JPS6023888A - Display controller - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

TECHNICAL FIELD The present invention relates to a display control device for controlling the display of a display screen of a data processing device, etc., and in particular, the present invention relates to a display control device for controlling the display of a display screen of a data processing device, etc. 〇Prior art relating to improvements in effectively utilizing free space in a video memory for storing video images Generally, video memories used in display devices include, for example, 1024 bytes), 2048 bytes, or 163 bytes.
84. A general purpose memory with a capacity of 21, such as 32,768 bytes, is used.

On the other hand, the screen size of a display device, for example, in the case of character display, is 40 characters horizontally and 20 lines vertically, for a total of 80 characters.
0 characters, 80 characters wide by 25 lines high, a total of 2,000 characters in size, etc. are commonly used. One character is associated with a character code of 1 byte and 2 bytes in the video memory. Therefore, the used capacity of the video memory of the display control device is not 2 m, and there is an unused empty area in the video memory in addition to the area required for storing character data of video characters.

In case of bitmap mode display, horizontal 640
Dots, 200 dots vertically for a total of 128,000 dots or 640 dots horizontally and 400 dots vertically for a total of 256,000
These display dots are divided into 8 bits and stored in 1 byte of the video memory (3 bytes in the case of color display), so they are stored in the video memory in the same way as the character code described above. The used capacity is not 2" and there is an empty area. That is, the conventional display control device has the disadvantage that there is an unused empty area in the video memory and the video memory is not effectively used.

OBJECTS OF THE INVENTION An object of the present invention is to provide a display control device that solves the above-mentioned conventional drawbacks and enables effective use of the video memory by using empty areas of the video memory for other purposes. There is K.

Components of the Invention In a display control device having a video memory for storing character codes or display dot data of characters to be displayed on a display screen, an alternative to supplying voltage power to the video memory when the display device is powered off. It is equipped with a power source and a means for externally accessing an empty area of the video memory other than the area storing the character code, etc., so that the empty area of the video memory can be used for any purpose. Features.

Embodiments of the Invention Next, the present invention will be described in detail with reference to the drawings.

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

That is, a video memory 2 for storing character codes of characters to be displayed or display data such as dot patterns on a display screen, a display address controller 3, and an address signal connected to the output of the display address controller 3. A multiplexer circuit 4 for connecting the video memory 2 by arbitrarily switching the line 11 and an address signal line 12 for accessing the video memory 2 from the outside, and converting data read from the video memory 2 into a video signal. The conversion circuit 7 that sends out to the display device, the synchronization signal that generates the synchronization signal to the display device, and the synchronization timing signal for the display control within the control device (Q generator 5 and the power supply supplied to the control device) An alternative power supply circuit 6 is provided which supplies power for operation of the video memory 2 in a disconnected state. Reference numeral 14 indicates a synchronization signal line, 15 indicates a data transfer line, and 16 indicates a video signal line. The display control of characters, etc. is the same as the conventional one, so the explanation is omitted, but in this embodiment, the empty area other than the area used for storing display data in the video memory 2 is used for any other purpose. In other words, the address signal line 12 and the multiplexer circuit 4 can be stored in the empty area from the outside.
The video memory 21C is accessed via the data transfer line 1.
Data can be read or written via 5.

In this embodiment, address signal lines 12. Multiplex circuit 4. The data transfer line 15 and the like constitute means for accessing the empty area of the video memory from the outside. Since the video memo 92 is supplied with operating power from the alternative power supply circuit 6 when the normal power of this device is turned off, the data stored in the empty area will not evaporate and disappear during a power outage or the like. There isn't. Therefore, this empty area can be used as an area for storing system configuration information of the entire data processing device including this control device.

In Figure 2, video memory 2 has a capacity of 2048 bytes, and 2000 bytes are 80 characters and 25 lines, totaling 2000.
FIG. 3 is a conceptual diagram showing a state in which the remaining 48 bytes of empty area, indicated by diagonal lines in the figure, which is used for storing character codes of characters, is used as a system configuration information storage area. Even in the case of a bitmap mode display control device, a similar configuration allows the empty area of the video memory to be used for other purposes. That is, there is an effect that 100 pieces of video memory can be used effectively.

Effects of the Invention As described above, in the present invention, when the power is cut off,
The contents of the video memory are held by power supply from the alternative power supply circuit, and the empty area in the video memory where display data is not stored can be accessed from the outside to write and read other arbitrary data. Therefore, there is an effect that 100 chips of video memory can be used effectively.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is a conceptual diagram showing a state in which the empty area of the video memory in the above embodiment is used as a system configuration information storage area. In the figure, 2...Video memory, 3...Display address controller, 4...Multiplex length circuit, 5...Synchronization signal generator, 6...Alternative power supply circuit, 7... ... Conversion circuit, 11.12... Address signal line, 15... Data transfer line. Agent Patent Attorney Toshimune Sumita Figure 1

Claims (1)

[Claims] In a display control device having a video memory for storing character codes or display dot data of characters to be displayed on a display screen, an alternative power source for supplying power to the video memory when the display device is powered off; A display control device comprising means for externally accessing an empty area of the video memory other than the area storing the character code, etc., so that the empty area of the video memory can be used for any purpose. .