Horizontal Scrolling
Each Scrolls can be scrolled horizontally on different basis :
- Overall
- One CELL unit
- One line unit
This is selected via the vdp register 0xB.
Table format
The HScroll table is in the VRAM and its address is setup via the vdp register 0xD.
ScrollA and ScrollB both use this table alternately.
| Address
|
Data
|
Affect
|
| 0
|
| Bit |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Free
|
Quantity of ScrollA
|
|
Overall, CELL 0, Line 0
|
| 2
|
| Bit |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Free
|
Quantity of ScrollB
|
|
Overall, CELL 0, Line 0
|
| 4
|
| Bit |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Free
|
Quantity of ScrollA
|
|
Line 1
|
| 6
|
| Bit |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Free
|
Quantity of ScrollB
|
|
Line 1
|
| ...
|
...
|
...
|
| 0x10
|
| Bit |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Free
|
Quantity of ScrollA
|
|
CELL 1, Line 8
|
| 0x12
|
| Bit |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Free
|
Quantity of ScrollB
|
|
CELL 1, Line 8
|
| ...
|
...
|
...
|
| 0x3FC
|
| Bit |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Free
|
Quantity of ScrollA
|
|
Line 511
|
| 0x3FE
|
| Bit |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Free
|
Quantity of ScrollB
|
|
Line 511
|
| ...
|
...
|
...
|
Vertical Scrolling
Each Scrolls can be scrolled vertically on two different basis :
The VScroll table is located in the [VSRAM]].
ScrollA and ScrollB both use this table alternately.
| Address
|
Data
|
Affect
|
| 0
|
| Bit |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Free
|
Quantity of ScrollA
|
|
Overall, CELL 0-1
|
| 2
|
| Bit |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Free
|
Quantity of ScrollB
|
|
Overall, CELL 0-1
|
| 4
|
| Bit |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Free
|
Quantity of ScrollA
|
|
CELL 2-3
|
| 6
|
| Bit |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Free
|
Quantity of ScrollB
|
|
CELL 2-3
|
| ...
|
...
|
...
|
| 0x4C
|
| Bit |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Free
|
Quantity of ScrollA
|
|
CELL 38-39
|
| 0x4E
|
| Bit |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Free
|
Quantity of ScrollB
|
|
CELL 38-39
|