JPH0250537A - Bidirectional simultaneous communication system - Google Patents

Abstract

PURPOSE:To reduce time loss by providing a receiver circuit to compare the average value of value corresponding to the high level signal and low level signal of the voltage sent to communication equipment with a threshold, and outputting a signal voltage lower than the high level threshold and higher than the low level threshold with a driver circuit. CONSTITUTION:Both devices connected to both sides of a communication line are composed of the same reference, a driver circuit 1 and a receiver circuit 2 are provided, and a supply voltage, respective thresholds corresponding to the input signal of the level higher and lower than the setting of a resistance and respective desired output voltages are generated. The receiver circuit 2 provides a comparator, the voltage value and the threshold corresponding to the own output signal are compared, and thus, the level of the signal of an opponent is identified. For such a reason, at the time of combining low and high levels, the supply voltage and the resistance are set so that the voltage formed on a communication line goes to the middle of such threshold levels. Thus, the bidirectional communication is executed by one signal line and without generating waiting time for transmitting and receiving, the time loss can be reduced.

Description

[Detailed Description of the Invention] [Summary] In a bidirectional communication system such as bus communication of an interface circuit, bidirectional communication is performed using a single signal line, and there is no waiting time for transmission and reception, thereby reducing time loss. A driver circuit that outputs a signal voltage such that the average value of the value corresponding to the high-level signal and the value corresponding to the low-level signal of the voltage sent to the communication device is a predetermined value, and the high-level signal a receiver circuit that compares the predetermined value with a high-level threshold value created by a high-level threshold value or a low-level threshold value created by a low-level signal, the predetermined value being lower than the high-level threshold value; The driver circuit is configured to output a signal voltage higher than a level threshold.

[Industrial application field]

The present invention relates to a bidirectional communication method such as bus communication for an interface circuit, and particularly to a bidirectional simultaneous communication method in which both devices can simultaneously transmit and receive data using a single signal line.

[Conventional technology]

In bus communication of interface circuits, it is essential to be able to perform bidirectional communication using one bus.
As for the communication method, while one device is transmitting to the bus, the other device is only receiving, and each device at a given moment is dedicated to either transmitting or receiving.

FIG. 3 is a configuration diagram showing an example of a conventional two-way communication system. In the figure, it is assumed that bidirectional communication is performed between device A and device B using one communication line, and each device is composed of a driver circuit 31 and a receiver circuit 32. In the first conventional example shown in FIG.
In the second conventional example shown in FIG. 3(b), the driver circuit 31 is composed of a 5T element and is composed of an open collector or an open drain. The 3-5T element is Hi and L.

It is an element that enables three-value states of Hz and Hz (high impedance), and has the advantage of high transmission speed.

[Problem to be solved by the invention]

The conventional circuit described above cannot perform simultaneous transmission and reception.

First, in the first conventional example, the driver circuit is a 3-5T element, and when the device sends a signal, the driver circuit of device B puts the output in a high impedance state, and when the device B sends a signal, The driver circuit to the device controls the output to be in a high impedance state for transmission.

Therefore, if the driver circuits of device A and device B try to send out signals at the same time, a bus fight may occur in which the outputs are shorted, and the device may be destroyed.

Next, in the second conventional example, the driver circuit is an open collector or an open drain, and when outputting a high level, the output is isometrically open, and the high level is determined by a pull-up resistor. Therefore, a short circuit as in the first conventional example does not occur, but for example, if device A outputs a high level,
If device B outputs a low level, the receiver circuit of device A should receive a low level, and the receiver circuit of device B should receive a high level, but device B
Since the driver circuit is outputting a low level, the receiver circuit cannot receive a high level.

In this way, conventional interface circuits cannot transmit and receive at the same time, so the other cannot start transmitting until the other has finished transmitting, creating a waiting time for transmitting and receiving, resulting in a large time loss. .

The present invention was created in view of these problems, and
The object of the present invention is to provide a simultaneous two-way communication system that performs two-way communication using one signal line, does not generate waiting time for transmission and reception, and reduces time loss.

[Means to solve the problem]

Means for solving the above problems in the present invention is that a pair of devices including a driver circuit and a receiver circuit are connected by one communication line, and one receiver circuit receives a signal sent from the other driver circuit at a high level. In the simultaneous communication system when performing two-way communication by identifying whether the voltage is high or low level, the average of the value corresponding to the high level signal and the value corresponding to the low level signal of the voltage sent to the communication line a driver circuit that outputs a signal voltage whose value becomes a predetermined value; and a receiver circuit that compares a high-level threshold value created from a high-level signal or a low-level threshold value created from a low-level signal with the predetermined value. The driver circuit is provided with a bidirectional simultaneous signal system in which the driver circuit outputs a signal voltage such that the predetermined value is lower than the high level threshold value and higher than the low level threshold value.

[Effect]

In the present invention, both devices connected to both sides of one communication line are configured based on the same standard, are equipped with a driver circuit and a receiver circuit, and can handle high or low level input signals by setting the supply voltage and resistance. Create each threshold and each desired output voltage. When signals are sent from both devices at the same time, the output voltage will be formed on the communication line by three types of combinations: high and low, high and high, and low and low, but the receiver circuit uses a comparator The level of the other party's signal is identified by comparing this voltage value with a threshold value corresponding to its own output signal. For this reason, the supply voltage and resistance are set so that when a combination of high and low occurs, the voltage formed on the communication line is between the high and low thresholds.

〔Example〕

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

FIG. 1 is a configuration diagram of an embodiment of the present invention.

In the figure, two-way communication is performed between device A and device B.
It is assumed that the communication is carried out using a real communication line, and each device is composed of a driver circuit 1 and a receiver circuit 2. The driver circuit 1 is composed of an open collector or oven drain, and the receiver circuit 2 is composed of a comparator.

Each part of device A1 and device B corresponds, R1=R6,
R2=R7°, R3=R8, R4=R9, and R5=10.

Device A is at H level (open because it is an open collector)
When device B sends out L level, the voltage VA at a point on the communication line is determined by: However, VoL is the L level voltage of each driver circuit.

If the receiver circuit of device A recognizes this voltage VA as L level and the receiver circuit of device B recognizes it as H level, then
Since simultaneous bidirectional transmission and reception is possible, the recognition function of the receiver circuit will be explained below.

At this time, since device A is sending out H level, signal S1 is H level (ViH), and the ffi pressure vB at the minus side 0 point of the comparator of device A is R1・R4+R3・R, +R,・R2.

Also, since device B is sending out the L level, the signal S2 is the L level (ViL), and the voltage VC at the minus side 0 point of the comparator of device B is R1・R4+R3
・R5+R4・R1.

As already mentioned, the resistance values of the two devices correspond, so it is okay to set VB as the H level threshold and VC as the L level threshold, as shown in Figure 2(a). Become. That is, when device A is sending out H level and device B is sending out L level, voltage VB becomes the H level threshold, and VA input to the positive side of device A comparator is lower (as a result, the receiver circuit of device A can recognize that device B is sending out the L level, and on the other hand, the voltage VC becomes the threshold of the L level, and the voltage is on the positive side of the comparator of device B. VA to be input
is higher, and the receiver circuit of device B is higher than that of device A.
You can recognize that the level is being sent.

FIG. 2(b) is an explanatory diagram when both sides send out the same level. First, if both sides send H level, 0
The voltage at the point is almost the VccO value, which is higher than the H level threshold, and the receiver circuits of both sides realize that the other side is H level.
You can recognize that the level is being sent. Furthermore, when both parties send out H level, the voltage at the 0 point is as follows, which is lower than the L level threshold, and both receiver circuits can recognize that the other party is sending out L level.

In this way, in this embodiment, the receiver circuit can identify the voltage on the communication line as H level or L level in any case, so simultaneous transmission and reception is possible.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to provide a simultaneous two-way communication system that performs two-way communication using one signal line, does not generate waiting time for transmission and reception, and reduces time loss. can.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an embodiment of the present invention, FIG. 2 is an explanatory diagram of an embodiment of the present invention, FIG. 3 is a configuration diagram of a conventional example. 1.31; Driver circuit, 2.32i receiver circuit. Circuit diagram of the present invention Figure 1 Explanatory diagram of -X' embodiment of the present invention Figure 2

Claims (1)

[Claims] A pair of devices including a driver circuit (1) and a receiver circuit (2) are connected by one communication line, and one receiver circuit (2) transmits the other driver circuit (1). In the simultaneous communication method when performing two-way communication by identifying whether the signal sent to the communication line is high level or low level, the value corresponding to the high level signal of the voltage sent to the communication line and the value corresponding to the low level signal are determined. A driver circuit (1) that outputs a signal voltage whose average value is a predetermined value (VA), and a high-level threshold (VB) created from a high-level signal.
Or a low level threshold (V
C) and the predetermined value (VA).
), the driver circuit (1) outputs a signal voltage such that the predetermined value (VA) is lower than a high level threshold (VB) and higher than a low level threshold (VC). Features a two-way simultaneous signal system.