DS Memory Maps Contents
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NDS9 Memory Map
  00000000h  Instruction TCM (32KB) (not moveable) (mirror-able to 1000000h)
  0xxxx000h  Data TCM        (16KB) (moveable)
  02000000h  Main Memory     (4MB)
  03000000h  Shared WRAM     (0KB, 16KB, or 32KB can be allocated to ARM9)
  04000000h  ARM9-I/O Ports
  05000000h  Standard Palettes (2KB) (Engine A BG/OBJ, Engine B BG/OBJ)
  06000000h  VRAM - Engine A, BG VRAM  (max 512KB)
  06200000h  VRAM - Engine B, BG VRAM  (max 128KB)
  06400000h  VRAM - Engine A, OBJ VRAM (max 256KB)
  06600000h  VRAM - Engine B, OBJ VRAM (max 128KB)
  06800000h  VRAM - "LCDC"-allocated (max 656KB)
  07000000h  OAM (2KB) (Engine A, Engine B)
  08000000h  GBA Slot ROM (max 32MB)
  0A000000h  GBA Slot RAM (max 64KB)
  FFFF0000h  ARM9-BIOS (32KB) (only 3K used)
The ARM9 Exception Vectors are located at FFFF0000h. The IRQ handler redirects to [DTCM+3FFCh].

NDS7 Memory Map
  00000000h  ARM7-BIOS (16KB)
  02000000h  Main Memory (4MB)
  03000000h  Shared WRAM (0KB, 16KB, or 32KB can be allocated to ARM7)
  03800000h  ARM7-WRAM (64KB)
  04000000h  ARM7-I/O Ports
  04800000h  Wireless Communications Wait State 0 (8KB RAM at 4804000h)
  04808000h  Wireless Communications Wait State 1 (I/O Ports at 4808000h)
  06000000h  VRAM allocated as Work RAM to ARM7 (max 256K)
  08000000h  GBA Slot ROM (max 32MB)
  0A000000h  GBA Slot RAM (max 64KB)
The ARM7 Exception Vectors are located at 00000000h. The IRQ handler redirects to [3FFFFFCh aka 380FFFCh].

Further Memory (not mapped to ARM9/ARM7 bus)
  3D Engine Polygon RAM (52KBx2)
  3D Engine Vertex RAM (72KBx2)
  Firmware (256KB) (built-in serial flash memory)
  GBA-BIOS (16KB) (not used in NDS mode)
  NDS Slot ROM (serial 8bit-bus, max 4GB with default protocol)
  NDS Slot FLASH/EEPROM/FRAM (serial 1bit-bus)

Shared-RAM
Even though Shared WRAM begins at 3000000h, programs are commonly using mirrors at 37F8000h (both ARM9 and ARM7). At the ARM7-side, this allows to use 32K Shared WRAM and 64K ARM7-WRAM as a continous 96K RAM block.

Undefined I/O Ports
On the NDS (at the ARM9-side at least) undefined I/O ports are always zero.

Undefined Memory Regions
16MB blocks that do not contain any defined memory regions (or that contain only mapped TCM regions) are typically completely undefined.
16MB blocks that do contain valid memory regions are typically containing mirrors of that memory in the unused upper part of the 16MB area (only exceptions are TCM and BIOS which are not mirrored).


extracted from no$gba v3.05 - homepage - patreon - whole doc htm/txt - copyright 2021 martin korth (nocash)