JPH0320783A - Display controller - Google Patents

Abstract

PURPOSE:To realize a sleeve function without changing the program of a CPU nor system hardware by adding a change in display contents detecting part, a counting part, a display data mask part and a counting control part to a display controller. CONSTITUTION:When the change in the display contents detecting part 11 detects that a signal showing that a picture memory is written into a display controller by the CPU or a signal showing that a cursor is moved is not active for a fixed period, and when the counting part 12 conunts that this period is continued more than the fixed time, a display data B 301 is fixed at a low level by the display data mask part 13 and a display screen is erased. Therefore, by adding this system to the display controller, a system prossesing the sleeve function can be constituted without changing the program of the CPU nor the system hardware, and thus, power consumption can be reduced and visual effect can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a display control device having a function of erasing a display screen.

Conventional technology A conventional display control device will be explained below.

FIG. 2 shows the system configuration of a conventional display control device. In Figure 2, 1 is the display control device, 2 is the C
PU (central processing unit), 3 is an image memory, and 4 is a display device.

The operation of the display control device system configured as described above will be described below.

First, in order to display on the display device 4, the display control device 1 sequentially reads out the contents of the image memory and outputs them to the display device 4. On the other hand, in order to rewrite the contents of the image memory, (5PU2 sends the address corresponding to the desired display position to the address bus and the write signal to the control bus,
Output data to the datapath. At this time, the display control device receives these signals and writes them into the image memory. 1. In order to move the cursor position without closing the input position from an input device such as a keyboard or mouse, the CPU 2 transmits the address to the address bus, the write signal to the control bus, and the data in the same manner as described above. output to the bus,
Writes the cursor position inside the display control device to a register that stores it.

This moves the cursor position on the screen of the display device 4.

Problems to be Solved by the Invention However, in order to reduce the power consumption of the system or to improve the visual effect, when there is no input from an input device such as a keyboard or mouse for a certain period of time, the above-mentioned conventional configuration can be used. When trying to realize a function to erase the display screen (hereinafter referred to as sleeve function), the conventional C
This method has the drawback of requiring changes to the PH program and system hardware.

The present invention solves the above-mentioned conventional problems, and by simply replacing the conventional display control device with the display control device of the present invention,
The object of the present invention is to construct a system having the sleeve function without changing the conventional CPH program and system hardware.

Means for Solving the Problems To achieve this object, the display control device of the present invention includes a display content change detection unit that detects a signal indicating a change in display content, and a counter that counts a period in which there is no change in display content. The present invention has a configuration in which a conventional display control device is provided with a display data mask section, a display data mask section for fixing display data, and a counting control section for stopping the counting section.

Depending on the configuration, when there is an input from an input device such as a keyboard or mouse, the CPU either writes the image memory or moves the cursor, and the CPU controls the display. It detects that the signal indicating that the image memory is to be written to the device or the signal indicating that the cursor has moved is not active for a certain period of time, and the output data to the display is fixed based on the detection signal, realizing the sleeve function. can do.

EXAMPLE An example of the present invention will be described below with reference to the drawings.

FIG. 1 shows a circuit that realizes the sleeve function of a display control device in an embodiment of the present invention. In FIG. 1, 11 is a display content change detection unit that detects a signal indicating a change in display content, 12 is a counting unit consisting of several stages of flip-flops for counting the period in which there is no change in display content, and 13 is a display. 14 is a display data mask unit that fixes display data in response to a signal indicating that there is no change in display content for a certain period of time; and 14 is a counting control unit that stops counting by the counter unit in response to a signal that indicates that there is no change in display content for a certain period of time. be.

1, 100 is a write signal (hereinafter referred to as *WR) indicating that the CPU writes data, and 101 is a memory select signal (hereinafter referred to as MES) decoded from the GPU address indicating that the OPU has selected the image memory. ), 1
02 is a cursor select signal (hereinafter OUR) that becomes active when the CPU changes the cursor display position.
200 is an output from the counting section 12, which becomes a low level when there is no change in the display content for a certain period of time (hereinafter referred to as INHB); 201 is a signal for resetting the counting section 12 (hereinafter referred to as INHB); RIS), 202 is a clock for the counting section 12, and is a periodic signal (hereinafter referred to as VSYNCt) indicating the end of one screen display, etc. 300
301 is the data displayed during normal use and other than when 1b is sleeved (hereinafter referred to as display data ▲), and 301 is the display data sent to the display 4 (hereinafter referred to as display data B).
The operation of the display control device configured as above will be described below.

The system operation of the display control device is similar to the conventional example except for the part that implements the sleeve function. Here, the operation for realizing the sleeve function will be explained separately into a general operation and a detailed operation.

First, the general operation will be explained. The system operates to change the content displayed on the display device used. 1. When the 0PU etc. rewrites the content of the image memory. 2. To change the display position of the cursor, etc., the cursor in the display control device This is classified when rewriting the contents of registers, etc. Accordingly, when the display content change detection unit detects that the operations 1 and 2 above do not occur, and the counting unit counts that the period has continued for a certain period of time or more, the display data mask unit detects the display data Bt- The three-one function is realized by fixing it to the low V bell and erasing the display screen. In order to return to the normal display from the sleeve state, one of the operations 1.2 above occurs.

Next, detailed operation will be explained. The display content change detection unit detects that CPυ has rewritten the content of the image memory when both the *WR signal and the MIC3 signal become active.
Furthermore, by activating the CUR 102, it is possible to detect a change in the cursor display position. Ct with
In UR102, the cursor register in the display control device is CP.
This is a signal indicating that it has been accessed by H.

In this way, if either of the above two conditions 1.2 occurs, the counter of the counting section is reset, and if not, the counting section continues counting by VSYNC 202. After this, if the counted value exceeds a certain value. When INHB200 is active, the display data mask section masks display data A regardless of its contents and fixes all display data B to low level.
At the same time, the Y3YNC 202 is masked by the counting control section 14, the counting of the counting section 12 is stopped, and the state of INHB 200 is maintained. As a result, the display screen on the display 3 is erased. Also, when in the sleeve state, the above 1.
When either of 2 occurs, the counter 2 is reset and pINHB200 becomes inactive, and the display data ▲ is output as is to the display data B because no mask processing is performed in the display data mask section, and the display returns to the normal display state. return.

As described above, there is a display content change detection unit that detects a signal indicating a change in display content, a counting unit that counts a period in which there is no change in display content, a display data masking unit that fixes display data, and a counting unit that detects a signal indicating a change in display content. A system that replaces a conventional display control device with the display control device of the present invention by providing a counting control section that stops counting, and has a sleeve function without changing the conventional CPU program and system hardware. can be constructed.

Effects of the Invention As described above, the present invention includes a display content change detection unit that detects a signal indicating a change in display content, a counting unit that counts a period in which there is no change in display content, and display data that fixes display data. By providing a mask section and a counting control section that stops the counting section, the conventional CPH program and system hardware can be changed simply by replacing the conventional display control device with the display control device of the present invention. It is possible to construct a system having a sleeve function without having to do so, and the power consumption of the system can be reduced and the visual effect can be improved.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram for realizing the sleeve function of a display control device in an embodiment of the present invention, and FIG. 2 is a system configuration diagram of a conventional display control device.

Claims (1)

[Claims] a display content change detection unit that detects a signal indicating a change in display content; a counting unit that counts a period in which there is no change in display content;
a display data mask unit that fixes display data in response to a signal indicating that there is no change in display content for a certain period of time; and a counting control unit that stops counting in the counter unit in response to a signal that indicates that there is no change in display content for a certain period of time; A display control device comprising: