JPS6020939B2 - Transmitting/receiving device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a receiving device that transmits signals bidirectionally between a pair of transmitters and receivers, and is designed to reliably prevent the inside of each transmitter and receiver from being damaged by the influence of noise. It is.

Figures 1 and 2 show general audio equipment for vehicle battles, where 1 is a first transceiver, 2 is a second transceiver, 3 is a speaker, and 4 is a display that displays frequency, etc. 5 is a group of key switches for tuning, 6 is a microcomputer that controls them, 7 is a radio receiving circuit, 8 is its antenna, 9 is a PLL circuit, 10 is a microcomputer that controls them, 11 is a microcomputer 6,10
A transmission line for transmitting and receiving signals between

By dividing one audio device into two transmitting and receiving parts in this way, it is possible to easily attach the first transmitter/receiver 1 to a dashboard. By the way, in such audio equipment, from the viewpoint of reducing power consumption during backup, it is conceivable that the microcomputers 6 and 10 are configured with one CMOS. However,
Since the input/output impedance of CMOS 1 is very high, if pulse noise such as ignition noise is induced in the transmission line 11, the CMOS LSI may be destroyed by this noise. Therefore, the present invention connects a buffer circuit to the input/output terminal of each transmitter/receiver, and uses this buffer circuit to prevent damage inside the transmitter/receiver.
Bidirectional signal transmission is also possible without any problems.

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 3, parts having the same functions as those in FIG. 1 are denoted by the same reference numerals, and explanations thereof will be omitted. a and b are input/output terminals of the microcomputers 6 and 10, respectively, Q, Q2 are buffer transistors, R2 . R4 is an emitter resistor, R, ., R3 are feedback resistors, and C, ., C2 are capacitors for absorbing pulse noise. It should be noted that the smaller the resistance value of the above-mentioned emitter resistor is, the more advantageous it is against external noise, but for practical purposes, it is selected to be about several hundred ohms. The feedback resistors R, , R3 are normally set to several tens of kilohms. Since the capacitors C and C2 are emitter resistors and the capacitors C and R4 are four resistors, they can be omitted. In the above configuration, let us consider a case where a pulse wave as shown in FIG. 7 is transmitted between the microcomputers 6 and 10 and is sent from the computer 6.

When the output of the microcomputer 6 is at L level, the emitter of transistor Q is at L level. Therefore, the emitter of transistor Q2 is also at L level, and the base of transistor Q2 is also at L level. Therefore, an L level signal is input to the input terminal b of the microcomputer 10. Next, if the output terminal a of the microcomputer 6 becomes H level, the base of the transistor Q becomes H level.
Therefore, a base current flows to the base of transistor Q, and the emitter of transistor Q becomes H level.

Therefore, the emitter of the transistor Q2 becomes H level, and the H level is applied to the input terminal b of the microcomputer 10 via the feedback resistor R3. Next, consider the case where a signal is transmitted from the microcomputer 10 to the microcomputer 6.

At this time, terminal b becomes an output terminal and terminal a becomes an input terminal.
Then, as in the case described above, the signal at output terminal b is applied to input terminal a. In this way, transistors Q,,Q
The buffer circuit composed of 2 can transmit signals in both directions, and since the terminal impedance of the transmission line 11 is regulated by the emitter resistors R2 and R4, it has a low value of about several hundred ohms.

Therefore, external noise is less likely to be induced in the transmission line 11, and damage to the microcomputers 6, 10 due to external noise can be reliably prevented. FIG. 4 shows another embodiment of the present invention, showing only the periphery of the microcomputer 6 on the first transceiver 1 side.

This is a feedback circuit constructed using a diode D instead of a resistor R. In this way, if a is an input terminal, when the output becomes H level, the transistor Q,
A base current flows through the base of transistor Q, the emitter of transistor Q becomes H level, and a signal is transmitted to microcomputer 10. Next, when an H level signal is transmitted from the microcomputer 10, the diode D,
An H level signal is input to input terminal a via. FIG. 5 shows a feedback circuit composed of a transistor Q3.

Even in this way, the same effect can be obtained. FIG. 6 generally illustrates the invention.

In FIG. 6, 12 is a high input/low output impedance common mode amplifier, R6 is a small resistance of about several hundred ohms, and R5 is a feedback resistor of about several tens of kilohms. When terminal a functions as an output terminal, the same signal as that at terminal a appears at terminal a' due to normal amplifier operation, and the signal is transmitted to microcomputer 10. On the other hand, when a signal is transmitted from the microcomputer 10, terminal a functions as an input terminal, and if terminal a' is at L level, an L level signal is applied to terminal a via resistor R5. Terminal a' is H
If the level is high, the H level is applied to the terminal a via the resistor Q5. Of course, in place of the resistor 5 shown in FIG. 6, a diode or a transistor may be used as shown in FIGS. 4 and 5. In this way, the present invention connects the input terminals of a pair of high-input, low-output impedance common-mode amplifiers to the input/output terminals of a pair of transmitters/receivers using an LSI configured with CMOS, and The output devices are connected via a transmission line, and a positive feedback circuit is connected between the input and output terminals of each of the common mode amplifiers.
The buffering effect of each of the common-mode amplifiers mentioned above sufficiently buffers the noise that enters the transmission line, preventing the circuits inside each transmitter and receiver from being destroyed, and also allows bidirectional signal transmission without any problems. You can get the same effect.

[Brief explanation of drawings]

Figures 1 and 2 are side views and block diagrams for explaining general sound equipment for car teaching, Figure 3 is a circuit diagram of one embodiment of the present invention, and Figures 4 and 5 are other diagrams. FIG. 6 is a circuit diagram showing the main part of the embodiment, FIG. 6 is a circuit diagram generally showing the present invention, and FIG.
The figures are transmission waveform diagrams of each of the above embodiments. 1...First transceiver, 2...Second transceiver, 6
, 10... Microcomputer, 12... Common mode amplifier, Q,, Q2... Transistor, R., R3, R5
,D,,Q...Element forming the feedback circuit, R2
, R4... Emitter resistance, C,, C2... Capacitor. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1 Connect the input terminals of a pair of high-input, low-output impedance common-mode amplifiers to the input/output terminals of a pair of transmitters and receivers using LSI configured with CMOS, and transmit data between the output terminals of each of the above-mentioned common-mode amplifiers. A transmitting/receiving device that is connected via a line and has a positive feedback circuit connected between the input and output terminals of each of the in-phase amplifiers.