KR940009751B1 - Cursor display control apparatus and method therefor - Google Patents

Abstract

A cursor display control device provides a software method to use a frame buffer to display various cursor sizes and patterns. The device control comprises a display control circuit (140) to generate a video address for cursor display, a comparator (160) to generate an interrupt to CPU (10), a frame buffer (150) to generate a cursor pattern data, a latch (110) to get a current cursor position from CPU (10), a buffer (120) to generate the video address to CPU (10), a decoder to enable the latch (110) and the buffer (120).

Description

Cursor Display Control Device and Method

1 is a block diagram of a conventional cursor display control device.

2 is an embodiment of a cursor display control device according to the present invention.

3 is another embodiment of a cursor display control apparatus according to the present invention.

4 is a flowchart of a cursor display control method according to the present invention.

5 is a cursor display position diagram.

6 is a cursor deletion position diagram.

Figures 7a to c or waveforms according to figure 3;

* Explanation of symbols for main parts of the drawings

10: central processing unit 20: pattern memory device

30: shift register 40: parallel-serial conversion means

100: decoder 110: latch

120: buffer 130: logic element

140: display control circuit 150: frame buffer

160: comparator 170: the first latch

180: the second latch 190: the first buffer

200: second buffer 210: first comparator

220: second comparator

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cursor display control device and method in a graphic display device, and more particularly to a cursor display control device and method for controlling cursor display in software.

In general, in a graphic display device, a cursor mark is a display mark used to indicate a position at which a text or graphic is input or modified on a display device.

1 is a block diagram of a conventional cursor display control apparatus, which is described in Japanese Patent Laid-Open Publication No. 91-6865 published on April 30, 1991.

In FIG. 1, the central processing unit 10 controls the overall system. The pattern memory device 20 is configured as a random access memory (RAM) as a device for storing a cursor pattern. The shift register 30 shifts parallel cursor data read out from the pattern storage device 20 in the non-display period of the cursor. The parallel-serial conversion means 40 converts the shifted parallel cursor pattern data into serial cursor pattern data at the timing of the display of the cursor. The converted serial cursor pattern data is returned to the pattern storage device 20 via the shift register 30.

The data returned to the pattern storage device 30 is temporarily stored in the register 80 and output to the register 80 by the cursor display signal output from the display position control circuit 70 and the cursor signal of the output circuit 90. The stored cursor pattern data is displayed on the display device.

By the way, the conventional cursor pattern control device has the advantage that the speed is fast because it controls the cursor display in hardware, but the disadvantage is that the cost is increased because the pattern memory device for storing the cursor pattern must be configured. In addition, there is a problem that the cursor can not be displayed in various ways because the cursor pattern or the cursor size is fixed.

Accordingly, the present invention provides a cursor display control apparatus and method that can control the cursor display in a software manner while using the existing frame buffer to solve the above problems.

In order to achieve the above object, a cursor display control device of a graphic display device includes a display control circuit for generating a video address for cursor display; Comparison means for comparing the video address with the current cursor position and generating an interrupt signal to the central processing unit when the video address and the current cursor position coincide; And a frame buffer which temporarily writes the cursor pattern data according to the interrupt signal and outputs the cursor pattern data according to the display line.

In order to achieve the above object, a cursor display control method of a graphic display device includes a process of checking whether a CPU displays a cursor; Displaying the current cursor pattern data when the display state is displayed by the checking of the display state; And comparing the display line with the position where the current cursor pattern data is displayed and deleting the current cursor pattern data when the display line exceeds the current cursor pattern data position.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the present invention.

2 is an embodiment of a cursor display control apparatus according to the present invention.

In FIG. 2, the central processing unit 10 handles the overall operation of the cursor display. The display control device 140 generates a video address. The frame buffer 150 temporarily stores text, graphics, or cursor pattern data. The decoder 100 decodes the address output from the CPU 10. The latch 110 temporarily stores cursor position data coming from the central processing unit 10. The buffer 120 reads the video address output from the display control device 140. The comparator 160 compares the video address output from the display control circuit 140 with the cursor position data stored in the latch 110.

5 is a cursor display position diagram.

6 is a cursor deletion position diagram.

7A is a video address signal generated in the display control circuit.

7B is a signal representing the latch 110 data.

7c is an interrupt generation signal.

The operation of FIG. 2 will be described with reference to FIGS. 5, 6, and 7A to 7C.

When the user moves the cursor using a keyboard or mouse key, the central processing unit 10 receives the data and has a horizontal and vertical position. Then, the vertical position data is converted to the time point at which the cursor pattern data is written into the frame buffer 150.

The decoder 100 decodes an address for the vertical position data and outputs a write enable (CE) signal to the logical sum element 130. The logic sum element 130 performs an OR on the write enable signal of the decoder 100 and the write signal WR of the CPU 10 to activate the enable (EN) end of the latch 110.

The latch 110 receives cursor position data as input from the central processing unit 10 when the enable signal is activated. The cursor position data is input to the input terminal BI of the comparator 160.

The display control circuit 140 generates a video address and inputs it to the input terminal AI of the buffer 120, the frame buffer 150, and the comparator 160, respectively. The decoder 100 decodes an address of a predetermined region of the CPU 10 to read a video address from the buffer 120, and outputs a read enable signal to the logical element 130. The logical sum element 130 logically sums the enable signal of the decoder 100 and the read signal RD of the CPU 10 to activate the enable EN end of the buffer 120.

When the enable signal is activated, the buffer 120 receives a video address output from the display control circuit 140 as an input and outputs the input to the central processing unit 1 through the data bus.

In the comparator 160, the interrupt enable signal IEN of the central processing unit 10 is connected to the video addresses inputted to both input terminals AI and BI while the enable end EN of the comparator 160 is activated. When the cursor position data is compared and matched, an interrupt signal is generated to the central processing unit 10. 7 shows the waveforms described above.

In FIG. 7, if the video address is the address of the cursor pattern data corresponding to 32 lines, and the current cursor vertical position data is 32, the interrupt signal is generated when the 7a and 7b coincide.

When the interrupt signal is generated, the cursor pattern data is written to the frame buffer 150 to display the cursor pattern on the display device. When the cursor pattern data is written to the frame buffer 150, the cursor pattern data should be written before the display line comes to the place where the cursor is located. After the written cursor pattern data is displayed at the cursor position, the current cursor pattern data of the frame buffer 150 is immediately deleted.

In Figs. 5 and 6, the size of the cursor is 16x16, the line n at the position where the cursor pattern data is output, and the line where the cursor pattern data ends is (n + 15). If the time taken to write the cursor pattern data into the frame buffer 150 takes the time passing by two to three display lines, an interrupt is generated before the (n + 3) lines to write the cursor pattern data. The cursor pattern data stored in the frame buffer 150 is outputted when the cursor position data passes n lines. When the display line (n + 16) is reached, the cursor pattern data temporarily stored in the frame buffer 150 is erased and returned to the original data.

3 is another embodiment of a cursor display control apparatus according to the present invention.

In FIG. 3, the latch is the first latch 170 and the second latch 180, the buffer is the first buffer 190 and the second buffer 200, and the comparator is the first comparator 210 and the first comparator 210. It consists of two comparators 220.

If the video address is output from the display control circuit 140, the lower address is input to the first comparator 210 and the first buffer 190, and the upper address is input to the second comparator 220 and the second buffer 200. Is entered. When the cursor position data corresponding to the upper address and the lower address are output from the second latch 190 and the first latch 170, respectively, the second comparator 220 compares the upper video address with the cursor position data and matches the first. 1 Enable comparator 210. When enabled, the first comparator 210 compares the lower video address with the cursor position data and sends an interrupt signal to the CPU 10 when the first comparator 210 matches.

4 is a flowchart of a cursor display control method according to the present invention.

The operation flow of FIG. 4 will be described in conjunction with the second diagram.

When an interrupt for the cursor display occurs in the central processing unit 10, the central processing unit 10 checks whether the cursor display state (Status). That is, when the Status Flag indicating the cursor display is On, the cursor pattern data corresponding to the current cursor position is written in the frame buffer 150. The cursor pattern data is displayed at the current cursor position (steps 10 and 11).

The cursor pattern data written in the next frame buffer 150 is output to the display device until the display is finished. In the method of checking whether the cursor pattern data is displayed on the display device, the CPU 10 reads the video address through the buffer 120 and compares it with the display line where the cursor pattern data ends.

While the cursor pattern data is displayed on the display device, the central processing unit 10 performs another task (network polling, etc.) (step 12).

The next display line is compared with the position of the currently displayed cursor pattern data, and when the display line exceeds the position of the currently displayed cursor pattern data, the data temporarily stored in the current frame buffer 150 is erased, and the original data is reset. (13th to 15th steps). Next, the pattern data is prepared and the pattern data is prepared, and the process ends (step 16).

As described above, the present invention can simplify the display and movement of the cursor like the hardware processing method, and can arbitrarily adjust the size of the cursor that cannot be taken in the hardware processing method. Access Memory Digital Analog Convertor) can be used to display various colors of the cursor.

Claims (5)

A graphic display device comprising: a display control circuit (140) for generating a video address for cursor display; Comparison means 160 for comparing the video address with the current cursor position and generating an interrupt signal to the CPU 10 when the video address and the current cursor position coincide with each other; And a frame buffer (150) for writing and outputting the cursor pattern data in accordance with the display line. The display apparatus of claim 1, wherein the cursor display control device comprises a latch 110 and a display control device 140 for retrieving current cursor position data input to the comparison means 160 from the CPU 10. And a buffer (120) for outputting an output video address to the central processing unit (10). The apparatus of claim 1, wherein the latch (110) and the buffer (120) are enabled by decoding an address output from the central processing unit (10) at a decoder (100). In the graphic display device, a process of checking whether a cursor is displayed in the CPU 10 when an interrupt for cursor display occurs, and the current cursor pattern when the display state is displayed in the process of checking the display state. Displaying the data; and comparing the display line with the position where the current cursor pattern data is displayed and deleting the current cursor pattern data when the display line exceeds the currently displayed cursor pattern data position. Control method. The method of claim 4, wherein the checking of the cursor display state is after an interrupt signal is generated from the central processing unit (10).