JPH01282594A - Screen display device - Google Patents

Abstract

PURPOSE:To output optional characters and patterns by utilizing the output of a display data RAM as a character display output in addition to the output of a display character ROM. CONSTITUTION:An input control circuit 3 processes control data 21, latches a command in a display control register 6, and stores display contents in a display memory 4. The character ROM 5 is stored with characters or the front of patterns to be displayed on a screen and is accessed with the output of the memory 4. A ROM/RAM output switching circuit 10 determines the output 32 of the ROM 5 or the output 31 of a RAM 4 with the control instruction 33 of a register 6 and outputs it to a display control circuit 9. The circuit 9 determines a character position by passing a synchronizing signal 22 from a video signal through an input circuit 7 and a display position detecting circuit 8 and outputs it on a display device according to the contents of the register 6.

Description

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

[Conventional technology]

FIG. 3 shows an example of the configuration of a conventional screen display device of this type. In FIG. 3, 1 is an oscillation circuit, 2 is a timing generator that generates various timings using signals oscillated by the oscillation circuit 1, and 3 is a timing generator that generates various timings using signals oscillated by the oscillation circuit 1. An input control circuit 4 stores control data, which inputs the output of the timing generator 2 and control data (commands and character codes for display on/off, etc.) 21 from a microcomputer, etc. for controlling the screen display device. A display memory 5 is a character R that stores characters and patterns to be displayed in the font configuration shown in FIG.
OM, 6 is a display control register that latches commands such as display control among the outputs of the input control circuit, 7 is a synchronization signal input circuit that inputs the synchronization signal 22 of the video signal, and 8 is a display position control register for displaying characters, patterns, etc. A display position detection circuit 9 is a display control circuit for controlling the display of the output of the character ROM 5 in accordance with display commands from the display control register 6. This screen display device is composed of the above-mentioned circuits, and the output of the display control circuit 9 is outputted as a display character output 23 to a display device such as a cathode ray tube.

The human power control circuit 3, whose operation will be explained next, processes control data 21 from a microcomputer, etc., latches commands such as display control in the display control register 6, and stores display contents such as character codes in the display memory 4. 0 to be stored in
When displaying, the character code stored in the display memory 4 accesses the character ROM 5 as output data,
The display character font outputted from this character ROM 5 is manually input to the display control circuit 9. Here, the display memory (RAM) 4 is composed of a total of (a+b)·C bits, where one word 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 character ROM 5 is composed of (j2xm) bits, and there are n characters of types.

Also, the timing at the time of display is the synchronization signal 2 from the video signal.
2 is input to the synchronizing signal input circuit 7, and this synchronizing signal is counted by the display position detecting circuit 8, thereby determining the position of the displayed character. The display control circuit 9 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 sends it to a display device such as a cathode ray tube.

[Problem to be solved by the invention]

Since the conventional screen display device is configured as described above, it has been impossible to display display characters and patterns other than the data stored in the display character ROM.

The present invention has been made to solve the problems of the conventional devices as described above, and its purpose is to provide a screen display device capable of displaying data other than the data contained in the display character ROM.

[Means to solve the problem]

The screen display device according to the present invention is configured so that, in addition to outputting the display character ROM, the character or pattern code written therein using the output data of the display data RAM can also be output as a character display output. It is something.

[Effect]

In the present invention, the display character output was previously limited to the data held in the display character ROM, but since the output of the display data RAM can also be used as character display output, any character or pattern can be displayed. It is now possible to output.

〔Example〕

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

FIG. 1 shows a screen display device according to an embodiment of the present invention,
In the figure, the same reference numerals as in FIG. 3 indicate the same parts. 1
0 is a ROM/RAM output switching circuit, which is added in this embodiment. This ROM/RAM output switching circuit 1
0 inputs the output 32 of the conventional character ROM (second display memory circuit) 5 or the display RAM according to the control command 35 output from the display control register 6.
(First display storage circuit) It is determined whether the output 31 of 4 is to be input, and it is output to the display control circuit 9.

Here, the operation will be explained using a specific example.

In a screen display device that can display C characters on one screen,
It is assumed that the display RAM 4 is composed of one word (a+b) bits. It is assumed that this one word consists of a character code a bit for accessing the character ROM 5 and a b bit as its attribute.

(a+b) C bits/word Here, assuming that this display RAM 4 can display C characters, the amount of information will be (a+b)Xc bits.

On the other hand, 1 font of character ROM5 is (IXm)
If it is made up of dots, one font is l-
This is m-bit information. In other words, if a font of (lXm) dots is created using the output data of the display RAM 4, it is possible to construct a character bone of ((a+b).C/(j!-m)).

However, this value does not need to be an integer. Furthermore, a.

b, c, l, and m are each positive integers.

When the ROM/RAM output switching circuit 10 selects the output 31 of the display RAM 4, the character code data (a bit) and attribute data (b bit), which are data in the display RAM 4, do not have their original meaning. The output data becomes the font composition information as it is.

In the above embodiment, when configuring the font font with the output 31 of the display RAM 4, the font configuration of the character ROM 5 was explained using (jlxm) dots, but this is different from the font configuration of the character ROM 5. x x y) It goes without saying that there is no problem at all with a dot configuration.

However, in this case, if x and y are arbitrary integers, (a+
b) It is necessary to satisfy the relationship: XC≧xxy.

〔Effect of the invention〕

As described above, according to the screen display device according to the present invention,
Conventionally, display output was limited to character ROM output, and characters and patterns could not be changed, but by making it possible to output characters even using display data RAM, any character or pattern can be output. It became.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a screen display device according to an embodiment of the present invention, FIG. 2 is a diagram showing the configuration of a one-font font dot of a character ROM, and FIG. 3 is a diagram showing a conventional screen display device. In the figure, 1 is an oscillation circuit, 2 is a timing generator, 3 is an input control circuit, 4 is a display memo + JRAM, and 5
1 is a character ROM, 6 is a display control register, 7 is a synchronizing signal input circuit, 8 is a display position detection circuit, 9 is a display control circuit, and 10 is a ROM/RAM output switching circuit.

Claims (1)

[Claims] (1) In a screen display device that displays characters or patterns on a display device such as a cathode ray tube, there is a display control register for latching commands related to display control, and a display control register that controls the characters or patterns to be displayed on the screen. A first display memory circuit to be written, and accessed by the output of this first display memory circuit,
a read-only second display memory circuit from which the font of the character or pattern to be displayed on the screen is read; and a read-only second display memory circuit that is controlled by the display control register, and which outputs the output of the first display memory circuit and the second display memory circuit. A screen comprising a switching circuit for switching between the output of the memory circuit and the output of the memory circuit, and capable of outputting the code itself output from the first display memory circuit as data constituting a font to be displayed on the screen. Display device.