Nintendo DMG-01 Manual - Page 22

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2.7.3. Low-Power Mode Game BoyTM CPU Manual ; **** V-Blank Interrupt Routine **** Vblnk: push af push bc push de push hl call SpriteDma ; Do sprite updates ld a,1 ld (VblnkFlag),a pop hl pop de pop bc pop af reti 2.8. Video 2.8.1. Tiles The main GameBoy screen buffer (background) consists of 256x256 pixels or 32x32 tiles (8x8 pixels each). Only 160x144 pixels can be displayed on the screen. Registers SCROLLX and SCROLLY hold the coordinates of background to be displayed in the left upper corner of the screen. Background wraps around the screen (i.e. when part of it goes off the screen, it appears on the opposite side.) An area of VRAM known as Background Tile Map contains the numbers of tiles to be displayed. It is organized as 32 rows of 32 bytes each. Each byte contains a Page 22 V 1.01

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2.7.3. Low-Power Mode
Game Boy
TM
CPU Manual
; **** V-Blank Interrupt Routine ****
Vblnk:
push
af
push
bc
push
de
push
hl
call
SpriteDma
; Do sprite updates
ld
a,1
ld
(VblnkFlag),a
pop
hl
pop
de
pop
bc
pop
af
reti
2.8.
Video
2.8.1.
Tiles
The main GameBoy screen buffer (background) consists
of 256x256 pixels or 32x32 tiles (8x8 pixels each).
Only 160x144 pixels can be displayed on the screen.
Registers SCROLLX and SCROLLY hold the coordinates of
background to be displayed in the left upper corner of
the screen. Background wraps around the screen (i.e.
when part of it goes off the screen, it appears on the
opposite side.)
An area of VRAM known as Background Tile Map contains
the numbers of tiles to be displayed. It is organized
as 32 rows of 32 bytes each. Each byte contains a
Page 22
V 1.01