Bg Display - Nintendo GAME BOY Programming Manual

Game Boy Programming Manual

1.4 BG Display

Address
9800h
CHR Code (8 bits)
9FFFh
Display Priority Flag
0: Display according to OBJ display priority flag
1: Highest priority to BG
Up/Down Flip Flag
0: Normal
1: Flip up/down
Two screens of BG display can be held, Data 1 or Data 2.
Whether the BG display data are allocated to 9800h-9BFFh or to 9C00h-9FFFh is determined by
bit 3 of the LCDC register (FF40h).
Because bank switching is not available in DMG mode, Bank 1 on the right side of the figure is
not present in this mode.
Data for 32 x 32 character codes (256 x 256 dots) can be specified from 9800h or 9C00h as BG
display data. Of these, data for 20 x 18 character codes (160 x 144 dots) are displayed to the
LCD screen.
The screen can be scrolled vertically or horizontally one dot at a time by changing the values of
scroll registers SCX and SCY.
Bank 0
*
Bank 0
9800h
9C00h
9FFFh
54
Bank 1 (CGB only)
７ ６ ５ ４ ３
Unused (unusable) bit; same meaning in following pages
Bank 1 (CGB only)
BG Display Data 1
BG Display Data 2
２ １ ０
R/W
Specifies the color
palette
Specifies the character
bank
Left/Right Flip Flag
0: Normal
1: Flip left/right