JPH0253796B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a change color circuit for a color CRT display equipped with a processor.

[Conventional technology]

Color CRT (cathode ray tube) displays equipped with a processor (CPU or MPU) are widely used in personal computers and the like. The display colors are red R, green G, and blue B because it is a digital system.
Seven colors can be obtained by combining these two colors, but there are also some that add luminance (I) to these and use tile painting techniques to create a wide variety of colors.

Operations such as filling figures displayed on the color tube surface with a specified color (Paint) and changing figures displayed in one color to another color (Change Color) are easy on a CRT display. , which increases the effectiveness of the device.

[Problem that the invention seeks to solve]

Conventionally, change color is performed by software, in which a program reads color data within a specified range of VRAM (video random access memory) one dot at a time, compares it with the specified color, and if it matches, the color data is stored in the memory. The color data to be changed is written into the cell, that is, the stored contents of the memory cell are updated to the changed color data, and this operation is repeated for all memory cells within the specified range. This takes time.

Sometimes I use the palette function to change colors. This changes the color code, for example
Color code 2 as COLOR=(2,6)
(red) instructs to change to color code 6 (yellow), then COLOR2, PRINT “X”,
The letter X is displayed in yellow. However, since this method changes the color code, the color of the entire screen changes, and it is not possible to change the color of only a portion of the screen. A multi-page method is sometimes adopted in which the screen of a CRT is divided into multiple sections and each section is used for a mutually independent page. This is effective when processing data while viewing only a portion of the data at the same time. In such a multi-page system, it is generally undesirable for the colors to change across all pages when the colors are changed, and it is common to only change the colors on that page, or even only on the problem part within that page.

Therefore, the present invention aims to make it possible to quickly change the color and only change the color of a part of the screen.

[Means for solving problems]

The present invention provides a change color circuit for a display device that includes a video random access memory that stores red, blue, and green data of a dot pattern to be displayed on a cathode ray tube, and a processor that controls the display. A register into which the start and end addresses of the change color target area are written, a comparison color register into which color data to be changed is written, a change color register into which color data to be changed is written, and a register in which the change color target area is written. an address generating section that generates each address in a television scan manner and reads out the memory; a comparison circuit that compares the read color data in the memory with color data in a comparison color register; and an output control circuit that outputs the color data of the change color register, inputs it to the memory, and writes it to the same address where it was read. The configuration and operation will be explained with reference to examples.

[Example] FIG. 1 shows an example of the present invention, and 10 is
It is a VRAM and consists of four parts for R, G, B, and I.
Each part R to I has the same number of memory cells as the number of dots on the tube surface of a CRT (not shown).Imagining that the number of dots on the tube surface is m×n, each part R to I has the same m×n memory cells. It is displayed by setting the data of the relevant cell in the R part to "1" and setting the data of the relevant cells in the other G, B, and I parts to "0". This also applies to blue dots. Note that I=0 indicates a certain level of brightness, and I=1 indicates the same other level. Tile painting is a technique in which the colors of the dots are alternately colored so that the human eye perceives a color somewhere in between. 12 is an address generation section;
An address for accessing each cell is provided to each R/I section of the VRAM 10. 14 is a circuit that latches data read from VRAM.
Since writing and reading of the VRAM 10 is performed in units of multiple bits, in this example 8 bits, the latch circuit 14 also has a capacity of 8 bits for each portion of R to I. Reference numeral 16 is a register for setting the data of the comparative color, that is, the color to be changed.It has 1 bit each for R, G, B, and I, but if it also handles tile painting, it is better to have 2 or more bits each. Reference numeral 18 is a register for setting the data of the color to be changed, that is, the color to be changed, which is also 1 bit or more each for R, G, B, and I. Here, we will briefly explain registers 16 and 18.
Assume that R to I have 1 bit each. Reference numeral 20 denotes a comparator circuit that successively compares the 8-bit data of each of R to I of the latch circuit 14 and the 1 bit of each of R to I of the register 16, and if they match, the bit is set to 1, for example, and if they do not match, the bit is set to 1 in this example. 0, and the first and second bits of each 8-bit data R to I
Take the AND of the bits, and set the bits that are 1 from R to 14 bits to 1, and the other bits to 0,
The 8-bit data is input to the output data selection circuit 22. A "1" bit in the 8-bit output of the comparison circuit 20 means that the dot colors match, and a "0" means that they do not match.

The address generator 12 also outputs mask data MD, which is input to the other select circuit 22. The mask data indicates bits (dots) that do not require color matching or mismatch. For example, if a CRT screen is multi-paged and the left and/or right edges of the page are in the middle in the 8-bit unit, there is no need to worry about the part that protrudes from the page; It is a mask. Specifically, in the case of the above example, it is preferable to forcibly replace the bits in the protruding portion with 0s, regardless of whether they are 1s or 0s. In other words, with change color, etc., there is a "1" bit in this protruding part, and if you leave it as is, the dot in question will also be repainted, which is inconvenient, but if you force 0, you can do it like this. The problem will disappear. 24 is an output control circuit, and if the input bit input to the select terminal SEL is 1, the bits of terminals 1B to 4B are output to terminals 1Y to 4.
If the input bit is 0, output to terminals 1A to 4.
Output the bit of A to terminals 1Y to 4Y. 26 is a start point address register, and 28 is an end point address register.

Next, to explain the operation, when performing a change color, the CPU (not shown) inputs the registers 26 and 28.
Starting point address of change color target area X ₀ , Y ₀
and write the end point addresses X ₁ and Y ₁ . 3 in Figure 2
Assuming that 0 is the screen of a CRT (display) and the change color target area is the shaded area, the starting point A and ending point B are the illustrated positions. The CPU also writes the color data to be compared into the register 16 and the changed color data into the register 18, and causes the address generator to start operating. _{The address generation unit 12 generates each address in the designated areas A, X 0 , Y 0 to B ,}
0 and read out the stored data 8 bits at a time. In personal computers and the like, the CPU performs operations other than display, so display control is performed by cycle stealing. FIG. 3 is a diagram showing this, where DISP is a period during which display processing is possible, and CPU is a period during which processing other than display is possible. The address generator 12 generates addresses during periods 1, 2, 3, . . . in FIG. 3 to read out the VRAM 10, and the read data is taken into the latch circuit 14 when the latch pulse VLATCH is generated.

The VRAM read data taken into the latch circuit 14 is compared with the comparison color data in the register 16 and the comparison circuit 2.
0, but this comparison is made in the period τ ₁ during which display processing is allowed. The comparison result passes through the select circuit 22, where any bits that should be masked are masked, and the processed 8-bit data is input to the output control circuit 24, where bits "0",
In response to "1", input switching is performed as described above. Each of the 8-bit R to I outputs of the output control circuit 24 are sent to the VRAM 10 and written to the same address from which they were read. This write is executed by the clock WREND as shown in Figure 3.
This is done by going to L (low) level during the CPU period. This clock WREND is input to the address generator 12 as shown in Fig.
Generates the same address as the read address. In other words, they are the same as VRAM addresses 2 and 1 in FIG. When one 8-bit block has been updated in this way, the address generating section 12 generates the next VRAM read address 3, and the same operation is repeated thereafter.

〔Effect of the invention〕

As explained above, in the present invention, a comparison color register, a change color register, a comparison circuit, an address generation section, etc. are provided, and these hardware
The color data in the specified range of VRAM is compared with the comparison color, and if there is a match, it is rewritten to the specified color, so change color can be executed faster than conventional software methods. In addition, the range for color comparison can be set arbitrarily, making it easy to change colors for each page when using multiple pages. Furthermore, since the processor only needs to write the start and end point coordinates, comparison color, and change color data in the register, the burden on the processor is lightened, and the processor can do other work while changing color is being performed. Furthermore, by increasing the number of comparison colors, it is possible to change a plurality of comparison colors. For example, processing such as changing red and blue to white can be performed simultaneously.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram of a change color target area, and FIG. 3 is an explanatory diagram of various timings. In the drawing, 10 is video random access memory,
26 and 28 are registers into which the start and end addresses are written, 16 is a comparison color register, 18 is a change color register, 12 is an address generator, 20 is a comparison circuit,
24 is an output control circuit.

Claims (1)

[Claims] 1. The dot pattern displayed on the display device is red, blue,
In a change color circuit of a display device that is equipped with a video random access memory that stores green data and a processor that performs display control, a register into which the start and end addresses of the change color target area on the display screen of the display device are written. A comparison color register into which color data to be changed is written, a change color register into which color data to be changed is written, and each address within the change color target area is generated in a television scan manner and read out from the memory. an address generator; a comparison circuit that compares the read color data of the memory with color data of a comparison color register; and when the comparison circuit indicates that the two color data match;
A change color circuit comprising: an output control circuit that outputs color data from a change color register, inputs the color data to the memory, and writes the data to the same address where it was read.