JPH06186939A - Display controller - Google Patents

Abstract

PURPOSE:To update the storage contents of a video memory without disturbance of screen and without increasing the load of a central processing unit in a display controller displaying an image on a display device according to the contents while updating the storage contents of a video memory under the control of the central processing unit. CONSTITUTION:This controller is constituted so that pattern data and display attribute data are stored in a ROM 63, a display command outputted from the central processing unit 1 is held temporarily, the display attribute data stored in the ROM 63 are written in the video memory 3 based on the display command in the vertical fly-back interval of a display device 5, and the image is displayed on the display device 5 based on the data stored in the video memory 3 and the pattern data stored in the ROM 63 synchronizing with the horizontal scanning of the display device 5.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, this type of device is used in a system including a display device such as a personal computer and a game machine. FIG. 2 is a block diagram showing the configuration of a system using this type of display control device. In this figure, 1 is a CPU that controls the entire system, and 2
Is a memory in which software used in the CPU 1 is stored, and 3 is V in which information to be displayed on the display device is stored.
RAM 4 is a display control device for performing display control of the display device based on the stored information in the VRAM 3 under the control of the CPU,
Reference numeral 5 is a display device. In this case, the VRAM 3 stores pattern names that specify each display target, display attribute data that specifies the display mode of each display target (for example, color, display start position, presence / absence of clipping, etc.). If it is necessary to change the contents of each data, the CPU
This is performed by sending data from 1 to rewrite the stored contents of the VRAM 3 to the display control device 4. For example, in the game machine, when the operation of moving the currently displayed character is performed or the operation of causing a new character to appear, data for rewriting the VRAM 3 is sent from the CPU 1 to the display control device 4. This data includes a pattern name that specifies a display target to be moved or newly displayed, and display attribute data. Further, the display control device 4 controls horizontal scanning and vertical scanning in the display device 5. Before scanning each horizontal scanning line, the stored information in the VRAM 3 is referred to determine the display target to be displayed on the horizontal scanning line, and
The pixels lined up on the horizontal scanning line that constitute the display target are obtained. Then, a color signal corresponding to each pixel is generated, and the color signal corresponding to each pixel is given to the display device 5 at a timing corresponding to each pixel in the horizontal scanning period.

[0003]

By the way, in the above-mentioned conventional display control device, since the data change of the VRAM 3 is carried out at a timing which is completely unrelated to the horizontal scanning and the vertical scanning, the display (horizontal scanning) is being performed. There is a problem that the contents of the data used for display control are rewritten, and the screen may be temporarily disturbed. Also,
Although it is possible to send data during the vertical blanking period when the CPU does not display, doing so causes a problem that the control load of the CPU becomes heavy. Furthermore, CP
Since the U directly generates information such as the pattern name and the display attribute data, there is a problem that the load on the CPU increases when the display screen is initially set or when the display screen is largely changed.

The present invention has been made under such a background, and a display capable of rewriting the contents of data in the video memory without disturbing the screen and increasing the load on the CPU. An object is to provide a control device.

[0005]

SUMMARY OF THE INVENTION A display control device according to the present invention is a display control device for updating storage contents of a video memory under the control of a central processing unit and displaying an image on the display device in accordance with the storage contents of the video memory. In the device,
A ROM that stores pattern data that specifies a display shape when a display target is displayed on the display device and display attribute data that specifies a display mode, and a transfer command that is output from the central processing unit are held. During the vertical blanking period, the display attribute data designated by the transfer command is read from the ROM and written in the video memory, and the horizontal scanning of the display device is performed in synchronization with the horizontal scanning of the display device. The R of the display target to be displayed
A control means for generating a color signal based on the pattern data stored in the OM and the display attribute data stored in the video memory and outputting the color signal to the display device.

[0006]

According to the above structure, when the transfer command is output from the central processing unit, the control means temporarily holds it and displays the display attribute data from the ROM based on the transfer command during the vertical blanking period of the display device. Read and write to video memory.
Further, in synchronization with the horizontal scanning of the display device, a color signal is generated based on the display attribute data stored in the video memory of the display target to be displayed in the horizontal scanning and the pattern data stored in the ROM. And output to the display device.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a personal computer using a display control device 6 according to an embodiment of the present invention. In this figure, the CPU 1
The pattern name, the display attribute data and the like can be directly transferred to the VRAM 3, but when it is necessary to greatly change the display state of the display device 5, a data transfer command for that is output. The data transfer instruction is output at a timing that is completely asynchronous with the synchronization signals VSYNC and HSYNC output from the CRT timing generation circuit 61 described later. This data transfer command is stored in the ROM 63
The pattern name for the display screen and the address information for selectively designating the display attribute data are included. The CRT timing generation circuit 61 outputs the vertical synchronization signal VSYNC at regular intervals. In addition, the CRT timing generation circuit 61
The horizontal sync signal HSYNC is generated within one cycle from the output of the vertical sync signal VSYNC to the generation of the next vertical sync signal.
Is output a predetermined number of times. The display device 5 uses the vertical synchronization signal VS.
When YNC is given, vertical scanning corresponding to a new screen is started, and when horizontal synchronizing signal HSYNC is given, horizontal scanning corresponding to a new horizontal scanning line is started. 62 is a transfer timing adjusting circuit, which is a CRT
Vertical sync signal VSYNC from timing generation circuit 61
Based on the above, the address signal AD for selecting the pattern name and the display attribute data from the ROM 63 is adjusted in timing and output. This address signal AD is displayed on the display device 5.
Is output when enters the vertical blanking period. ROM 63
Stores pattern data, pattern names, and display attribute data. The pattern name and display attribute data read from the ROM 63 are written in the VRAM 3.
Reference numeral 64 denotes a display data generating circuit, which is a horizontal synchronizing signal HSY.
Each time NC is generated, the pattern name of each display target to be displayed is read from the VRAM 3 by the horizontal scanning immediately thereafter, and is output to the control unit 65.

The control unit 65 performs the following operations during the vertical blanking period and the horizontal scanning period, respectively. <During the vertical blanking period> When the data transfer command is output from the CPU 1, the data transfer command is temporarily held during the horizontal scanning period (during the display period). Then, in the vertical blanking period, the pattern name and display attribute data designated by the held data transfer command are read from the ROM 63 and written in the VRAM 3. <During horizontal scanning> Based on the pattern name sent from the display data generation circuit 64, the pattern data of each display target to be displayed in the horizontal scanning is read from the ROM 63, the display attribute data is read from the VRAM 3, and these data are stored in these data. Based on this, color codes of pixels to be displayed on the horizontal scanning line are sequentially created and output to the color palette 66.

The color palette 66 converts the color code output from the ROM address control unit 65 into color data. 67 is a digital / analog converter,
The color data output from the color palette 66 is converted into a color signal which is an analog signal and supplied to the display device 5.

The VRAM 3 also stores a pattern name and display attribute data for specifying each display object to be displayed on the display device 5. Of these data, the pattern name and the display position data are collectively updated by a data transfer command from the CPU 1, and the data read from the ROM 63 is stored. Here, for a small change of the display screen, even if the CPU 1 transfers the pattern name and the display attribute data to the VRAM 3, the load on the CPU 1 does not increase so much, but in the case of a large change of the display screen, it is stored in the ROM 63. Since the address information for selecting the pattern name and the display attribute data for one display screen is generated, the load on the CPU 1 does not increase so much.

Next, the operation of the personal computer having the above configuration will be described. First, when the display device 5 is in the display period, the display control device 6 performs horizontal scanning based on the horizontal synchronization signal HSYNC output from the CRT timing generation circuit 61. During this horizontal scanning period, the display data generation circuit 64 reads out the pattern name in the VRAM 3 and outputs it to the control unit 65. Then, the control unit 65 reads the pattern data from the ROM 63 based on this pattern name, and also reads the display attribute data of each display target from the VRAM 3. Then, based on these data, the control unit 65 sets the color code of the pixel to be displayed in accordance with the scanning timing of the display device 5 in the color palette 66.
Output to. The color palette 66 converts the color code output from the control unit 65 into color data and outputs the color data to the digital / analog converter 67. The color data is converted into a color signal which is an analog signal in the digital / analog converter 67 and is supplied to the display device 5. Then, the above operation is repeated until the display device 5 finishes displaying all the horizontal scanning lines of one frame and enters the vertical blanking period.

On the other hand, when it is necessary to change the display state of the display device 5, the CPU 1 outputs a data transfer command. For example, this may be the case when an operation of moving the character being displayed on the game machine is performed, or when an operation of causing a new character to appear on the display screen is performed. When the data transfer instruction is output during the display period of the display device 5, the data transfer instruction is held by the transfer timing adjusting circuit 62.

When it is detected by the vertical synchronizing signal VSYNC from the CRT timing generating circuit 61 that the display device 5 has finished scanning the last horizontal scanning line and has entered the vertical blanking period, the transfer timing adjusting circuit 62 The address signal AD of the ROM 63 is output to the control unit 65. As a result, the control unit 65 outputs the pattern name and the address for reading the display attribute data to the ROM 63. Then, the pattern name and the display attribute data read from the ROM 63 in this way are written in the VRAM 3.

After that, when the display period starts again, the VRAM
The same operation as described above is repeated based on each data newly written in 3.

[0015]

As described above, according to the present invention, even if the CPU outputs a display command at an arbitrary timing, the display attribute data and the like in the video memory are updated during the vertical blanking period. . Therefore, there is an effect that the display screen is not disturbed. Further, since the display attribute data and the like in the video memory are updated by reading from the ROM instead of transferring from the CPU, the update is completed in a short time. Therefore, there is an effect that the display can be switched at high speed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a personal computer to which a display control device according to an embodiment of the present invention is applied.

FIG. 2 is a block diagram showing a configuration of a personal computer to which a conventional display control device is applied.

[Explanation of symbols]

1 ... CPU, 3 ... VRAM, 5 ... display device, 6 ...
... Display control device, 63 ... ROM, 64 ... Display data generation circuit, 65 ... Control unit

Claims (1)

[Claims] 1. A display control device for updating storage contents of a video memory under the control of a central processing unit and displaying an image on a display device according to the storage contents of the video memory, wherein a display target is displayed on the display device. A ROM storing pattern data for designating a display shape and display attribute data for designating a display mode, a transfer command output from the central processing unit, and a vertical retrace period of the display unit, The display attribute data designated by the transfer command is read from the ROM and written in the video memory, and in synchronization with the horizontal scanning of the display device, in the ROM to be displayed in the horizontal scanning. The display is performed by generating a color signal based on the stored pattern data and the display attribute data stored in the video memory. Display control apparatus characterized by comprising a control means for outputting to the location.