Chapter 13 Color offset function

The color offset function is a function that changes the screen color without changing the color RAM data by adding an offset value when outputting the color data of sprites and each scroll screen, and can be used for fade in, fade out, etc. Masu.

■13.1 Color offset specification

Two color offset values, Color Offset A and Color Offset B, can be set for each RGB, and you can specify which of these two to use for each screen. The color offset value is 9-bit data corresponding to each RGB, and if the color data resulting from adding each RGB is smaller than 00H, that color data is set to 00H and becomes larger than FFH. In all such cases, FFH is used.

Since the processing of the color offset function is performed after the processing of the color calculation function, the color offset value is added to the color data resulting from the color calculation. Also, since the color operation result screen is considered to be the top image screen, the color offset enable register is specified using the top image screen bits.

Color offset data is shown in Figure 13.1.

Figure 13.1 Color offset data

   7  6  5  4  3  2  1  0
  ┌──┬──┬──┬──┬──┬──┬──┬──┐
  │   Color data 8 bits   │
  └──┴──┴──┴──┴──┴──┴──┴──┘
              　
              +　
              　
   8  7  6  5  4  3  2  1  0　
  ┌──┬──┬──┬──┬──┬──┬──┬──┬──┐
  │  │   Color data 8 bits   │
  └──┴──┴──┴──┴──┴──┴──┴──┴──┘
 Sign　
              ↓　
  　
   7  6  5  4  3  2   1  0　
  ┌──┬──┬──┬──┬──┬──┬──┬──┐
  │Output color data 8 bit│
  └──┴──┴──┴──┴──┴──┴──┴──┘

●Color offset enable register

The color offset enable register specifies whether to use the color offset function for each screen. This is a 16-bit write-only register located at address 180110H. The value is cleared to 0 after power-on or reset, so be sure to set it.

CLOFEN 180110H

15	14	13	12	11	10	09	08
-	-	-	-	-	-	-	-

07	06	05	04	03	02	01	00
-	SPCOEN	BKCOEN	R0COEN	N3COEN	N2COEN	N1COEN	N0COEN

Color offset enable bit : Color offset enable bit

(N0COEN, N1COEN, N2COEN, N3COEN, R0COEN, BKCOEN, SPCOEN)
Specify whether to use the color offset function.

N0COEN	180110H	bit 0	For NBG0 (or for RBG1)
N1COEN	180110H	bit 1	For NBG1 (or for EXBG)
N2COEN	180110H	bit 2	For NBG2
N3COEN	180110H	bit 3	For NBG3
R0COEN	180110H	bit 4	For RBG0
BKCOEN	180110H	bit 5	For BACK
SPCOEN	180110H	bit 6	for sprites

xxCOEN	process
0	Do not use color offset function
1	Use the color offset function

[Note] xx in the bit name is N0, N1, N2, N3, R0, BK, or SP.

If you are using the color calculation function, specify it using the color offset enable bit on the screen on the top image side.

●Color offset select register

The color offset select register specifies the color offset register to use for each screen. This is a 16-bit write-only register located at address 180112H. The value is cleared to 0 after power-on or reset, so be sure to set it.

CLOFSL 180112H

15	14	13	12	11	10	09	08
-	-	-	-	-	-	-	-

07	06	05	04	03	02	01	00
-	SPCOSL	BKCOSL	R0COSL	N3COSL	N2COSL	N1COSL	N0COSL

Color offset select bit : Color offset select bit

(N0COSL, N1COSL, N2COSL, N3COSL, R0COSL, BKCOSL, SPCOSL)
Specify the color offset register to use when using the color offset function.

N0COSL	180112H	bit 0	For NBG0 (or for RBG1)
N1COSL	180112H	bit 1	For NBG1 (or for EXBG)
N2COSL	180112H	bit 2	For NBG2
N3COSL	180112H	bit 3	For NBG3
R0COSL	180112H	bit 4	For RBG0
BKCOSL	180112H	bit 5	For BACK
SPCOSL	180112H	bit 6	for sprites

xxCOSL	process
0	Use color offset A value
1	Use color offset B value

[Note] xx in the bit name is N0, N1, N2, N3, R0, BK, or SP.

If you are using the color calculation function, specify it using the color offset select bit on the top image side screen.

●Color offset register

The color offset register specifies the RGB values of the color offset value. This is a 16-bit write-only register located at addresses 180114H to 18011EH. The value is cleared to 0 after power-on or reset, so be sure to set it.

COAR 180114H

15	14	13	12	11	10	09	08
-	-	-	-	-	-	-	COARD8

07	06	05	04	03	02	01	00
COARD7	COARD6	COARD5	COARD4	COARD3	COARD2	COARD1	COARD0

COAG 180116H

15	14	13	12	11	10	09	08
-	-	-	-	-	-	-	COAGR8

07	06	05	04	03	02	01	00
COAGR7	COAGR6	COAGR5	COAGR4	COAGR3	COAGR2	COAGR1	COAGR0

COAB 180118H

15	14	13	12	11	10	09	08
-	-	-	-	-	-	-	COABL8

07	06	05	04	03	02	01	00
COABL7	COABL6	COABL5	COABL4	COABL3	COABL2	COABL1	COABL0

COBR 18011AH

15	14	13	12	11	10	09	08
-	-	-	-	-	-	-	COBRD8

07	06	05	04	03	02	01	00
COBRD7	COBRD6	COBRD5	COBRD4	COBRD3	COBRD2	COBRD1	COBRD0

COBG 18011CH

15	14	13	12	11	10	09	08
-	-	-	-	-	-	-	COBGR8

07	06	05	04	03	02	01	00
COBGR7	COBGR6	COBGR5	COBGR4	COBGR3	COBGR2	COBGR1	COBGR0

COBB 18011EH

15	14	13	12	11	10	09	08
-	-	-	-	-	-	-	COBBL8

07	06	05	04	03	02	01	00
COBBL7	COBBL6	COBBL5	COBBL4	COBBL3	COBBL2	COBBL1	COBBL0

Color offset data bit

(COARD8〜COARD0, COAGR8〜COAGR0, COABL8〜COABL0, COBRD8〜COBRD0, COBGR8〜COBGR0, COBBL8〜COBBL0)
Set the RGB values for color offset A and color offset B. Set negative numbers using two's complement.

COARD8〜COARD0	180114H	bits 8-0	For RED data with color offset A
COAGR8～COAGR0	180116H	bits 8-0	For GREEN data of color offset A
COABL8〜COABL0	180118H	bits 8-0	For BLUE data of color offset A
COBRD8～COBRD0	18011AH	bits 8-0	For RED data with color offset B
COBGR8～COBGR0	18011CH	bits 8-0	For GREEN data of color offset B
COBBL8〜COBBL0	18011EH	bits 8-0	For BLUE data of color offset B