JP3517713B2 - Screen display device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screen display device for displaying characters such as characters, symbols and patterns on a display device such as a CRT or LCD.

[0002]

2. Description of the Related Art FIG . 5 is a block diagram showing a configuration of a conventional screen display device, in which 1 is a central processing unit (hereinafter referred to as CPU) and 2 is a data bus. The CPU 1 displays the character code data of the characters to be displayed on the screen, the color code data indicating the color of the characters, and the blanking code data indicating the presence / absence of the blanking output of the characters via the data bus 2 from the RAM for display. Store in the data memory 3. Figure 6 shows "HELLO" output to the image displayed on the display device .
The following shows blanking in which the background of the character display area is filled with black so that the character string of can be easily seen. The display data memory 3 has a storage area of 1-bit blanking code data for each character code data outside the character code data storage area, and the CPU 1 stores blanking code data corresponding to the character code data to be blanked. Set the bit to "1".

The image signal output circuit 5 gives an address where data to be displayed is stored to the display data memory 3. The display data memory 3 outputs the character code data designated by this address to the character memory 4 (made of ROM) in which the font pattern of the character is stored. The character memory 4 outputs the font pattern of the character designated by the character code data to the image signal output circuit 5. The display data memory 3 also outputs the similarly designated color code data to the image signal output circuit 5. The image signal output circuit 5 displays the vertical sync signal VSYNC and the horizontal sync signal in order to display the image corresponding to the designated location.
In synchronism with HSYNC and the horizontal dot clock output from the oscillator circuit 8, serial digital data of a character font pattern and a color signal corresponding to the color code data are output from the color signal output terminal 9.

The display data memory 3 outputs blanking code data designated by an address given by the image signal output circuit 5 to the blank generation circuit 11. The blank generation circuit 11 included in the image signal output circuit 5 outputs a blanking output so as to correspond to a location designated by the image signal output circuit 5 when the blanking code data stored in the display data memory 3 is "1". Vertical sync signal VS
A blanking signal is generated in synchronization with YNC, the horizontal synchronizing signal HSYNC, and the dot clock, and is output from the blank terminal 10.

The blanking output area may be expanded to make it even easier to see. For example, as shown in FIG. 7 , blanking output is also performed in the display area for one character on the left side of the character output area and on the right side of the right end.
To do. In this way, when performing blanking output to the part where there is no character output to make the character easier to see,
The bit of the blanking code data corresponding to the character code data of "blank" is set to "1", and the image signal output circuit 5 may specify the place where the character code and blanking code are to be displayed.

[0006]

In the conventional screen display device, it is necessary to set blanking code data for each character in order to perform blanking output. Therefore, compared to a device that does not have a blanking output function, the processing of software is complicated and the load on the CPU 1 is heavy. Further, it is necessary to provide an area for storing the blanking code data in the display data memory 3,
Therefore, there is a problem that the area of the display data memory 3 becomes large.

The present invention has been made in view of this problem. By providing a decoder for decoding the character code data stored in the display data memory, blanking output is performed at the place where the character is displayed. An object of the present invention is to provide a screen display device capable of reducing the load on the CPU and the area of the display data memory. Further, the data output from the decoder is used as input data, and a circuit for generating a signal for performing blanking output in a region in which a character is displayed and a region adjacent to this is provided, thereby performing blanking output. An object of the present invention is to provide a screen display device capable of expanding the area and reducing the load on the CPU and the area of the display data memory.

Furthermore, by providing a register for holding data that determines prohibiting or permitting blanking output, it is possible to inhibit or allow blanking output, thereby reducing CPU load and display data. An object of the present invention is to provide a screen display device capable of reducing the area of memory.

[0009]

A screen display device according to a first aspect of the present invention comprises a decoder for decoding character code data stored in a display data memory, and performs blanking output by the data output by the decoder. It is characterized as being configured. A screen display device according to a second aspect of the present invention includes a decoder that decodes character code data stored in a display data memory, and an area in which a character is displayed and an area adjacent to the character are displayed by the data output from the decoder. It is characterized in that it is configured to generate data for ranking output.

The screen display device according to the third aspect of the invention is provided with a register for holding data for determining prohibition or permission of blanking output with the above-mentioned decoder, and the data held by this register and the decoded data by the decoder are used. It is characterized in that the blanking output is prohibited or permitted.

[0011]

According to the first aspect of the invention, the decoder decodes the character code data read from the display data memory, and when this is the character to be displayed, blanking output is performed in the area where the character is displayed. In the second invention, a signal for blanking and outputting an area adjacent to the area in which the character is displayed is generated from the data output by the decoder, and the area for performing the blanking output is expanded.

[0012] In the third aspect, the register is inhibited or permitted to blanking output over area character is displayed on the data held.

[0013]

【Example】

The present invention will be described in detail below with reference to the drawings showing an embodiment thereof. FIG. 1 is a block diagram showing an embodiment of a screen display device according to the first invention. In the figure, 1 is a CPU, 2
Indicates a data bus. The CPU 1 stores the character code data of the characters to be displayed on the screen and the color code data indicating the color of the character via the data bus 2 in the display data memory 3 (RA
M). The image signal output circuit 5 displays the address where the data to be displayed is stored in the display data memory 3
Give to. The display data memory 3 outputs the character code data designated by this address to the character memory 4 (made of ROM) which stores the font pattern of the character and the decoder 12 which decodes the character code data and designates it in the same manner. The generated color code data is output to the image signal output circuit 5. The character memory 4 stores the font pattern of the character designated by the character code data in the image signal output circuit 5
Output to.

The image signal output circuit 5 displays a vertical synchronizing signal VSYN so as to display a character corresponding to a place designated by the image signal output circuit 5.
C, the horizontal synchronizing signal HSYNC, and the serial digital data of the character font pattern and the color code data stored in the display data memory 3 in synchronization with the horizontal dot clock output from the oscillation circuit 8. And a color signal corresponding to the color signal are output from the color signal output terminal 9.

The decoder 12 decodes the character code data provided by the display data memory 3 and outputs the data "0" only to the character code data indicating the blank font pattern, for example, all the bits "0". Data "1" is output for character code data other than the above.

The decoder 12 outputs the decoded "0" or "1" data to the blank generating circuit 11 included in the image signal output circuit 5, and the blank generating circuit 11 outputs the decoded data. When 1 ", the background of the area where the characters are displayed in synchronization with the vertical sync signal VSYNC, the horizontal sync signal HSYNC, and the dot clock to display the characters corresponding to the location designated by the image signal output circuit 5 A blanking signal for blackening out is generated and output from the blank terminal 10. According to such a screen display device, a blank font pattern is stored in the character memory 4 as all bits "0" of the character code data, so that blanking output can be automatically performed in the character display area. Is.

FIG. 2 is a block diagram showing the configuration of an embodiment of the screen display device according to the second invention. In the figure, 12 is a decoder, which has the same configuration as that of the first embodiment of the invention. The decoder 12 gives the data obtained by decoding the character code data of the character string to the D terminal of the 3-input OR circuit 18 and the flip-flop circuit 19, and the set output Q of this flip-flop circuit 19 is given.
Is applied to the D terminal of the OR circuit 18 and the flip-flop circuit 20. Further, the set output Q of the flip-flop circuit 20 is given to the OR circuit 18, and the output of the OR circuit 18 is outputted from the blank terminal 10 as the blanking signal TD .

The signal output from the oscillating circuit 8 is applied to a frequency dividing circuit 21 which divides the frequency by 4, and the frequency divided signal output from the frequency dividing circuit 21 has a period corresponding to one character display area. It is given to the CK terminals of the flip-flop circuits 19 and 20. The configuration of FIG. 2 is the same as the configuration of FIG. 1 except for the above configuration, and corresponding parts are designated by the same reference numerals and description thereof is omitted.
The OR circuit 18, the flip-flop circuit 19, the flip-flop circuit
Blanking signal by the drop circuit 20 and frequency divider circuit 21
Configure a circuit to generate TD. FIG. 3 is a timing chart when the character string "AB" is displayed. CLK is an output signal of the oscillator circuit 8, and BCLK is a frequency division output of the frequency divider circuit 21.

ADDR is the address of the display data memory 3, and DATA is the character code data stored in this address. Character code data D1 corresponding to "A" stored in address AD1 of display data memory 3 and "B" stored in address AD2 of display data memory 3
The character code data D2 corresponding to is supplied to the decoder 12. The decoder 12 decodes the character code data D1 and D2,
Generate a blanking signal TA. The blanking signal TA is
It is given to the OR circuit 18. The flip-flop circuit 19 is set at the rising timing of BCLK after the blanking signal TA is given to the D terminal of the flip-flop circuit 19, and the set output Q is one cycle of BCLK from the blanking signal TA, that is, one character. The blanking signal TB delayed by the display area is given to the OR circuit 18 and the D terminal of the flip-flop circuit 20.

The flip-flop circuit 20 is set at the rising timing of BCLK after the blanking signal TB is applied to the D terminal of the flip-flop circuit 20, and the set output Q is 2 cycles of the BCLK from the blanking signal TA. That is, as one blanking signal TC delayed by two character display area
It is given to the OR circuit 18. 3 blanking signals TA, TB,
The OR circuit 18 to which TC is given, gives the blanking signal TD of the logical sum to the blank terminal 10 for the number of scanning lines corresponding to one character for each scanning line. Therefore, this blanking signal TD is 4
It becomes the character part.

The display data memory 3 is character code data.
DATA is given to the character memory 4. The character memory 4 outputs the font pattern of the character designated by the character code data DATA to the image signal output circuit 5, and the image signal output circuit 5 serializes the character font pattern from the rising timing of the blanking signal TB. And the color signal corresponding to the color code data stored in the display data memory 3 are output from the color signal output terminal 9.

The blanking signal TD is the blanking signal TB.
Since one cycle of the divided output BCLK appears earlier than the rising edge of, the blanking display is also displayed on the left side of the character "A", and the blanking signal TD is the divided output BCLK further than the output period of A and B2 characters. Since it lasts for one cycle later, a blanking display is also displayed on the right side of the character "B". As described above, according to the second aspect of the invention, it is possible to perform blanking output to an area that is adjacent to the area where the character is displayed on the left and right.

[0024]

FIG . 4 is a block diagram showing the configuration of an embodiment of the screen display device according to the third invention. This device enables / prohibits blanking output as required. That is, the register 16 is provided for storing the permission / prohibition data. Permission / prohibition data (“1” /
"0") is previously given to it by software or given from another circuit, and this data is written from the CPU 1 to the register 16 via the data bus 2.

The image signal output circuit 5 reads the enable / disable data from the register 16 and supplies it to the blank generating circuit 17. The blank generation circuit 17 generates a blanking signal when the data stored in the register 16 and the data decoded by the decoder 12 are both “1”,
It is provided to the blank terminal 10. The configuration of FIG. 4 is the same as the configuration of FIG. 1 except for the above configuration, and corresponding parts are designated by the same reference numerals and description thereof is omitted. Therefore the first
In the device of the third invention , blanking output of the character display area can be prohibited by setting the permission / prohibition data to "0". Therefore, it is possible to perform a display with or without blanking depending on the state.

[0027]

As described above, in the screen display device according to the present invention, the decoder decodes the character code data stored in the display data memory and performs the blanking output by the decoded data. Therefore, compared to the case where the blanking output is performed on the conventional screen display device, the burden on the CPU can be reduced, and the storage capacity of the display memory can be reduced to reduce the price.

In the screen display device according to the second invention,
The blanking output can be extended outside the character display area. Further, it is necessary for the screen display device according to the third invention.
The present invention has excellent effects, such as prohibiting or permitting blanking output as necessary .

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a screen display device according to a first invention.

FIG. 2 is a block diagram showing an embodiment of a screen display device according to a second invention.

FIG. 3 is a timing chart showing generation of a blanking signal of the screen display device according to the second invention.

FIG. 4 is a block diagram showing an embodiment of a screen display device according to a third invention.

FIG. 5 is a block diagram showing a configuration of a conventional screen display device.
is there.

6 is a blanking output by the screen display device shown in FIG .
It is explanatory drawing which shows the example of force display.

7 is an explanatory diagram showing an example of the blanking output display by the screen display device shown in FIG.

[Explanation of symbols]

1 CPU 2 data bus 3 Display data memory 4 character memory 5 Image signal output circuit 8 oscillator circuits 11 Blank generation circuit 12 decoder 13 Expansion circuit 16 registers 17 Blank generation circuit 18 OR circuit 19 flip-flop circuit 20 flip-flop circuit 21 frequency divider

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G09G 5/22-5/32 H04N 5/445

Claims (3)

(57) [Claims] 1. A character memory that stores a font pattern of a character, and a display data memory that stores character code data that specifies a character that is stored in the character memory, and is specified by the character code data. In a screen display device capable of performing blanking output in a region in which the displayed character is displayed, a decoder for decoding the character code data stored in the display data memory is provided,
A screen display device, which is configured to perform blanking output based on data output by the decoder. 2. A circuit for generating a signal for blanking output to a region adjacent to a region where a character is displayed, using data output from the decoder as input data. Screen display device. 3. A character memory that stores a font pattern of a character, and a display data memory that stores character code data that specifies a character that is stored in the character memory, and is specified by the character code data. In a screen display device capable of performing a blanking output in a region where a displayed character is displayed, a decoder for decoding the character code data stored in the display data memory and a decoder for decoding the character code data are obtained. Blanking by data
There stores range forces and means for specifying, on the prohibition or a register for storing the de-<br/> over data defining permission, the data and the register in which the decoder is obtained by decoding of the blanking output Blanking output according to data
And a means for prohibiting or allowing the screen display device.