<27/86>VDP2 User's Manual/4.7 Plane

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

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VDP2 User's Manual/Chapter 4 Scroll screen

■4.7 Plane

A plane is a pattern name table (page) arranged in a 1x1, 2x1, or 2x2 size, and the size is specified in each register.

●Plane size

If a plane consists of multiple pattern name tables (pages), store the pattern name tables used for one plane contiguously in VRAM. Figure 4.13 shows the relationship between pattern name table placement and pattern name table according to plane size (number of plane pages).

Figure 4.13 Arrangement of pattern name table by plane size

          Character pattern table 
Specified─→┌────────┐ 
character  │        │ ●For 1 page horizontally 
pattern    │        │    x 1 page vertically
address    │ Page 0 │ ┌──────┐┬ 
           │        │ │      ││ 
           │        │ │Page 0││64 cells 
           ├────────┤ │      ││ 
           │        │ └──────┘┴ 
           │        │ ├──────┤ 
           │ Page 1 │ 64 cells 
           │        │ 
           │        │ ●For 2 pages horizontally
           ├────────┤    x 1 page vertically 
           │        │ ┌──────┬──────┐┬ 
           │        │ │      │      ││ 
           │ Page 2 │ │Page 0│Page 1││ 64 cells 
           │        │ │      │      ││ 
           │        │ └──────┴──────┘┴ 
           ├────────┤ ├─────────────┤ 
           │        │    128 cells 
           │        │ 
           │ Page 3 │ ●For 2 pages horizontally
           │        │    x 2 pages vertically 
           │        │ ┌──────┬──────┐┬ 
           ├────────┤ │      │      ││ 
           │        │ │Page 0│Page  ││ 
           │        │ │      │      ││ 
           │ Page 4 │ ├──────┼──────┤│128 cells
           │        │ │      │      ││ 
           │        │ │Page 2│Page 3││ 
           ├────────┤ │      │      ││ 
           │        │ └──────┴──────┘┴ 
           │        │ ├─────────────┤ 
                          128 cells

●Plane size register

The plane size register controls the plane size and specification of screen over handling for rotating scroll screens. This is a 16-bit write-only register located at address 18003AH. The value is cleared to 0 after power-on or reset, so be sure to set it.

PLSZ 18003AH

RBOVR1	RBOVR0	RBPLSZ1	RBPLSZ0	RAOVR1	RAOVR0	RAPLSZ1	RAPLSZ0
15	14	13	12	11	10	09	08

07
06
05
04
03
02
01
00

N3PLSZ1
N3PLSZ0
N2PLSZ1
N2PLSZ0
N1PLSZ1
N1PLSZ0
N0PLSZ1
N0PLSZ0

Plane size bit

07	06	05	04	03	02	01	00
N3PLSZ1	N3PLSZ0	N2PLSZ1	N2PLSZ0	N1PLSZ1	N1PLSZ0	N0PLSZ1	N0PLSZ0

(N0PLSZ1, N0PLSZ0, N1PLSZ1, N1PLSZ0, N2PLSZ1, N2PLSZ0, N3PLSZ1, N3PLSZ0, RAPLSZ1, RAPLSZ0, RBPLSZ1, RBPLSZ0)
Specify the plane size (number of pages) for each scroll screen.

N0PLSZ1, N0PLSZ0	18003AH	bit 1,0	For NBG0
N1PLSZ1, N1PLSZ0	18003AH	bit 3,2	For NBG1
N2PLSZ1, N2PLSZ0	18003AH	bit 5,4	For NBG2
N3PLSZ1, N3PLSZ0	18003AH	bit 7,6	For NBG3
RAPLSZ1, RAPLSZ0	18003AH	bit 9,8	For rotation parameter A
RBPLSZ1, RBPLSZ0	18003AH	bit 13,12	For rotation parameter B

xxPLSZ1	xxPLSZ0	plane size
0	0	1 page horizontal x 1 page vertical
0	1	2 pages horizontally x 1 page vertically
1	0	Setting prohibited (Please do not set)
1	1	2 pages horizontally x 2 pages vertically

[Note] xx in the bit name is N0, N1, N2, N3, RA, or RB.

If NBG0 and NBG1 are set to be able to be reduced to 1/4, the plane size of that screen should not be 2 pages wide x 2 pages tall.

Screen over processing bit : Over bit (RAOVR1, RAOVR0, RBOVR1, RBOVR0)

Specifies the process to be performed when the display coordinate value exceeds the display area on a rotating scroll screen (screen over process).

RAOVR1,RAOVR0	18003AH	bit 11,10	For rotation parameter A
RBOVR1, RBOVR0	18003AH	bit 15,14	For rotation parameter B

RxOVR1	RxOVR0	Screen over processing
0	0	Images set in the display area are repeated outside the display area.
0	1	Outside the display area, the character specified in the screen over pattern name register is displayed. Repeat the pattern (only when the rotating scroll screen is in cell format)
1	0	Make everything outside the display area transparent
1	1	Force display area to 0≦ regardless of plane size or bitmap size X＜ 512, 0≦Y＜ 512 to make everything outside that area transparent.

[Note] A or B can be substituted for x in the bit name.

If the rotating scroll screen is in bitmap format, do not set the process to repeat the character pattern specified in the screen over pattern name register.
If the rotating scroll screen is in bitmap format and the vertical size of the bitmap is 256 dots, force the display area to 0≦X＜ 512, 0≦Y＜ If you set it to 512 and make everything outside that area transparent, the same image will be displayed twice in each vertical direction with 256 dots each.

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