JPH06188677A - Signal input/output circuit - Google Patents

Abstract

PURPOSE:To allow one system to sent/receive a signal by a photocoupler. CONSTITUTION:A primary side circuit A is provided with a 1st input output terminal 10 whose level is switched alternately to an L or an H level, a 1st light receiving element TR1 connecting to a power supply Vac, a 1st charge discharge circuit 11 comprising a resistor R1 and a capacitor C1, a 1st logic element 14 whose output is inverted under a prescribed condition in response to a voltage level appearing across the 1st charge discharge circuit and a 1st light emitting element D1 operated in response to an output of the 1st logic element, and a secondary circuit B is configured similarly and a same level appears at other terminal by switching a level of the 1st input output terminal 10 or a 2nd input output terminal 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal input / output circuit, and more particularly to a signal input / output circuit for transmitting / receiving a signal via a photocoupler.

[0002]

2. Description of the Related Art For example, when there are two circuits and their power supply potentials are different from each other, the respective circuits are usually connected via a photocoupler in an electrically insulated state.

In FIG. 3, for example, if the left side is a controller side and the right side is a controlled machine such as a robot machine controlled by the controller, a signal from the controller to the controlled machine is shown in FIG. Is shown, and the input circuit from the controlled device is shown in FIG.

That is, in the output circuit of FIG. 1A, the photodiode D1 is provided on the controller side, while the phototransistor TR1 as the counterpart is provided on the controlled device side. Further, in the input circuit of FIG. 7B, the phototransistor TR2 is provided on the controller side.
On the other hand, the photodiode D2 is provided on the controlled device side.

[0005]

As described above, the circuit configuration itself is relatively simple, but since the output side and the input side are separated, there is a drawback that two systems are required for signal transmission / reception. there were.

[0006]

The present invention has been made to solve the above-mentioned conventional drawbacks, and its structural feature is that the primary side circuit and the secondary side circuit are connected by a photocoupler. In the signal input / output circuit consisting of
A first input / output terminal that is selectively switched between an L level and an H level; a first light receiving element connected to a predetermined power source;
A first charging / discharging circuit including a resistor and a capacitor connected between the first light receiving element and the first input / output terminal;
The secondary side circuit includes a first logic element that inverts an output under a predetermined condition according to a voltage level appearing across the charge / discharge circuit, and a first light emitting element that operates according to an output of the first logic element. Is a second input / output terminal that is selectively switched between an L level and an H level, a second light receiving element that is connected to a predetermined power source and receives light from the first light emitting element, and a second light receiving element. A second charge / discharge circuit including a resistor and a capacitor connected between the second input / output terminal and the second input / output terminal, and under the same condition as the first logic element according to a voltage level appearing across the second charge / discharge circuit. A second logic element that inverts the output; and a second light emitting element that operates according to the output of the second logic element and emits light toward the first light receiving element, and the first input / output terminal or the above By switching the level of either one of the second input / output terminals Is to have to appear the other identical level to the terminal.

Here, when inverting elements for inverting the voltage levels are connected to both ends of each of the charge / discharge circuits, the first logic element and the second logic element are connected to each other.
An INVERT-NOR circuit that uses the inverted output as two inputs is used.

On the other hand, in the case where the inverting element is not used, the first logic element and the second logic element have two inputs of the voltage level appearing at both ends of the charge / discharge circuit.
It may be an OR circuit.

[0009]

As described above, since the primary side circuit and the secondary side circuit have symmetrical circuit configurations, for example, the first input / output terminal is switched from L level to H level (or from H level to L level). As a result, the level of the second input / output terminal is switched from the L level to the H level (or from the H level to the L level).

Similarly, the second input / output terminal is changed from L level to H level.
By switching to the level (or from the H level to the L level), the level of the first input / output terminal is switched from the L level to the H level (or from the H level to the L level).

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS. First, in the block diagram of FIG. 1, for convenience, the left side is a primary side circuit A such as a controller, and the right side is a secondary side circuit B of the controlled device.

According to this, the primary side circuit A is selectively switched between the H level and the L level by the first input / output terminal 1
0, and a phototransistor TR1 and a photodiode D1 connected to the primary side circuit power supply Vac.

When a signal is output from the primary side circuit A to the secondary side circuit B, the first input / output terminal 10 becomes H level by being opened, and is connected to the ground terminal at a switching terminal (not shown). As a result, the L level is set.

The collector side of the phototransistor TR1 is connected to the power supply Vac via an appropriate resistor R, but the first input / output terminal 10 is connected to the collector side of the phototransistor TR1 via resistors R1 and R2. Has been done. Between the connection point of the resistors R1 and R2 and the ground, a capacitor C1 that constitutes the charging / discharging circuit 11 together with the resistor R1 is provided.
Are connected.

Because of the charging / discharging circuit 11, when the first input / output terminal 10 is connected to the ground side, a sudden flow of voltage due to the power supply Vac to the terminal 10 side is prevented.

According to this embodiment, the charge / discharge circuit 11 described above is used.
The inverters 12 and 13 for inverting the voltage level are connected to both ends of the INVERT-N and the inverted outputs of the inverters 12 and 13 are two inputs.
An OR circuit 14 is provided. And this INVE
To the output side of the RT-NOR circuit 14, a gate element G1 for turning on / off by the same output to blink the photodiode D1 is connected.

The secondary circuit B is constructed almost symmetrically with the above-mentioned primary circuit A. That is, the secondary side circuit B is also selectively switched between the H level and the L level, the second input / output terminal 20, the phototransistor TR2 and the photodiode D2 connected to the secondary side circuit power supply Vbc.
It has and.

Even when a signal is output from the secondary side circuit B to the primary side circuit A, the second input / output terminal 20 becomes H level by being opened, and becomes a ground terminal by a switching terminal not shown. It is set to L level by being connected.

The collector side of the phototransistor TR2 is connected to the power supply Vbc via an appropriate resistor R, but the second input / output terminal 20 is connected to the collector side of the phototransistor TR2 via resistors R3 and R4. Has been done. Between the connection point of the resistors R3 and R4 and the ground, a capacitor C2 that forms a charging / discharging circuit 21 together with the resistor R3.
Are connected.

According to this embodiment, the charge / discharge circuit 21 is
The inverters 22 and 23 for inverting the voltage level are connected to both ends of the INVERT-N and the inverted outputs of the inverters 22 and 23 are used as two inputs.
An OR circuit 24 is provided. And this INVE
To the output side of the RT-NOR circuit 24, a gate element G2 for turning on / off by the same output to blink the photodiode D2 is connected.

Next, the operation of the present invention will be described with reference to the timing chart of FIG. The reference numerals in the figure correspond to the parts shown in the circuit diagram of FIG.

A case where a signal is output from the primary side circuit A to the secondary side circuit B will be described. First, it is assumed that the first input / output terminal 10 is connected to the ground side. In this case, the voltage levels of the terminals are both “L”,
Therefore, the outputs of the inverters 12 and 13 are both "H".
Therefore, the output of the INVERT-NOR circuit 14 is "H", which turns on the gate element G1 and causes the photodiode D1 to emit light.

In the secondary circuit B, the phototransistor TR2 is turned on upon receiving this light, so that the second input / output terminal 2
0 is set to the “L” level. This means that the terminals are at the “L” level, and therefore the outputs of the inverters 22 and 23 are both at the “H” level, which causes the INV
Since the output of the ERT-NOR circuit 24 becomes "H" and the photodiode D2 emits light, the phototransistor TR1 of the primary side circuit A is also turned on.

In this state, when the first input / output terminal 10 is switched from the ground side to the open terminal side at t1, the voltage level of the terminal 10 (terminal) shifts to "H", so that the output of the inverter 12 becomes "L". Invert. " This allows
Since the output of the INVERT-NOR circuit 14 is "L", and the gate element G1 is turned off accordingly, the photodiode D1 is turned off. As a result, the phototransistor TR2 of the secondary circuit B is turned off, and the charge / discharge circuit 2
At time t2 after a predetermined charging time of 1, the level of the terminal, that is, the second input / output terminal 20, becomes "H".

In response to this, the output of the inverter 22 is inverted to "L", so the INVERT-NOR circuit 24
Output turns to "L", the gate element G2 turns off,
The photodiode D2 is turned off.

As a result, the phototransistor TR1 of the primary side circuit A is also turned off, and the terminal portion is kept at "H" level.

When the first input / output terminal 10 is connected to the ground side at t3 and the terminal is set to the "L" level, the terminal instantly becomes the "L" level, but the terminal becomes the charge / discharge circuit 1.
Since the output of the INVERT-NOR circuit 14 is delayed by the discharge time of 1 and becomes the “L” level at t4,
Sometimes it becomes "H". As a result, as described above, the phototransistor TR2 of the secondary side circuit B is turned on, so that the terminal becomes "L" level at t5 after the discharge time of the charge / discharge circuit 21 has passed, and this is received. INVE
The output of the RT-NOR circuit 24 turns to "H", and the phototransistor TR1 of the primary side circuit A is also turned on.

The case where a signal is sent from the primary side circuit A to the secondary side circuit B has been described above. However, since the circuit configuration is symmetrical, the secondary side circuit B similarly performs the primary side circuit A. The signal can be transmitted to.

In the above embodiment, the inverters 12, 1
3, 22, 23 and INVERT-NOR circuits 14, 24
Is used in combination, but this logic circuit is NOR
It can be replaced with a circuit.

[0030]

As described above, according to the present invention, a signal input / output circuit can be provided by which a signal can be transmitted / received by a photocoupler in a single system, which is suitable for expansion I / O and the like.

[Brief description of drawings]

FIG. 1 is a circuit diagram according to an embodiment of the present invention.

FIG. 2 is a timing chart for explaining the operation of the embodiment.

FIG. 3 is a circuit diagram showing a conventional example.

[Explanation of symbols]

 10, 20 Input / output terminals 11, 21 Charge / discharge circuit 12, 13, 22, 23 Inverter 14, 24 INVERT-NOR D1, D2 Photodiode TR1, TR2 Phototransistor G1, G2 Gate element

Claims (3)

[Claims] 1. A signal input / output circuit in which a primary side circuit and a secondary side circuit are connected by a photocoupler, wherein the primary side circuit is selectively switched between an L level and an H level. A first input / output terminal, a first light receiving element connected to a predetermined power source, and a first charging / discharging circuit including a resistor and a capacitor connected between the first light receiving element and the first input / output terminal. A first logic element that inverts an output under a predetermined condition according to a voltage level appearing across the first charge and discharge circuit, and a first light emitting element that operates according to an output of the first logic element, The secondary side circuit has a second input / output terminal that is selectively switched between an L level and an H level, a second light receiving element that is connected to a predetermined power source, and receives light from the first light emitting element.
A second charging / discharging circuit including a resistor and a capacitor connected between the second light receiving element and the second input / output terminal;
A second logic element that inverts the output under the same conditions as the first logic element according to the voltage level appearing across the charge / discharge circuit;
A second light emitting element that operates according to the output of the second logic element and emits light toward the first light receiving element, and either one of the first input / output terminal or the second input / output terminal A signal input / output circuit characterized in that the same level appears at the other terminal by switching the level. 2. An inverting element that inverts the voltage level is connected to both ends of each of the charge and discharge circuits, and
The logic element and the second logic element have an inverted output of 2
The signal input / output circuit according to claim 1, comprising an INVERT-NOR circuit as an input. 3. The first logic element and the second logic element are NOR circuits having two inputs of a voltage level appearing at both ends of the charging / discharging circuit.
The signal input / output circuit described in.