JPH07264481A - Respective circuits for generating respective vertical and horizontal synchronizing signals of character generating circuit, and respective methods therefor - Google Patents

Abstract

PURPOSE: To obtain a synchronizing signal generating circuit which sets the character start position of a character generating circuit of simple constitution, by equipping the circuit with a vertical synchronizing signal generating means which inputs a composite signal and generates a vertical synchronizing signal and a horizontal synchronizing signal generating means which generates a horizontal synchronizing signal. CONSTITUTION: A horizontal vertical synchronizing signal generating circuit consists of a vertical synchronizing signal generating circuit 100 and a counter 200, which is used as a horizontal synchronizing signal generating circuit. The vertical synchronizing signal generating circuit 100 inputs the composite synchronizing signal and generates the vertical synchronizing signal. The counter 200, on the other hand, is reset with the vertical synchronizing signal and uses the 4fsc signal of a crystal oscillator as a clock signal to count clock pulses, thereby generating the horizontal synchronizing signal. Consequently, the stable vertical and horizontal synchronizing signals which are immune to noise can be generated only by the vertical synchronizing signal generating circuit 100 and counter 200 to eliminate the need for any extra circuit, and the vertical and horizontal synchronizing signals are generated by inputting the composite signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a character generation circuit and a character generation method, and more particularly to a vertical and horizontal synchronizing signal generation circuit for setting the character start position of the character generation circuit and the character start position of the character generation circuit. And a vertical and horizontal synchronization signal generating method.

[0002]

2. Description of the Related Art A conventional method for setting a horizontal character start position of a character generating circuit uses a horizontal synchronizing signal. A system using this character generating circuit is a video tape recorder, The instability phenomenon of horizontal characters in a weak electric field such as television and multimedia was not recognized as a serious problem. However, as the artificial satellite broadcasting system is introduced in earnest, such a character instability phenomenon is recognized as a serious problem.

There are the following two horizontal and vertical synchronizing signal generating methods for setting the character start position of the conventional character generating circuit. One method is to separate the horizontal sync signal from the composite sync signal input from the outside and set it as the reference signal for the horizontal start position and vertical start position of the character. This is a method to set the horizontal and vertical start position of the character by _dividing the 4f _sc signal oscillated from the crystal oscillator to generate a horizontal sync signal and a vertical sync signal when there is no signal input from the.

When no signal is input from the outside, the oscillation frequency of the crystal oscillator is divided by the 4f _sc signal to generate a horizontal synchronizing signal and a vertical synchronizing signal for use, so that there is no character shaking phenomenon. Further, there is no problem even when the reference signal is input to the normal electric field from the outside. However, when the input reference signal is weak, the screen sways to the left and right, which causes the characters to sway to the left and right in synchronization with the screen, and in the worst case, it is difficult to identify the characters. .

FIG. 1 is a block diagram of a character start position setting circuit of a general character generation circuit. The character start position setting circuit shown in FIG. 1 comprises a vertical synchronizing signal generating circuit 1, a horizontal synchronizing signal generating circuit 2 and an automatic frequency adjusting circuit 3.

The function of each part of the character start position setting circuit shown in FIG. 1 will be described as follows.

The vertical synchronizing signal generating circuit 1 inputs a composite synchronizing signal and generates a vertical synchronizing signal. The horizontal synchronizing signal generating circuit 2 inputs the composite synchronizing signal and generates a horizontal synchronizing signal. The automatic frequency adjusting circuit 3 inputs the horizontal synchronizing signal and automatically adjusts the frequency. FIG. 2 is a detailed block diagram of the automatic frequency adjustment circuit shown in FIG.

The automatic frequency adjusting circuit shown in FIG. 2 includes a phase detecting circuit 10, a loop filter 20, and a voltage controlled oscillator 3.
0 and a distributor 40.

The function of each part of the automatic frequency adjustment circuit shown in FIG. 2 will be described as follows. The phase detecting circuit 10 compares and detects the phases of the horizontal synchronizing signal output from the horizontal synchronizing signal generating circuit 2 and the horizontal synchronizing signal fed back from the output. The loop filter 20 removes the high frequency component generated from the phase detection circuit 10. Voltage controlled oscillator 30
Converts the self-oscillation frequency into the frequency of the output signal of the phase detection circuit 10. The distributor 40 receives the output signal of the voltage controlled oscillator 30, frequency-divides it, and outputs it to the phase detection circuit 10.

FIGS. 3A to 3E show output waveforms of the respective parts of the block diagram shown in FIG. 1. FIG. 3A shows a composite signal, and FIG. 3B shows a composite signal shown in FIG. The composite sync signal generated by a pass-pass filter (not shown) and a sync generator (not shown) is shown in FIG.
C shows the output signal of the horizontal synchronizing signal generating circuit 2, FIG. 3D shows the output signal of the automatic frequency adjusting circuit 3, and FIG. 3E shows the output signal of the vertical synchronizing signal generating circuit 1.

The operation of the vertical and horizontal synchronizing signal generating circuits of the character generating circuit shown in FIG. 1 will be described with reference to FIGS.

By passing the composite signal shown in FIG. 3A through a low pass filter (not shown) and a synchronization generating circuit (not shown), a composite synchronizing signal as shown in FIG. 3B is generated. The horizontal synchronizing signal generating circuit 2 inputs the composite synchronizing signal and generates a signal as shown in FIG. 3C. The automatic frequency adjusting circuit 3 receives the signal shown in FIG. 3C and generates a horizontal synchronizing signal as shown in FIG. 3D. The vertical sync signal generation circuit 1 receives the composite sync signal as shown in FIG. 3B and generates the vertical sync signal as shown in FIG. 3E.

Therefore, according to the conventional method of setting the character start position of the character generating circuit, the horizontal synchronizing signal generating circuit 2 uses the automatic frequency adjusting circuit to obtain the optimum condition with the horizontal synchronizing signal which is synchronously separated from the composite synchronizing signal. Generate a synchronized horizontal sync signal. Therefore, when a signal swaying left and right is input from the outside, that is, when the electric field is weak or the signal is dirty, the characters sway left and right.

If there is no external signal by a method different from the above method, the signal oscillated from the crystal oscillator is divided by the 4f _sc signal to generate a horizontal synchronizing signal and a vertical synchronizing signal, and the horizontal and vertical start of characters is started. Set the position. In such a case, there is no shaking of the characters. However, when the input signal is weak, the screen sways left and right, so that the characters are also swayed left and right in synchronization with the screen. In severe cases, there is a problem that it is difficult to identify characters.

[0015]

SUMMARY OF THE INVENTION An object of the present invention is to provide a horizontal and vertical synchronizing signal generating circuit for setting a character start position of a character generating circuit having a simple circuit configuration.

Another object of the present invention is to provide a horizontal and vertical synchronizing signal generating method for setting a character start position of a character generating circuit in which the character does not shake even when an input signal is extremely weak or a weak electric field is applied. That is.

[0017]

In order to achieve the above object, the horizontal and vertical synchronizing signal generating circuits of the present invention according to claim 1 and 2 are provided for setting the character start position of the character generating circuit. In a circuit for inputting a composite signal to generate a vertical synchronizing signal and a horizontal synchronizing signal, vertical synchronizing signal generating means for inputting the composite signal and generating the vertical synchronizing signal, and resetting the vertical synchronizing signal And a horizontal synchronizing signal generating means for generating a horizontal synchronizing signal by counting clock pulses by using a signal having a sampling frequency of 4 times as a clock signal. Further, the horizontal synchronizing signal generating means comprises a counter.

According to another aspect of the present invention, there is provided a horizontal and vertical synchronizing signal generating method for setting a character start position of a character generating circuit according to the present invention. It is characterized in that it comprises a step of generating a signal and a step of generating a horizontal synchronizing signal by counting clock pulses using the vertical synchronizing signal as a reset signal and a sampling frequency signal of 4 times as a clock signal.

[0019]

According to the first to third aspects of the present invention, stable vertical and horizontal synchronizing signals resistant to noise can be generated only by the vertical synchronizing signal generating circuit and the counter. No special circuit is required, and a composite signal is input to generate vertical and horizontal synchronizing signals.

[0020]

The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 4 is a block diagram of a horizontal and vertical sync signal generating circuit for setting the character start position of the character generating circuit of the preferred embodiment of the present invention.

In FIG. 4, the horizontal and vertical synchronizing signal generating circuit of the present invention comprises a vertical synchronizing signal generating circuit 100 and a counter 200. Here, the counter 200
Is used as a horizontal synchronizing signal generating circuit.

The vertical synchronizing signal generating circuit 100 receives the composite synchronizing signal and generates a vertical synchronizing signal. The counter 200 is reset by the vertical sync signal,
_{The sc} signal is used as a clock signal to count clock pulses and generate a horizontal synchronization signal.

5A to 5D are waveform charts for explaining the operation of each part of the block diagram shown in FIG.

FIG. 5A shows a composite synchronizing signal input to the vertical synchronizing signal generating circuit 100, FIG. 5B shows an output signal of the vertical synchronizing signal generating circuit 100, and FIG. 5C shows a generated signal from a voltage controlled oscillator (not shown). 4 times the sampling frequency (4
f _sc ) and FIG. 5D shows the horizontal sync signal generated from the counter 200.

The vertical synchronizing signal generating circuit 100 shown in FIG.
Inputs the composite sync signal shown in FIG. 5A to generate a vertical sync signal as shown in FIG. 5B. The counter 200 counts clock pulses by using a 4 times sampling frequency (4f _sc ) signal as a clock signal and generates a horizontal synchronizing signal as shown in FIG. 5D.

That is, the horizontal and vertical sync signal generating circuit of the present invention shown in FIG. 4 receives the composite sync signal to separate the vertical sync signal, and the separated vertical sync signal is used as a reset signal to change the sampling frequency. A horizontal synchronizing signal is generated by counting clock pulses using a clock signal (4fsc) having a frequency four times as a clock signal, and a composite signal input from the outside is as shown in FIG. 5A. The vertical sync signal is more stable than the horizontal sync signal in noise characteristics and in a weak electric field. That is, the vertical and horizontal synchronizing signal generating circuit of the present invention uses the method of generating the horizontal synchronizing signal using the vertical synchronizing signal. That is, the horizontal synchronizing signal is generated by using a stable vertical synchronizing signal without using the horizontal synchronizing signal in the composite synchronizing signal input from the outside as the reference signal of the horizontal character start position of the character generating circuit. That is.

[0028]

The invention described in claims 1 to 3 has the following effects.

As shown in FIG. 1, the conventional vertical and horizontal synchronizing signal generating circuit is composed of a horizontal synchronizing signal generating circuit, a vertical synchronizing signal generating circuit and an automatic frequency adjusting circuit, but the structure is complicated. In the present invention, only the vertical synchronizing signal generating circuit and the counter can generate stable vertical and horizontal synchronizing signals resistant to noise.

Further, since the composite signal is input and the vertical and horizontal synchronizing signals are generated instead of the composite synchronizing signal being input to generate the vertical and horizontal synchronizing signals, the composite signal is converted into the composite synchronizing signal. No additional circuitry is needed, i.e. a low pass filter or sync separation circuitry.

The horizontal and vertical sync signal generating circuit for setting the start position of the character of the character generating circuit of the present invention generates the horizontal sync signal by using the vertical sync signal which is relatively strong against noise, thereby causing the fluctuation of the character. Can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram of a vertical and horizontal synchronizing signal generating circuit for setting a character position of a conventional character generating circuit.

FIG. 2 is a detailed block diagram of the automatic frequency adjustment circuit shown in FIG.

3A to 3E show output waveforms of respective parts of the block diagram shown in FIG.

FIG. 4 is a block diagram of a vertical and horizontal synchronizing signal generating circuit for setting a character position of a character generating circuit according to a preferred embodiment of the present invention.

5A to 5D show output waveforms of respective parts of the block diagram shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Vertical synchronizing signal generating circuit, 2 ... Horizontal synchronizing signal generating circuit, 3 ... Automatic frequency adjusting circuit, 10 ... Phase detector, 20 ... Loop filter, 30 ... Voltage controlled oscillator, 40 ... Distributor, 100 ... Vertical synchronizing signal Generation circuit, 200 ... Reset counter.

Claims (3)

[Claims] 1. A circuit for inputting a composite signal to set a character start position of a character generating circuit to generate a vertical synchronizing signal and a horizontal synchronizing signal, wherein the composite signal is input to output the vertical synchronizing signal. Vertical synchronizing signal generating means for generating the horizontal synchronizing signal for generating a horizontal synchronizing signal by counting the clock pulses by using the vertical synchronizing signal as a reset signal and a quadruple sampling frequency signal as a clock signal. A vertical and horizontal synchronizing signal generating circuit for a character generating circuit, comprising: generating means. 2. The vertical and horizontal synchronizing signal generating circuit of the character generating circuit according to claim 1, wherein the horizontal synchronizing signal generating means is composed of a counter. 3. A method for inputting a composite signal to set a character start position of a character generating circuit to generate a vertical synchronizing signal and a horizontal synchronizing signal, wherein the composite signal is input to generate a vertical synchronizing signal. And a step of generating a horizontal synchronizing signal by counting clock pulses using the vertical synchronizing signal as a reset signal and a quadruple sampling frequency signal as a clock signal, respectively. Method of generating vertical and horizontal sync signals in a circuit.