JPS62142A - Data transmission system - Google Patents

Abstract

PURPOSE:To prevent transmission of useless data by not receiving data to a buffer before the transmissible state is not reached. CONSTITUTION:A low-speed line interface circuit 5 controlling an interface opposite to a communication controller or a terminal equipment a buffer 6 storing transmission data, a relay line interface circuit 7 controlling the interface opposite to the communication line and a control circuit 8 controlling the entire time-division multiplexer are provided. The control circuit 8 is so designed that the circuit 8 gives a command to the low-speed line interface circuit 5 not to send SD to the buffer 6 until a carrier detection signal CD is received from the relay line interface circuit 7. Thus, the time division multiplexer stores no waste data and sends normal data after a fault of a communication line or an opposite station equipment is restored.

Description

[Detailed Description of the Invention] [1 Already Required] In a time division multiplexing device having a buffer for storing transmission data on the transmitting side, a transmission preparation completion is notified even if a carrier transmitted by a partner station cannot be detected, and this notification is performed. The data sent by the carrier is ignored without being stored in the buffer until the carrier is detected, thereby preventing unnecessary data from being sent.

[Industrial application field]

The present invention relates to a transmission device such as a time division multiplexing device, and is particularly concerned with isochronous transmission (transmission data becomes meaningless due to delays in sending data due to failures in communication lines or partner station equipment, etc.). This invention relates to a data transmission method that prevents transmission of lost data.

In recent years, data transmission between data terminal devices via communication lines has become popular. For example, terminal devices distributed in rural areas are connected to a centrally installed computer system via communication lines to transmit data.

In this case, the computer system is usually provided with a communication control device for controlling data transmission, and a transmission device for transmitting data onto a communication line is connected through the communication control device.

Then, a transmission device of the other station is connected via a communication line, and a terminal device is connected to this transmission device.

The transmission equipment used is a modem, time division multiplexing equipment, etc., but if the transmission equipment on the other side is unable to complete transmission preparations due to a failure in the other station's transmission equipment or a line failure, etc. , the transmission preparation completion signal CS may not be returned in response to the transmission request signal R3 from the communication control device or the terminal device.

If there is no response from this CS, the communication control device or the terminal device will erroneously determine that the transmission device of its own station is at fault, and the system will stop as a serious fault and will be in a state where automatic recovery is not possible. Therefore, when there is no failure in the transmission device of the own station, there is a system that returns the CS even if the transmission preparation is not completed.

When C8 is returned, transmission data will be sent, but it is necessary to ensure that the isochronism of this transmission data is not lost.

[Conventional technology]

FIG. 2 is a block diagram illustrating an example of a conventional data transmission system.

The communication control device 1 sends R3 to the transmission device 2 when transmitting data. The transmission device 2 communicates with the transmission device 3 based on the transmission control procedure, and returns the CS to the communication control device 1 when preparation for transmission is completed. When the communication control device 1 receives CS, it sends out transmission data SD. Transmission device 2 sends this data to transmission device 3 via a communication line.

The case where the terminal device 4 transmits data is similar to the above, and sends R3 to the transmission device 3, and upon receiving CS, sends out SD.

Here, if C8 is sent to the communication control device 1 even though the transmission preparation of the transmission device 2 is not completed due to a failure in the transmission device 3, for example, the communication control device 1 sends out the SD. In this case, the transmission device 2 is a time division multiplexing device that multiplexes several characters at a time, and has a buffer on the transmitting side, so even though it cannot transmit to the other station,
When the SD is sent, it is stored in the buffer.

[Problem that the invention seeks to solve]

When a time division multiplexing device with a buffer on the transmitting side is used as a transmission device as described above, conventionally it is incorrectly judged as a failure in the own station's transmission device, and it is treated as a serious failure that cannot be recovered unless the operator clears it as described above. In order to avoid a halt state, if you use the method of returning C8, the transmitted data will be accumulated in a buffer, and by the time it is ready to be transmitted and sent, it will have already lost its equal characteristics, and useless data will be transmitted. There's a problem.

In view of these problems, the present invention aims to prevent data that has lost isochronism from being accumulated, and to allow data to be accepted into the buffer only when it becomes ready to be transmitted. There is.

[Means for solving problems]

FIG. 1 is a block diagram of a circuit showing one embodiment of the present invention.

5 is a low-speed line interface circuit that controls the interface facing the communication control device or terminal device; 6 is a buffer that stores transmission data; 7 is a relay line interface circuit that controls the interface facing the communication line; 8
is a control circuit that controls the entire time division multiplexing device.

The control circuit 8 is configured to instruct the low-speed line interface circuit 5 not to send the SD to the buffer 6 until it receives the carrier detection signal CD from the relay line interface circuit 7.

[Effect]

With the above configuration, the time division multiplexing device does not accumulate unnecessary data, and can transmit normal data after a failure in the communication line or the partner station device is recovered.

〔Example〕

In FIG. 1, when the control circuit 8 is notified of the arrival of R3 from the low-speed line interface circuit 5, it controls the trunk line interface circuit 7 to prepare for transmission based on a transmission control procedure.

When preparations for transmission are completed, the carrier is sent from the other station,
The CD is sent from the trunk line interface circuit 7 to the control circuit 8. When the control circuit 8 receives this CD, it causes the low-speed line interface circuit 5 to send out the CS.

SD is sent by sending CS. The low-speed line interface circuit 5 stores this SD in the buffer 6, and the relay line interface circuit 7 multiplexes the data in the buffer 6 by several characters and sends it out.

If there is a failure in the communication line or the other party's device, the CD is sent to the control circuit 8 via the relay line interface circuit 7.
is not detected. However, since the control circuit 8 is healthy, the control circuit 8 causes the low-speed line interface circuit 5 to send out C8.

Therefore, for example, an SD is sent from the communication control device 1 in FIG.

Here, the communication control device 1 determines that there is a failure in the terminal device 4 of the partner station according to the transmission control procedure, and performs processing.

The control circuit 8 controls the low-speed line interface circuit 5 to transmit the S
D is stored in buffer 6.

〔Effect of the invention〕

As described above, the present invention can prevent the transmission of unnecessary data in a time division multiplexing apparatus having a buffer on the transmitting side.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a circuit showing an embodiment of the present invention, and FIG. 2 is a block diagram illustrating an example of a conventional data transmission system. In the figure, l is a communication control device, 2 and 3 are transmission devices, 4 is a terminal device, 5 is a low-speed line interface circuit, 6 is a buffer, 7 is a relay line interface circuit, and 8 is a control circuit. - Constant force safe, 1 reversible opening, 77 Figure 1 rfJ Vertical Pig Buddha U-style illustration 2 Leap

Claims (1)

[Scope of Claims] In a device that transfers data from a connected device on its own side stored in a buffer (6) on a transmitting side after confirming a state in which data can be received from the other station, it is possible to receive data from the other station. Means (5) and (8) are provided for preventing storage of transmission data in the buffer (6) until a signal notifying the other station is received, and even if the signal from the other station is not received, the connection on the local station side is maintained. A data transmission method characterized by notifying a device that transmission preparation is complete and preventing data to be transmitted from being stored in the buffer (6) based on the notification.