JPS59218063A - Data transmission equipment - Google Patents

Abstract

PURPOSE:To attain ease of retrieval of a failed equipment by interlocking a switch connecting a transmission line of a bus type data transmission system and a transmission/reception circuit with an on-line/off-line mode selecting switch so as to attain respectively electric connection/disconnection. CONSTITUTION:Data transmission lines 1, 2 and 3 are connected by a single transmission line 4 and transmit/receive data mutually. The transmission line 4 is terminated at a termination resistor. Each data transmission equipment consists of a connecting terminal 20 to the transmission line 4, a relay 21 inserted between the terminal 20 and transmission and reception circuits 22, 23 and conducting connection/disconnection for the transmission line 4 and the transmission/receptoin circuits 22, 23 a logical section 24 controlling transmission of data and processing of reception data between the transmission/reception circuits 22, 23, and a mode setting switch 25 setting the operation of the on-line mode or the off-line mode for the data transmission equipment. The relay 21 is interlocked with a mode setting switch 25 opening/closing the contact.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a data transmission device, and more particularly to a data transmission device used in a DC-coupled bus type data transmission system.

[Conventional technology and problems]

A bus-type data transmission system that connects a large number of devices through a single transmission path is simple in configuration and can be realized at low cost, so it is often used in distributed processing systems consisting of various terminal devices and personal computers.

Among these bus type data transmission systems, the DC 1H type transmission system connects the transmission line and each device in an all-DC manner, but is it a transformer? Compared to the AC coupling type transmission system used, it has all the excellent features of being able to connect a large number of devices at low cost.

However, when one of the devices in the transmission system breaks down and communication becomes impossible, it may take a lot of effort to search all the devices to find out which device is defective. For example, if the transmitting circuit of one of the devices in the transmission system is damaged and the Deba circuit becomes short-circuited, the fault will occur and even if the power to the 7C device is turned off, the value line and ground wire of the transmission line will be short-circuited. It is difficult to determine which device is defective because the device is in such a state that it is left unattended. As described above, the conventional bus type data transmission system has the disadvantage that when even one of the plurality of connected devices fails, it requires a great deal of effort to restore the entire system.

[Purpose of the invention]

An object of the present invention is to connect a transmission line and a transmitting/receiving circuit via a switch in a data transmission device used in a DC-coupled bus type data transmission system, and to connect the transmission path and the transmitting/receiving circuit through a switch, and to operate the switch in conjunction with an online/offline mode selection switch. It is an object of the present invention to provide a data transmission device which eliminates the above-mentioned drawbacks by electrically connecting/disconnecting the transmission line with each other, and which makes it easy to search for a failed device.

[Summary of the invention]

According to the present invention, in a data transmission device used in a data transmission system that uses all bus-type transmission lines, a logic section that controls and processes data, and a data transmission system are provided. A transmitting/receiving circuit for transmitting data, a setting means for instructing whether to use the online mode in which all data is transmitted or in an offline mode in which all data is not transmitted, and when the setting means indicates the online mode, the transmitting/receiving circuit and the transmitting circuit There is obtained a data transmission device characterized in that it comprises a switch that is fully connected to the transmission line and disconnects from the transmission line when in the off-line mode.

[Embodiments of the invention]

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing an example of the configuration of a DC coupled bus type data transmission system using the data transmission equipment of the present invention. In the figure, data transmission devices 1, 2.3 are connected by a single transmission line 4 and mutually transmit and receive data.

Note that the transmission line 4 is terminated by terminating resistors 5 and 6.

Next, FIG. 2 is a circuit block diagram showing an embodiment of the data transmission device of the present invention. In the figure, a data transmission device is interposed between a connection terminal 20 to a transmission line 4 (shown in FIG. 1), and between this connection terminal 20 and a transmitting circuit 22 and a receiving circuit 23. A relay 21 that performs all connection/disconnection with circuits 22 and 23, and the transmitting/receiving circuit 2
2. A logic unit 24 that controls data transmission and processes received data to and from 23, and operates the data transmission device in online mode (transmits data) or offline mode (does not transmit all data). Or? It consists of a mode setting switch 25 to be set. Note that the mode setting switch 25 provides a setting mode instruction to the logic section 24, and the relay 21 provides a setting mode instruction to the logic section 24.
The contacts open and close in conjunction with the

In this embodiment, when the offline mode is selected by the mode setting switch 25, the contacts of the relay 21 are closed, the transmitter/receiver circuits 22 and 23 are connected to the transmission line, and the offline mode is selected by the mode setting switch 25. The contacts of the relay 21 are opened and the transmitting/receiving circuits 22 and 23 are disconnected from the transmission line. That is, in the bus-type data transmission system shown in FIG. 1, only data transmission devices set to online mode are electrically connected to the transmission line 4'.

Generally, in this type of data transmission system, if one of the data transmission devices fails and the entire system becomes unable to communicate, for example, in a bus-type data transmission system in which the transmitter/receiver circuit is directly coupled to the transmission line, When a short circuit occurs in the transmitting circuit, conventional data transmission devices require a lot of effort and effort to search for all failed data transmission devices by disconnecting the connecting cables one by one.
A bus-type data transmission system configured with the data transmission device of the present invention does not require such work, and can search for and disconnect a failed data transmission device by simply setting the mode setting switch of each data transmission device offline. Therefore, the data transmission system can be quickly restored. Additionally, the data transmission device separated in this way can be operated in an offline mode depending on the case, so that the influence on the entire system can be minimized.

Note that this example does not completely limit the present invention. In other words, in a boat where a relay is used as an example of a switch, an electronic switch may be used in conjunction with the mode setting means.

〔Effect of the invention〕

As is clear from the above description, according to the data transmission device of the present invention, by providing a switch interlocked with the mode setting means between the transmission path and the transmitting/receiving circuit, it is extremely easy to search for a lost device. This has the effect that a complete bus-type data transmission system with excellent maintainability can be constructed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of the configuration of a DC-coupled bus type data transmission system using a data transmission device according to the present invention, and FIG. 2 is a circuit block diagram showing an embodiment of the data transmission device according to the present invention. be. In the figure, 1, 2.3... data transmission device,
4...Transmission line, 5.6...Terminal resistor, 20...Connection terminal, 21...Relay, 22...Transmission circuit , 23... Receiving circuit, 24... Logic section, 25... Mode setting switch.

Claims (1)

[Claims] A data transmission device used in a data transmission system with a completely blind bus-type transmission path includes a logic section that performs all data control and processing, a transmitting/receiving circuit that transmits data, and whether or not it is used in online mode for transmitting data. A setting means for instructing whether to use an offline mode in which no transmission is performed, and a setting means for instructing whether to use the setting means in an offline mode in which all transmissions are performed. and a metal release switch.