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VDP1 User's Manual / Chapter 6 Command Table

■ Transparent pixel invalid

Transparent pixel disable bits: see-through pixel disable (SPD), bit 6
Specifies whether to disable transparent pixels in the character pattern. A value of 0 enables transparent pixels, and a value of 1 disables transparent pixels.
The transparent pixel invalid bit is valid only for sprite drawing with a character pattern. Be sure to set this bit to 1 for polygons, polylines, and lines.
If transparent pixels are enabled (SPD = 0), the transparent color code in the character pattern will be transparent pixels and will not be drawn. If you disable the end code (SPD = 1), the transparent color code will be treated like any other color code.
Please note that when transparent pixels are enabled (SPD = 0), only one less color can be used. For example, when ECD = 0, SPD = 0 and color mode = 0, only 14 colors can be displayed.

 SPD
 Processing transparent pixels
 0
 Transparent pixel enabled, does not draw transparent color code,
 Transparent color code will be transparent
 1
 Transparent pixels disabled, transparent colorcodes are not processed,
 Draw in the color according to the code

The relationship between the color mode and the transparent color code is as follows. The number of bits of the transparent color code differs depending on the color mode.

 Color mode
 Transparent color code
 0
 16 colors (color bank mode)
 0H (4 bits)
 1
 16 colors (look-up table mode)
 0H (4 bits)
 2
 64 colors (color bank mode)
 00H (8 bits)
 3
 128 colors (color bank mode)
 00H (8 bits)
 Four
 256 colors (color bank mode)
 00H (8 bits)
 Five
 32768 colors (RGB mode)
 0000H (16 bits)

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★ HARDWARE Manual ★ VDP1 User's Manual
Copyright SEGA ENTERPRISES, LTD., 1997