JPH0724832Y2 - Automatic transmission / reception switching circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a transmission / reception automatic switching circuit, and more particularly to a transmission / reception automatic switching circuit for automatically switching between transmission and reception in a communication control device.

[Conventional technology]

Conventionally, this type of automatic transmission / reception switching circuit has been configured to switch transmission / reception by a transmission / reception switching signal V _S , as shown in FIG.

In this circuit, first, when transmitting data from the transmitting circuit 1a, the transmitting data is output to the communication path 8 via the driver circuit 2. Further, the transmission / reception switching signal V _S is output at the same time when the output of the transmission data is started, the operation of the receiver circuit 3a is prohibited, and the transmission mode is set so that the transmission data is not input to the reception system.

At the same time as the transmission is completed, the transmission / reception switching signal V _S enters the reception mode, enables the receiver circuit 3a, and prepares to receive the reception data from another station propagating through the communication path 8.

When receiving the reception data from the communication path 8, the reception data is input via the receiver circuit 3a, and the reception clock generation circuit 5 synchronizes with the bit cycle of this reception data and has a predetermined frequency. A signal is generated, the clock signal is input to the CK terminal of the flip-flop circuit 6, the output signal of the receiver circuit 3a is input to the D terminal, and the reception data synchronized with the clock signal is extracted from the Q terminal and transmitted to the reception circuit 7. It was a composition.

[Problems to be solved by the invention]

Since the above-mentioned conventional transmission / reception automatic switching circuit switches the transmission / reception by the transmission / reception switching signal, if the transmission / reception switching signal cannot be generated for some reason, the transmission / reception cannot be switched and the transmission and reception of the communication control device is difficult. There is a drawback that

An object of the present invention is to provide a transmission / reception automatic switching circuit that can automatically switch between transmission and reception without generating a special transmission / reception switching signal and can smoothly perform transmission and reception of a communication control device.

[Means for solving problems]

The automatic transmission / reception switching circuit of the present invention includes: a transmission circuit that outputs predetermined transmission data at the time of transmission and a signal of a constant level at the time of reception; a driver circuit that transmits the output signal of the transmission circuit to a communication path; A receiver circuit that receives a signal of a communication path, an exclusive OR circuit that takes an exclusive OR of the output signal of the transmission circuit and the output signal of the receiver circuit, and the output signal of the exclusive OR circuit , A receiver outputs a clock signal of a predetermined frequency synchronized with a predetermined signal cycle of the transmission data during transmission, and outputs a clock signal of a predetermined frequency synchronized with a specific signal cycle of the output signal of the receiver circuit during reception A clock generation circuit,
The output signal of the exclusive OR circuit is fetched in synchronization with the clock signal from the reception clock generation circuit, a signal of a constant level is output during transmission, and a signal corresponding to the output signal of the receiver circuit is output during reception. And a flip-flop circuit.

〔Example〕

Next, an embodiment of the present invention will be described with reference to the drawings.

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

In this embodiment, a transmitter circuit 1 for outputting transmission data to a communication path 8, a driver circuit 2, a receiver circuit 3 for inputting data from the communication path 8, an exclusive OR circuit 4, and a reception clock generation. It has a configuration including a circuit 5, a flip-flop circuit 6, and a receiving circuit 7.

Next, the operation of this embodiment will be described.

FIG. 2 is a waveform diagram of signals when this embodiment is operated.

When transmitting the transmission data V _T from the transmission circuit 1 (during transmission), the transmission data is output to the communication path 8 via the driver circuit 2. At that time, the transmission data V _T directly from the transmission circuit 1 is input to one of the input ends of the exclusive OR circuit 4, and the driver data 2, the communication path 8 and the receiver circuit 3 are input to the other input end. The signal V _I is input. This signal V _I is
Since it passes through the driver circuit 2 and the receiver circuit 3, it is input later than the transmission data V _T , and the output signal V _X of the exclusive OR circuit 4 has a waveform in which the hazard V _H is generated.

The reception clock generation circuit 5 generates a clock signal V _CK having a predetermined frequency in synchronization with this hazard period, that is, the bit period of the transmission data V _T , and outputs this clock signal V _CK to the CK terminal of the flip-flop circuit 6. To remove the hazard V _H input to the D terminal and set the terminal to a high level to inhibit transmission data from being input to the receiving circuit 7.

Next, when receiving the reception data from the communication path 8 (during reception), first, the reception data is input via the receiver circuit 3.

At that time, the output signal V _T of the transmission circuit 1 is input to one of the input terminals of the exclusive OR circuit 4 at a constant high level indicating the reception mode, so that the output signal V _I of the receiver circuit 3 is exclusive. It is inverted by the logical OR circuit 4 and becomes the output signal V _X.

Receiving clock generating circuit 5 inputs the output signal V _X, synchronized with the bit period of the received data included in the output signal V _X, generates a clock signal V _CK having a predetermined frequency, the clock signal V _CK Is input to the CK terminal of the flip-flop circuit 6, and the reception data included in the output signal V _X input to the D terminal is extracted from the terminal in synchronization with the clock signal V _CK, and is slightly smaller than the original reception data. And is transmitted to the receiving circuit 7 as the received data V _R which is delayed.

Therefore, the transmission / reception can be automatically switched by utilizing the waveform at the time of transmission and the waveform at the time of reception of the output signal V _T of the transmission circuit 1 without generating the transmission / reception switching signal, and the transmission / reception is smoothly performed.

[Effect of device]

As described above, according to the present invention, the output signal of the transmission circuit is the transmission data at the time of transmission and the signal of the constant level is at the time of reception, and the exclusive logic between the output signal of this transmission circuit and the signal of the communication path input through the receiver circuit. An exclusive-OR circuit that takes the sum is provided, a clock signal is generated by the output signal of this exclusive-OR circuit, the output signal of the exclusive-OR circuit is fetched in synchronization with this clock signal, and at a certain level during transmission. Since the signal corresponding to the signal of the communication path is transmitted to the internal circuit at the time of reception, it is possible to automatically switch between transmission and reception without generating a special transmission / reception switching signal. There is an effect that can be done smoothly.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram of signals when the embodiment shown in FIG. 1 is operated, and FIG. 3 is a conventional transmission / reception automatic switching circuit. It is a block diagram which shows an example. 1,1a ... Transmitting circuit, 2 ... Driver circuit, 3,3a ... Receiver circuit, 4 ... Exclusive OR circuit, 5 ... Reception clock generation circuit, 6 ... Flip-flop circuit, 7 ... Reception Circuit, 8 ... Communication path.

Claims (1)

[Scope of utility model registration request] 1. A transmission circuit which outputs predetermined transmission data at the time of transmission and outputs a signal of a constant level at the time of reception, a driver circuit which transmits an output signal of the transmission circuit to a communication path, and a signal of the communication path. A receiver circuit for receiving, an exclusive OR circuit that takes an exclusive OR of the output signal of the transmitter circuit and the output signal of the receiver circuit, and an output signal of the exclusive OR circuit, A reception clock generation circuit that outputs a clock signal of a predetermined frequency that is synchronized with a predetermined signal period of transmission data, and outputs a clock signal of a predetermined frequency that is synchronized with a specific signal period of the output signal of the receiver circuit when receiving; , The output signal of the exclusive OR circuit is fetched in synchronization with the clock signal from the reception clock generation circuit, and a signal of a constant level is output during transmission and reception Receive automatic switching circuit, characterized in that it comprises a flip-flop circuit for outputting a signal corresponding to the output signal of the receiver circuit is.