<50/86> VDP2 User's Manual / 6.4 Coefficient Table Control-4

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

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VDP2 User's Manual / Chapter 6 Rotating Scroll Screen

● Coefficient table address offset register

The coefficient table address offset register specifies the start address offset value of the coefficient table. A write-only 16-bit register located at address 1800B6H. After turning on the power or resetting, the value will be cleared to 0, so be sure to set it.

KTAOF 1800B6H

---	---	---	---	---	RBKTAOS2	RBKTAOS1	RBKTAOS0
15	14	13	12	11	Ten	09 09	08 08

07 07
06 06
05 05
04
03 03
02 02
01 01
00
---
---
---
---
---
RAKTAOS2
RAKTAOS1
RAKTAOS0

Coefficient table address offset bits: Coefficient table address offset bit

07 07	06 06	05 05	04	03 03	02 02	01 01	00
---	---	---	---	---	RAKTAOS2	RAKTAOS1	RAKTAOS0

(RAKTAOS2 ~ RAKTAOS0, RBKTAOS2 ~ RBKTAOS0)
Specify the offset value of the start address of the coefficient table stored in the rotation parameter table.

RAKTAOS2 ~ RAKTAOS0	1800B6H	Bits 2-0	For rotation parameter A
RBKTAOS2 ~ RBKTAOS0	1800B6H	Bits 10-8	For rotation parameter B

These bits are prepended to the coefficient table start address (KAst) read from the rotation parameter table.
The actual start address of the coefficient table depends on the size of the coefficient data and is calculated by the following formula. If the VRAM capacity is 4M bits, the most significant bit of the address is ignored.

☆ When the coefficient data size is 2 words ☆

(Coefficient table start address)
= (Lower 2 bits of coefficient table address offset register value)
× 40000H
＋ (KAst integer part 16 bits) × 4H


☆ When the coefficient data size is 1 word ☆

(Coefficient table start address)
= (Coefficient table address offset register value 3 bits)
× 20000H
＋ (KAst integer part 16 bits) × 2H

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