JPS5930342A - Carrier wave detecting circuit - Google Patents

Abstract

PURPOSE:To improve the transmission efficiency, by outputting a signal opening a transmission line after the elapsed time from the detection of the end of carrier to the message processing time of a carrier and starting equally each transmitter of a system. CONSTITUTION:A signal from a transmission line L is applied to a binary counter 1 and a latch 2 as a receiving clock (a) at a demodulation circuit D. When the signal (a) is lost at a time t1, the counter 1 is shifted at a basic clock phi (waveform c), the clock is given to the latch 2 from a terminal 1QB of the counter 1 at a time t2, and the latch 2 outputs a mirror image (waveform d) of a carrier from a terminal Q. The counter 1 outputs a signal to be accessed (waveform e) from a terminal 2QD when the time reaches a t3. Thus, after the end of carrier from a terminal Y, a mirror image signal representing the end of required processing is transmitted from a terminal X.

Description

[Detailed description of the invention] Technical fields> The present invention relates to improvements in carrier wave detection circuits.

Prior Art Conventionally, a carrier detection circuit installed in a transmitting/receiving device detects an empty space on a transmission line, and is used as a means for starting transmission. That is, the purpose was simply to confirm the presence or absence of carrier waves on the transmission line. However, the device that previously received the signal naturally requires a predetermined processing time to process the information from the signal, and even if the transmission line is empty within the processing time, it will not actually work. This means that it cannot be sent. In other words, for a device that has previously received data and is attempting to transmit data, the transmission line will not be empty unless there is a carrier wave on the transmission line and the receiving process has not been completed.

Therefore, the present invention improves the conventional carrier wave detection circuit so that the carrier wave detection circuit outputs a signal to open the transmission line after the transmission processing time of the carrier wave has elapsed since the end of the carrier wave is detected. I made it.

<Example> The configuration of the present invention will be described based on examples.

FIG. 1 shows a circuit configuration of a receiving section of a device having a carrier detection circuit according to this embodiment. L is a transmission line, R is a receiver, and D is a demodulation circuit.

The carrier detection circuit consists of binary counter 1 and latch 2.
Consists of. Here, the carrier wave detection operation of this embodiment will be explained using the time chart shown in Fig. @2.

The signal received from the transmission line L becomes a receive clock (@Figure 2 (a)) in the demodulation circuit and is input to the binary counter 1 and latch 2.Then, there is no signal on the transmission line L, and the above receive clock disappears. and (second
1+) in figure fa), CL of binary counter 1
(Clear) The terminal is cleared and the corresponding binary counter 1
The count is advanced by the basic clocker # (FIG. 2(C)), and when the count reaches a predetermined value at time t2, the tarlock is transmitted to the latch circuit 2 from the output terminal IQB of the binary counter I. Then, this latch circuit 2 emits a mirror image of the carrier wave from the output terminal Q (@Fig. 2 (d)).

Now, when the binary counter l further advances the count and reaches time t8, it outputs a detection signal from the output terminal 2QD of the binary counter l (@2 (e))
). This detection signal means that the device is now ready to respond to access requests from other devices.

In the above case, the time from when the binary counter 1 outputs the mirror image signal until it outputs the detection signal is the processing time during which the device receives information from the carrier wave and processes the information. Therefore, in this embodiment, the time during which a carrier wave message occupies the transmission line L is from when the device detects the beginning of the carrier wave to when it detects the end of the carrier wave until a predetermined processing time elapses. .

In this embodiment, the carrier wave detection circuit has two output terminals, and the mirror image signal is output from the first output terminal (X in Figure 1) and the mirror image signal is output from the second output terminal (Y in Figure 1). After the carrier wave ends, a detection signal indicating that the necessary processing has been completed is output. Of course, the processing time, that is, the basic clock count corresponding to the processing time, can be freely changed by the device (eg, electronic register) VC.

Now, the use of the carrier wave detection circuit of this embodiment provides the following conveniences.

Conventionally, in order to save processing time, there is a device that sends a dummy signal md after the message signal ml to prevent the carrier signal from turning off, as shown in Figure 3 fal, but the dummy signal md is not sent. In the dark, the transmission line was to be exclusively used for the dummy signal m4VC. On the other hand, in this embodiment, as shown in FIG. 3(b), the transmission line becomes empty when the message signal ml ends, so sequential messages such as the reply message ma are carried out using the carrier wave. It is sufficient to transmit the mirror image of the dummy signal md, which eliminates the need to create a time-consuming dummy signal md. Note that m2 in the figure is a signal of another message.

<Effects> As described above, according to the present invention, all the transmitting devices 2 of the transmission system can start transmitting equally without determining priorities among the transmitting devices, so that the efficiency of the transmission system increases.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram of a receiving section of a device having a carrier wave detection circuit of the present invention, FIG. 2 is a time chart diagram showing a carrier wave detection operation of the carrier wave detection circuit of the present invention, and FIG. 3(a),
(b) is an explanatory diagram illustrating the operation of the carrier wave detection circuit using the exclusive state on the transmission line. 1...Binary counter, 2...Latch,
L...Transmission line, R...Receiver-1D...
・Demodulation circuit.

Claims (1)

[Claims] 1. An output means for outputting a signal detecting the presence or absence of a carrier wave on the transmission line, and opening the transmission line after the time necessary for processing the message by the carrier wave in the receiving device after the carrier wave disappears. and output means for outputting a signal.