JPS61223788A - Clipping control system - 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] [Summary] When data is written only within a limited area of a bitmap memory, the boundary of the limited area can be detected by hardware and drawing can be performed at high speed. do.

[Industrial application field]

The present invention relates to a display device that expands display contents in a bitmap memory and then reads and displays them. In particular, the present invention relates to a display device that develops display contents in a bitmap memory and then reads and displays them. In particular, the present invention is controlled so that display data can be written only in a certain area in a bitmap memory that has a limited display area such as a window display. The present invention relates to a method that can perform so-called clipping control at high speed.

With the spread of information processing devices, various display devices have been developed.
In general, many display devices are used that develop one screen of display content from main memory onto a bitmap memory, read it out by rask scanning, and display it on a cathode ray tube.

When performing window display on this display device, clipping control is used to limit a certain area on the bitmap memory, write data to be displayed within that area, and prevent data from being written outside that area. It is being done.

In this case, it is desirable to be able to write data within the window at high speed.

[Conventional technology]

FIG. 2 is a diagram illustrating a clipping control method.

When displaying a window by providing a window on the display surface of the display device, a certain area of the bitmap memory 1 is limited to provide a window area 2, and data is written only inside this window area 2.

In this case, it is necessary to perform clipping control so that data is not written to areas other than the window area 2 of the B-7 map memory l. For example, if a part 3 of the circumference is to be drawn in the window area 2, a part 4 of the circumference indicated by a dotted line must not be drawn.

Conventionally, when drawing the circumference 3, the boundaries 5 and 6 of the window area 2 are detected by software, and the next drawing point is calculated without drawing the portion corresponding to the circumference 4. That is, when calculating one drawing point, it is always determined whether or not to draw.

[Problem that the invention seeks to solve]

As described above, conventional methods have the problem of slow processing speed because it is necessary to determine whether or not to draw for each drawing point.

The present invention was created in view of these problems, and aims to provide a clipping control method that improves processing speed by setting the drawable area using hardware instead of determining the drawing effective area using software. It is said that

[Means for solving problems]

FIG. 1 is a block diagram of a circuit showing one embodiment of the present invention.

The present invention is directed to the address area + of the window area 2 shown in FIG.
an effective area start address register 12 indicating Y+, a lateral distance register 13 storing an address indicating the lateral length (x2xl) of the window area 2;
A vertical distance register 14 that stores an address indicating the vertical length y2 >'I), and each of the above registers 12
.

Then, based on the address sent by the drawing control circuit 17 and the address sent from the effective area generation circuit 15, which draw circumferences 3 and 4, for example, in the bitmap memory 1, the drawing judgment circuit 1
6 sends a write signal only to addresses inside the window area 2.

[Effect]

By configuring as described above, the effective area generation circuit 15
calculates the effective area in the bitmap memory 1 of the window area 2 based on the address sent by the effective area start address register 12 and from the address indicating the length and width indicated by the vertical distance register 14 and the horizontal distance register 13. The indicated address can be sent to the drawing determination circuit 16.

Therefore, the drawing determination circuit 16 sends a write signal to the bitmap memory 1 that allows the circumference 3 to be written only inside the window area 2, thereby preventing unnecessary writing of the circumference 4.

By doing so, it is not necessary to determine whether drawing is possible for each drawing point, and it becomes possible to draw the circumference 3 in the bi-nodmap memory 1 at high speed.

〔Example〕

In FIG. 1, the processor 10 is located at the starting address 8.0 of the window area 2 shown in FIG. 2 of the bitmap memory 1. and yl are set in the effective area start address register 12.

The horizontal distance register 13 stores the horizontal length of the window area 2 (X2 XI), that is, the difference in addresses.

Further, the vertical distance register 14 stores (y2)'I) indicating the vertical length of the window area 2, that is, the difference in addresses.

The valid area generating circuit 15 calculates the horizontal length of the window area 2 indicated by the horizontal distance register 13 and the vertical direction of the window area 2 indicated by the vertical distance register 14 based on the address sent by the effective area start address register 12. Based on the length of , an address indicating the moving area of the window area 2 is sent to the drawing determination circuit 16 .

The processor 1 reads data to be drawn on the bitmap memory l from the main memory 1) and sends it to the drawing control circuit 17. The drawing control circuit 17 uses the address specified to write this data in the bitmap memory 1 to the drawing judgment circuit 1.
6 and also sends it to bitmap memory 1. At the same time, data is also sent to the bitmap memory l.

The drawing determination circuit 16 compares the address sent by the effective area generation circuit 15 with the address sent by the drawing control circuit 17, and sends a write signal to the bitmap memory l only when the address indicates the inside of the window area 2. do.

Therefore, for example, the circumference 3 shown in FIG. 2 is drawn, but the write signal is blocked for the circumference 4, so the via map memory l
is not drawn.

The P/S conversion circuit 18 converts the contents of the bitmap memory 1 into a video signal and sends it to the display section 19 for display.

〔Effect of the invention〕

As described above, in the case of drawing only within a limited range, the present invention allows the boundary line to be determined by hardware, so that drawing processing can be performed at high speed.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a circuit showing one embodiment of the present invention, and FIG. 2 is a diagram explaining a clipping control method. In the figure, 1 is a bitmap memory, 2 is a window area, 10 is a processor, 1) is a main memory, 12 is an effective area start address register, 13 is a horizontal distance register, 14 is a vertical distance register, and 15 is an effective area. 16 is a drawing determination circuit; 17 is a generation circuit;
18 is a drawing control circuit, 18 is a P/S conversion circuit, and 19 is a display section. 1st Place Kazuaki's Ichirinta Hiroki Lr Town Washi-atmosphere Block 1 Tea 1
mouth

Claims (1)

[Scope of Claims] In a display device that expands display content in a bitmap memory (1) and then reads and displays the content, a first memory that stores a start address of a limited area (2) of the bitmap memory (1) is provided. a second storage means (13) for storing an address indicating the length of the limited area (2) in the width direction; the limited area (2) based on the outputs of the third storage means (14) for storing an address indicating the length, and the first, second and third storage means (12, 13, 14); a valid area generating means (15) that sends out an address indicating a valid area range; and a bit map memory (15) based on the address of data to be written to the bit map memory (1) and the address sent by the valid area generating means (15). 1) is provided with a drawing determination means (16) for sending a write signal, and detects an address for writing the data into the limited area (2) and sends a write signal to the bitmap memory (1). A clipping control method characterized by transmitting.