JPH0274991A - Liquid crystal display density control circuit - Google Patents

Abstract

PURPOSE:To easily execute the conversion of screen display density to a subordinate kind of machine by monitoring a change instruction of screen display density of a host controller by an instruction decoder, changing the screen display density to a set value of low density of the subordinate kind of machine by a set value changing circuit, and writing this set value in a liquid crystal display control circuit. CONSTITUTION:An instruction decoder 4 works so as to monitor an instruction by a host controller 1 for changing a screen of high display density by a host kind of machine to a screen of low display density by a subordinate kind of machine. A set value changing circuit 5 works so as to change the screen display density to a set value of low density of the subordinate kind of machine by a notice of a change instruction by the instruction decoder 4. A mode setting circuit 6 works so as to connect the set value changing circuit 5 and a liquid crystal display control circuit 3 in order to write the set value in the liquid crystal display control circuit 3. In such a way, the conversion of the screen display density to the subordinate kind of machine can be executed easily.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a liquid crystal display density control circuit. The display density is changed by changing the display format.

(Prior Art) FIG. 2 is a diagram illustrating a screen display of a program for a lower-level machine on a higher-level machine. When a high-end model with a high screen display density attempts to convert to a low-end model with a low display density, in other words, in Figure 2, when a program developed for a low-end model is considered to run on a high-end model, the screen Conventionally, there have been three methods for converting the display:

The first method is to display it on a part of the screen of a higher-end model. The entire screen of the lower model is displayed in part of the displayable area of the higher model, and nothing is displayed in the other parts.

The second method is to change the setting of the liquid crystal display density control circuit of the higher-end model to lower the display density and display. If it is desired to lower the display density, the settings of the liquid crystal display density control circuit are changed using a display density changing program.

The third method is to enlarge the characters and figures on the screen of a lower model to be displayed on a higher model using an image enlargement program. Characters, figures, etc. are enlarged by the program before being written into the image memory, and then stored in the image memory and displayed.

(Problem to be solved by the invention) However, in response to each of the above three methods,
The following problems arise when converting the screen display to run a conventional program for lower-level models on higher-level models.

The first conventional method has the problem that only a portion of the entire display area is used, and the actual displayed area is small, making it difficult to see.

The second conventional method has the problem that the settings of the liquid crystal display density control circuit must be rewritten in the program before loading the program for the lower model, making it complicated to use.

In the conventional third method, an enlargement process is required as a new program, and the display speed decreases because the enlargement process is required every time writing is performed on the screen. Also, in programs that directly write data to the screen, the data is displayed without being enlarged.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a liquid crystal display density control circuit which can solve the problems of the prior art and which can easily convert the screen display density between lower models.

(Means for Solving the Problems) The present invention provides a liquid crystal display control circuit that receives commands from a higher-level control device to control image display, from a screen with a high display density by a higher-level model to a screen with a lower display density by a lower-level model. a command decoder that monitors commands from a higher-level control device to be changed; a set value change circuit that changes the screen display density to a lower density set value of a lower-level model upon notification of a change command from the command decoder; It is characterized by comprising a mode setting circuit that connects the set value changing circuit and the liquid crystal display control circuit in order to write data into the control circuit.

(Function) According to the present invention, since the liquid crystal display density control circuit is configured as described below, each technical means functions as follows.

The command decoder monitors commands from the host controller to change from a screen with a high display density in a host model to a screen in a lower display density in a lower model.

The setting value changing circuit operates to change the screen display density to a lower density setting value of a lower-level model in response to a notification of a change command from the command decoder.

The mode setting circuit serves to connect the set value changing circuit and the liquid crystal display control circuit in order to write the set value into the liquid crystal display control circuit.

The liquid crystal display control circuit changes the display format so that the display data read out from the image memory is the same data for two lines, and displays a screen density of 200 lines on a 400 line liquid crystal display unit.

Therefore, the present invention can provide a liquid crystal display density control circuit which can eliminate the above-mentioned problems and can easily convert the screen display density between lower models.

(Example) An example of the present invention will be described below with reference to the drawings.

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

1 is the upper control unit (CPU), 4 is the instruction decoder, 5
6 is a setting value changing circuit, 6 is a mode setting circuit, 2 is a command changing circuit, and is composed of 4, 5, 6, 3 is a liquid crystal display control circuit, 7 is an image memory, and 8 is a liquid crystal display unit. The instruction decoder 4 and the liquid crystal display control circuit 3 each include a mode control register and a character pitch register (not shown).

Next, the operation will be explained. The upper control device 1 generates a screen setting command. There are two types of screen setting commands; one is a command for the higher model exclusive mode, and the other is a command for the lower model conversion mode. If the screen setting command is a command for the higher model exclusive mode, the mode setting circuit 6 in the command change circuit 2
becomes the host model exclusive mode, and the contents of the commands in the host model exclusive mode of the host controller 1 are directly transmitted to the liquid crystal display control circuit 3.
will be written to. On the other hand, if the screen setting command is a lower model conversion mode command, the mode setting circuit 6 in the instruction change circuit 2 becomes the lower model conversion mode, and the instruction decoder 4
The contents of the lower model conversion mode command of the host controller 1 are written into the liquid crystal display control circuit 3 via the setting value changing circuit 5.

The command decoder 4 in the command change circuit 2 monitors the screen setting command of the host control device 1. That is, the mode control register of the instruction decoder 4 stores a graphic mode command or a character display mode command, and the character pitch register stores a vertical character and a pitch of "1" or "2".

"2" is a mode in which vertical (line) 2 in "1" is changed to vertical (line) 1. When changing from higher model exclusive mode to lower model conversion mode, the graphic mode command in the mode control register is changed to a character display mode command, and the vertical character pitch "1" is changed in the character pitch register.
" is changed to "2". When the setting value changing circuit 5 is informed of the instruction written in the instruction decoder 4 in this way, the setting value changing circuit 5 changes the necessary bits of the instruction.

The result of this change is stored in the mode control register and character pitch register of the liquid crystal display control circuit 3.

Specifically, a case will be described in which the screen display density of the lower model is 640 horizontally and 200 vertically (lines), and the screen display density of the higher model is 640 horizontally and 400 vertically (lines). When the command enters the lower model conversion mode, the image memory 7 stores 200 lines of data for the lower model as shown in FIG. 3, which shows data for the lower model stored in the image memory. As shown in FIG. 4, which shows the data displayed on the liquid crystal display unit, the liquid crystal display control circuit 3 receives the data of the lower model from the image memory 7 (
■,■,----9■) so that two lines have the same data (
■', ■I---"-"'-I■'). In the character pitch register, the vertical character pitch is “2”.
”, so when the liquid crystal display control circuit 3 displays the data on the liquid crystal display unit 8, it is displayed so that two lines constitute one line.As shown in FIG. Compared to Figure 3, 1 dot consists of 1 horizontal dot and 2 vertical dots.In this way, in a display format with lower display density on higher-end models, it is possible to display data on lower-end models without shrinking the screen. It became.

Conversely, when the host controller 1 reads the contents of the mode control register and character pitch register of the liquid crystal display control circuit 3, when the instruction decoder 4 detects that these registers are to be read, the liquid crystal display Necessary bits of the data read from the control circuit 3 are changed by the setting value conversion circuit 5 and sent back to the host control device 1.

(Effects of the Invention) As described above in detail, according to the present invention, the command decoder monitors the command to change the screen display density of the host controller, and the set value changing circuit changes the screen display density to the low density of the lower model. By changing the setting value and writing this setting value into the liquid crystal display control circuit, it is now possible to easily display a lower-level model program on a higher-level model. Unlike in the past, there is no need to change the program for lower-level models at all, and the screen to be displayed is projected onto the entire display area, so the screen can be easily obtained.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a diagram illustrating the screen display of a program for a lower model on a higher model, and Fig. 3 shows the data of a lower model stored in the image memory. The figure shown in FIG. 4 is a diagram showing data displayed on the liquid crystal display unit. Upper control device 2: Command change circuit 3: Liquid crystal display ftdJ control circuit 4: Command decoder 5: Setting value change circuit 6: Mode setting circuit 7 Two-image memory 8: Liquid crystal display unit

Claims (1)

[Scope of Claims] In a liquid crystal display control circuit that controls image display in response to commands from a higher-level control device, the higher-level control device changes from a screen with a high display density in a higher-level model to a screen with a lower display density in a lower-level model. an instruction decoder that monitors instructions in the instruction decoder, a setting value change circuit that changes the screen display density to a lower density setting value of a lower model based on a notification of a change instruction in the instruction decoder, and writes the setting value to the liquid crystal display control circuit. A liquid crystal display density control circuit comprising a mode setting circuit connecting the set value changing circuit and the liquid crystal display control circuit.