JPH02201399A - screen display device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a screen display device for displaying characters and patterns such as channel numbers in broadcast images displayed on a display device such as a cathode ray tube.

[Conventional technology]

FIG. 6 shows an example of the configuration of a conventional screen display device of this type. In FIG. 6, 1 is a display oscillation circuit to which the oscillation output of the π-type LC oscillation element circuit 1a is supplied, 2 is a timing generator that generates various timings using the signal oscillated by the display oscillation circuit 1, and 3 is a Each input terminal 3a is connected to an external control circuit such as a microcomputer (not shown) for controlling the output of the timing generator 2 and the screen display device.

Control data input to 3b and 3c (display on).

4 is a data control circuit, 5 is an address control circuit, 7 is a display data memory for storing control data,
Consists of RAM. A display character memory 8 stores characters and patterns to be displayed in the font structure shown in FIG. 7, and is composed of a ROM. 6 is a display control register that latches commands such as display control among the outputs of the input control circuit; 9 is a display control register that inputs the horizontal synchronization signal and vertical synchronization signal of the video signal supplied to terminals 9a and 9b; 11 is a display position detection circuit for detecting the display position of characters, patterns, etc. on the display device; 13 is a display control circuit that controls the output of display character memory 8; The zero-screen display device that performs display control according to display commands from the display control register 6 is composed of the above-mentioned circuits, and the display control circuit 13
The output is supplied to the video mixer 17, and the video mixer 17 outputs a composite video signal via the CVTDEO terminal 17a. In addition, the above display control circuit 1
3, R, G, B color signals etc. are sent to terminals 13a to 13f.
Output via .

10 is an H counter, 14 is a shift register, 15 is an oscillation circuit for generating a synchronizing signal to which the oscillation output of the oscillation element circuit 15a is supplied, 16 is a timing generator for generating a synchronizing signal, and 21 is a blinking circuit.

Next, the operation will be explained. The input control circuit 3 processes control data input from a microcomputer or the like through terminals 3a, 3b, and 3c, causes the display control register 6 to latch commands for display control, etc., and displays the display contents, such as character codes. data memory 7. During display, the character code stored in the display data memory 7 accesses the display character memory 8 as output data, and the display character font output from this character memory 8 is input to the display control circuit 13 via the shift register 14. do. Here, the display data memo I77 is composed of (a+b) bits in total (a+b), assuming that the word (1) is (a+b) bits and the number of characters to be displayed is C. On the other hand, it is assumed that one font of the display character memory 8 is composed of (j!xm) bits, and there are n characters of types. In addition, the timing at the time of display is determined by inputting the synchronization signal from the video signal to the synchronization signal switching circuit 9, counting this synchronization f words by the H counter 10, and based on this count value, the display position detection circuit 11 controls the display device. Determines the position of displayed characters.

The display control circuit 13 synchronizes the display character output with an external video signal, controls the display according to the contents of the display control register 6, outputs it, and supplies it to the video mixer 17.

Note that the synchronizing signal generation oscillation circuit 15 is the oscillation element circuit 1
5a, it is possible to generate a synchronization signal of the NTSC system or PAL system, and this switching is performed by a signal from the N/P terminal 15b, thereby outputting oscillation of 4 fsc or 2 fsc, and the timing generator 16 for generating the synchronization signal.
Since a synchronizing signal is generated at , it is possible to display on the TV screen even when there is no signal. However, fsc is a color subcarrier, which is 3.58 MHz in the NTSC system and 4.43 M1 (z) in the PAL system.

Furthermore, the video mixer 17 is capable of generating composite video signals of the NTSC system and PAL system and superimposing them onto external composite video signals. Composite video signals include character level (LECHA), external composite video input (CVIN), and blanking level (LEBK).
), background carrier color signal input (R3IN), color burst input (CBIN), and sync chip level are switched and synthesized by an analog switch and output from the CVIDEO terminal 17a.

(Problem to be solved by the invention) By the way, in the conventional screen display device, the output RG
Since the B video signal is output as is from the port output terminal even when RGB output is not required, there is a problem that the RGB video signal output from this output terminal may cause noise in other circuits. there were.

This invention was made to solve the above problems, and when the RGB output is not required, the RGB output value is stabilized to eliminate noise factors, and when only the port output of the external control circuit is used, the port output The purpose is to make it possible to use it as an expansion port terminal when there is a shortage of expansion ports, and to synchronize the switching to the expansion port with the vertical synchronization signal to eliminate disturbances in the displayed screen and stabilize switching. .

[Means to solve the problem]

Therefore, the screen display device according to the present invention is provided with a port register 61 that stores a predetermined value in the display control register, and also provides an RGB image in the port output control circuit 19 based on the value stored in the port register 61. switching means 131 for switching port output terminals 19a to 19c that output signals to expansion port terminals that output values stored in the port register 61; and synchronization means for switching to expansion ports in synchronization with a vertical synchronization signal. 132.

[Effect]

When a predetermined value is held in the port register 61, the switching means 131 in the port output control circuit 19 switches the port output terminals 192 to 19c to output RGB video signals according to the value held in the port register 61. Switch to the expansion port terminal, and output a predetermined value from the expansion port terminal.

At this time, switching from the RGB output terminal to the expansion port terminal is performed by the synchronization means 132 in synchronization with the vertical synchronization signal.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

Note that the same components as those in the prior art are given the same numbers and their explanations are omitted.

FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 18 is a video signal generation circuit that generates each internal video signal, and 19 is a port output control circuit that outputs various signals from port output terminals 19a to 19f. circuit, 61 is a port register in the display control register 6 that stores a predetermined value;
131 switches the port output terminals 19a to 19C that output RGB video signals according to the value in the port register 61 to expansion port terminals, and outputs the value corresponding to the value set in the port register 6e from the expansion port terminal. A switching means provided in the port output control circuit 19 for outputting, 1
Reference numeral 32 denotes synchronization means for switching to the expansion port terminal in synchronization with the vertical synchronization signal. Further, the port output terminals 19d to 19f output printer signals and the like input from the display control circuit 13.

Next, the operation will be explained.

When the address indicating the address of the port register 61 and the value to be stored in the port register 61 are sequentially input to the input control circuit 3 as a serial signal from an external control circuit such as a microcomputer,
A predetermined value is stored in the port register 61.

When a predetermined value is stored in the port register 61, the switching means 131 in the port output side wE circuit 19 is activated, and the R
Port output terminals 19a to 19c that output GB video signals
is switched to the expansion port terminal, and outputs an output corresponding to the value set in the port register 61 to the expansion port terminal. Switching to the expansion port terminal at this time is performed by the vertical synchronization means 132 in synchronization with the vertical synchronization signal.

FIG. 2 is a diagram showing in detail a specific example of this switching means 131, in which 131a is a selector, 132a is a flip-flop as the synchronization means 132, and 61a determines the output value of a port in the port register 61. Dekanilia,
61b is a flag area that controls switching of the selector 131a.

In such a configuration, for example, when the selector terminal S of the selector 131a is "1", RGB video No. 43 is selected and output, and when it is 0°, the stored value of the output canister 61a in the port register 61 is selected. In other words, when RGB video signals are selected, input terminals Al,
A2°A3, when selecting the stored value of the output canister 61a, the input terminals Bl, B2. A signal from B3 is input and output to port output terminals 193 to 19C.

Therefore, when the output of RGB video signals is not required, by storing a predetermined value such that the value of the flag area 61b is "1" in the port register 61, the RGB output terminal can be output as an expansion port terminal. The value set in 61a will be output.

In this case, the selector 131a does not switch to the expansion port terminal when the value of the flag area 61b becomes 1, but due to the action of the flip-flop 132a,
In response to the clock input CK of the vertical synchronization signal, the output terminal T of the flip-flop is switched from 0' to "1'," and at the time of this switching, the selector 131a switches to the expansion port terminal.

[Effects of the Invention] As explained above, according to the present invention, a port register for storing a predetermined value is provided in a display control register, and a port register is provided in a port output control circuit based on the value stored in the port register. switching means for switching a port output terminal that outputs an RGB video signal to an expansion port terminal that outputs a value corresponding to the value stored in the port register;
A synchronization means is provided to synchronize the switching to the expansion port with the vertical synchronization signal, so when the RGB output is not required, the RGB output value is stabilized, noise factors are removed, and the external control circuit is It can be used as an expansion port terminal when the port output alone is insufficient, and it also has the effect of eliminating disturbances in the screen being displayed and improving the stability of the switching described above.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a detailed block diagram of a specific example of the switching means and synchronization means in FIG. 1, and FIG. 3 is a block diagram of a conventional screen display device. , FIG. 4 is a diagram showing the configuration of fonts in a conventional display character memory. DESCRIPTION OF SYMBOLS 1... Display oscillation circuit, 2... Timing generator, 3... Input control circuit, 4... Data control circuit, 5... Address control circuit, 6... Display control register, 7... ... Display data memory, 8... Display character memory, 9... Synchronization signal switching circuit, 11... Display position detection circuit, 13... Display control circuit, 17...
Video mixer 18...Video signal generation circuit, 19
...Port output control circuit, 19a-19f...Port output terminal, 61...Port register, 131...
Switching means, 132...Synchronizing means, 131a...Selector, 132a...Flip-flop, 61a...
- Dekanilia, 61b...Flag area. In the drawings, the same reference numerals indicate the same or corresponding components.

Claims (1)

[Scope of Claims] A screen display device that displays characters and patterns on a display device such as a cathode ray tube includes an oscillation circuit that generates signals that serve as a reference for various timings, and various timings based on the oscillation signals of the oscillation circuit. A timing generator that generates a signal, an input control circuit that accepts and processes a control signal from an external control circuit such as a microcomputer, a synchronization signal switching circuit that inputs a synchronization signal for a video signal to be displayed on the display device, and A display position detection circuit that counts synchronization signals to detect the display position of the display device, and control data such as characters, pattern codes, blinking information, etc. that are processed by the input control circuit and are to be displayed on the display device. a display data memory for storing; a display character memory for storing fonts of characters displayed as the display contents;
a display control circuit that outputs a predetermined display signal and R, G, and B RGB video signals to display display contents at a predetermined position on the display device based on the position detection signal from the display position detection circuit; a video mixer that mixes the RGB video signal into a video signal, a display control register that holds data input from the external control circuit to the input control circuit, and a port control circuit that outputs the RGB video signal from the port output terminal. , and the display control register has a port register that stores a predetermined value, and the port output control circuit controls the port output terminal that outputs the RGB video signal based on the value stored in the port register. It has a switching means for switching to an expansion port terminal that outputs a value corresponding to the value stored in the port register, and a synchronization means for switching to the expansion port terminal in synchronization with a vertical synchronization signal. A screen display device featuring: