<20/86> VDP2 User's Manual / 4.2 Scroll screen configuration

★ HARDWARE Manual ★ VDP2 User's Manual ★ Chapter 4 Scroll screen

▲ Back ｜ Forward ▼

VDP2 User's Manual / Chapter 4 Scroll Screen

■ 4.2 Scroll screen configuration

There are two screen formats for scrolling screens: cell format and bitmap format.

● Cell format

The cell-type scroll screen has a "cell" that is a picture pattern of 8 dots horizontally x 8 dots vertically, a "character pattern" that arranges cells horizontally 1 x vertically 1 or horizontally 2 x vertically 2, and a character pattern horizontally. 32 x vertical 32 or horizontal 64 x vertical 64 "pages", horizontal 1 x vertical 1, horizontal 2 x vertical 1 or horizontal 2 x vertical 2 "plains", plains horizontal 2 x vertical 2 It consists of 2 (for normal scroll screen) or 4 horizontal x 4 vertical (for rotary scroll screen) "maps". Figure 4.1 shows the configuration of the cell-type scroll screen.

Figure 4.1 Cell-type scroll screen configuration

Cell data is the dot color data stored in VRAM as a character pattern table. The color data can be 4, 8, 16 or 32 bits depending on the number of character colors. Character pattern data is obtained by arranging 1 or 4 cell data. The page data is the one that stores the character pattern name data (character pattern data address) as a pattern name table. A plane is one, two, or four page data arranged side by side. The map specifies the start address of the pattern name table in the map register and map offset register. Figure 4.2 shows the correspondence between the cell format scroll screen configuration and the data settings.

Figure 4.2 Correspondence between cell format scroll screen configuration and data settings

[note]
The size of the character pattern and plane changes depending on the register settings, and the size of the map changes depending on the type of scroll screen. Figure 4.2 is an example of a normal scroll screen (2 horizontal planes x 2 vertical planes) with a character pattern of 2 horizontal cells x 2 vertical cells and a plane of 2 horizontal pages x 2 vertical pages.

● Bitmap format

The bitmap format scroll screen consists of a bitmap pattern with a size of 512 dots or 1024 dots horizontally and 256 dots or 512 dots vertically. To display the screen in bitmap format, set the bitmap size in the register and store the bitmap pattern of the set size in VRAM.
Figure 4.3 shows the configuration of the bitmap format scroll screen, and Figure 4.4 shows the relationship between the bitmap format scroll screen and the registers.

Figure 4.3 Bitmap format scroll screen configuration

512 dots wide x 256 dots high
512 dots wide x 512 dots high
1024 dots wide x 256 dots high
1024 dots wide x 512 dots high

Figure 4.4 Relationship between bitmap format scroll screen configuration and data settings

Map offset register　
┌────────┐ Character control register │ Map offset │ → ┌───────────┐ ┌─────────┐　
└────────┘ │ Color data of dot 0 │ ← │ Number of character colors │　
├───────────┤ └─────────┘　
│ │　
│ │　
│ │　
Bitmap format │ │　
┌───┬───┐ │ │　
│ │ │ │ │ │　
│ │ │ │ Bitmap │　
┌ → ├───┼───┤ │ │　
│ │ │ │ │ │ │　
│ │ │ │ │ │ │　
│ └───┴───┘ │ │ │　
│ │ │　
│ │ │　
│ │ │　
│ └───────────┘　
│　
│ Character control register　
│ ┌─────────┐　
└─┤ Bitmap size │　
└─────────┘

▲ Back ｜ Forward ▼

★ HARDWARE Manual VDP2 User's Manual ★ Chapter 4 Scroll screen