JPH02189626A - Screen display control system - Google Patents

Abstract

PURPOSE:To reduce the cost of a device without requiring a complicated hardware by constituting a text screen with a software. CONSTITUTION:A display control part 1 is activated every fixed time by an interval timer 2 to compare the contents of a virtual text VRAM 8 with the contents of a comparing text VRAM 4 one by one byte. When both values are equal to each other, no operation is executed, but when respective values are different, the data in the VRAM 3 are transferred to the VRAM 4 and a character font corresponding to the text code is read out from a font ROM 5 and developed to a bit map VRAM 6. Consequently, the hardware can be simplified and the cost can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a computer screen display control method, and particularly to a text screen display method.

[Conventional technology]

In the conventional screen display control method, when text code data is written into a text VRAM, the hardware automatically develops it into a bitmap VRAM.

In addition, if the character string data displayed on the screen contains a code (such as LF) that causes screen scrolling, display all the display data for one line and then scroll one line.
Display next line.

[Problem to be solved by the invention]

In the conventional screen display control method described above, screen control is performed by hardware, which has the disadvantage that the hardware becomes complicated and the cost increases.

Furthermore, in the case of a device that employs a screen display method in which character fonts are transferred to a bitmap screen using software, the speed at which the screen is rewritten is slow, so there is a drawback that the slowness of scrolling is particularly noticeable.

[Means to solve the problem]

The screen display control method of the present invention uses a bitmap VRAM and a virtual text VRAM that emulates a text screen.
M, a comparison text VRAM for detecting changes in the contents of the virtual text VRAM, and text data of the virtual text VRAM to the bitmap VRAM.
and an interval timer that activates the display control unit at regular intervals, or if there is a code that causes screen scrolling in the displayed character string, screen scrolling is performed rather than character display. Prioritize and execute
The display pointer block memorizes how far the characters in a line have been displayed, and after all screen scrolling specified in the display string is completed, the display pointer block is referenced to display undisplayed characters. configured.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of a first embodiment of the present invention. In the figure, the display control section 1 is activated at regular intervals by an interval timer 2, and compares the contents of the virtual text VRAM 3 and the contents of the comparison text VRAM 4 one byte at a time. When the values are the same, nothing is done, but when the values are different, the data in the virtual text VRAM 3 is transferred to the comparison text VRAM 4, the character font corresponding to that text code is read from the font ROM 5, and expanded to the bitmap VRAM 6. do.

FIG. 2 is a block diagram of a second embodiment of the invention. In the figure, when a display character string is given to the display control unit 11, the display control unit 11 scans whether the given display character string contains a code (such as LF) that causes screen scrolling. If the scroll occurrence code is not included, the display control unit 11 displays character code 1.
The bytes are transferred to the virtual text VRAM 12, and further provided to the display BIOS i 3, and the display pointer block 16 stores whether or not the first column has been displayed this time, and the scan is executed again. The display BIO 313 stores the character font for the given character code in the font ROM.
14 and transfer it to the bitmap VR and AM15.

If a scroll generation code is found in the display character string, the display control unit 11 starts the scroll BIOS 17,
Run the scan again. The scroll BIO 317 has a virtual text VRAM 12, a bitmap VRAM 15,
and scroll the data in the display pointer block 16. If there is no scroll generation code in the displayed character string, the display control unit 11 reads the column position of the undisplayed data stored in the display pointer block 16, and reads the character code corresponding to that position from the virtual text VRAM 12. and display it on the screen using the display BIO 313.

〔Effect of the invention〕

As explained above, since the text screen is configured by software, the present invention does not require complicated hardware, and has the advantage of being able to reduce the cost of the device.

Furthermore, it is possible to prevent a decrease in scrolling speed due to slow screen display, and to achieve efficient screen display.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a first embodiment of the present invention, and FIG. 2 is a block diagram of a second embodiment. 1.11... Display control unit, 2... Interval timer, 3, 12... Virtual text VRAM, 4... Comparison text VRAM, 5. 14-7t ROM, 6
．． 15...Bitmap VRAM, 13...Display B
IO3, 16...Display pointer block, 17...
Scroll B I O8゜

Claims (2)

[Claims] (1) A bitmap VRAM, a virtual text VRAM that emulates a text screen, a comparison text VRAM for detecting changes in the contents of the virtual text VRAM, and a text data VRAM that stores the text data of the virtual text VRAM in the bitmap VRAM. 1. A screen display control method, comprising: a display control section that operates on the display; and an interval timer that activates the display control section at regular intervals. (2) If there is a code that causes screen scrolling in the displayed character string, screen scrolling is given priority over character display, and the display pointer block stores and displays how far the characters in the line have been displayed. A screen display control method characterized in that after all screen scrolling specified in a character string is completed, undisplayed characters are displayed by referring to the display pointer block.