JPS58203491A - Graphic CRT display 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 (1) Technical Field of the Invention The present invention relates to a graphic CRT display circuit for displaying characters.

(2) Prior Art and Problems In a graphic CRT display, suppose that a CRT display drawing is displayed with 80 characters horizontally and 25 lines vertically as shown in Figure 1(a), and one of the characters is as shown in Figure 1(b). It is assumed to be composed of 8×8 dots.

Conventionally, this graphic CRT display is shown in Figure 1 (b).
) characters J+0, J+1,..., J+7 words are stored at memory addresses 0 and 8, respectively, as shown in Figure 2 (a).
It was stored in discrete locations such as address 0, etc.

The relationship between this CRT display screen and the address of the random access memory element (hereinafter referred to as RAM) is shown in Figure 2 (b).The relationship between ifiRAM and address counter is shown in Figure 2 (C). In addition, in FIG. 2(b), the dotted line part A on the left side corresponds to the leftmost character of the superlative character in FIG. ) shows the case of 8×8 dots, 64 horizontal characters and 24 vertical lines.

As mentioned above, conventionally, when storing character data in RAM to display characters on a CRT, an address was calculated and then the data was stored in the corresponding RAM. That is, when characters are displayed at 1XJO point, data for five words must be stored in the CRT horizontal display character interval, and address calculation is performed by a software program, which requires wasted time.

(3) Purpose of the Invention In view of the above-mentioned drawbacks of the conventional art, it is an object of the present invention to provide a graphic CR1 display circuit that reduces the time required to access the RAM.

(4) Structure of the Invention According to the present invention, in a graphic CR1 display circuit comprising a random access storage element, a random access means, and a CR1 display driving means,
When one character is displayed at the point of
The words up to the first word are displayed vertically on the CRT screen as one character, and the next five words are displayed as one character next to the horizontal character (3
), and thereafter J in the order of the addresses of the random access storage elements.
This is achieved by providing a graphic CR1 display circuit characterized in that it is equipped with a random access means for selecting the next character (horizontally) on a CRT screen word by word.

(5) Embodiments of the Invention Below, embodiments of the present invention will be described in detail with reference to the drawings.

Assuming that the CRT display screen is displayed with 80 characters horizontally and 25 lines vertically, and one character consists of 8 x 8 dots, then RA
The relationship between the access order of M and CRT scanning is as follows.

The letter words J00, J+1, shown in Figure 1(b)
....

As shown in Figure 3 (a), J+6 and J+7 are read out sequentially from the first address, totaling 80 words of data, and then transferred to the CRT.
The data is displayed on one horizontal scanning line.

Next, from the first address +1, the addresses are sequentially advanced in 8-word increments, 80 words of data are read out, and the scanning line of the second main port is displayed. If you perform this operation eight times, one horizontal line of characters (640 words of data) will be displayed4). The display of the next line is completed by the same operation as above, with the 641st word 0 data from the beginning as the starting address.

The relationship between the CRT display screen and RAM addresses according to the present invention is shown in FIG. 3(b). Corresponds to the first character on the left. FIG. 3C shows the relationship between the address counter and the RAM in the embodiment of the present invention, and it should be noted that the addresses of the scanning line counter and the addresses of the digit counter are converted.

FIG. 4 shows a block diagram of a circuit for implementing the present invention, in which the address counter 2 is constituted by a binary counter and includes a row counter, a scanning line counter, and a digit counter. The 3-bit output of the scanning line counter and the b-bit output of the digit counter are converted into b-bit and 3-bit output by the address switching circuit 3, respectively, and the converted output address is applied to the RAM block 4. R
The data read from the AM block is sent to the parallel-to-serial conversion circuit 5.
The data is converted into serial data and displayed sequentially on the screen. Note that the timing circuit 1 is a circuit that takes timing of the entire circuit system.

(6) Effects of the Invention As explained in detail above, the present invention stores five words of character data displayed on a CRT in an area of five consecutive words in RAM and automatically reads them when displaying the characters. j9RA
The time required for accessing M is reduced.

[Brief explanation of the drawing]

1 and 2 are diagrams for explaining the operation of a conventional graphic CR1 display circuit, FIG. 3 is a diagram for explaining the operation in an embodiment according to the present invention, and FIG. 4 is a diagram for explaining the operation of the conventional graphic CR1 display circuit. It is a block diagram showing an example of. In the figure, 1 is a timing circuit, 2 is an address counter, 3 is an address switching circuit, 4 is a RAM block, and 5 is a parallel-serial circuit.

Claims (1)

[Claims] In a graphic CRT display circuit comprising a random access memory element, a random access means, and a CRT display driving means, when one character is displayed at a point of 1 horizontally x vertically J, the character is arranged in the order of the addresses of the random access memory element. Up to five words are displayed one word at a time in the vertical direction of the CRT screen to form one character, and the next five words are displayed as one character next to it horizontally. A graphic CRT display circuit characterized in that it is equipped with a random access means that allows each word to be the next character (in the horizontal direction) on a CRT screen.