AGB Programming Manual
System Configuration
©1999 - 2001 Nintendo of America Inc.
17
D.C.N. AGB-06-0001-002B4
2.3 Memory Configuration and Access Width
DMA
CPU
Memory Type
Bus
Width
Read
Width
Write
Width
Read
Width
Write
Width
OAM
32
16/32
16/32
16/32
16/32
Palette RAM
16
16/32
16/32
16/32
16/32
VRAM
16
16/32
16/32
16/32
16/32
CPU Internal Working RAM
32
16/32
16/32
8/16/32
8/16/32
CPU External Working RAM
16
16/32
16/32
8/16/32
8/16/32
Internal registers
32
16/32
16/32
8/16/32
8/16/32
Game Pak ROM
(Mask ROM, Flash Memory)
16
16/32
16/32
8/16/32
16/32
Game Pak RAM
(SRAM, Flash Memory)
8
--
--
8
8
Good execution efficiency is obtained when programs that operate from the Game Pak
use 16-bit instructions (16-bit compiler), and those that operate from CPU Internal
Working RAM use 32-bit instructions (32-bit compiler).
2.4 Little-Endian
In the AGB CPU, memory addresses are allocated in 8-bit increments, and little-
endian format is used in implementing the 8-, 16-, and 32-bit access widths.
A
B
C
D
0000h
0001h
0002h
0003h
Memory
Register
A
B
C
D
d31
d24
d23
d16 d15
d08
d07
d00