Chapter 5 Normal scroll screen

There are four normal scroll screens, NBG0 to NBG3, all of which allow you to scroll the entire screen up, down, left, and right. NBG0 and NBG1 can be further scaled, line scrolled, and vertical cell scrolled.

■ 5.1 Screen scroll function

The normal scroll screen can perform dot scrolling up, down, left, and right on a face-by-face basis for all four screens, and the screen scroll value specifies the coordinates of the dots displayed in the upper left corner of the TV screen in the screen scroll value register. The screen scroll value is valid up to the value that does not exceed the display area set for each screen, and if a value that exceeds is specified, the screen of the display area is repeated. Also, the decimal part of the screen scroll values for NBG0 and NBG1 is used only for coordinate calculation and is truncated at the final display coordinate value. Horizontal screen scroll value Integer part bit and horizontal screen scroll value Specify the horizontal (X) direction coordinates with the fraction part bit, and vertical screen scroll value integer part bit and vertical screen scroll value with the fraction part bit vertical (Y) ) Specify the coordinates of the direction.
A decimal bit is added immediately below the integer bit. The bit configuration is shown in Figure 5.1.

Figure 5.1 Configuration of screen scroll value bits

● Horizontal and vertical screen scroll value registers (NBG0, NBG1)　
Bit　
31 26 16 15 8 7 0　
┌─┬─┬─┬─┬─┰─┬─┬─┬─┬─┬─┬─┬─┬─┬─┬─┰─┬─┬─┬─┬─┬─┬─┬─ ┬─┬─┬─┬─┬─┬─┐
│ − │ − │ − │ − │ − ┃ │ │ │ │ │ │ │ │ │ │ │ │ ┃ │ │ │ │ │ │ │ ┃ − │ − │ − │ −
└─┴─┴─┴─┴─┸─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┸─┴─┴─┴─┴─┴─┴─ ┴─┴─┴─┴─┴─┴─┘
└───────────────────┘└───────────┘　
Integer part Decimal part　
　
● Horizontal and vertical screen scroll value registers (NBG2, NBG3)　
Bit　
15 100　
┌─┬─┬─┬─┬─┰─┬─┬─┬─┬─┬─┬─┬─┬─┬─┬─┐　
│ − │ − │ − │ − │ − ┃ │ │ │ │ │ │ │ │ │ │ │ │ │　
└─┴─┴─┴─┴─┸─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┘　
└───────────────────┘　
Integer part　

● Screen scroll value register

The screen scroll value register specifies the screen scroll value. It is a write-only 16-bit or 32-bit register located at addresses 180070H to 180076H, 180080H to 180086H, and 180090H to 180096H. After turning on the power or resetting, the value will be cleared to 0, so be sure to set it.

SCXIN0 180070H

15	14	13	12	11	Ten	09 09	08 08
---	---	---	---	---	N0SCXI10	N0SCXI9	N0SCXI8

07 07	06 06	05 05	04	03 03	02 02	01 01	00
N0SCXI7	N0SCXI6	N0SCXI5	N0SCXI4	N0SCXI3	N0SCXI2	N0SCXI1	N0SCXI0

SCXDN0 180072H

15	14	13	12	11	Ten	09 09	08 08
N0SCXD1	N0SCXD2	N0SCXD3	N0SCXD4	N0SCXD5	N0SCXD6	N0SCXD7	N0SCXD8

07 07	06 06	05 05	04	03 03	02 02	01 01	00
---	---	---	---	---	---	---	---

SCYIN0 180074H

15	14	13	12	11	Ten	09 09	08 08
---	---	---	---	---	N0SCYI10	N0SCYI9	N0SCYI8

07 07	06 06	05 05	04	03 03	02 02	01 01	00
N0SCYI7	N0SCYI6	N0SCYI5	N0SCYI4	N0SCYI3	N0SCYI2	N0SCYI1	N0SCYI0

SCYDN0 180076H

15	14	13	12	11	Ten	09 09	08 08
N0SCYD1	N0SCYD2	N0SCYD3	N0SCYD4	N0SCYD5	N0SCYD6	N0SCYD7	N0SCYD8

07 07	06 06	05 05	04	03 03	02 02	01 01	00
---	---	---	---	---	---	---	---

SCXIN1 180080H

15	14	13	12	11	Ten	09 09	08 08
---	---	---	---	---	N1SCXI10	N1SCXI9	N1SCXI8

07 07	06 06	05 05	04	03 03	02 02	01 01	00
N1SCXI7	N1SCXI6	N1SCXI5	N1SCXI4	N1SCXI3	N1SCXI2	N1SCXI1	N1SCXI0

SCXDN1 180082H

15	14	13	12	11	Ten	09 09	08 08
N1SCXD1	N1SCXD2	N1SCXD3	N1SCXD4	N1SCXD5	N1SCXD6	N1SCXD7	N1SCXD8

07 07	06 06	05 05	04	03 03	02 02	01 01	00
---	---	---	---	---	---	---	---

SCYIN1 180084H

15	14	13	12	11	Ten	09 09	08 08
---	---	---	---	---	N1SCYI10	N1SCYI9	N1SCYI8

07 07	06 06	05 05	04	03 03	02 02	01 01	00
N1SCYI7	N1SCYI6	N1SCYI5	N1SCYI4	N1SCYI3	N1SCYI2	N1SCYI1	N1SCYI0

SCYDN1 180086H

15	14	13	12	11	Ten	09 09	08 08
N1SCYD1	N1SCYD2	N1SCYD3	N1SCYD4	N1SCYD5	N1SCYD6	N1SCYD7	N1SCYD8

07 07	06 06	05 05	04	03 03	02 02	01 01	00
---	---	---	---	---	---	---	---

SCXN2 180090H

15	14	13	12	11	Ten	09 09	08 08
---	---	---	---	---	N2SCX10	N2SCX9	N2SCX8

07 07	06 06	05 05	04	03 03	02 02	01 01	00
N2SCX7	N2SCX6	N2SCX5	N2SCX4	N2SCX3	N2SCX2	N2SCX1	N2SCX0

SCYN2 180092H

15	14	13	12	11	Ten	09 09	08 08
---	---	---	---	---	N2SCY10	N2SCY9	N2SCY8

07 07	06 06	05 05	04	03 03	02 02	01 01	00
N2SCY7	N2SCY6	N2SCY5	N2SCY4	N2SCY3	N2SCY2	N2SCY1	N2SCY0

SCXN3 180094H

15	14	13	12	11	Ten	09 09	08 08
---	---	---	---	---	N3SCX10	N3SCX9	N3SCX8

07 07	06 06	05 05	04	03 03	02 02	01 01	00
N3SCX7	N3SCX6	N3SCX5	N3SCX4	N3SCX3	N3SCX2	N3SCX1	N3SCX0

SCYN3 180096H

15	14	13	12	11	Ten	09 09	08 08
---	---	---	---	---	N3SCY10	N3SCY9	N3SCY8

07 07	06 06	05 05	04	03 03	02 02	01 01	00
N3SCY7	N3SCY6	N3SCY5	N3SCY4	N3SCY3	N3SCY2	N3SCY1	N3SCY0

　　　　　　　　

Screen scroll value bit : Scroll bit

(N0SCXI10~N0SCXI0, N0SCXD1~N0SCXD8, N0SCYI10~N0SCYI0, N0SCYD1~N0SCYD8, N1SCXI10~N1SCXI0, N1SCXD1~N1SCXD8, N1SCYI10~N1SCYI0, N1SCYD1~N1SCYD8, N2SCX10~N2SCX0, N2SCY10~N2SCY0, N3SCX10~N3SCX0, N3SCY10~N3SCY0) each Specify the horizontal and vertical screen scroll values (coordinate values) of the normal scroll screen.

N0SCXI10 to N0SCXI0	180070H	Bits 10-0	NBG0 Horizontal direction (integer part)
N0SCXD1 to N0SCXD8	180072H	Bits 15-8	NBG0 for horizontal direction (decimal part)
N0SCYI10 to N0SCYI0	180074H	Bits 10-0	NBG0 for vertical direction (integer part)
N0SCYD1 to N0SCYD8	180076H	Bits 15-8	NBG0 for vertical direction (decimal part)
N1SCXI10 to N1SCXI0	180080H	Bits 10-0	NBG1 for horizontal direction (integer part)
N1SCXD1 to N1SCXD8	180082H	Bits 15-8	NBG1 for horizontal direction (decimal part)
N1SCYI10 to N1SCYI0	180084H	Bits 10-0	NBG1 for vertical direction (integer part)
N1SCYD1 to N1SCYD8	180086H	Bits 15-8	NBG1 for vertical direction (decimal part)
N2SCX10 to N2SCX0	180090H	Bits 10-0	NBG2 for horizontal direction
N2SCY10 to N2SCY0	180092H	Bits 10-0	NBG2 for vertical direction
N3SCX10 to N3SCX0	180094H	Bits 10-0	NBG3 for horizontal direction
N3SCY10 to N3SCY0	180096H	Bits 10-0	NBG3 for vertical direction

The value of the screen scroll value register is valid up to the range that does not exceed the display area of each screen. If the display area is exceeded, the display area screen will be displayed repeatedly.
Specify all screen scroll values as positive values.
You can also change the scroll value from the middle of the screen by changing the value during the horizontal blanking interval.