JPS60201763A - Data transmission system - Google Patents

Abstract

PURPOSE:To perform the transmission of data with high efficiency by giving the transmission right only to the carrier signal that is delivered first between communication media and therefore omitting the complicated transmission control of a transmitter. CONSTITUTION:A transmitter checks whether a carrier is detected from a communication medium 5 through a carrier detecting part 34. If no carrier is not detected, a carrier is transmitted from the medium 5 by a transmission circuit 32. A collision detecting part 35 checks a collision between transmitted carriers. When no collision is produced, the data to be stored to a transmission buffer 33 is sent to the medium 5 from the circuit 32. While the transmission is discontinued and the reception processing is carried out in case a collision is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a data transmission system between transmission devices that perform half-duplex communication.

[Prior Art] Conventionally, when data is transmitted between transmission devices using half-duplex communication, data communication rights are granted only to a specific transmission device, and when communication rights are not delegated, other transmission rights are granted. The device was controlled in such a way that it was not given the right to transmit, which was inefficient and complicated to control.

In addition, there were cases in which the transmission device that started transmission first acquired the right to transmit, but if multiple transmission devices started transmitting at almost the same timing, data collisions could occur. When a collision occurs, generally called the C3MA/CD method, all transmission devices that were transmitting at the time of the collision are controlled to stop transmitting for a certain period of time, or a synchronization signal is output before the data signal, The length of this synchronization signal was set with priority for each transmission device, and control was performed so that only the transmission device with the longest length acquired the right to transmit.

However, this is troublesome because priorities must be set for each transmission device and special control must be applied to the transmitted signal.

[Objective] The present invention has been made in view of the above-mentioned drawbacks of the prior art, and its purpose is to provide a simple mechanism between communication media without requiring complicated transmission control in the transmission device. The purpose of the present invention is to propose a data transmission method that enables highly efficient data transmission without making any special changes to the transmitted signal.

[Example] An example of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an example of the configuration of a data transmission system in which a repeater device according to an embodiment of the present invention is arranged, in which 1 and 2 are transmission devices, 3 is a repeater, and 5a.

5b is a communication medium.

Details of this repeater 3 are shown in FIG.

In the figure, 5a and 5b are the communication media shown in FIG.
0 to 14 are amplifiers, 12.15 is a carrier detection section, and the carrier detection section a12 detects the carrier sent from the communication medium 5a side.
The output signal 20 from 12 enables the output of amplifier Bll and inhibits the output of amplifier C13. The carrier detection section b15 detects the carrier sent from the communication medium 5b side, and uses an output signal 21 to inhibit the output of the amplifier AIO and to permit the output of the amplifier D14. Since the carrier detection circuit of the carrier detection section is well known, a description thereof will be omitted.

Next, the transmission device 1 (2) will be explained with reference to the block diagram of FIG.

In FIG. 3, 30 is a receiving circuit, 31 is a receiving/output buffer, 32 is a transmitting circuit, 33 is a transmitting buffer, 34 is a carrier detection unit for detecting carriers in the communication medium 5;
3 is a collision detection section, 36 is a control section that performs transmission control, and 37 is an information processing section.

When sending data from the information processing unit 37, the control unit 3
6, the transmission data is stored in the transmission buffer 33, and the carrier detection unit 34 checks whether the data is being sent to the communication medium 5. If the communication medium 5 is free, the transmission circuit 32
The carrier is sent out for a certain period of time, and then the transmission buffer 3
The transmission data stored in 3 is sent out onto the communication medium 5 via the transmission circuit 32.

When receiving data, first a carrier is detected by the carrier detection section 34, and then data is sent, so that the data is received by the reception buffer 31 via the reception circuit 30 under the control of the control section 36. The received data is further sent to the information processing section 37 as necessary.

In the above explanation, if a carrier collision is detected in the collision detection unit 35 when the transmission circuit 32 sends out a carrier when transmitting data, it means that data transmission has been started by another device before the own device sends out the carrier. , cancels transmission, and enters reception mode. This control will be explained in detail with reference to the flowchart shown in FIG.

First, in step 100, the transmission device l checks whether or not a carrier is detected from the communication medium 5a by using the output of the carrier detection section 34. If no carrier is detected, the process proceeds to step 102, and the transmitting circuit 32 detects the carrier from the communication medium 5a. Send carrier to. Then, the process proceeds to step 104, where the collision detection section 35 checks whether or not a collision has occurred in the carrier sent out by the own device. If no collision has occurred, the data stored in the transmission buffer 33 is sent from the transmission circuit 32 to the communication medium 5 in step 106.

If a collision has occurred in step 104, the process proceeds to step 108, where the transmission is stopped, and in step 110, the mode is set to receive mode, and the process proceeds to step 112, which is a reception process. Also, if a carrier is detected in step 100, step 11
0 and executes reception processing. For example, communication medium 5
When a carrier signal is sent from the b side, this carrier signal is amplified by the amplifier C13 and input to the carrier detection section b15, where the carrier is detected and an output signal 21 is output. This output signal 21
The amplifier DI4 output is enabled and the amplifier AIO output is disabled. Therefore, even if the carrier signal is output from the transmission device 1 after this, the amplifier AIO of the repeater 3
It is not sent further and is not sent to the communication medium 5b side.

Therefore, the transmission device 1 is placed in a reception mode in preparation for receiving data sent from the transmission device 2.

By controlling in this way, very efficient data transmission can be performed without causing data collisions that disrupt the transmission control procedure or providing wait time.

[Effects] As explained above, according to the present invention, only the signal on the communication medium side that the carrier reached first is passed between the communication media,
By simply controlling the signal from the communication medium on the opposite side so that it is not sent to the other side, it is possible to easily determine which transmission device is capable of transmitting with priority over the transmission device that is trying to transmit, which is highly efficient and does not interrupt data transmission. Data transmission method can be provided.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a transmission system according to an embodiment of the present invention, FIG. 2 is a configuration diagram of a repeater device according to an embodiment of the invention, FIG. 3 is a diagram showing a configuration of a transmission device according to an embodiment of the invention, FIG. 4 is a transmission control flowchart of the transmission apparatus of this embodiment. In the figure, 1.2... Transmission device, 3... Repeater, 5a
, 5b... Communication medium, 10-14... Amplifier, 12
．． 15.34...Carrier detection unit, 30...Reception circuit, 31...Reception buffer, 32...Transmission circuit, 3
3... Transmission buffer, 35... Collision detection section, 36.
...it, II control section, 37... information processing section. 1st cause 2nd cause 3rd cause Figure 4

Claims (1)

[Claims] In a data transmission method of a data transmission system in which data is transmitted by connecting at least two transmission devices via a communication medium, a first carrier detects a carrier signal from one communication medium at a predetermined location of the communication medium. a detection means, a first transmission prohibition means for prohibiting transmission of a signal from the one communication medium to the other communication medium when the first carrier detection means detects the carrier, and a carrier from the other communication medium. a second carrier detection means for detecting a signal; and a second transmission prohibition means for prohibiting a signal from the other communication medium from entering the one communication medium when the second carrier detection means detects the carrier. , the transmission device is provided with collision detection means for detecting the occurrence of a collision of transmitted signals, and the transmission device is controlled to switch from transmission processing to reception processing when a collision occurs in carrier signals transmitted from the transmission device itself. A data transmission method characterized by