JPS63163392A - Display controller - 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 The present invention relates to a display control device, and particularly to a CRT (catho
(delay tube) relates to a display control device that controls the display of character data on a monitor.

Conventionally, the display control device (hereinafter referred to as CRT controller) of this scale has a video RAM (random access memory), a control section, a CPU interface, a character generator using a ROM (read only memory),
It consisted of a CRT monitor interface.

The control section of the CRT controller decodes display data and commands received from the CPU (Central Processing Unit) via the CPU interface, writes them to the video RAM, reads them from the video RAM at regular intervals, and outputs them to the character generator. is converted into a display signal by This display signal was supplied to the CR and T monitors via the CRT monitor interface, and characters were displayed at arbitrary positions within the range of the pattern possessed by the character generator.

In such conventional CRT controllers, the content of the character generator is fixed, so only fixed characters can be displayed, and in order to display special figures as characters, it is necessary to reconfigure the character generator. However, there was a drawback that it was not possible to share hardware.

In addition, in the case of a CRT controller that has a graphic function, it is possible to freely display special figures using a program, but since processing by CPLJ is required in extreme heat, the screen display on the CRT monitor will be delayed. ,
There is a drawback that when a fixed pattern is displayed many times, the processing time of the CPU is wasted compared to when displaying characters.

The present invention was made in order to eliminate the above-mentioned drawbacks of the conventional ones.Special characters can be displayed by sharing hardware, saving CPU processing time and improving system efficiency. An object of the present invention is to provide a display control device that can improve processing performance.

Structure of the Invention A display control device according to the present invention is a display control device that controls character data to be read from a read-only memory and displayed on a display device, and includes a read/write memory in which the character data can be freely written and read; The present invention is characterized in that the read-only memory and the write/read memory can be freely switched.

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. In the figure, one embodiment of the present invention is comprised of a CPU interface 1, a control section 2, a video RAM 3, a character generator 4, and a CRT monitor interface 5.

The character generator 4 includes a write/read circuit 41,
It is composed of an address generation circuit 42, a RAM 43, and a ROM 44.

When displaying on the CRT monitor 20, display data and commands from the CPU 10 are supplied to the control section 2 via the CPU interface 1, and the display data is written into the video RAM 3 in accordance with the commands.

The control section 2 periodically reads out the video RAM 3 independently of the above operation. The read display data is supplied to the address generation circuit 42 together with a timing signal outputted from the control section 2, and is converted into an address signal by the address generation circuit 42 and supplied to the RAM 43 or ROM 44. R.A.
M43 or ROM44 outputs a display signal corresponding to the address signal to CRT monitor interface 5. CR
The T monitor interface 5 controls the RAM 43 or R according to the periodic signal and timing signal output from the control section 2.
The display signal supplied from the OM 44 is converted and output to the CRT monitor 20.

In the initial state, the address generation circuit 42 is in the ROM 44.
A character corresponding to a fixed standard character pattern written in the ROM 44 is displayed on the CRT monitor 20.

If you want to display a character that the ROM 44 does not have in a CPLI 10 program, you can display the character pattern that the program has in the RAM 43 via the CPU interface 1 and the read/write circuit 41.
write to. When all the character patterns of the program are written into the RAM 43, control is performed from the CPUIO via the CPU interface 1 and the write/read circuit 41 to cause the address generation circuit 42 to select the RAM 43.

Thereafter, when the RAM 43 is selected, a character corresponding to the character pattern written in the RAM 43 is displayed on the CRT monitor 20, and when the ROM 44 is selected, a character corresponding to the standard character pattern is displayed on the CRT monitor 2.
It will be displayed as 0.

In this way, in addition to the ROM 44 provided in the character generator 4 and having standard character patterns, a RAM 43 is provided in which character patterns can be written and read freely by the CPU 10, and the CPU 10 can freely select between the RAM 43 and the ROM 44. By making this possible, special characters that ROM and /14 do not have can be displayed using the same hardware.

In addition, since the character display makes the processing of the CPU 10 simpler than that of the graphic display, the display speed becomes faster, the processing time of the CPU 10 can be saved, and the processing capacity of the system can be improved.

As explained above, according to the present invention, by providing a RAM from which character data can be freely read and by making it possible to freely switch between the ROM possessed by the character generator and this RAM, Special characters can be displayed by sharing hardware, and CPL
Save J's processing time and improve your system! ! ! It has the effect of improving abilities.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention. Explanation of symbols of main parts

Claims (1)

[Claims] A display control device that controls reading character data from a read-only memory and displaying it on a display device, the display control device comprising a read-write memory in which the character data can be freely written and read; A display control device characterized in that switching can be made freely.