JPH0246956B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Technical Field of the Invention The present invention relates to a display device that changes the number of raster scanning lines to change the scanning density, and switches and displays a plurality of maximum numbers of characters that can be displayed on the same screen. In particular, the buffer memory that stores the displayed character information and the display contents of the status information display line (indicator line) normally displayed at the bottom of the screen is shared, and the display character capacity (the number of characters that can be displayed on the screen) can be switched. The display of the indicator row relates to a screen control method of a display device that can continue to display the display.

(b) Technical background The maximum number of characters that can be displayed on the same screen of a display device such as a CRT display device is limited to one type of capacity, such as 1920 characters or 3440 characters, and the maximum display capacity is limited to 1920 characters. It is not possible to switch the display between 3440 characters and 3440 characters. However, while it would be convenient to display by switching between multiple maximum display capacities, display devices using the raster scanning method
There is a one-to-one correspondence between the CRT screen and the screen buffer memory, and it is necessary to prepare the CRT screen and the screen buffer memory on a one-to-one basis. In addition, the contents of the indicator line that indicates the status of the control device and display device, which are displayed outside the display character area, are unrelated to changes in display capacity, so even if the display capacity is changed, the display contents of the indicator line will not be retransmitted. Not done. Therefore, when the screen buffer memory is cleared by switching the display capacity, the display contents of the indicator row will also be erased, and as the amount of hardware increases, a countermeasure is required.

(c) Object of the Invention Based on the above-mentioned needs, the object of the present invention is to provide a display device in which the screen buffer memory is shared regardless of the display capacity, thereby preventing an increase in the amount of hardware, and in which the screen buffer memory can be easily controlled by a microprogram. The purpose is to provide a screen control method.

(d) Structure of the Invention The structure of the present invention is a display device that can switch and display the maximum number of characters that can be displayed on the same display screen by changing the raster scanning line interval, and that displays status information on a part of the display screen. Regardless of the maximum number of characters,
The displayed characters are stored in a common buffer memory, the status information is stored in a specific area of the buffer memory according to the maximum number of characters, and a memory area is provided for saving the display contents of the status information display area, Each time the number of characters is switched, the display content of the status information display area being displayed is saved to the save memory area, and after the maximum number of characters is switched, the display content of the status information display area saved to the save memory area is saved. The information is read out and stored again in the buffer memory.

(e) Embodiment of the Invention FIG. 1 is a block diagram of a display device illustrating an embodiment of the invention. The microprocessor 1 accesses the memory 4 via the multiplexer 2, and stores the display data transferred from the host device in the screen buffer memory area 5 of the memory 4 depending on whether it is 1920 characters or 3440 characters, for example. The dynamic memory access circuit 3 transfers the memory 4 to the display unit 1 via the multiplexer 2 depending on whether the microprocessor 1 issues a 1920 character instruction or a 3440 character instruction.
The dynamic memory is repeatedly accessed in synchronization with a raster scanning period of 0, and the display data stored in the screen buffer memory area 5 is read out to the line buffer memory 7 line by line. The display data read out to the line buffer memory 7 enters a character generation circuit 8 to generate a character pattern. The character pattern converted into a serial signal by the parallel/serial (P/S) conversion circuit 9 is sent to the display section 10 and displayed by raster scanning. The display unit 10 switches and displays the number of raster scanning lines depending on whether the microprocessor 1 specifies 1920 characters or 3440 characters.

FIG. 2 is a diagram explaining how to display 1920 characters and 3440 characters. The memory 4 is divided into a screen buffer memory area 5 and a work area 6 as shown in FIG. 2a. The screen buffer memory area 5 is the second
In the case of 1920 characters as shown at 5' in Figure A, 1920 characters and the characters for one indicator line are stored between the first address 11 and the last address 12, and in the case of 3440 characters, as shown in 5', from the first address 11 to the last address. During the period of 13, 3440 characters and characters for one line of indicator are stored. Assuming that the number of characters displayed in one line of the display section 10 is 80 characters, 1920 characters can be displayed in 24 lines. Also, 3440 characters can be displayed in 43 lines. Accordingly
In the case of 1920 characters, display section 1 as shown in 14 in Figure 2 b.
The display screen status of 0 is displayed in 24 lines with 80 characters per line, and an indicator as shown by 15 is displayed on the 25th line. In the case of 3440 characters, the state of the display screen of the display unit 10 is 43 lines with 80 characters per line as shown at 16 in FIG. The screen buffer memory area 5 only needs to have a capacity for 3440 characters and 80 characters for the indicator, that is, a capacity up to the final address 13, and the display screen c
correspond on a one-to-one basis. Further, the screen buffer memory area 5' corresponds to the display screen b on a one-to-one basis.

When the microprocessor 1 instructs to switch the screen size between 1920 character display and 3440 character display, the microprocessor 1 accesses the address where the indicator display contents in the screen buffer memory area 5' or 5 is stored, reads out the indicator display contents, and reads the indicator display contents from the work area 6. evacuate to. Then set the new screen size parameters. At this time, the screen buffer memory area 5 is cleared and preparations are made to store data to be displayed with the new screen size. After completion of this clearing, the microprocessor 1 reads the indicator display contents from the work area 6 and stores them in the screen buffer memory area 5' or the indicator display contents storage area of 5 corresponding to the parameters. Then, data based on the new parameters is transferred from the host device to the screen buffer memory area 5.

(f) Effects of the Invention As explained above, in the present invention, when displaying by switching between multiple maximum display capacities, since the screen buffer memory is shared, the screen buffer memory and its access means can also be shared, which increases the amount of hardware. In addition, there is no need to retransmit the indicator display when the screen size is changed, and control by a microprogram can be simplified.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a display device explaining one embodiment of the present invention, and Fig. 2 shows 1920 characters and 3440 characters.
FIG. 3 is a diagram illustrating a method of displaying characters. 1 is a microprocessor, 2 is a multiplexer, 3 is a dynamic memory access circuit,
4 is a memory, 5 is a screen buffer memory area, 6 is a work area, 7 is a line buffer memory, 8 is a character generation circuit, 9 is a flat/direct conversion circuit, and 10 is a display section.

Claims (1)

[Claims] 1. The maximum number of characters that can be displayed on the same display screen can be switched and displayed by changing the raster scanning line interval,
A display device that displays status information on a part of a display screen, wherein the displayed characters are stored in a common buffer memory regardless of the maximum number of characters, and the status information is stored in a specific area of the buffer memory according to the maximum number of characters. A memory area is provided for storing and saving the display contents of the display area of the status information, and each time the maximum number of characters is switched, the display contents of the display area of the status information being displayed are saved to the save memory area, and the display contents of the display area of the status information being displayed are saved to the save memory area, 1. A screen control method for a display device, characterized in that after switching the number of characters, the display content of the status information display area saved in the save memory area is read out and stored again in the buffer memory.