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★ HARDWARE Manual ★ VDP2 User's Manual ★ Chapter 8 Window
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VDP2 User's Manual/Chapter 8 Window

●Sprite window

A sprite window can be obtained by specifying the value of the most significant bit of the sprite's frame buffer data when all of the sprite's frame buffer data is palette-based data and the sprite type is 2 to 7. The area where the most significant bit is 1 is inside, and the other areas are outside. For sprite types, see "Sprite Types" in " 9.1 Sprite Data ." The sprite window is shown in Figure 8.5.

Figure 8.5 Sprite window

●Sprite control register

The sprite control register controls sprites. This is a 16-bit write-only register located at address 1800E0H. The value is cleared to 0 after power-on or reset, so be sure to set it.

SPCTL 1800E0H
   15   
   14   
   13   
   12   
   11   
   10   
   09   
   08   
 -
 -
 SPCCCS1
 SPCCCS0
 -
 SPCCN2
 SPCCN1
 SPCCN0

   07   
   06   
   05   
   04   
   03   
   02   
   01   
   00   
 -
 -
 SPCLMD
 SPWINEN
 SPTYPE3
 SPTYPE2
 SPTYPE1
 SPTYPE0

Sprite color calculation condition bit : Sprite color calculation condition bit
(SPCCCS1, SPCCCS0), bits 13, 12
See 9.2 Priority and Color Operations .

Sprite color calculation condition number bit : Sprite color calculation condition number bit
(SPCCN2 to SPCCN0), bits 10 to 8
See 9.2 Priority and Color Operations .

Sprite color mode bit : Sprite color mode bit (SPCLMD), bit 5
Please refer to " 9.1 Sprite Data ".

Sprite window enable bit : SW enable bit (SPWINEN), bit 4
Specify whether to use sprite window SW.

SPWINEN process
0 Don't use sprite window
1 Use the sprite window

This bit is valid only when sprite color mode is mode 0 and sprite type is type 2-7.
When this bit is 1, the most significant bit of the sprite's frame buffer is used as the bit for the sprite window, so MSB shadows cannot be used. For details on shadows, see 14.1 Shadow Processing.

Do not set this bit to 1 if the SPCLMD bit is set to 1.

Sprite type bit : Sprite type bit (SPTYPE3 to SPTYPE0), bits 3 to 0
Please refer to " 9.1 Sprite Data ".

●Window effective area for the screen

You can specify whether to use normal windows and sprite windows for each scroll screen. You can specify whether the inner or outer area of the window to be used is enabled for each window, and color calculations and transparency processing are performed on the enabled area. When using multiple windows, you can choose how to stack them using AND or OR logic.

Figure 8.6 shows the effective area when the normal window and sprite window are overlapped using AND or OR logic.

Figure 8.6 Effective area of window

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★ HARDWARE Manual ★ VDP2 User's Manual ★ Chapter 8 Window
Copyright SEGA ENTERPRISES, LTD., 1997