JPH04238434A - Transmission equipment - Google Patents

Abstract

PURPOSE:To realize full duplex communication whose control is easy with two transmission lines by deciding the voltage of the transmission line for signal to be intermediate voltage when signals in different levels are outputted with two transmission equipments, detecting the state and estimating the output level of an opposite equipment. CONSTITUTION:Two transmission lines 1 and 15 are connected by two transmission line for signal 3 and the signal line for ground 5. The voltage level of the transmission line 3 is divided into H, L and M which is the middle of them by a level deciding means 10 so as to detect it. A reception data reproducing means 14 outputs L as reception data Rx when the transmission line 3 is H or M and transmission data Tx added to a driver 6 is L. When the transmission line 3 is L or M and Tx is H, L is outputted as Rx. Thus, the output of the opposite equipment can be estimated in two transmission equipments 1 and 15 and full duplex communication can easily be executed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission device used for digital wire communication.

0002

2. Description of the Related Art FIG. 2 shows the configuration of a conventional transmission device. In FIG. 2, reference numerals 21 and 22 indicate transmission devices that are communication partners with each other. The driver 23 of one transmission device 21 and the receiver 24 of the other transmission device 22 are
They are connected to each other by a signal transmission line 25 and a ground transmission line 26. The receiver 27 of one transmission device 21 and the driver 28 of the other transmission device 22 are also connected to each other by a signal transmission line 29 and a ground transmission line 30.

The signal output from the driver 23 of one transmission device 21 is received by the receiver 24 of the other transmission device 22, and the signal output from the driver 28 of the other transmission device 22 is received by the receiver 24 of the other transmission device 22. is received by the receiver 27 of.

[0004] In this way, even with the conventional transmission devices described above, full-duplex communication can be performed by connecting the two transmission devices with each other using four wires.

[0005]

However, the conventional transmission device described above requires four transmission lines, which poses a problem in that the cost of the transmission lines increases. Further, although full-duplex communication is possible with two transmission lines, there is a problem in that control becomes difficult.

[0006] The present invention is intended to solve such conventional problems, and an object thereof is to provide an excellent transmission device that can perform full-duplex communication using two transmission lines with simple control.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides two transmission line connection terminals, one for signals and the other for ground, so that each signal can be connected between two transmission devices. Connect terminals for transmission and ground terminals together using a transmission line, and make sure that the driver to which transmission data is input has an output resistance, and determine whether the signal level on the signal transmission line is high (H) level, low (L) level, or A means is provided to determine whether the signal level on the transmission line is at the middle (M) level, or when the signal level on the transmission line is at the H level, or when the signal level is at the M level and the transmission data of the own transmission device is about to transmit at the L level. , when the other transmission device is determined to be transmitting H level, and conversely, the signal level on the transmission line is L level, or when it is M level and the transmission data of the own transmission device is about to transmit H level. In this case, it is determined that the other party's transmission device is transmitting L level.

[0008]

[Operations] The present invention has the following functions due to the above structure. That is, when focusing on the signal level on the transmission line, the signal level is H level when both transmission devices are outputting H level, and the signal level is L level when both transmission devices are outputting L level. However, if they are outputting different levels, the H level and L level are divided by the output resistance of the driver, resulting in an M level on the transmission line, so the level that the own device is trying to send and the transmission From the signal level on the line, it is possible to infer the signal level that the other device is trying to transmit.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the structure of an embodiment of the present invention. In FIG. 1, 1 is a transmission device, 2 is a signal terminal for connecting a signal transmission line 3, and 4 is a ground terminal for connecting a ground transmission line 5. 6 is a driver having a non-zero finite output impedance, and 7 is a resistor that serves to increase the output resistance of the driver 6. Comparators 8 and 9 constitute a level determining means 10. The values of the thresholds Va and Vb of the comparators 8 and 9 are set so that Vl<Vb<(Vh+Vl)/2<Va<Vh, where the H level output voltage of the driver 6 is Vh and the L level output voltage is Vl. stipulated in Reference numerals 11, 12, and 13 are gate circuits for obtaining received data Rx, and constitute received data reproducing means 14. The received data reproducing means 14 is configured to set the received data Rx to H when the output of the comparator 8 is H, or when the output of the comparator 8 is L and the output of the comparator 9 is H and the transmitted data Tx is L. has been done. 15 is the other transmission device connected by two wires, the signal transmission line 3 and the ground transmission line 5;
It has the same configuration as .

Next, the operation of the above embodiment will be explained. First, when the transmission data Tx in one transmission device 1 is H, and the other transmission device 15 is also transmitting H, the signal transmission line 3 becomes H level, the output of the comparator 8 becomes H, and the received data Rx becomes H. When the other transmission device 15 is transmitting L, the level of the signal transmission line 3 becomes the M level between Va and Vb due to the voltage drop across the resistor 7. Therefore, the output of comparator 8 is L and the output of comparator 9 is H, but the transmission data Tx is H.
Therefore, the received data Rx becomes L.

Conversely, the transmission data Tx of one transmission device 1
is at L level, and when the other transmission device 15 is transmitting H, signal transmission line 3 becomes M level between Va and Vb due to the voltage drop across resistor 7, and comparator 8
The output of the comparator 9 becomes L, the output of the comparator 9 becomes H, and the received data Rx becomes H. When the other transmission device 15 is transmitting L, the signal transmission line 3 becomes L, the output of comparator 8 becomes L, the output of comparator 9 becomes L, and the received data Rx becomes L.

The following table summarizes the above relationships.

[Table 1]

As described above, according to the above embodiment, even when signals of different levels are output between the two transmission devices 1 and 15, the state on the signal transmission line 3 is detected as M level. , it has the advantage that the output level of the other device can be estimated in relation to the transmission level of the own device, and full-duplex communication can be performed by simple control using two transmission lines.

[0014]

Effects of the Invention As is clear from the above embodiments, when two transmission devices output signals of different levels, the voltage of the signal transmission line is between the H level and the L level. Since the output level of the other device is estimated based on the relationship with the output level of the own device when that state is detected, full-duplex communication is possible with two simple transmission lines. It has this effect.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram of a transmission device in an embodiment of the present invention.

[Figure 2] Block configuration diagram of a conventional transmission device

[Explanation of symbols]

1 Transmission device 2 Signal terminal 3 Signal transmission line 4 Ground terminal 5 Transmission line for ground 6 Driver 7 Resistor 8,9 Comparator 10 Level determination means 11, 12, 13 Gate circuit 14 Received data reproduction means 15 Transmission device Tx Transmission data Rx Received data

Claims (1)

[Claims] [Claim 1] A signal terminal for connecting a signal transmission line, a ground terminal for connecting a ground transmission line,
a driver that is connected to the signal terminal and receives transmission data and has a non-zero finite output impedance; and a driver that is connected to the signal terminal and has a voltage level of the signal transmission line at a high level, a low level, or an intermediate level thereof. a level determining means for determining whether the level is a middle level;
outputting a high level when the signal transmission line indicates a high level or when the signal transmission line indicates a middle level and the transmission data indicates a low level;
A transmission device comprising received data reproducing means for outputting a low level when the signal transmission line indicates a low level or when the signal transmission line indicates a middle level and the transmission data indicates a high level.