VDP Scrolls
Note: This article talk about the table attribute and not the scrolling details, see VDP Scrolling to learn about scrolling.
Description
The VDP have two scrollable region, ScrollA and ScrollB.
After uploading some patterns in the VRAM, the programmer must select a size for the screens using the register 0x10 and setup the table address (registers 0x2 and 0x4).
A total of six possibility of size is selectable :
- 32 x 32
- 32 x 64
- 32 x 128
- 64 x 32
- 64 x 64
- 128 x 32
Table Address
The table address is 1024 to 4096 word long (depending on the sizes) and follow a left to right/top to bottom schema.
TODO: Do image to represent the CELL organization
Pattern Name
| Bit | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| Def | priority bit | Color palette ID | 1: Vertical reverse
0: no reverse | 1 : Horizontal reverse
0: no reverse | Pattern number | |||||||||||