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

On the Sega Saturn, it is possible to display up to five scrolling screens simultaneously on one screen. Scrolling is divided into normal scroll screen and rotary scroll screen, and normal scroll screen is further divided into four types. SGL allows a total of five types of scroll screens to be output to the monitor at the same time. The table below summarizes the types of scroll screens and their main functions (details regarding the scroll function and how to set it are described in “Section 8-6: Scroll function settings”).

Table 8-3 Scroll screen
scroll screen name name function remarks
move Scaling rotate It can be displayed
Number of colors
 normal scroll
 Normal scroll 0
 NBG0 ○ ○ 16.77 million colors Magnification settings are 1/4 to 256x
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 magnification

note)
For details on the scroll function, please refer to the scroll function section.

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

The scroll screen is set to 256 colors by default.

Regarding the limit on the number of scroll pages

Up to 5 scroll screens can be output at the same time, but it is not always possible to output all 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 TUTORIAL
Copyright SEGA ENTERPRISES, LTD., 1997