication, signals from each slave station are superimposed on the receiving line of the master station. Therefore, even if a digital leased line branch network service that is optimal for multi-drop communication is launched, there is a problem that multi-drop communication cannot be performed using this network.

In view of the above-mentioned problems, the present invention provides a multi-drop communication system that connects a time division multiplexing device to a master station and each slave station of a digital leased line branch network and enables multi-drop communication via these devices. For the purpose of providing.

[Means for solving problems]

FIG. 1 is a block diagram of the principle of the present invention.

The line on the transmitting side from master station A is for each slave station B, C,
Branches at D, . . ., and the line on the receiving side is connected to AND circuits 10, 11, 1 at each slave station B, C, D, .
Using a digital private line branch network in which data can be inserted via terminals 2, . . . , the master station A and each slave station B, C, D, . A time division multiplexing device 30 for time division multiplexing is connected to the master station, and a time division multiplexing device 31 is connected to each slave station. 20 and the terminal interface unit 21 between the terminal
When the control signal of the terminal is off, the frame format signal is controlled to all 1s, and when the control signal is on, the frame format signal is transmitted in synchronization with the frame bits.

Then, the slave station that is called by the polling method from the desired channel of the master station A via the time division multiplexer 30 turns on the control signal at the terminal interface section 21 of the called channel and turns on the frame bit. A response signal is transmitted synchronously, and the control signal is turned off at the terminal interface section 21 of the corresponding channel of the slave station that is not called, and an all-1 signal is transmitted.

[Effect]

According to the present invention, when a desired CH of a master station A calls a terminal of a corresponding CH of a slave station C, for example, by a polling method via the time division multiplexer 30, this signal is sent to the slave stations B, D, The terminal interface unit 21 of the terminal of the corresponding CH of slave station C turns on the control signal and transmits a response signal of the frame format signal synchronized with the frame bits, and The terminal interface section 21 of the terminal of the corresponding CH of stations B, D, .

That is, only the signal synchronized with the frame bit of the corresponding CH of the called slave station C is sent to the AND circuit 1.
1 and 10 and is input to the time division multiplexing device 30 of the master station A, making multi-drop communication possible.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

Fig. 2 is a block diagram of an embodiment of the present invention, and Fig. 3 is a time chart of signals of each part in Fig. 2, A to D.
correspond to points a to d in FIG. FIG. 4 is a block diagram of the terminal interface section of the embodiment of the present invention, and FIG. 5 is a time chart of signals of each part in FIG. 4, and A to E correspond to points a to e in FIG. 4. .

FIG. 2 shows a case where a computer 70 performs multi-drop communication to terminals 1, 2, and 3 of CH1 of slave stations B, C, and D using the polling method using CH1 of the time division multiplexer 30 of the master station A. The time division multiplexing device 31-1 used for slave stations B, C, and D
31-2 and 31-3 are different from the conventional time division multiplexer 30 used in the master station A in the terminal interface unit 21.

For this terminal interface section 21, FIG.
This will be explained using FIG.

When the control signal RS shown in FIG. 5A, which is at the 1 level when transmitting data, and the 6-bit transmission data CD shown in FIG. 6-bit transmission data between frame bits F
Compress SD, insert control bits S sampled from the control signal RS, and create one frame 8 as shown in D.
Output as a bit signal.

On the other hand, the control signal RS is input to the delay control section 41,
It is inverted and set to 0 level when transmitting data, and set to 1 level when not transmitting data, but this switching timing is controlled to be at the position of frame bit F of the system clock as shown in E, and the master station Avoid pseudo synchronization at A. The output of the frame assembly section 40 and the output of the delay control section 41 are logically summed by an OR circuit 42 and output.

Therefore, referring to FIG. 2, the operation of performing multi-drop communication will be explained.

In the computer 70 of the master station A, using a polling method using a continuous signal as shown in FIG. When terminal 1 is called, this signal is sent to slave stations B, C, and D, and sent to terminals 1, 2, and 3 via time division multiplexers 31-1, 31-2, and 31-3.

In slave stations C and D, since terminals 2 and 3 are not being called, the terminal interface section 21 corresponding to terminals 2 and 3 sends out all 1 level signals, and the multiplexing section 20, line termination device 34, 35 to the AND circuits 11 and 12, making it possible to transmit data through the AND circuit.

On the other hand, since terminal 1 of CH1 of slave station B is called, the terminal interface section 2 corresponding to terminal 1
1, a response signal as shown in B synchronized with the frame bit F is transmitted, and is placed on the receiving line to the master station A via the multiplexer 20, the line termination device 33, and the AND circuit 10 as shown in D. It is sent to the computer of the master station A via the line termination device 32.

Next, when terminal 2 of CH1 of slave station C is called using the polling method, this signal is also sent to slave stations B, C, and D, and time division multiplexers 31-1, 31-2, 3
1-3 to terminals 1, 2, and 3.

In slave stations B and D, since terminals 1 and 3 are not called, the terminal interface section 21 corresponding to terminals 1 and 3 sends out all 1 level signals, and the multiplexing section 20, line termination device 33, 35 to the AND circuits 10 and 12, allowing the data to be transmitted through the AND circuit.

On the other hand, since terminal 2 of CH1 of slave station C is called, the terminal interface section 2 corresponding to terminal 2
1, a response signal as shown in C synchronized with the frame bit F is transmitted, and is placed on the receiving line to the master station A via the multiplexer 20, the line termination device 34, and the AND circuit 11 as shown in D. It is sent to the computer of the master station A via the line termination device 32.

Therefore, multi-drop communication can be performed.

〔Effect of the invention〕

As described in detail above, according to the present invention, a time division multiplexing device is connected to a master station and a slave station of a digital leased line branch network to enable multi-drop communication.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the principle of the present invention, Fig. 2 is a block diagram of an embodiment of the invention, Fig. 3 is a time chart of signals in each part of Fig. 2, and Fig. 4 is a terminal of the embodiment of the invention. Block diagram of interface section, 5th
The figure is a time chart of the signals of each part in Figure 4,
The figure is a block diagram of a conventional time division multiplexing device, and FIG. 7 is a time chart of signals at various parts in FIG. In the figure, 1, 1-1, 2, 3 are terminals, 1
0, 11, 12 are AND circuits, 20 is a multiplexing section,
21, 60, 61 are terminal interface sections, 3
0, 31, 31-1, 31-2, 31-3 are time division multiplexing devices, 32 to 36 are line termination devices, 40
41 is a frame assembly unit, 41 is a delay control unit, A is a master station, and B, C, and D are slave stations.

Claims (1)

[Claims] 1. The transmitting line from the master station A is connected to each slave station B, C,
Branches at D, . . ., and the line on the receiving side is connected to AND circuits 10, 11, 1 at each slave station B, C, D, .
Using a digital private line branch network in which data can be inserted via terminals 2, . . . , the master station A and each slave station B, C, D, . Time division multiplexing devices 30 and 31 for time division multiplexing are connected to each slave station B, C, D, . . .
The terminal interface unit 21 between the multiplexer 20 of the time division multiplexer 31 and the terminal controls the frame format signal to all 1s when the control signal of the terminal is off, and controls the frame format signal to all 1 when the control signal is on. transmits a frame format signal in synchronization with frame bits, and a slave station called by a polling method from a desired channel of the master station A via the time division multiplexer 30 is a terminal of the called channel. The interface section 21 transmits a response signal in synchronization with the frame bit when the control signal is on, and the terminal interface section 21 of the corresponding channel of the slave station that is not called transmits an all-1 signal when the control signal is off. A multi-drop communication method characterized by: