JPH067315B2 - Large scale integrated circuit for CRT display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention generates a video signal for displaying numbers, characters, figures, etc. on a CRT screen, and outputs these characters out of 7 colors for each character. The present invention relates to a large-scale integrated circuit for CRT display that can select one color from the above and display it extremely clearly on a CRT screen.

2. Description of the Related Art Conventionally, CR is achieved by using a single CRT display semiconductor integrated circuit.
When displaying characters of different colors on the T screen, as shown in FIG. 3, an AND gate for outputting the character display output 2 of the CRT display semiconductor integrated circuit 1 and the RGB color outputs 10-12. The color of the character display is changed by inputting 3 to 5 and turning on and off these AND gates by the control signals 7 to 9 from the control microcomputer 6. In this conventional example, it is impossible to change the color for each character due to the limitation of the calculation speed of the microcomputer 6, and it is generally limited to change the color for each field of the screen.

Further, in the conventional example, when a character is superimposed and displayed on a TV broadcast image on a CRT screen, if only a character display signal is output on the screen, the TV image overlaps the part where the character is displayed. Since the flicker of the character occurs due to the movement of the TV image because it is displayed, the method of blanking only the part of the TV image displayed on the screen to prevent the flicker of the character. Was taken. Further, in order to blank the image of the TV broadcast in the portion overlapping the character on the screen, the semiconductor integrated circuit for CRT display 1
As shown in FIG. 3, an OR gate 14 is provided externally to the background output 17 for blanking if any of the outputs 3 to 5 of each color of RGB is at a high level. It was common.

Problems to be Solved by the Invention However, when displaying characters by the method shown in FIG. 3, the AND gates 3 to 5 and the OR gate 14 are inevitably mounted separately. However, since the background output signal has a high frequency like the character display signal, the signal delay due to the wiring capacitance is a problem that cannot be ignored. That is, as shown in FIG. 4, this signal delay appears as it is on the CRT screen as a deviation between the character display and the blanked portion of the TV broadcast image. In addition, the CRT display large-scale integrated circuit 1 and "O
Since the R "gate 14 and the R" gate 14 are on different chips, it is difficult to make the transistor characteristics of both transistors uniform, and therefore, there is a drawback that the R "gate 14 is easily affected by temperature changes in the operating environment. In addition to the large scale integrated circuit, there are problems such as an increase in the mounting area due to mounting the logic gate.

Means for Solving the Problems The present invention is to solve the above problems, and stores a first memory for storing display data and screen control data for one screen and a character such as a character or a graphic. A data memory unit including a second memory and a control circuit for controlling the second memory and data output from the data memory unit are CR.
It is composed of an output circuit section for outputting as T display data and also generating a background output for TV image blanking synchronized with this output, and the background output is only for a portion where a character output is present on the CRT screen. A large-scale integrated circuit for CRT display having three CRT display character output terminals capable of blanking an image and independently controlling ON / OFF of the character display output.

Effect According to the present invention, since it is possible to blank the TV image only on the portion where the character output exists on the CRT screen, the character can be displayed clearly. In addition, since the background output circuit and the character display circuit are formed on the same chip, the characteristics are well aligned and the stability is good.

Embodiment FIG. 1 is a circuit diagram of an embodiment of the present invention, which is a circuit for outputting a background output signal for blanking a background image only in a portion where a character is superimposed on a CRT screen. In this figure, X, Y and Z are character output terminals R and R, respectively.
These signals are for turning on and off the G and B color signal outputs independently, and by switching these three signals for each character, one of seven colors can be selected and displayed for each character. That is, the serial character data 27 (▲
▼) and color control signals 19, 20, 21 (X, Y,
NORs 22, 23 and 24 of Z) are input to the DFFs 29, 30 and 31 by the display clock 18 (HCK) and become character display outputs 33, 34 and 35 (R, G, B).

In addition, character display outputs R, G, B (33, 34, 3
5) even one of them is on, that is, the color control signals 19, 2
If even one of 0, 21 (X, Y, Z) has a low level output (hereinafter abbreviated as “L”), AND gate 25
Output becomes “L”, the background output enable signal 28
When (BLK) is "L", the character data 27 (▲ ▼) is input from the NOR gate 26 to the DFF 32 by the display clock 18 (HCK), and the image is blanked only on the portion where the character is on the screen. For the background output 36 (Y).

Next, FIG. 2 shows an embodiment of a circuit for blanking the image on the CRT screen by the background output signal 36 (Y).
In this figure, the image signals 37, 38, 39 (R, G, B) are C
The image signals of the TV or the like displayed on the RT screen and the on-screen R, G, B (40, 41, 42) are the CRT of the present invention.
The respective character display outputs of the large scale integrated circuit for display are shown. In FIG. 2, the transistor 50 (Q7) to which the background output signal 43 (Y) is input is the background output signal 43 (Y).
Is converted from + 5V level to + 12V level.

When this signal is "L", the transistor 51 (Q8) is turned on and the output of the transistor 51 (Q8) becomes "L", so that the transistors 44, 45, 46 (Q1, Q3, Q5) operate. , Display an image on the CRT screen. Background output 43
When (Y) is at a high level (hereinafter abbreviated as “H”), the transistor 51 (Q8) is turned off, and the image is CR.
Blanking occurs on the T screen. At this time, the transistors 47, 48, 49 (Q2, Q4, Q6) are operated and only the character output is displayed on the CRT screen.

Background output 43 (Y) is character display output 40, 41,
If even one of 42 (R, G, B) is "H",
Since it is "H", the image is blanked only on the portion where the character is superimposed on the CRT screen.

As described above, according to the present invention, not only can a character be selected from 7 colors for each character in a 1-chip semiconductor integrated circuit and displayed on the CRT screen, but also from the same integrated circuit. By blanking the image of the portion overlapping the character by the output background, the character can be displayed very clearly without being disturbed by the movement of the image. Moreover, since the background output circuit and the character display output circuit are formed on the same semiconductor chip, there is no difference in the temperature environment of the transistors and the characteristics are easily aligned, so that the background output and the character are prevented from being misaligned on the screen. There is an effect and a reduction in mounting area.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an essential part of an embodiment of the present invention, FIG. 2 is a circuit diagram of a CRT drive part according to an embodiment circuit of the present invention, FIG. 3 is a circuit diagram of a conventional example, and FIG. 4 is a CRT display pattern according to a conventional example. It is a figure. 22-24, 26 ... NOR gate, 25 ... AND gate, 29-32 ... DFF, 33, 34, 35 ... Character output R, G, B terminals, 36 ... Background output terminal.

Claims (1)

[Claims] 1. A data memory comprising a first memory for storing display data for one screen and screen control data, a second memory for storing characters such as characters and figures, and a control circuit for controlling these. And a data output from the data memory unit as CRT display data, and an output circuit unit for generating a background output for TV image blanking synchronized with this output, and the background output is a CRT. Only the part where the character output exists on the screen, T
A large-scale integrated circuit for CRT display having three CRT display character output terminals capable of blanking a V image and independently controlling ON / OFF of the character display output.