★ SGL User's Manual ★ PROGRAMMER'S STRUCT
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8-4. Scroll screen

With Sega Saturn, it is possible to display up to 5 scroll screens at the same time on one screen. Scrolling is divided into a normal scroll screen and a rotary scroll screen, and the normal scroll screen is further divided into four types. With SGL, it is possible to output these five types of scroll screens to the monitor at the same time. The table below summarizes the types of scroll screens and their main functions (details and setting methods for scroll functions are described in Section 8-6: Scroll Function Settings).

Table 8-3 Scroll screen
Scroll screen name name function remarks
Move Scale rotate Number of colors that can be displayed
 Normal scroll
 Normal scroll 0
 NBG0 ○ ○ 16.77 million colors Magnification setting is 1/4 to 256 times
Normal scroll 1 NBG1 ○ ○ 32768 colors
Normal scroll 2 NBG2 ○ 256 colors
Normal scroll 3 NBG3 ○ 256 colors
 Rotating scroll screen
 Rotation scroll 0 RBG0 ○ ○ ○ 16.77 million colors Magnification setting is arbitrary

note)
For details on the scroll function, refer to the item of scroll function.

The maximum number of colors that can be set and the enlargement / reduction function differ for each of the normal scroll screens “NBG0 to 3” (see “8-6: Scroll function” for details).

The scroll screen is set to 256 colors by default.

About the limit of the number of scrolling faces

The scroll screen can output up to 5 screens at the same time, but it is not always possible to output 5 screens. This is because the maximum number of accesses to the VRAM that stores scroll data during one processing period is fixed, which imposes some restrictions on scroll drawing.
For details, refer to "HARDWARE MANUAL vol.2: VDP2 User's Manual".

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★ SGL User's Manual ★ PROGRAMMER'S STRUCT
Copyright SEGA ENTERPRISES, LTD., 1997