JPH04150480A - Screen display device - Google Patents

Abstract

PURPOSE:To use a display outputting stage as a mask so that a blank output can be performed easily by making the outputs of a displaying position detection circuit and conventional shift register selectable by providing a register. CONSTITUTION:When character font data are forcibly fixed to an 'L' state depending upon the setting method of a register, a no-character displaying state, namely, a blank displaying state can be set on the screen of a color display 2 by supplying blank information to an R-, G-, and B-terminals synchronously to the scanning of the scanning line of the display 2 by sending the 'L' value to an output control circuit 6. When a register 8 is set to an 'L' state, on the other hand, the character font data outputted from a shift register 5 are conventionally sent to the display through the circuit 6 and desired characters are displayed on the display 2, since the output of an AND circuit is not activated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a screen display device for displaying characters on a screen of a television or the like, and particularly to a control circuit for character display.

[Conventional technology]

FIG. 3 is a block diagram showing an example of a conventional screen display device. In the figure, (1) is a display integrated circuit, and (2) is a color display, which here shows a television.

(3) is a display data RAM that stores character code data that specifies arbitrary pattern data in the display character ROM (4), (4) is a display character ROM that stores character pattern data, and (5) is a display character ROM that stores character code data that specifies arbitrary pattern data. A shift register converts parallel data output from the display character ROM (4) into serial output, and (6) is a display output control circuit that controls the output of display character data from the shift register (5).

Next, the operation will be explained. In FIG. 3, first, data for displaying a desired character or pattern (in this case, character data giving blank information) is written into the display data RAM (3) one character at a time according to the address. 2. Sequentially, display data RAM
The character code data written in (3) is read out by the display character ROM (4) as character font data corresponding to this code. Then, by sending the read character font data to a shift register (5), the character font data is converted from parallel format to serial format. Finally, by giving the serially converted character font data to the display output control circuit (6), R (red) is output in synchronization with the scanning of the scanning line of the color display (12) according to the shape of the character to be displayed. , G (green), and B (blue) terminals to display desired characters and patterns on the screen of the color display (2). In this way, by sequentially writing only the character data giving blank information to the display data RAM (3) according to the address, the blank output of the entire line and the entire screen is performed by the process shown above. Ta.

[Problem to be solved by the invention]

Conventional screen display devices are configured as described above, so when blank output is to be performed on a color display, addresses are sequentially specified for each character in the display data RAM, and
Since it is necessary to write the desired character code data, that is, blank data, the CPU (Central Processing Unit)
number of instructions are required, which poses problems such as placing a load on the software and requiring writing time.

This invention was made in order to solve the above-mentioned problems, and it is possible to use a one-chip integrated circuit to erase characters or symbols displayed on the screen of a color display. Another object of the present invention is to obtain a screen display device having a function of performing blank output by masking data indicating symbols.

[Means to solve the problem]

The screen display device according to the present invention is provided with means for forcibly controlling the output of blank output data in addition to the character font data having character data to be displayed on the screen, based on the set value of the register.

[Effect]

The screen display device according to the present invention can perform blank output by masking character font data necessary for display.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings. FIG. 1 is a block configuration diagram showing a screen display device according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing the circuit configuration within the broken line frame (10) in FIG.

In FIGS. 1 and 2, (1) to (6) are the same as those in FIG. 3, so their explanations will be omitted. (7) is a display position detection circuit that detects the display position of characters, patterns, etc. to be displayed;
(8) is a register, and (9) is a selection circuit, specifically the second
The circuit is as shown in the figure.

Next, the operation will be explained.

In FIG. 1, first, data for displaying a desired character or pattern is sequentially written into the display data RAM (3), character by character, according to the address. The character code data written in the display character ROM (4) reads character font data corresponding to this code. Then, by sending the read character font data to a shift register (5), the character font data is converted from parallel format to serial format.

Here, when displaying one line of blank characters, conventionally, data is sequentially written character by character according to the address in the storage element of the display data RAM (3"), and character font data corresponding to the written code data is written. Read from display character ROM (4) and shift register (
5) Blank output was generated and outputted to the R, G, and B terminals via the display output control circuit (6), but in the present invention, as shown in FIG. When set to a value (in this case, set to "H"), the output signal of the display position detection circuit (7) becomes active.Then, as soon as the output signal of this display detection circuit (7) is in the "H" state, The characters corresponding to the status display line are in the display start state, and by NOR processing this signal and the shift register (5), the output of the NOR circuit becomes the "l L +" state.

This is because the character font data is forcibly fixed to the IIL'' state by the register settings, and by sending this value to the output control circuit (6), the color display ( 12) R, G,
B Give blank information to each terminal, color display (2)
This means that no characters are displayed on the screen, that is, a blank screen is displayed.

Also, if register (8) is set to “°L”,
Since the output of the AND circuit is not in the active state,
As before, the character font data output from the shift register (5) is sent to the color display (2) via the display output control circuit (6), and desired characters are displayed. As mentioned above, depending on how to set register (8),
Blank output can be performed not only line by line, but also screen by screen.

〔Effect of the invention〕

As described above, according to the present invention, in addition to the conventional circuit, a register is provided so that the output of the display position detection circuit and the output of the conventional shift register can be selected. This has the effect of making it possible to mask and easily perform blank output.

[Brief explanation of drawings]

Fig. 1 is a block configuration diagram showing a screen display device according to an embodiment of the present invention, Fig. 2 is a circuit diagram showing the circuit configuration within the broken line frame (10) in Fig. 1, and Fig. 3 is a conventional screen display. FIG. 2 is a block configuration diagram showing the device. In the figure, (1) is a display integrated circuit, (2) is a color display, (3) is a display data RAM, (4) is a display character ROM1, (5) is a shift register, and (6) is a display output. Control circuit, (7) is display position detection circuit, (8)
is a register, and (9) is a selection circuit. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] In screen display devices that display characters on the screen,
By controlling the output of the shift register and the output of the display position detection circuit that determines the display position of characters,
A screen display device characterized by displaying characters and blank output.