<43/86> VDP2 User's Manual / 6.3 Rotation Parameter Control-3

★ HARDWARE Manual ★ VDP2 User's Manual ★ Chapter 6 Rotating scroll screen

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VDP2 User's Manual / Chapter 6 Rotating Scroll Screen

● Rotation parameter table address register

The rotation parameter table address register specifies the start address of the rotation parameter table. This is a write-only 16-bit register located at addresses 1800BCH to 1800BEH. After turning on the power or resetting, the value will be cleared to 0, so be sure to set it.

RPTAU 1800BCH

---	---	---	---	---	---	---	---
15	14	13	12	11	Ten	09 09	08 08

07 07
06 06
05 05
04
03 03
02 02
01 01
00
---
---
---
---
---
RPTA18
RPTA17
RPTA16

07 07	06 06	05 05	04	03 03	02 02	01 01	00
---	---	---	---	---	RPTA18	RPTA17	RPTA16

RPTAL 1800BEH

RPTA15	RPTA14	RPTA13	RPTA12	RPTA11	RPTA10	RPTA9	RPTA8
15	14	13	12	11	Ten	09 09	08 08

07 07
06 06
05 05
04
03 03
02 02
01 01
00
RPTA7
RPTA6
RPTA5
RPTA4
RPTA3
RPTA2
RPTA1
---

Rotation parameter table address bits: Rotation parameters table address bit (RPTA18~RPTA1 )

07 07	06 06	05 05	04	03 03	02 02	01 01	00
RPTA7	RPTA6	RPTA5	RPTA4	RPTA3	RPTA2	RPTA1	---

Specify the start address of the rotation parameter table.

RPTA18 ~ RPTA16	1800BCH	Bits 2-0
RPTA15 ~ RPTA1	1800BEH	Bits 15 to 1

The RPTA 6 bit is ignored when writing data. It is fixed at 0 for rotation parameter A and 1 for rotation parameter B.

The actual start address of the rotation parameter table is calculated by the following formula. If the VRAM capacity is 4M bits, the most significant bit of the address is ignored.


(Start address of rotation parameter A)
= (Rotation parameter table address register value upper 12 bits) x 100H
+ (Rotation parameter table address register value lower 5 bits) x 4H

(Start address of rotation parameter B)
= (Rotation parameter table address register value upper 12 bits) x 100H
+ (Rotation parameter table address register value lower 5 bits) x 4H + 80H

For example, if 00170H or 00130H is specified, the start address of rotation parameter A will be 00260H and the start address of rotation parameter B will be 002E0H.

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★ HARDWARE Manual VDP2 User's Manual ★ Chapter 6 Rotating scroll screen