JPS63147192A - Display control circuit - 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 display control circuit for displaying characters and symbols in a raster scan method on a display device using a cathode ray tube or the like.

[Conventional technology]

FIG. 4 is a block diagram showing the basic configuration of the display control circuit. In the figure, 1 is a basic control circuit, which has a pointer (not shown) for the currently displayed position, and a display device (
A timing signal necessary for display control is generated in synchronization with a raster scan horizontal synchronization signal and vertical synchronization signal (not shown).

2 is an address control circuit which synchronizes with the timing signal generated by the basic control circuit 1 and which controls the display refresh memory 3.
Generates an address signal to access. The display refresh memory 3 stores character and symbol codes and their control codes, each corresponding to one character at one address position. Reference numeral 4 denotes a character pattern generation circuit, which uses the code of a character or symbol as an address to read out a pattern memory (not shown) in which the tone pattern of that character or symbol is stored, and generates a tone pattern of the character. The character code read out from the display refresh memory 3 in response to the address signal from the address control circuit 2 becomes an address for the pattern memory of the character pattern generation circuit 4, and the dot pattern of that character is read out.

Reference numeral 5 denotes an output control circuit, which outputs the character dot pattern read out from the character pattern generation circuit 4 into a bit serial signal to be displayed using a raster scan method according to the timing signal from the basic control circuit 1. do.

Next, using Figures 4 to 7, we will explain the operation of the basic display control circuit.Before displaying 0, the code of the characters (9 characters from A to I in this example) to be displayed on one screen is ,
Corresponding address of all display refresh memory 3 (
0 to 8) in this example, and is stored by some other means (not shown). First, an address counter (not shown) in the address control circuit 2 is cleared by a signal from the basic control circuit 1 that has detected the display position and becomes O, which is output as an address signal. 1 row of letters A
The code is read. Then, the contents of the address counter increase by 1 for each character, and 0. 1. 2. ...
On the other hand, when the contents of the address counter reach 8, a display end signal is sent from the address control circuit 2 to the basic control circuit 1, and the display for one scanning line is completed. This number corresponds to the number of rask scanning lines constituting one line (this is stored in the pattern memory of the character pattern generation circuit 4. It is determined by the size of one character)
If you repeat this, the display will end. In this way, one screen's worth of display is performed.

FIG. 5 shows a detailed example of the above explanation as time passes, and shows the display of the n-th character of 6 dots with respect to the reference signal. The address of the n-th character changes to the (n-1)th character, which causes the output of the refresh memory to be output from the 2-character pattern ROM, which is latched into the shift register and shifted out at the end of the n-1 character. represents.

[Problem that the invention seeks to solve]

As described above, in conventional display control circuits, the character size of output data in response to a reference signal in the horizontal direction is fixed for each row, and cannot be changed for each character depending on the display character or pattern. When enlarging and displaying the image, there is a drawback that two additional characters of the display ROM must be used.

The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide a display control circuit that can specify the horizontal size of displayed characters on a character-by-character basis.

[Means for solving problems]

The display control circuit according to the present invention has horizontal character size data for each character in the display refresh memory,
By reading it out for each character, latching it, and using the latch signal to switch the reference signal for display control to its frequency divided signal, it is possible to switch the horizontal character size for each character. This is what I did.

[Effect]

The selector switches the horizontal character size for each character.

〔Example〕

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

1 and 2 are block diagrams showing one embodiment of the present invention. FIG. 1 shows a block configuration corresponding to the conventional circuit shown in FIG. 4, and FIG. 2 shows the basic control circuit shown in FIG. 1. Part of the inside of the circuit is shown.

The same reference numerals as in FIG. 4 indicate the same or equivalent parts, and in FIG. 1, C is an output line for character size data in units of characters sent from the display refresh memory 3 to the basic control circuit l.

A selector 8 selects the reference signal A and the frequency division ratio cuff a of the circuit 7 according to the character size data C from the refresh memory 3, and displays the output B. It is used as a reference signal for control.

The output signal C from the display refresh memory 3 is used as the select signal for determining whether to select the original reference signal A or the frequency division ratio cuff a from the frequency divider circuit 7 as the reference signal B. The signal 6a obtained by launching at the signal is used.

Next, the operation of the circuits shown in FIGS. 1 and 2 will be explained with reference to the timing diagram shown in FIG. 3.

The character codes for characters A to 1 to be displayed prior to display are:
It is assumed that the display refresh memory 3 is stored in corresponding addresses O to 8 in advance. Also, regarding the character size control bit data, it is assumed that only H is written in address 2 and L is written in the others.The sequence for starting 0 display is the same as in the conventional example, so we will explain how the character size being displayed changes. do.

The left end of the timing diagram in FIG. 3 is the beginning of the timing diagram, where the output of the character B at address 1 is about to begin. When character B of address 1 begins to be output, the address counter is incremented by 1 and becomes 2. This address output is sent from the address control circuit 2 to the display refresh memory 3, and in accordance with the signal from the basic control circuit 1,
The code of the character C is sent to the character pattern generation circuit 4 as memory output 1. On the other hand, the character size control signal C from the display refresh memory 3 is output at H level to the basic control circuit 1, and is latched by the latch 6 at the falling edge of the signal. Then, the output signal B has been selected as the reference signal A until now, but the output signal a of the 1/2 frequency divider 7
Therefore, when the character C at address 2 is output, it is output at twice the cycle. In this way, the character size in the horizontal direction can be changed by the output of the display refresh memory 3.

In the above embodiment, for the sake of explanation, the output of the 1-bit display refresh memory was used to explain switching between small and large horizontal character sizes. It is also possible to switch the font size, which produces the same effect as above.

〔Effect of the invention〕

As described above, according to the display control circuit according to the present invention, the character size in the horizontal direction of the display can be changed by simply adding a launch circuit and a selector circuit to the basic control circuit. It is possible to display a variable horizontal character size for each character. Also, a character pattern ROM for display to change the horizontal size of the display.
There is no need to create separate ROMs, and the character pattern ROM can be used effectively.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of a display control circuit according to an embodiment of the present invention, FIG. 2 is a block diagram of a part of the basic control circuit 1 shown in FIG. 1, and FIG. 3 is an embodiment of the present invention. FIG. 4 is a block diagram showing the basic configuration of a conventional display device. FIG. 5 is a timing diagram showing the operation of the conventional display device shown in FIG. 4. FIG. 6 is a conventional display device. FIG. 7, which is a diagram showing an example of display by the device, is an explanatory diagram showing addresses of the fresh memory. 1 is a basic control circuit, 2 is an address control circuit, 3 is a display refresh memory, 4 is a character pattern generation circuit, 5 is an output control circuit, A is a basic clock signal, B is a reference signal for display control, and C is a reference signal for display control. Character size control signal from refresh memory, D is latch signal of signal C. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) A refresh memory, a basic control circuit that controls the read operation of the refresh memory, a character pattern generation circuit that generates a character dot pattern corresponding to the character code read from the refresh memory, and the generated dot pattern. In a display control circuit that includes an output control circuit that displays data using a raster scan method, the refresh memory stores character size data that indicates the horizontal character size of each character; A latch means for latching the character size data read from the refresh memory at the same time as the character code is read, and selecting either the fundamental frequency signal or its frequency division signal according to the latch output and supplying it to the output control circuit. 1. A display control circuit comprising: selection means for obtaining a reference signal for display control to be performed.