★ HARDWARE Manual ★ VDP2 User's Manual ★ Chapter 4 Scroll screen
▲ Back ｜ Forward ▼
VDP2 User's Manual / Chapter 4 Scroll Screen

■ 4.8 Map

A map is a square pattern consisting of 2x2 or 4x4 planes. The map of the normal scroll screen consists of 2x2 planes, and the map of the rotary scroll screen consists of 4x4 planes. By specifying the start address of the pattern name table in the register of each plane, you can specify how to arrange the planes.

● Map specification register

The map consists of 4 planes (normal scroll screen) or 16 planes (rotary scroll screen), and each screen has a 6-bit map register for specifying the start address of the pattern name table for each plane. I have each number of planes. It also has one 3-bit map offset register that is attached to the upper level of the map register. In the 9-bit map specification register, the bits used and the address value indicated by the register change depending on the pattern name data size and character size. The relationship between the map register and the map offset register is shown in Figure 4.14.

Figure 4.14 Map specification register
┌───────────┐ ┌───────────────────────┐
│ Map offset │ │ Map register A │
│ Register │ ├───┬───┬───┬───┬───┬───┤
├───┬───┬───┤ │ 5 │ 4 │ 3 │ 2 │ 1 │ 0 │
│ 8 │ 7 │ 6 │ └───┴───┴───┴───┴───┴───┘
└───┴───┴───┘┌───────────────────────┐
│ │ Map register B │
│ ├───┬───┬───┬───┬───┬───┤
│ │ 5 │ 4 │ 3 │ 2 │ 1 │ 0 │
│ └───┴───┴───┴───┴───┴───┘
└──┐:　
│:　
│ │　
│ │　
↓ ↓　
┌───────────┬───────────────────────┐
│ Map offset │ Map register │
│ Register │ │ │
├───┬───┬───┼───┬───┬───┬───┬───┬───┤
│ 8 │ 7 │ 6 │ 5 │ 4 │ 3 │ 2 │ 1 │ 0 │
└───┴───┴───┴───┴───┴───┴───┴───┴───┘

Map specification by pattern name data size and character size The bits used in the register and the address values of the register are shown in Table 4.8.

Table 4.8 Address values of map specification registers according to settings
Plain size Pattern name data size Character size Bits used and actual address value
1 horizontal page x 1 vertical page 1 word 1 horizontal cell x 1 vertical cell (Value of bits 6 to 0) x 2000H
2 horizontal cells x 2 vertical cells (Value of bits 8 to 0) x 800H
2 words 1 horizontal cell x 1 vertical cell (Value of bits 5 to 0) x 4000H
2 horizontal cells x 2 vertical cells (Value of bits 7 to 0) x 1000H
2 horizontal pages x 1 vertical page 1 word 1 horizontal cell x 1 vertical cell (Value of bits 6 to 1) x 4000H
2 horizontal cells x 2 vertical cells (Value of bits 8 to 1) x 1000H
2 words 1 horizontal cell x 1 vertical cell (Value of bits 5 to 1) x 8000H
2 horizontal cells x 2 vertical cells (Value of bits 7-1) x 2000H
2 horizontal pages x 2 vertical pages 1 word 1 horizontal cell x 1 vertical cell (Value of bits 6 to 2) x 8000H
2 horizontal cells x 2 vertical cells (Value of bits 8 to 2) x 2000H
2 words 1 horizontal cell x 1 vertical cell (Value of bits 5 to 2) x 10000H
2 horizontal cells x 2 vertical cells (Value of bits 7 to 2) x 4000H
Note If the VRAM capacity is set to 4M bits, the most significant bit of the bits used will not be used.

▲ Back ｜ Forward ▼
★ HARDWARE Manual VDP2 User's Manual ★ Chapter 4 Scroll screen
Copyright SEGA ENTERPRISES, LTD., 1997