JPH1131065A - Image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the processing speed nearly without an increase in cost when image data of a frame memory are displayed on the display screen of the display device and a cursor consisting of a combination of straight lines is displayed at an arbitrary specific position on the display screen. SOLUTION: When respective set values by a CPU 1 are sent from a display control circuit 4, a timing generator 3 generates various synchronizing signals according to them. At this time, when the position of a cross hair-line cursor to be displayed on the display screen of the display device 9 is specified in dot units, a cursor signal is also generated in timing corresponding to the specified position. The display control circuit 4 reads image data as parallel data out of a frame memory 7 according to the frame synchronizing signal from the timing generator 3. A shift circuit 20 ORs the parallel data and the said cursor signal and the composite image data are displayed on the display screen of the display device 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a raster scan type image display device.

[0002]

2. Description of the Related Art As such an image display device, image data (image information such as characters and patterns) of a frame memory of a parallel data input / output system is read as parallel data.
There is a graphic display device that sequentially transfers the data to a display device using a CRT (cathode ray tube), LCD (liquid crystal device), or the like, and displays it on the display screen.

As shown in FIG. 4, for example, such an image display device includes a CPU 1, a ROM 2, a timing generator 3, a display control circuit 4, a bus driver 5, a multiplexer 6, a frame memory 7, a latch 8, a display device 9, and the like. It is constituted by. The CPU 1 is a central processing unit that controls the entire image display device, and executes a program stored in a ROM (read only memory) 2. The ROM 2 stores graphic data (image data) for graphic display in addition to programs.
Is stored.

The display control circuit 4 mainly includes an address generator, and has a function of repeating a cyclic (regular) display operation asynchronously with the CPU 1 in accordance with a synchronization signal generated from the timing generator 3. Therefore, the display control circuit 4 has a priority in accessing the frame memory 7, and the CPU 1
Is controlled by the timing generator 3 so that the display control circuit 4 can rewrite or read the graphic data at the timing of the non-access state.

First, the CPU 1 stores, in each register in the display control circuit 4, a display start address (start address) on the frame memory 7, the number of characters to be displayed on the display screen in the horizontal direction (horizontal display screen width), and The number of characters to be written in the horizontal direction (horizontal virtual screen width) is set. The set values are also sent to the timing generator 3, and the timing generator 3 generates various synchronization signals for display according to the set values.

The CPU 1 draws graphic data at a predetermined address in a frame memory 7 (frame buffer) according to a program in the ROM 2. Display control circuit 4
Is a graphic display address bus 10 according to a frame synchronization signal generated from the timing generator 3.
The graphic display addresses (GA0 to GA14) are output above. Thereby, graphic data according to the address is read from the frame memory 7 and transferred to the display device 9 via the latch 8.

In such an image display device, a so-called cross hairline cursor display for displaying two straight lines orthogonal to each other on a display screen is generally used as a method for specifying a position or a partial area in a display screen. It is used. The following methods (1) and (2) are known as methods conventionally used to display a cursor (hereinafter also simply referred to as a “cursor”) based on such a combination of straight lines.

(1) A cursor is drawn together with image data (for example, graphic data) in a frame memory (VRAM). (2) In addition to a frame memory for drawing image data, a frame memory for displaying a cursor is provided, the cursor is drawn in the frame memory, and a logical sum of the cursor and image data is displayed on the display screen.

[0009]

However, (1)
According to the method, a cursor of an arbitrary shape can be displayed at an arbitrary position on the display screen, and the hardware circuit configuration is simplified. However, when the cursor is gradually moved as a visual effect when the cursor is moved, the Since it is necessary to draw the moved cursor while restoring the background after moving the, there is a problem in the operation speed. That is, high-speed processing is required to perform such display.

In the method (2), a frame memory for at least one screen must be separately provided in addition to the frame memory for drawing the image data. Also, since the image data is not rewritten, there is no need to perform the operation of restoring the background of the cursor.
Although the operation speed is higher than that of the method (1), it takes time to draw the cursor.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and displays image data of a frame memory on a display screen of a display device at an arbitrary designated position on the display screen with little increase in cost. It is an object of the present invention to improve the processing speed when displaying a cursor using a combination of straight lines.

[0012]

In order to achieve the above object, the present invention provides an image data drawing means for drawing image data in a frame memory, and an image data reading means for reading out the image data drawn in the frame memory by the means. In a raster scan type image display device having means and an image display control means for displaying image data read by the means on a display screen of the display device, a cursor position based on a combination of straight lines to be displayed on the display screen A cursor position designating means for designating a dot on a dot basis, a cursor signal generating means for generating a cursor signal at a timing corresponding to the position designated by the means, and Cursor display control means for displaying a cursor.

In the image display device according to the present invention, when the cursor position is specified in units of dots by the cursor position specifying means by the combination of straight lines to be displayed on the display screen of the display device, the cursor is displayed at a timing corresponding to the specified position. The signal generating means generates a cursor signal, and the cursor display control means causes the cursor to be displayed at the specified position on the display screen according to the cursor signal.

Therefore, by constituting the cursor signal generating means by hardware, the load on software is reduced,
The processing speed when displaying the image data of the frame memory on the display screen of the display device and displaying the cursor by combining the straight lines at an arbitrary designated position on the display screen can be improved. Further, since it is not necessary to draw the cursor in a dedicated frame memory, it is possible to suppress an increase in cost.

[0015]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration example of a control system of an image display device according to an embodiment of the present invention, and portions corresponding to FIG. 4 are denoted by the same reference numerals.

The CPU 1 is a central processing unit for controlling the entire image display device, and functions as image data drawing means for drawing image data (graphic data) stored in the ROM 2 in the frame memory 7; It functions as a cursor position specifying means for specifying the position of a cursor (here, a cross hairline cursor) by a combination of straight lines to be displayed on the display screen of the device 9 in dot units.

The display control circuit 4 includes a vertical cursor line address register and a horizontal cursor line address for specifying the position of a cross hairline cursor to be displayed on the display screen of the display device 9 in dot units, in addition to the above-described registers. A register is provided, and functions as image data reading means for reading image data drawn in the frame memory 7 in accordance with a synchronization signal generated from the timing generator 3.

The timing generator 3 generates various synchronization signals for display in accordance with the set values of the registers sent from the display control circuit 4, and generates a cursor signal (vertical cursor) at a timing corresponding to the designated position. Signal, horizontal cursor signal).

The shift circuit 20 combines the image data from the frame memory 7 with the cursor signal and the like from the timing generator 3 to display the result on the display screen of the display device 9. Image display control means for displaying the read image data on the display screen of the display device 9; and cursor display control for displaying a cross hairline cursor at the designated position on the display screen of the display device 9 by a cursor signal from the timing generator 3. Serves as a means.

FIG. 2 is a block diagram showing a configuration example of the shift circuit 20. The shift circuit 20 includes shift registers 21 to 25, multiplexers (MPX) 26 to 29,
Flip-flop circuit (F / F) 30, OR gate group 3
1 and the like. The OR gate group 31 performs a logical sum synthesis of the image data from the multiplexer 29 and the vertical cursor signal from the timing generator 3 and outputs the result.

The flip-flop circuit 30 normally latches data input from the data input terminals D0 to D7 at the rising edge of the signal DDLT input from the clock input terminal and outputs the data from the data output terminals Q0 to Q7. Also,
When the horizontal cursor signal input from the preset terminal PR becomes "0", the outputs of the data output terminals Q0 to Q7 are all set to "1".

Next, the operation of the image display device according to the present invention will be specifically described with reference to FIG. First, the CPU 1 sets various values in each register of the display control circuit 4. At this time, when there is a request to display a cross hairline cursor on the display screen of the display device 9, by setting required address values in the vertical cursor line address register and the horizontal cursor line address register of the display control circuit 4, The position of the cross hairline cursor to be displayed on the display screen of the display device 9 is designated in dot units.

For example, as shown in FIG. 3, a vertical cursor line KL and a horizontal cursor line K are displayed on a display screen 9a of the display device 9.
In order to display the cross hairline cursor composed of H and H, the display address, that is, the vertical cursor line address AD1 which is the display address of the vertical cursor line KL, and the horizontal cursor line address AD2 which is the display address of the horizontal cursor line KH, are respectively set vertically. Set in the cursor line address register and horizontal cursor line address register.

When various values are set in each register, the display control circuit 4 (here, it is assumed that the position of the cross hairline cursor to be displayed on the display screen of the display device 9 is specified in dot units). Are sent to the timing generator 3. Timing generator 3
Generates various synchronization signals for display according to the set values.

Here, since the position of the cross hairline cursor to be displayed on the display screen of the display device 9 is specified in dot units, a vertical cursor signal and a horizontal cursor signal are generated at timings corresponding to the specified positions. The display control circuit 4 reads out image data from the frame memory 7 as parallel data (for example, in units of 1 byte) in accordance with the frame synchronization signal from the timing generator 3,
The signals are sequentially transmitted to the shift circuit 20.

The shift circuit 20 converts the image data sequentially sent from the frame memory 7 into shift registers 21 to 2
5 and the OR gate group 31 through the multiplexers 26 to 29. The OR image is synthesized with the vertical cursor signal from the timing generator 3, and the synthesized image data is input to the flip-flop circuit 30. The combined image data with the horizontal cursor signal from 3 is sequentially transferred to the display device 9 and displayed on the display screen.

Here, the vertical cursor signal generated from the timing generator 3 is an 8-bit signal as shown in FIG. 2, and each time a line is displayed, the vertical cursor signal is required at a timing corresponding to the vertical cursor line address AD1. Since the bit signal becomes "1", a vertical cursor line having an arbitrary thickness can be displayed at the vertical cursor line address AD1 on the display screen 9a.

The horizontal cursor signal is a 1-bit signal, and becomes "0" at a timing corresponding to the horizontal cursor line address AD2 (depending on the thickness of the horizontal cursor line to be displayed, during the display period of a plurality of lines). "0"), a horizontal cursor line having an arbitrary thickness can be displayed at the horizontal cursor line address AD2 on the display screen 9a.

The details of the display control (excluding the display control of the cross hairline cursor) by the shift circuit 20 shown in FIG. 2 are described in detail in Japanese Patent Application No. 9-15 / 1998 filed earlier by the present applicant.
No. 8838, as described in the specification.

As described above, in this embodiment, since the timing generator 3 (hardware) functions as a cursor signal generating means, the load on the CPU 1 (software) is reduced, and the display screen of the display device 9 has a frame memory. 7, the processing speed when displaying the cross hairline cursor at an arbitrary designated position on the display screen is improved. Also, since there is no need to draw the cross hairline cursor in the dedicated frame memory,
The increase in cost can be suppressed.

[0031]

As described above, according to the image display device of the present invention, the image data of the frame memory is displayed on the display screen of the display device with little cost increase, and the display screen can be arbitrarily selected. The processing speed when displaying the cursor by the combination of the straight lines at the designated position can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of a control system of an image display device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration example of a shift circuit 20 of FIG.

FIG. 3 is a diagram showing an example of a cross hairline cursor display on a display screen of the display device 9 of FIG. 1;

FIG. 4 is a block diagram illustrating a configuration example of a control system of a conventional image display device.

[Explanation of symbols]

 1: CPU 2: ROM 3: Timing generator 4: Display control circuit 7: Frame memory 9: Display device 9a: Display screen 20: Shift circuit 21 to 25: Shift register 26 to 29: Multiplexer 30: Flip-flop circuit 31: OR Gate group

Claims (1)

[Claims] 1. An image data drawing means for drawing image data in a frame memory, an image data reading means for reading image data drawn in the frame memory by the means, and displaying the image data read by the means. A raster scan type image display device having an image display control means for displaying on a display screen of the device, a cursor position designation means for designating a cursor position by a combination of straight lines to be displayed on the display screen in dot units; A cursor signal generating means for generating a cursor signal at a timing corresponding to a position designated by the means; and a cursor display control means for displaying the cursor at the designated position on the display screen by the cursor signal generated by the means. An image display device characterized by the above-mentioned.