<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 1x1, 2x1, or 2x2 sizes, and the size is specified in each register.

● Plain size

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

Figure 4.13 Arrangement of pattern name table by plane size

Character pattern table　
Specified ─ → ┌────────┐　
Character │ │ ● In the case of 1 horizontal page x 1 vertical page　
Pattern │ │　
Address │ Page 0 │ ┌──────┐┬　
│ │ │ │ │ │　
│ │ │ Page 0 │ │ 64 cells　
├────────┤ │ │ │　
│ │ └──────┘┴　
│ │ ├──────┤　
│ Page 1 │ 64 cells　
│ │　
│ │　
├────────┤ ● In the case of 2 horizontal pages x 1 vertical page　
│ │ ┌──────┬──────┐┬　
│ │ │ │ │ │ │　
│ Page 2 │ │ Page 0 │ Page 1 │ │ 64 cells　
│ │ │ │ │ │ │　
│ │ └──────┴──────┘┴　
├────────┤ ├─────────────┤　
│ │ 128 cells　
│ │　
│ Page 3 │　
│ │ ● In the case of 2 horizontal pages x 2 vertical pages　
│ │ ┌──────┬──────┐┬　
├────────┤ │ │ │ │ │　
│ │ │ Page 0 │ Page 1 │ │　
│ │ │ │ │ │ │　
│ Page 4 │ ├──────┼──────┤ │ 128 cells │ │ │ │ │ │ │　
│ │ │ Page 2 │ Page 3 │ │　
├────────┤ │ │ │ │ │　
│ │ └──────┴──────┘┴　
│ │ ├─────────────┤　
128 cells

● Plain size register

The plane size register controls the plane size and the specification of screen over processing for the rotating scroll screen. A write-only 16-bit register located at address 18003AH. After turning on the power or resetting, the value will be cleared to 0, so be sure to set it.

PLSZ 18003AH

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

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

Plane size bit : Plane size bit

07 07	06 06	05 05	04	03 03	02 02	01 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) of each scroll screen.

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

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

Note The bit name xx can be N0, N1, N2, N3, RA, or RB.

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

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

On the rotation scroll screen, specify the processing (screen over processing) when the display coordinate value exceeds the display area.

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

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

Note: The x in the bit name can be A or B.

If the rotary 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, the process of forcibly setting the display area to 0 ≤ X <512, 0 ≤ Y <512 and making everything outside that area transparent. When set, the same image is displayed twice, 256 dots each in the vertical direction.

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