JPH08251497A - On-screen display circuit - Google Patents

Abstract

PURPOSE: To display a function list on a screen in characters or symbols as a menu pattern independently of a synchronizing signal frequency of an input video signal in the video display device displaying video signals of plural modes where horizontal synchronizing signal frequency and vertical synchronizing signal frequency differ. CONSTITUTION: The circuit is provided with a character generating circuit 3 generating characters with output information from a microcomputer 2 operating a main body and controlling on-screen display, a synchronizing signal generating circuit 10 generating a horizontal synchronizing signal and a vertical synchronizing signal, an input changeover circuit 4 selecting an input video signal or an output signal from the synchronizing signal generating circuit 10, and an on-screen changeover circuit 6 selecting a character generating output signal or the input video signal. Thus, the input changeover circuit 4 is thrown to the position of the synchronizing signal generating circuit 10 by menu display operation and a deflection output circuit 9 is scanned by the internal synchronizing signal generating circuit 10 only for the menu display operation, then a function list menu display is displayed on the screen independently of the synchronizing signal frequency of the input signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-screen display circuit capable of displaying a list of operation menus of a video display device capable of displaying a plurality of video signals having different horizontal and vertical sync frequencies.

[0002]

2. Description of the Related Art In recent years, a video display device has been developed as a dedicated video display device for television signals, high-definition signals or video signals having different horizontal and vertical sync signals from a personal computer, etc. However, a device for displaying these signals on one video display device has been developed. At present, these devices are operated by a microcomputer, and the function display is performed by using another liquid crystal display device or a single function display is performed by on-screen display.

An on-screen display circuit of a conventional video display device for displaying a plurality of video signals having different horizontal and vertical synchronizing signals will be described below. FIG. 2 shows Japanese Patent Laid-Open No. 4-349.
1 shows an on-screen display circuit of a conventional video display device disclosed in Japanese Patent Publication No. 794. This on-screen display circuit is a circuit for preventing a change in size of a character or symbol to be displayed on-screen on a video signal due to switching of the horizontal scanning frequency mode. The read-only memory 25 for storing the character font of the character or symbol displayed by the display control unit 13 is divided into two, and the character font data of 18 scanning lines is assigned to one of the same addresses designated by the output data of the video memory 24 and the other is assigned to the other. The character font data of 15 scanning lines is stored in advance, and the vertical and horizontal synchronizing signals 12a and 12b separated from the input video signal are output to the mode discriminating circuit 27.
The horizontal scanning frequency is determined by the mode discriminating signal 27a determined by the number of horizontal scanning lines within one vertical scanning line.
In the mode of 75 kHz, character font data of 18 scanning lines is used. In the modes of 24.43 kHz and 31.5 kHz, character font data of 15 scanning lines and 18 characters are used.
The data of the same scan line of the character font of the scan line configuration is repeatedly read twice and output as the display signal 13a via the serial-parallel conversion circuit 26, thereby preventing the change of the display size. Here, 14a is control unit output data, 14b is display device data, 20 is a clock oscillation circuit, 21 is a horizontal character position counter, 22 is a vertical character position counter, and 23 is a selector.

[0004]

However, in such a conventional configuration, since two character font data are selected and displayed at the input synchronizing signal frequency, the range of the input horizontal and vertical synchronizing signal frequencies is selected. Is limited. Further, there is a limitation in preventing the size from being changed by the synchronization frequency, and there is a problem that the number of characters is limited even when the function list display of the microcomputer is performed on the screen.

An object of the present invention is to solve the above problems, and an object thereof is to provide an on-screen display circuit capable of displaying a list of functions of a microcomputer without being restricted by horizontal and vertical synchronizing signal frequencies.

[0006]

To achieve this object, an on-screen display circuit of the present invention comprises a microcomputer for operating the main body and controlling the on-screen display,
An on-screen character generation circuit that generates characters based on the output information from the microcomputer, a synchronization signal generation circuit that generates horizontal and vertical synchronization signals, an input switching circuit that switches between the input video signal and the synchronization signal generation circuit output signal, and on An on-screen switching circuit for switching between a screen character generation output signal and a video signal is provided, and the input switching circuit is switched to the synchronization signal generation circuit side by a menu display operation.

[0007]

According to the present invention, when the menu display operation is performed, the microcomputer switches the input switching circuit to the synchronizing signal generating circuit side and scans the deflection output circuit with this synchronizing signal. On the other hand, the microcomputer outputs the menu display signal of the function list and transmits it to the on-screen character generation circuit, the on-screen character generation circuit outputs the menu display screen signal, and the on-screen switching circuit switches to the on-screen display side. The replacement screen is the function display menu screen. Since the deflection output circuit is scanned by the internal synchronizing signal generating circuit only when the menu display operation is performed in this way, the menu display of the function list can be displayed on-screen regardless of the synchronizing signal frequency of the input video signal. .

[0008]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an on-screen display circuit according to an embodiment of the present invention. In FIG. 1, 1 is an operating unit for operating the main body, 2 is a microcomputer for operating the main body circuit and controlling on-screen display, 3 is an on-screen character generation circuit for generating characters or symbols by a signal from the microcomputer, and 4 is An input switching circuit 5 that switches between the input video signals a and b and switches between these signals and a synchronizing signal generation circuit signal is an image amplification circuit that amplifies the video signal and adjusts the black level and brightness. Reference numeral 6 is an on-screen switching circuit for switching between an input video signal and an on-screen display signal, 7 is a CRT output circuit for amplifying the video signal to a size necessary for displaying on a cathode ray tube, 8
Is a sync separation circuit for separating the sync signal from the video signal selected by the input switching circuit 4, 9 is a deflection output circuit for vertically and horizontally scanning the cathode ray tube according to the sync signal, and 10 is a horizontal
It is a sync signal generation circuit that generates a vertical sync signal.

The operation of the on-screen display circuit configured as described above will be described. First, the operation unit 1
When the menu display operation for displaying the operation function is performed by the microcomputer 2, the input switching circuit 4 is switched to the side of the synchronizing signal generating circuit 10 by the microcomputer 2, and the signal of only the synchronizing signal from the internal periodic signal generating circuit 10 is received to provide a dark screen. Becomes on the other hand,
The microcomputer 2 outputs a menu display signal to the on-screen character generation circuit 3, and the screen character generation circuit 3 adjusts the character size and display position by the horizontal and vertical blanking signals from the deflection output circuit 9 to display the on-screen menu. Output a character signal. The on-screen switching circuit 6 switches only when there is a character on the side of the on-screen character generation circuit 3 in the video signal, and because there is no video signal, only the synchronizing signal, the on-screen menu screen of characters or symbols is displayed in the dark. Becomes Further, when the function is selected directly by the operation unit 1 or when the function is selected from the menu screen, the menu screen disappears, the input switching circuit 4 receives the original selected video signal, and the on-screen displays the function. Only the screen is displayed, and the screen can be adjusted by the input video signal.

As described above, according to this embodiment, the synchronizing signal generating circuit 10 is provided, and the input switching circuit 4 is switched to the synchronizing signal generating circuit 10 side only when the menu display operation is performed, regardless of the input video signal. The menu display screen that enables a stable function list by receiving the fixed synchronization signal can be displayed on-screen.

[0011]

As described above, according to the present invention, in an on-screen display device for receiving a plurality of input signals having different horizontal and vertical synchronizing frequencies, the output from the microcomputer for operating the main body and controlling the on-screen display. On-screen character generation circuit that generates characters with information, horizontal,
A sync signal generation circuit for generating a vertical sync signal, an input switching circuit 4 for switching between an input video signal and a sync signal generation circuit output, and an on-screen switching circuit 6 for switching between an on-screen character generation circuit output signal and a video signal are provided. As a result, a free function list display screen can be created using the entire screen regardless of the periodic signal frequency of the input video signal, and an inexpensive on-screen display circuit with good operability can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram of an on-screen display circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional display control unit for on-screen display.

[Explanation of symbols]

 1 Operation unit 2 Microcomputer 3 On-screen character generation circuit 4 Input switching circuit 5 Video amplification circuit 6 On-screen switching circuit 7 CRT output circuit 8 Sync separation circuit 9 Deflection output circuit 10 Sync signal generation circuit a, b Video input signal

Claims (1)

[Claims] 1. In a video display device for receiving a plurality of input signals having different horizontal and vertical synchronizing frequencies, a microcomputer for operating the main body and controlling on-screen display,
An on-screen character generation circuit that generates characters based on the output information from the microcomputer, a synchronization signal generation circuit that generates horizontal and vertical synchronization signals, an input switching circuit that switches between the input video signal and the synchronization signal generation circuit output signal, and on An on-screen display circuit, comprising: an on-screen switching circuit for switching between a screen character generation circuit output signal and a video signal, wherein the input switching circuit is switched to the synchronization signal generation circuit side by a menu display operation.