JPS61244149A - Data transmission system - Google Patents

Abstract

PURPOSE:To prevent an error in basic data transmission control procedure and to reduce the maintenance of a data transmission system and a load in an operation time by discarding a data signal block to be transmitted to the opposite terminal device next unless an answer signal is received within a specific time. CONSTITUTION:A timer circuit 3 is started with timer start information from a received signal processing circuit 1, but if an answer time is sent back within the prescribed time owing to data transmission delay, etc., it is decided that the timer circuit enters a time-out state and then while actuation information for actuating a negative acknowledgement signal generating circuit 4 is generated and sent out to the generating circuit 4, the timer is started so as to monitor the next time-out state. The negative acknowledgement signal generating circuit 4 generates a negative acknowledgement signal NAK with the start information from the timer circuit 3 and sent out to the transmitted signal processing circuit 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a data transmission system that performs data transmission using a basic data transmission control procedure.

[Conventional technology]

The basic data transmission control procedure is well known in JIS 08382 and the like. FIG. 3 is a block diagram of a data system according to this control procedure, and FIG. 4 is a flowchart of the data signals.

Data transmission systems are usually provided with various functions, such as a reception timeout function, to prevent errors during data transmission from adversely affecting the system. In the case of Figure 4,
The data signal that was expected to be received was incorrect on the data transmission path and could not be received within the specified time, so the reception timed out, so a makeshift signal was sent to check the status and the computer 5 and the terminal device 6 were matched. The aim is to maintain future data transmission. In this case, in order to prevent data signal block order errors, DL is used as an acknowledgment signal.
E O and DLE 1 are alternated.

In response to this basic form, there have been demands for various additional functions, such as longer distances for data transmission lines and more efficient use of the transmission lines themselves.
Various data transmission devices, such as modem and multiplexing devices, have been invented to meet the demands.

FIG. 5 shows an example of a configuration in which these data transmission devices are introduced into a system. When a data transmission device is introduced, some data transmission delay will occur in principle. If this data transmission delay is small, it will not affect data transmission, but if the data transmission delay increases significantly, it will impede data transmission. As an example of this, Fig. 6 shows a data signal flowchart. Fig. 6 shows that the acknowledgment signal DLEO, which was expected to be received, did not arrive within the specified time and the reception timed out, so the timing signal ENQ was Since the acknowledgment signal DLE O arrived after the transmission,
D as an acknowledgment signal to the 0th order that sent the next text 1
When LE_1 was expected, the acknowledgment signal DLE_O of the timing signal ENQ was received as if it were a response signal to the text 1 signal, indicating that a control procedure failure had occurred.

Note that the broken line indicates data transmission delay.

[Problem that the invention seeks to solve]

As mentioned above, in conventional data transmission systems, when a data transmission device that causes a significant data transmission delay is introduced into the system, the data transmission delay may cause an error in the data transmission control procedure, and it is necessary to prevent this failure. The disadvantage is that more sophisticated fault recovery methods must be used to recover.

An object of the present invention is to provide a data transmission system that does not cause failures in data transmission control procedures even when a data transmission device that causes a significant data transmission delay is introduced.

[Means for solving problems]

According to the present invention, if a signal block expecting a response signal from the other party's terminal device is not received within a predetermined time after a signal block expecting a response signal from the other party's terminal device is transmitted from the white terminal device, By discarding the data signal block to be transmitted next to the side terminal device, errors in the basic data transmission control procedure are prevented.

That is, the data transmission system of the present invention uses a basic data transmission control procedure and transmits data between terminal devices via data transmission devices provided in each terminal device. It receives and sends it to the data transmission device of the other party's terminal device, and if it detects a signal block that expects a response signal from the other party's terminal device among the received data signals, it creates timer activation information and sends a negative response. When the signal transmission information is received, the receiving signal processing circuit discards the data signal block that is sent next from the white terminal device as a data signal block corresponding to the negative response signal. , a negative response signal generation circuit that generates a negative response signal, and a data signal transmitted from the other party's terminal device via the other party's data transmission device and the own party's data transmission device, and transmits it to the white terminal device; When the reception signal processing circuit detects a response signal corresponding to the detected signal block, timer stop information is created, and when the negative response signal is sent from the negative response signal generation circuit, the timer stop information is generated. a transmission signal processing circuit that temporarily suspends transmission, transmits the negative response signal to the white terminal device, and transmits the negative response signal transmission information indicating that the negative response signal has been transmitted to a reception signal processing circuit; It is activated by timer activation information, and is reset if the timer stop information comes within a preset time, and if it does not arrive, it is determined as a timeout and the negative response signal generation circuit is activated to generate the negative response signal. , a circuit block consisting of a timer circuit to be restarted is installed between the data transmission device and the terminal device.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a circuit block constituting an embodiment of the data transmission system according to the present invention. It will be installed. Since the method is the same whether the data transmission device is connected to a computer or the like or a terminal device, etc., in this embodiment, it is possible to The data signal processing method will be explained.

Received data signals sent in blocks from the computer 5 in accordance with the basic data transmission control procedure are input to the received signal processing circuit l. The received signal processing circuit 1 monitors the basic data transmission control procedure of the received data signal, and when it detects a signal block in the received data signal that expects a response signal from the other party's terminal device 6, it starts the timer circuit 3. Create timer activation information to activate the timer and send it to the timer circuit 3. Further, the received signal passes through the received signal processing circuit 1 without being processed in any way unless the signal discarding process described below is performed, is sent to the data transmission device 7.8, and is finally transmitted to the terminal device 6. be done.

Next, the data signal transmitted from the terminal device 6 is input to the transmission signal processing circuit 2 via the data transmission devices 8 and 7. The transmission signal processing circuit 2 also monitors the basic data transmission control procedure of the transmission data signal, and stops the timer of the timer circuit 3 when a response signal corresponding to the signal block detected by the reception signal processing circuit 1 is detected. Create timer stop information and send it to the timer circuit 3. In addition, unless the transmitted data signal conflicts with the negative acknowledgment signal NAK, which will be described later,
It passes through the transmission signal processing circuit 2 as it is and is sent to the computer 5.
transmitted to.

The timer circuit 3 is activated by timer activation information from the received signal processing circuit l, but if a response signal is returned from the terminal device 6 within a preset specified time, the transmitted signal processing circuit 2 detects this. This information will stop the timer, return the value to the initial value, and prepare for the next timer activation. No special processing will be performed, but the impact of data transmission delay etc. If a response signal is not returned within a specified time, it is determined as a timeout, and startup information for activating the negative response signal generation circuit 4 is created and sent to the negative response signal generation circuit 4, and the next timeout is monitored. , restart the timer. The negative response signal generation activation information and the number of restarts of the timer are predefined in accordance with the operating conditions of the system in use.

The negative response signal generation circuit 4 creates a negative response signal NAK based on the activation information from the timer circuit 3, and sends it to the transmission signal processing circuit 2. The transmission signal processing circuit 2 normally transmits the data signal transmitted from the terminal device 6 and passed through the data transmission device 8.7 to the computer 5.
When the negative response signal NAK is sent from the negative response signal generation circuit 4, the transmission of the transmission data signal from the terminal device 6 is temporarily interrupted, the negative response signal NAX is transmitted to the computer 5, and the received signal processing is performed. It sends negative response signal transmission information to the effect that the negative response signal NAK has been transmitted to circuit l. When the received signal processing circuit 1 receives this negative acknowledgment signal transmission information, it assumes that the next data signal block sent from the computer 5 is a data signal block corresponding to the negative acknowledgment signal NAK, and processes this data signal block. It is discarded and not sent to the data transmission device 7.

The circuit on the computer 5 side has been explained above, but the terminal device I! The same applies to the 6th side.

By performing the above operations, errors in the basic data transmission control procedure can be prevented.

FIG. 2 shows an example of data transmission in this embodiment, in which the acknowledgment signals DLE O, DL that specify reception are
Since E1 did not arrive within the specified time, a negative acknowledgment signal NAK is sent to the computer 5 and the text O,
The data of Text 1 has been discarded, and no control procedure failure has occurred.

〔Effect of the invention〕

As explained above, the present invention provides a method for transmitting a signal block expecting a response signal from a terminal device on the other side after a signal block expecting a response signal from the terminal device on the other side is not received within a predetermined time. By discarding the next data signal block to be transmitted to the other party's terminal device, errors in the basic data transmission control procedure can be prevented, reducing the burden on maintenance and operation time of the data transmission system. It has a mitigating effect.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram configuring an embodiment of the data transmission system according to the present invention, FIG. 2 is a diagram showing an example of the flow of data signals in the data transmission system of FIG. 1, and FIG. 3 is a diagram of the data transmission system. FIG. 4 is a diagram showing an example of the flow of data signals in a $3 data transmission system, FIG. 5 is a block diagram of another conventional example of a data transmission system, and FIG. FIG. 3 is a diagram showing an example of the flow of data signals in the data transmission system shown in the figure. l: Reception signal processing circuit, 2: Transmission signal processing circuit, 3: Timer circuit. 4: Negative response signal generation circuit, 5: Computer, 6: Terminal device, 7.8: Data transmission device. Patent applicant: NEC Corporation - PJ1 Figure 3 Figure 5

Claims (1)

[Claims] In a data transmission system that uses a basic data transmission control procedure to transmit data between terminal devices via data transmission devices provided in each terminal device, a data signal from the own terminal device is received and a data signal from the other terminal device is transmitted to the other device. sends it to the data transmission device of the side terminal device, and creates timer activation information if it detects a signal block that expects a response signal from the other side terminal device among the received data signals,
When negative response signal transmission information is received, reception signal processing that discards this data signal block, assuming that the next data signal from the local terminal device is a data signal block corresponding to the negative response signal. a circuit, a negative response signal generation circuit that generates a negative response signal, and a data signal transmitted from the other party's terminal device via the other party's data transmission device and the own party's data transmission device, and transmits it to the own party's terminal device. At the same time, when the reception signal processing circuit detects a response signal corresponding to the detected signal block, timer stop information is created, and when the negative response signal is sent from the negative response signal generation circuit, the transmission data is generated. a transmission signal processing circuit that temporarily suspends signal transmission, transmits the negative response signal to the local terminal device, and transmits the negative response signal transmission information indicating that the negative response signal has been transmitted to a reception signal processing circuit; , The timer is activated by the timer start information, and is reset if the timer stop information arrives within a preset time, and if the timer does not arrive, a timeout occurs and the negative response signal generation circuit is activated to generate the negative response signal. A data transmission system characterized in that a circuit block comprising a timer circuit that is activated and restarted is installed between the data transmission device and the terminal device.