DISPLAY CONTROL SYSTEM

Abstract: A display control system for use in a display system (10) having digital interfaces is disclosed which, when software using color display is executed (CG33, 14 & 15) in the display system (10) with digital interfaces, is capable of disting­ uishing the display contents thereof from one another. Specifically, the display control system (10) is adapted to generate a given number of pieces of brightness information different from one another in duty correspondingly to respective pieces of color code information or brightness code information, to set up the dots of a display screen (20) in two mutually adjacent areas, and to shift the above-­ mentioned brightness information to be given to one of the above-mentioned areas from the above-mentioned bright­ ness information to be given to the other area in phase. Also, a the above-mentioned code information may be converted into hatch patterns correspondingly to the dot and raster positions in display means (20).

Description: The present invention relates to a display control system provided with digital interfaces. Current display systems of both monochrome and color monitors can have either digital or analogue interfaces. In general, the monochrome monitor system using a CRT or liquid crystal is more common than the color monitor system, because the former is less expensive than the latter. On the other hand, however, since the use of the color monitor system is gradually increasing, a large amount of software using a color display is now found on the market. In the display system with digital interfaces, when the software utilizing the color display is executed by the conventional system using a monochrome monitor, there is a problem in that the display contents thereof can not be distinguished from one another. This is because the above-mentioned conventional monochrome monitor system is only able to perform a black-and-white display and not discriminate between display colors. Also, in order to be able to distinguish colors from one another in the system using a digital interface monochrome monitor, color code information may be read out prior to writing into a VRAM, the read-out color code information may be converted into a hatch pattern signal, and then the converted hatch pattern signal may be written again into the VRAM. However, there arises another problem that other kinds of software are necessary to realize this. US-A-4 225 861 shows a method of creating roughness or texture in a color display system by using replicated patterns. US-A-4 236 175 shows a converter circuit for a monochrome display device to convert color signals into monochrome signals of suitable luminance. In view of the above-mentioned circumstances in the prior art, an object of the present invention is to eliminate or at least mitigate the drawbacks found in the above-mentioned conventional display control system. Another object of the invention is to provide an improved display control system for use in a display system with digital interfaces, which, when software utilizing a color display is executed in the above-mentioned display system, is capable of distinguishing the resultant display contents from one another. According to the invention there is provided a display control system for use in a display system having digital interfaces, said display control system comprising: colour or brightness code information conversion means for generating a given number of brightness information signals different from one another corresponding to respective pieces of colour or brightness code information, characterized by: area setting means for setting up dots on a display screen in two mutually adjacent areas; said conversion means being operable to cause said brightness information signals to differ in duty cycle over a plurality of frame periods; and phase shift means for phase shifting said brightness information duty cycles to be given to one of said two areas relative to said brightness information duty cycles to be given to the other area. The invention will now be described by way of example with reference to the following description of preferred embodiments of the invention and with reference to the accompanying drawings, in which: Fig. 1 is a general view of one embodiment of the present invention; Fig. 2 is a table to illustrate in part I/0 registers included in a display system shown in Fig. 1; Fig. 3 is a block diagram of another embodiment of the invention; Fig. 4 is a view to illustrate the relationship between the code and brightness information in the above embodiment; Fig. 5 is a view to illustrate a portion of display means suitable for use in carrying out the invention; Fig. 6 is a table to illustrate the patterns of a ROM shown in Fig. 3; Fig. 7 is a block diagram of a further embodiment of the invention; Fig. 8 is a table to illustrate the patterns of a ROM shown in Fig. 7; Fig. 9 is a block diagram of another embodiment of the invention; Referring first to Fig. 1, there is illustrated a block diagram of an embodiment of the invention. A display system 10 is a system which controls the display of an LCD or a CRT. Display System 10 includes a CRT controller 11, a driver 12 for amplifying data signals, an attribute graphic 13, an alpha 14, a color selector 15, a color palette 16 for performing a color conversion, a composite color generator CG, and a mode select register 71. CRT Controller 11 is used to generate a timing signal in accordance with a parameter when it is set. Color Selector 15 outputs a 4-bit digital signal for specifying a color, when a color CRT is used as display means 20. Composite Color Generator CG has code information/brightness information conversion means CG1, CG2, and CG3. These code information/brightness information conversion means CG1, CG2, CG3 respectively generate the brightness information of duties different from each other correspondingly to the respective color code information or brightness code information, and also shift the above-mentioned brightness information in a predetermined area from the brightness information in other areas in phase. The shift amount is about 180 degrees. Display System 10 further includes an internal control register 18 and circuits shown in Fig. 1. For Display Means 20, a CRT or an LCD can be used. Externally of Display System 10, there are provided a VRAM (a RAM for video) 30 consisting of a DRAM or a SRAM, an address latch 31 for latching an address signal from a CPU, a data latch 32 for latching data from Display System 10, a character generator 33 for converting character information into dots according to a signal from Data Latch 32, and an external control register 34 for receiving data from Internal Control Register 18. Next, we will give an outline of the operation of the above-mentioned embodiment of the invention. Referring here to Fig. 2, there is illustrated a table to show a portion of an I/O register contained in Display System 10. This I/O register is provided with a plurality of register functions which differ from one another. Here, to display characters on the CRT as Display Means 20, data signals from the CPU (not shown) are once written into VRAM via Driver 12. Display System 10 reads out VRAM 30 repeatedly to the synchronization/scanning of the CRT. The thus-read-out data are latched by Data Latch 32. The data are converted into dots by Character Generator 33 and Alpha 14, then converted into color signals by Color Selector 15 and finally sent to the CRT. On the other hand, when it is desired to perform a color conversion, Color Palette 16 is used. The above-mentioned color signals are D/A converted by Composite Color Generator CG and the resultant Y signals are sent to the CRT. In this case, since Display Means 20 is not a color monitor, the execution of the above-mentioned color conversion operation means the brightness conversion. On the other hand, when the LCD is employed as Display Means 20, the D/A conversion of the color signals in Composite Color Generator CG is not carried out, but other operation is used to control the display of the LCD. Referring now to Fig. 3, there is illustrated a block diagram of an example of code information/brightness information conversion means employed in the invention. In this figure, EXOR Circuit 50 is an exclusive-or operation circuit which receives a line count 0 signal and a dot count 0 signal. Line Count 0 Signal is LSB (0-bit signal) of a line count signal, while Dot Count 0 Signal is LSB (0-bit signal) of a dot count signal. When the output of EXOR Circuit 50 is "0", then signals shown by solid lines in Fig. 4 are output from ROM51 and areas shown by oblique solid lines in Fig. 5 are displayed. When the output of EXOR Circuit 50 is "1", then signals shown by broken lines in Fig. 4 are output from ROM51 and areas shown by oblique broken lines in Fig. 5 are displayed. EXOR Circuit 50 is adapted to create so-called "checkered" selection switching signals on Display Means 20. ROM 51 is adapted to output the brightness information of different duties from one another correspondingly to the respective color code information A0, A1, A2 received from Color Palette 16. The relationship between the above-mentioned color code information and brightness information is illustrated in Fig. 4. For example, when the color code information is "110", if the output of EXOR Circuit 50 is "0", then a parallel signal (shown by a solid line) in which only the first frame thereof is "Low" is output, while if the output of EXOR Circuit 50 is "1", then a parallel singal (shown by a broken line) in which only the fourth frame thereof is "Low" is output. Selector 52 is adapted to output the signal out of the output signals of ROM 51 that corresponds to the number of frames. In the above-mentioned case, 8 frames 0 - 7 are used and the frame number is determined according to frame count 0, 1, 2 signals. In Fig. 3, reference CG1 designates code information/brightness information conversion means. Next, we will describe the operation of the above-mentioned embodiment of the invention. A given piece of color code information is output from Color Palette 16 and, according to this given color code information, brightness code information is output, as shown in Fig. 4. In this case, if the output of EXOR Circuit 50 is "0", "1", then the signals are output in the wave forms respectively shown by the solid and broken lines in Fig. 4. And, Selector 52 outputs a 1-bit signal in accordance with the then frame, which signal is then transmitted to Display Means 20. Therefore, in the above embodiment, even when a certain dot is being displayed with the same brightness at a certain instance, if the then frame is different, the average brightness of the dot is also different so as to be able to display an intermediate brightness. And, the intermediate brightness is made to correspond to its associated color and thus, even in a monochrome monitor, differences between colors can be recognized visually. Also, since every dot of Display Means 20 is displayed by a signal which is different in phase, a flicker is also 180 degrees out of phase so that flickers cancel each other to become quiet. Fig. 6 is a table to illustrate the patterns of ROM 51 shown in Fig. 3. Now, in Fig. 7, there is illustrated a block diagram of a second embodiment of the invention. In this embodiment, a single ROM 51a is used to take the place of EXOR Circuit 50 and ROM 51 in Fig. 3. In Fig. 7, reference CG2 designates code information/brightness information conversion means. The patterns of the above-mentioned ROM 51a are shown in Fig. 8. In Fig. 8, reference characters A, B designate the same portions as with A, B in Fig. 6, respectively. Now in Fig. 9, there is illustrated a block diagram of a third embodiment of the invention. In this embodiment, a single ROM 51b is employed to take the place of ROM 51a and Selector 52. In this figure, reference CG3 designates code information/brightness information conversion means. It should be noted that the operations of the embodiments illustrated in Figs. 7 and 9 are similar to that of the embodiment in Fig. 3. Although in the foregoing explanation the code information/brightness information conversion means or circuit is composed of a ROM and an EXOR circuit for purposes of generalization of the description, it is also possible to make an equivalent circuit by using other elements such as AND, OR, INV and the like. As described hereinbefore, the present invention has two effects that it has software compatibility and that the time necessary for its processings can be reduced, because it is capable of recognizing the differences between colors even in a system using a digital interface monochrome monitor.

Claims: A display control system for use in a display system having digital interfaces, said display control system comprising colour or brightness code information conversion means (CG1) for generating a given number of brightness information signals different from one another corresponding to respective pieces of colour or brightness code information, characterized by: area setting means (50,51,52) for setting up dots on a display screen in two mutually adjacent areas; said conversion means being operable to cause said brightness information signals to differ in duty cycle over a plurality of frame periods; and phase shift means (CG1) for phase shifting said brightness information duty cycles to be given to one of said two areas relative to said brightness information duty cycles to be given to the other area. A display control system as defined in claim 1, wherein the amount of phase shift provided by said phase shift means (CG1) is about 180 degrees. A display control system as defined in claim 1 or 2, wherein said area setting means is adapted to set up areas such that the horizontally mutually adjacent areas of said display screen (20) differ from each other and the vertically mutually adjacent areas of said display screen differ from each other in terms of brightness information duty cycle phase.

Inventors: ISHII, TAKATOSHI
Applicants: ASCII CORPORATION
Application year: 1985
Main classification: G09G1
IPC codes: G09G5