JPS6149859B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a two-wire full-duplex data transmission device that eliminates the adverse effects of signal leakage.

The two-wire full-duplex data transmission system has the advantage that the number of transmission lines is halved and is economical compared to the conventional four-wire data transmission system. This two-wire full-duplex data transmission system is constructed as shown in FIG. That is, data output from the data transmitter 1 is sent to the transmission line 3 via the hybrid circuit 2. Further, the data transmitted via the transmission line 3 is extracted via the hybrid circuit 2 and supplied to the data receiving section 4, where it is received. In a two-wire full-duplex data transmission device, the clock component contained in the signal transmitted from the main station and received is detected, the clock signal is extracted and reproduced, and the data is extracted from the received signal according to this clock signal. It receives and reproduces the data, and also encodes and transmits the transmitted data according to the clock signal. However, the transmission line 3 seen from the hybrid circuit 2
The circuit impedance of is not pure resistance. For this reason, data output from the transmitter 1 may leak to the receiver 4 via the hybrid circuit 2. This signal leakage has a significant adverse effect on the extraction and reproduction of the clock signal in the above device, leading to errors in data reception and reproduction due to the erroneous clock signal and erroneous encoding of transmitted data. In order to prevent this, a matching box shown at 5 in the figure is connected to the transmission line 3 via the hybrid circuit 2 to balance the circuit impedance. However, the circuit impedance of the transmission line 3 varies greatly depending on the line length. For this reason, it is difficult to adjust the balance of the matching box 5, and it is also very difficult to design the matching box 5 itself.

The present invention was made in consideration of these circumstances, and its purpose is to provide two-wire full-duplex data that has a simple configuration, is economical, and does not cause any adverse effects due to data leakage. The purpose is to provide transmission equipment.

The outline of the present invention is to pass the received signal when the latch signal is not applied, and to latch the previous received signal for a predetermined time (time width of the latch signal) when the latch signal is applied. By taking in the clock signal and reproducing and extracting the clock signal from the output signal of this latch circuit, input of the signal leakage component from the hybrid circuit to the receiving section is prevented. This eliminates the need for complicated design and adjustment of a matching box, resulting in a simpler and more economical device.

The present invention was made by focusing on the fact that the pulse width of the received signal is longer than the leakage time of the transmitted signal.Hereinafter, with reference to FIGS. 2 and 3, one embodiment of the device of the present invention will be described. Explain.

FIG. 2 is a schematic configuration diagram of the device of the same embodiment, and numeral 11 in the figure is a transmission line. This transmission line 11 is connected to a hybrid circuit 12 and transmits data to be sent and received. An encoder circuit 13 of a data transmitting section is connected to a transmitting end 12a of this hybrid circuit 12. This encoder circuit 13
encodes transmission data based on a synchronization signal, which will be described later, and sends it to the transmission line 11. On the other hand, the receiving end 12b of the hybrid circuit 12 is connected to a decoder circuit 14 of a data receiving section and a latch circuit 15. This latch circuit 15 receives a latch signal, which will be described later, and
This circuit latches the received signal just before the latch signal is applied, holds it while the latch signal is applied, and passes the received signal as is when the latch signal is not applied, and is known as a sample-and-hold type latch circuit. be. This latch circuit 1
A synchronization extracting circuit 16 is connected to the output end of the signal generator 5, and extracts a synchronization signal from the received signal. That is, this synchronization extraction circuit 16 is, for example, the latch circuit 1.
By differentiating the received signal which is the output signal of 5, generating pulse signals corresponding to the rising and falling signals of the differentiated waveform, and inverting the flip-flop by this pulse signal, the synchronizing signal included in the received signal is generated. , that is, the clock component is extracted.

The extracted synchronization signal is supplied to the encoder circuit 13 and decoder circuit 14 as well as to the monostable multivibrator 17. This monostable multivibrator 17 outputs a pulse signal of a predetermined time width in response to the rising and falling edges of the extracted synchronization signal, and uses this as a latch signal to connect the latch circuit 1 to the latch circuit 1.
5 is applied. Note that the predetermined time width of the pulse signal is set to a period that is shorter than the period of the extracted synchronization signal and that sufficiently includes a period in which signal leakage from the transmitting side occurs. The latch circuit 15 latches the immediately preceding input data, that is, the received signal, by the rising edge of this pulse signal, for example,
The latched signal is held while the pulse signal is at HIGH level. Further, when the pulse signal is not applied, that is, when the pulse signal is at the LOW level, the received signal passes through the latch circuit 15 as it is and is applied to the synchronization extraction circuit 16. In other words, the received signal is temporarily stored only during the application period of the pulse signal. The latch circuit 15, the synchronization extraction circuit 16, and the monostable multivibrator 17 constitute a signal detection circuit. The signal transmitted via the transmission line 11 is decoded by the decoder circuit 14 based on the extracted synchronization signal, and the data in the received signal is received and reproduced and output to a predetermined device. In addition, 18 in the figure is the hybrid circuit 1
This is a matching box connected to the transmission line 11 via 2.

The operation of the device configured in this way will be explained with reference to the signal waveform diagram shown in FIG.

Now, when a bipolar signal with a waveform as shown by the solid line in FIG. 3a, which includes a clock component transmitted from the main station, is received, this signal is
The signal is supplied to the synchronization extraction circuit 16 via. Upon receiving such a bipolar signal, the synchronization extraction circuit 16 detects the positive and negative unipolar components of the signal, and calculates the differential signal of each unipolar component.The synchronization extraction circuit 16 extracts the synchronization signal from the equal signals as shown in FIG. 3b. It is extracted as follows. The decoder circuit 14
performs bipolar-unipolar conversion by detecting the signal phase change of the bipolar received signal according to the synchronization signal, and converts the received signal shown in FIG. 3a to data as shown in FIG. 3c. are receiving and playing. On the other hand, the encoder circuit 13 encodes the transmission data shown in FIG. 3d as shown in FIG. 3e based on the synchronization signal and transmits the encoded data.
This encoding of the transmission data is done because, for example, the main station has a clock component for the transmission signal.
This is done by simply converting the unipolar signal into bipolar according to the extracted synchronization signal. The signal encoded and transmitted in this manner leaks to the receiving section via the hybrid circuit 12, as described above, and has an adverse effect on the receiving side. That is, this leakage signal is superimposed on the received signal as a waveform as if the transmitted signal was differentiated. For this reason,
A so-called whisker occurs in the signal received at the receiving side, as shown by the broken line in FIG. 3a. This whisker causes the generation of a pseudo-synchronization signal as shown by the broken line in FIG. 3b during synchronization extraction processing such as differential processing of the received signal. This pseudo-synchronization signal disrupts the synchronization of the device, causing adverse effects such as erroneous signal processing.

However, in this device, the monostable multivibrator 17 is activated by the rising and falling edges of the extracted synchronization signal, and a HIGH level pulse signal is output for a predetermined period of time as shown in FIG. As a result, the latch circuit 15 is driven. Note that the predetermined time width of this pulse signal is shorter than the pulse width of the synchronizing signal and sufficiently longer than the signal leakage time, as described above. Therefore, the latch circuit 15 latches the immediately preceding received signal by the rising edge of this pulse signal, and holds this latched signal for a predetermined period of time during which the pulse signal is applied, as described above. Therefore, the leakage component of the signal shown in FIG.
5, its passage is blocked and it is not supplied to the synchronization extraction circuit 16. That is, the latch circuit 15 prevents the leakage signal from passing during the period shown in FIG. 3g. Therefore, the synchronization extraction circuit 16 includes a third
Only the original received signal component shown by the solid line in Figure a will be supplied.

Thus, according to the present device, unlike conventional devices, there is no adverse effect caused by leaked signals, and data can be transmitted and received favorably. Also, especially matching box 1
The negative influence of the leakage signal can be removed without finely adjusting the matching box 18, and no complicated adjustment or strict design of the matching box 18 is required. Therefore, it is possible to simplify the device. Furthermore, it has a simple configuration in which the received signal is latched to prevent leakage signals, and it can be easily realized using a digital circuit or the like, making the device extremely economical. Further, even if the circuit impedance of the line changes significantly due to connection switching of the line, there is almost no problem.

Note that the present invention is not limited to the above embodiments. For example, the form of the transmission signal may be a unipolar type instead of the bipolar type described above. Further, the means for extracting a synchronization signal, the means for generating a predetermined time, etc. may be set according to the specifications and uses thereof. Furthermore, the signal supplied to the decoder circuit 14 is supplied to the latch circuit 1 as shown by the broken line in FIG.
It may be obtained from the output of 5. Furthermore, it goes without saying that the type of signal transmitted via this device is not limited to, for example, a coded audio signal or a computer data signal. In short, the present invention:
Various modifications can be made without departing from the gist of the invention.

As described in detail above, the apparatus according to the present invention prevents leakage signals from flowing in by holding the received signal immediately before the transmission of the transmitted signal for a predetermined period of time. Therefore, according to the present invention, it is possible to simplify the device and improve its economical efficiency without requiring precise adjustment of the matching box or strict design at all, and moreover, it is possible to effectively prevent the occurrence of adverse effects due to signal leakage. It is possible to provide a two-wire full-duplex data transmission device that has various special advantages, such as being able to transmit and receive data with improved quality.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a two-wire full-duplex data transmission device, Fig. 2 is a schematic configuration diagram showing an embodiment of the device of the present invention, and Fig. 3 is a signal waveform for explaining the operation of the embodiment. It is a diagram. 11...Transmission line, 12...Hybrid circuit, 1
3... Encoder circuit (data transmitting section), 14... Decoder circuit (data receiving section), 15... Latch circuit, 16... Synchronization extraction circuit, 17... Monostable multivibrator.

Claims (1)

[Claims] 1 Connected to a two-wire full-duplex data transmission line via a hybrid circuit, extracts a clock signal from a received signal containing a clock component from the main station, and receives data in the received signal according to this clock signal. In a two-wire full-duplex data transmission device that encodes and transmits transmission data in accordance with the clock signal, the receiving section passes the received signal when the latch signal is not applied, and also transmits the received signal when the latch signal is not applied. The clock signal in the received signal is extracted from the output signal of a latch circuit that holds the received signal at the trailing edge for a latch signal application period, and the latch is activated in accordance with the extracted clock signal with a predetermined time width shorter than the clock signal period. A two-wire full-duplex data transmission device characterized by generating signals.