JP2858831B2 - Bitmap display method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a bitmap display system, and more particularly, to a bitmap display system having a superimpose function.

[Background Art] Bitmap display is a display method in which a memory address is associated with each pixel on a screen and display data is stored in the memory. In this display method, as a means for superimposing character information or the like, the method shown in FIG. 4 has been conventionally used. That is, the original data to be displayed is stored in the display memory 10, a superimpose memory 20 having a capacity equivalent to this is provided separately, and the superimpose data is stored in this memory. Was. The output of each memory is switched in the data synthesizing unit 30 to which the information of the superimposed portion is input in advance to obtain display data.

[Problems to be Solved by the Invention] In the above-described conventional bitmap display method, a memory for two screens is required to perform superimposing,
Further, since it is necessary to input information for switching data of two screens, a heavy burden is imposed on hardware.

Accordingly, it is an object of the present invention to provide a bitmap display method that enables superimposed display with a simple configuration without increasing the load on software.

[Means for Solving the Problems] In order to achieve the above object, the present invention assigns a plurality of bits (for example, 8 bits) to each pixel in the display memory 1 as shown in FIG. One bit is used for superimpose selection data indicating whether or not to display superimpose data on the pixel. The register 2 stores superimposed data corresponding to the gray level of the superimposed portion. When the superimposed selection data is “0”, the display data of the display memory 1 is output from the selector 4. When the superimpose selection data is "1", the selector 4 outputs superimpose data.

Example Next, an example of the present invention will be described with reference to the drawings.

FIG. 2 is a block diagram showing one embodiment of the present invention.
In the figure, 3 is a superimpose control circuit for selectively outputting superimpose selection data to a selector 4 by a superimpose control signal, 5 is a microcomputer for controlling each part of the display device, and 6 is a display. This is a bidirectional buffer arranged in a bus between the memory 1 and the microcomputer 5.

Next, the operation of the display device of FIG. 2 will be specifically described with reference to FIG. FIG. 3 is a diagram showing the correspondence between each pixel of the display screen and the address of the display memory 1. Now
As shown in FIG. 3, it is assumed that white is superimposed on the third to fifth columns of the fourth row.

First, the normal display device (when superimposition is not performed) will be described. In this case, the superimpose control signal is set to "0", and the superimpose control circuit 3 controlled by this signal does not output the superimpose selection data from the display memory. That is, in this case, the superimpose selection data becomes invalid. In this state, the display data read from the display memory 1 is output as it is through the selector 4.

Next, a case where superimpose is performed will be described. The superimpose function is realized through the following steps.

The microcomputer 5 sets white data (all bits are “1”) as superimpose data in the register 2. This data is input to the selector 4.

The microcomputer 5 rewrites “bits allocated for superimpose selection data” in the third to fifth columns of the fourth row of the display memory 1 to “1” through the bidirectional buffer 6.

After rewriting "", the superimpose control signal is set to "1".

The data read from the display memory 1 is supplied to the selector 4
Is input to The “bit allocated for superimpose selection data”, that is, the superimpose selection data, is input to the superimpose control circuit 3.

The superimpose control circuit 3 outputs the superimpose selection data to the selection signal input of the selector 4 as a display data switching signal when the superimpose control signal is set to "1".

The selector 4 switches and outputs “display data” and “superimpose data” according to the display data switching signal.

As a result, the superimposed data is output as display data only between the third column and the fifth column of the fourth row,
On the display, a portion corresponding to the third column to the fifth column of the fourth row is displayed in white, and in other portions, a display according to the display data is displayed on the display memory.

[Effects of the Invention] As described above, in the bitmap display method of the present invention, information on whether or not superimposing is performed on a pixel is stored in a memory area corresponding to each pixel on the display memory. Therefore, the present invention has the following effects.

Since it is not necessary to prepare a memory for two screens, it is not necessary to store information for selecting data and to perform a process of synthesizing the data, so that the hardware configuration can be simplified.

Since the display data and the superimpose setting bit are stored at the same address, processing by the microcomputer is facilitated.

[Brief description of the drawings]

FIG. 1 is a block diagram for explaining the principle of the present invention,
FIG. 2 is a block diagram showing an embodiment of the present invention, FIG. 3 is a diagram showing correspondence between addresses of display memories and pixels, and FIG. 4 is a block diagram of a conventional example. REFERENCE SIGNS LIST 1 display memory 2 register 3 superimpose control circuit 4 selector 5 microcomputer
6. Bidirectional buffer.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-2-127879 (JP, A) JP-A-61-65690 (JP, A) JP-A-3-127566 (JP, A) JP-A-60-690 27566 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) G09G 5/00-5/40 G06F 3/14-3/153 H04N 5/262-5/278

Claims (1)

(57) [Claims] 1. A display memory for storing display data and superimpose selection data for each pixel, holding superimpose data in a register provided separately from the display memory, and displaying the display data and the superimpose data. A bitmap display method in which either one of the data is output from a selector to which imposed data is input in accordance with the superimposed selection data.