JPH01310391A - Circuit for crt display - Google Patents

Abstract

PURPOSE:To minimize an increase in the capacity by storing only encoded data on a RAM in word units and storing the kinds and order of characters in the character string of a word on a ROM. CONSTITUTION:A 1st display data memory 13 is a RAM which stores the kinds of frequently used words in the form of binary codes. The codes are used to address a 2nd display data memory 14. The memory 14 is a ROM and outputs the kinds and order of characters in the character string of the word in the form of the binary codes. Those are used to address a 3rd display data memory 15. The memory 15 is also a ROM and stores the shapes of the characters. Its output is inputted to a shift register 16 for conversion to time-series CRT display data and further binary data is displayed on a screen through a CRT display output circuit 17 which converts the binary data into a display signal. The increase in the capacity of the RAM at the time of displaying many characters is minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a CRT display circuit for displaying characters such as two numbers on a CRT screen.

2. Description of the Related Art Conventionally, a CRT display circuit for displaying characters on a CRT screen has a first display circuit that stores the type of character and screen control data corresponding to the display position, as shown in the block diagram of FIG. a second display data memory 2 that stores the shape (font) of a character addressed by the output of the first display data memory 1; a shift register 3 for converting the output data of 2 into CRT display data; a CRT display output circuit and horizontal synchronizing signal 6 for displaying the data from the shift register on the CRT; The vertical synchronization signal 7 and the dot clock signal 8 cause the first display data memory 1. It is comprised of a second display data memory 2, a shift register 3, and a control circuit 9 that generates a timing signal to be applied to a CRT display output circuit 4.

Problems to be Solved by the Invention However, according to this configuration, as shown in FIG. Since the display data memory address 12 is 1,
If the number of characters required is the same as the number of characters 11 that can be displayed on a field screen, and the number of characters that can be displayed on one field screen is large, an extremely large capacity memory is required as the first display data memory 1. Met. In particular, as the first display data memory 1, random access memory (hereinafter referred to as RAM) is often used due to the need to rewrite display contents, but due to its structure, RAM is read-only memory (hereinafter referred to as ROM). ), the area per bit is several times larger than that of CRT display circuits, so as the number of characters that can be displayed on the display screen 10 increases, the chip size increases when integrating CRT display circuits. There was a problem.

In addition, developing software for the microcomputer that controls the CRT display circuit was not easy (it was easy to misspell the words to be displayed).

Means for Solving the Problems The CRT display circuit of the present invention includes first display data and screen control data for storing words and screen control data corresponding to display positions.
a second display data memory that stores character string information constituting the word accessed by the first memory data; and a third display that stores fonts of characters included in the character string. a shift register for converting the output data of the third data memory into CR1 display data, a CRT display output circuit for displaying the data from the shift register on the CRT, and a horizontal The synchronization signal, the vertical synchronization signal and the dot clock signal cause the first. Second. a third display data memory, the shift register and the CR;
The control circuit includes a control circuit that generates a timing signal to be applied to the T display output circuit.

According to the present invention, display data is stored in a word unit rather than a character unit in a data memory that stores display data for one screen, and information on each character is stored in a RAM.
It can be stored in a ROM which has a higher degree of integration than the ROM.

In addition, when developing the microcomputer software that controls the CRT display circuit of the present invention, the character string to be displayed can be specified in words rather than characters, making the format easier for humans to understand. be able to.

Embodiment An embodiment of the CRT display circuit of the present invention will be described with reference to the functional block diagram shown in FIG.

This circuit includes a first display data memory 13 and a second display data memory 13.
display data memory 14, and a third display data memory 14.
It is composed of a memory 15, a shift register 16, a CRT display output circuit 17, and a control circuit 18.

The first display data memory 13 is, for example, -TIM
It stores frequently used word types, such as E'' and PLEASE-, in binary code, which is comprised of RAM. This code addresses the second display data memory 14.

The second display data memory 14 is composed of a ROM,
It stores the types of characters included in the string that corresponds to the word code, and outputs them as binary codes according to the order of the string. Furthermore, this data indicating the type of character addresses a third display data memory 15 that stores the shape of the character. Note that this third display data memory 15 is composed of a ROM. A CRT that inputs the output data of the third display data memory 15 to a shift register 16 to convert it into time-series CR1 display data, and further converts the binary data from the shift register 16 into a display signal. The data is displayed on the screen via the non-table output circuit 17.

In addition, 1. Second. Third display data memory 13.
14.15, shift register 16 and CRT display output circuit 17 receive horizontal synchronizing signal 6. Vertical synchronization signal7. Dot
It is controlled by a control circuit 18 which generates a timing signal using a clock signal 8.

Furthermore, with reference to FIG. 2, the principle of display on a CRT screen will be specifically explained.

Note that FIG. 2 shows an example of the display on the CRT screen shown in FIG. 4.

At address 0 of the first display data memory 13, there is a code "0" indicating the word "PLEASE", and at address 1 there is a code "1" indicating the word "CHECK".
is memorized.

This code accesses the second display data memory 14. At address O of the second data memory 14 are characters -P'', L''.

Codes "O" and "1" for specifying the characters "E", -A", "S-, -E", respectively.

"2", 3", "4", and "2° are stored in this order, and this code is chronologically stored in the order of character strings according to the timing signal output by the control circuit 18 shown in FIG. Output.

The output code "0" accesses the third display data memory 15 as shown in FIG. is stored in the form of a dot matrix as shown in the figure, and the horizontal timing signal of the output of the control circuit 18 is used to horizontally divide the dot matrix (5 dots in this example) along the horizontal scanning line 20 of the CTR 19. It is input to the shift register 16 as binary data (11110). The shift register 16 outputs this parallel data in time series according to the dot clock signal. This data passes through the CRT display output circuit 17 and is output as "11110°" from the left side along the horizontal scanning 120 on the CTRL 9, thereby displaying the top row of the character -P on the screen. By repeating the data transfer described above, the character string "°PLEASE" is displayed on the CRT screen.

“I have a problem with the CHECK- display (same thing).

Effects of the Invention As described above, according to the present invention, only encoded data in word units is stored in the RAM, and the types and order of characters included in the character string of the word are stored in the ROM. The increase in RAM capacity, which is a problem when displaying characters, can be suppressed to the necessary minimum. As a result, when integrated, the chip area can be reduced. Moreover, in the development of software for control microcomputers, it is possible to write in a form that is easier for humans to understand, rather than word by word, which has the effect of improving development efficiency.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a CRT display circuit according to the present invention, FIG. 2 is a diagram showing an example of a display on a screen according to the present invention and its display principle, and FIG. 3 is a diagram showing a conventional CRT display circuit. The block diagram in FIG. 4 is a diagram showing the correspondence between the display on the screen and the data memory address for storing display data for one screen according to the conventional example. 6...Horizontal synchronization signal, 7...Vertical synchronization signal, 8...Dot clock signal, 13...
...First display data memory, 14...
・Second display data memory, 15...Third
Display data memory, 16...shift register, 17.old...CR1 display output circuit, 18...
...Control circuit, 19.Old...CTR120...
...Horizontal scanning line. Name of agent: Patent attorney Toshio Nakao and 1 other person

Claims (1)

[Claims] The first one stores display data and screen control data for one screen.
a second display data memory that stores character string information addressed by the display data of the first display data memory; A third display data memory that stores the shape (font) of the character addressed by the data, and a shift register that converts the output data of the third display data memory into CRT display data in time series. and,
a CRT display output circuit for displaying data from the shift register on a CRT, the first display data memory, the second display data memory, and the third display data memory; , a control circuit for controlling the shift register and the CRT display output circuit.