JPS6054061A - Interface circuit - Google Patents

Abstract

PURPOSE:To prevent the influence of turning-off of a power supply unit in a certain terminal station upon the other terminal stations by providing break circuits and opening circuits between a common bus, a receiver, and a driver if the voltage of the power supply unit is lower than a prescribed value. CONSTITUTION:Break circuits BR1-BRn monitor the voltage of power supply units PU and open circuits between a common bus BUS, receivers R, and drivers DR if this voltage is lower than a prescribed voltage. That is, circuits BR1- BRn consist of voltage monitor parts SV, relays RL, common bus BUS, and relay contacts rl, and the monitor part SV stopts driving the relay RL if the voltage of the power supply unit PU is lower than the prescribed value. Then, the relay contact rl is opened to open circuits between the common bus BUS, the receiver R, and the driver VR, and thus, the influence upon the other terminal stations is prevented even if the power supply unit of one terminal station is turned off.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a system in which a plurality of carrier terminal devices, etc. are connected to a control device via a common bus, and data is sent and received via the common bus. This invention relates to improvements to interface circuits that interface with buses.

Conventional Techniques and Problems Traditionally, in order to control a plurality of carrier terminal devices, carrier terminal devices T, ~Tn are connected to a control device CON T via a common bus BUS, as shown in Fig. 1. , which exchanges data.

Each carrier terminal device Tl-Tn has an interface circuit for interfacing with the common bus BUS.
(before).

Each interface circuit includes a receiver R and a driver DR constituting an input/output coupler IOP, and a power supply unit PU that supplies electrophoresis to these receivers R and driver DR.

In this configuration, especially the disconnection receiver R and driver DR of the power supply unit PU may appear to have low impedance when viewed from the common bus BUS. Object of the Invention The present invention eliminates these drawbacks, and prevents even if the power station unit of one terminal station is disconnected from affecting other terminal stations. The purpose of the present invention is to provide an interface circuit that does not cause

According to the present invention, an input/output boat that receives data from a common bus and sends data to the common bus, a power source that supplies power to the input/output boat, and an input/output boat that receives data from a common bus and sends data to the common bus; An interface circuit characterized in that it is a break circuit that detects whether or not the m voltage is at a specified value, and disconnects the connection between the special skill common bus and the input/output board when it is detected that it is below the specified value υ. achieved by

Examples of the invention EMBODIMENT OF THE INVENTION The present invention will be explained based on examples below.

87! 2 ml is an example of the present invention, and t3R1 in the figure
-BRn is a break circuit, and the same members as in FIG. 1 are given the same reference numerals.

The break circuits BRI to BRn in the present invention monitor the voltage of the power supply unit PU, and when the voltage is below a predetermined voltage, the common bus 3U S and the receiver R2 driver D
I am trying to keep the distance between ILs open.

A specific example is shown in FIG.

The break circuit consists of a voltage monitoring section S-V, a relay RL, and a relay contact rz connected between the common bus BUS, the receiver, and the driver DR. At a certain time, relay I%L is being driven, and when the value is found to be below a predetermined value, driving of relay RL is stopped.

This opens relay contact rl and connects the common bus BUS.
, receiver R and driver DR are opened.

FIG. 4 shows another specific example.

In the figure, a transistor TR is used instead of a relay.

The voltage monitoring unit SvI'i causes a current to flow through the base of the cape 1 transistor TR where the voltage W is positive (-1), and turns off the base current when the voltage falls below a predetermined value, and turns off the transistor TR.

Since the collector TR between the transistors TR has a high impedance, it does not affect the common bus.0 Effects of the Invention As described above, according to the present invention, when the voltage of the power supply unit is below a predetermined value, the common bus is disconnected. Since the receiver and the driver are opened, it is possible to eliminate the influence on other units due to an abnormality in at least one of the plurality of units.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a conventional interface circuit, FIG. 2 is a diagram showing an interface circuit of the present invention, and FIGS. 3 and 4 are diagrams showing specific examples of break circuits. In the figure, [ti ~ BRn is the break circuit, RL is the relay +,
rl is a relay contact, TR is a transistor, 〇$1 Figure BuS Mushroom 3m

Claims (1)

[Claims] An input/output port that receives data from a common bus and sends data to the common bus, a power supply that supplies power to the input/output port, and detects whether the power supply voltage is a specified value,
An interface circuit characterized by having a break circuit that disconnects a special skill common bus and an input/output boat when it is detected that the voltage is below a specified value.