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■ Color

Color related functions and special functions are as follows.

∙ There are color bank method and RGB code method for expressing pixel color drawn (written) in the frame buffer. With the color bank method, 16, 64, 128, 256 colors can be expressed within one character, and with the RGB code method, 32768 colors can be expressed within one character.

Color bank method

The color bank method refers to the color stored in the color RAM of VDP2 by combining the color bank with the palette code of 16, 64, 128, 256 colors. In 16 colors, the pixel data of the character pattern is a 4-bit palette code, the upper 12 bits are added from the color bank, and the 16-bit data is written to the frame buffer. When 8 bits / pixel, the lower 8 bits are written. For 64, 128, and 256 colors, the character pattern is 8 bits / pixel. For 64, 128, and 256 colors, the lower 6, 7, and 8 bits are valid. The upper 10, 9, and 8 bits of the color bank are added.
* Data written in the color bank method is divided into the following function bits on the VDP2 side and processed. Refer to the VDP2 manual for details.

Figure 1.10 Color bank method bit configuration

RGB code system

The RGB code system represents colors with 5 bits each of RGB (red, green, blue). The brightness of each RGB is represented by 00H to 1FH. The closer to 00H, the darker the brightness, and the closer to 1FH, the brighter. There are 32768 colors that can be expressed in RGB code. RGB code is 16-bit data, and the most significant bit (MSB) is 1.

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