<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. This is a 16-bit write-only register located at address 1800B6H. The value is cleared to 0 after power-on or reset, so be sure to set it.

KTAOF 1800B6H

-	-	-	-	-	RBKTAOS2	RBKTAOS1	RBKTAOS0
15	14	13	12	11	10	09	08

07
06
05
04
03
02
01
00

-
-
-
-
-
RAKTAOS2
RAKTAOS1
RAKTAOS0

Coefficient table address offset bit : Coefficient table address offset bit

07	06	05	04	03	02	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 added to the upper part of the coefficient table start address (KAst) read from the rotation parameter table.
The actual start address of the coefficient table varies depending on the size of the coefficient data and is calculated using the following formula. If the VRAM capacity is 4Mbits, 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) x 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) x 2H

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