JPS61272784A - Display controller - 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 device that controls the display of characters or patterns on a display screen.

[Conventional technology]

FIG. 4 is a block diagram showing a conventional display control device.
In the figure, (1) is a memory device (hereinafter referred to as ROM) that stores display patterns, and (2) is the ROM (1).
) is an address decoder that sends out an address for reading pattern data, and (3) is a shift register that shifts the read pattern data to the display side.

Next, the operation of the conventional display control device having the above configuration will be explained. For example, when displaying a pattern with 5x7 dots as one font shown in Figure 5, first the address decoder (2) selects a ROM corresponding to the pattern.
Select address (1), specify the line of the font, and transfer the data to shift register (3). In (5b) of Figure 5, the third line (5a) of the above font
An example is shown in which data is transferred to shift register (3).

The data transferred to the shift register (3) is output in synchronization with the scanning line of the TV display device to draw a predetermined pattern on the TV display screen.

[Problem that the invention seeks to solve]

However, currently only one font (e.g. jf 5
This is a conventional device because it tends not only to display a single number or letter using a 7 dot ( This method requires a large number of fonts to form a mosaic, and also requires a large ROM capacity.

The present invention was made to solve these problems, and an object of the present invention is to provide a display control device that requires fewer fonts and can reduce memory capacity.

[Means for solving problems]

In the display control device according to the present invention, a shift register that converts pattern data read from a memory device into a serial signal and shifts it is a bidirectional shift register, and the shift direction of the serial signal can be controlled. be.

[Effect]

Therefore, according to the present invention, only one font is required for left-right symmetrical fonts, and the ROM capacity can be reduced.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, (1) is a memory device that stores the contents of the display pattern, (2) is an address decoder that controls the memory device (1), and (4) is a bidirectional device that latches the output of the memory device (1). Shift register, (5) is an output switching circuit that selectively outputs an output corresponding to the shift direction of the bidirectional shift register (4), and (6) is a shift direction and output switching circuit of the bidirectional shift register (4). This is a control input that controls (5).

Next, as an example to explain the operation, a case will be described in which the font shown in FIG. 2 is displayed on the display screen. First, the address decoder (2) selects address 4'' of the ROM (1) corresponding to the pattern, and the line where the pattern is located is specified in the font, and the bidirectional shift register (4) is selected. When transferring the pattern data of the second line of the font shown in Figure 2, it will be "01000".The data thus transferred to the bidirectional shift register register (4) will be transferred to the TV. It is shifted to the left by a control input (6) outputted in synchronization with the scanning line and display clock of the display device, and outputted through an output switching circuit (5) to draw a predetermined pattern on the TV display screen.

When displaying the font shown in Fig. 3, which has a symmetrical pattern to the font shown in Fig. 2, the R
Select OM (1) and transfer the data "01000" to the bidirectional shift register (4) in the same manner as above. Next, when the data is shifted from the bidirectional shift register (4), unlike the case where the font display data shown in Fig. 2 is transferred, the data is shifted to the right according to the control input (8) and the output switching circuit (5) and output. In this case, data "00010" is output from the output switching circuit (5), and the display pattern becomes a left-right symmetrical pattern with respect to the font shown in FIG. 2, and is drawn on the TV display screen. For this reason, the pattern data of a single font stored in the ROM (1) can be converted into the pattern data of a font symmetrical to the font and displayed on the display screen, so the limited memory capacity can be effectively saved. Can be expanded.

In the above embodiment, the case where the display is displayed on a TV display screen has been described, but it can also be applied to a liquid crystal display, a plasma display, etc.

In addition, in the above embodiment, RO is used to store display fonts.
Although M is used, similar effects can be obtained by using RAM or other memory elements.

〔Effect of the invention〕

As explained above, according to the present invention, by making the shift register used in the display control device bidirectional,
This has the effect that the number of memory devices for storing display fonts can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the display control device of the present invention, FIGS. 2 and 3 are explanatory diagrams showing an example of a font having a left-right symmetry, and FIG. 4 is a conventional display control device. FIG. 5 is an explanatory diagram showing an example of transfer of a font and display pattern data of the font. In the figure, (1) is a memory device, (2) is an address decoder, (4) is a bidirectional shift register, (5) is an output switching circuit, and (6) is a control input. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent Masuo Oiwa Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] A memory device that stores display pattern contents displayed on a display device, an address decoder that reads pattern data from the memory device based on an address signal, and latches the read data and outputs the latched data according to a control input. The device includes a bidirectional shift register that shifts in a predetermined direction, and an output switching circuit that selectively outputs latch data that is sequentially output in accordance with the shift direction, and displays the output from the output switching circuit on a display device. A display control device characterized by: