IO Registers and CPU interupts

GBA I/O Map

LCD I/O Registers 4000000h 2 R/W DISPCNT LCD Control 4000002h 2 R/W - Undocumented - Green Swap 4000004h 2 R/W DISPSTAT General LCD Status (STAT,LYC) 4000006h 2 R VCOUNT Vertical Counter (LY) 4000008h 2 R/W BG0CNT BG0 Control 400000Ah 2 R/W BG1CNT BG1 Control 400000Ch 2 R/W BG2CNT BG2 Control 400000Eh 2 R/W BG3CNT BG3 Control 4000010h 2 W BG0HOFS BG0 X-Offset 4000012h 2 W BG0VOFS BG0 Y-Offset 4000014h 2 W BG1HOFS BG1 X-Offset 4000016h 2 W BG1VOFS BG1 Y-Offset 4000018h 2 W BG2HOFS BG2 X-Offset 400001Ah 2 W BG2VOFS BG2 Y-Offset 400001Ch 2 W BG3HOFS BG3 X-Offset 400001Eh 2 W BG3VOFS BG3 Y-Offset 4000020h 2 W BG2PA BG2 Rotation/Scaling Parameter A (dx) 4000022h 2 W BG2PB BG2 Rotation/Scaling Parameter B (dmx) 4000024h 2 W BG2PC BG2 Rotation/Scaling Parameter C (dy) 4000026h 2 W BG2PD BG2 Rotation/Scaling Parameter D (dmy) 4000028h 4 W BG2X BG2 Reference Point X-Coordinate 400002Ch 4 W BG2Y BG2 Reference Point Y-Coordinate 4000030h 2 W BG3PA BG3 Rotation/Scaling Parameter A (dx) 4000032h 2 W BG3PB BG3 Rotation/Scaling Parameter B (dmx) 4000034h 2 W BG3PC BG3 Rotation/Scaling Parameter C (dy) 4000036h 2 W BG3PD BG3 Rotation/Scaling Parameter D (dmy) 4000038h 4 W BG3X BG3 Reference Point X-Coordinate 400003Ch 4 W BG3Y BG3 Reference Point Y-Coordinate 4000040h 2 W WIN0H Window 0 Horizontal Dimensions 4000042h 2 W WIN1H Window 1 Horizontal Dimensions 4000044h 2 W WIN0V Window 0 Vertical Dimensions 4000046h 2 W WIN1V Window 1 Vertical Dimensions 4000048h 2 R/W WININ Inside of Window 0 and 1 400004Ah 2 R/W WINOUT Inside of OBJ Window & Outside of Windows 400004Ch 2 W MOSAIC Mosaic Size 400004Eh - - Not used 4000050h 2 R/W BLDCNT Color Special Effects Selection 4000052h 2 R/W BLDALPHA Alpha Blending Coefficients 4000054h 2 W BLDY Brightness (Fade-In/Out) Coefficient 4000056h - - Not used Sound Registers 4000060h 2 R/W SOUND1CNT_L Channel 1 Sweep register (NR10) 4000062h 2 R/W SOUND1CNT_H Channel 1 Duty/Length/Envelope (NR11, NR12) 4000064h 2 R/W SOUND1CNT_X Channel 1 Frequency/Control (NR13, NR14) 4000066h - - Not used 4000068h 2 R/W SOUND2CNT_L Channel 2 Duty/Length/Envelope (NR21, NR22) 400006Ah - - Not used 400006Ch 2 R/W SOUND2CNT_H Channel 2 Frequency/Control (NR23, NR24) 400006Eh - - Not used 4000070h 2 R/W SOUND3CNT_L Channel 3 Stop/Wave RAM select (NR30) 4000072h 2 R/W SOUND3CNT_H Channel 3 Length/Volume (NR31, NR32) 4000074h 2 R/W SOUND3CNT_X Channel 3 Frequency/Control (NR33, NR34) 4000076h - - Not used 4000078h 2 R/W SOUND4CNT_L Channel 4 Length/Envelope (NR41, NR42) 400007Ah - - Not used 400007Ch 2 R/W SOUND4CNT_H Channel 4 Frequency/Control (NR43, NR44) 400007Eh - - Not used 4000080h 2 R/W SOUNDCNT_L Control Stereo/Volume/Enable (NR50, NR51) 4000082h 2 R/W SOUNDCNT_H Control Mixing/DMA Control 4000084h 2 R/W SOUNDCNT_X Control Sound on/off (NR52) 4000086h - - Not used 4000088h 2 BIOS SOUNDBIAS Sound PWM Control 400008Ah .. - - Not used 4000090h 2x10h R/W WAVE_RAM Channel 3 Wave Pattern RAM (2 banks!!) 40000A0h 4 W FIFO_A Channel A FIFO, Data 0-3 40000A4h 4 W FIFO_B Channel B FIFO, Data 0-3 40000A8h - - Not used DMA Transfer Channels 40000B0h 4 W DMA0SAD DMA 0 Source Address 40000B4h 4 W DMA0DAD DMA 0 Destination Address 40000B8h 2 W DMA0CNT_L DMA 0 Word Count 40000BAh 2 R/W DMA0CNT_H DMA 0 Control 40000BCh 4 W DMA1SAD DMA 1 Source Address 40000C0h 4 W DMA1DAD DMA 1 Destination Address 40000C4h 2 W DMA1CNT_L DMA 1 Word Count 40000C6h 2 R/W DMA1CNT_H DMA 1 Control 40000C8h 4 W DMA2SAD DMA 2 Source Address 40000CCh 4 W DMA2DAD DMA 2 Destination Address 40000D0h 2 W DMA2CNT_L DMA 2 Word Count 40000D2h 2 R/W DMA2CNT_H DMA 2 Control 40000D4h 4 W DMA3SAD DMA 3 Source Address 40000D8h 4 W DMA3DAD DMA 3 Destination Address 40000DCh 2 W DMA3CNT_L DMA 3 Word Count 40000DEh 2 R/W DMA3CNT_H DMA 3 Control 40000E0h - - Not used Timer Registers 4000100h 2 R/W TM0CNT_L Timer 0 Counter/Reload 4000102h 2 R/W TM0CNT_H Timer 0 Control 4000104h 2 R/W TM1CNT_L Timer 1 Counter/Reload 4000106h 2 R/W TM1CNT_H Timer 1 Control 4000108h 2 R/W TM2CNT_L Timer 2 Counter/Reload 400010Ah 2 R/W TM2CNT_H Timer 2 Control 400010Ch 2 R/W TM3CNT_L Timer 3 Counter/Reload 400010Eh 2 R/W TM3CNT_H Timer 3 Control 4000110h - - Not used Serial Communication (1) 4000120h 4 R/W SIODATA32 SIO Data (Normal-32bit Mode; shared with below) 4000120h 2 R/W SIOMULTI0 SIO Data 0 (Parent) (Multi-Player Mode) 4000122h 2 R/W SIOMULTI1 SIO Data 1 (1st Child) (Multi-Player Mode) 4000124h 2 R/W SIOMULTI2 SIO Data 2 (2nd Child) (Multi-Player Mode) 4000126h 2 R/W SIOMULTI3 SIO Data 3 (3rd Child) (Multi-Player Mode) 4000128h 2 R/W SIOCNT SIO Control Register 400012Ah 2 R/W SIOMLT_SEND SIO Data (Local of MultiPlayer; shared below) 400012Ah 2 R/W SIODATA8 SIO Data (Normal-8bit and UART Mode) 400012Ch - - Not used Keypad Input 4000130h 2 R KEYINPUT Key Status 4000132h 2 R/W KEYCNT Key Interrupt Control Serial Communication (2) 4000134h 2 R/W RCNT SIO Mode Select/General Purpose Data 4000136h - - IR Ancient - Infrared Register (Prototypes only) 4000138h - - Not used 4000140h 2 R/W JOYCNT SIO JOY Bus Control 4000142h - - Not used 4000150h 4 R/W JOY_RECV SIO JOY Bus Receive Data 4000154h 4 R/W JOY_TRANS SIO JOY Bus Transmit Data 4000158h 2 R/? JOYSTAT SIO JOY Bus Receive Status 400015Ah - - Not used Interrupt, Waitstate, and Power-Down Control 4000200h 2 R/W IE Interrupt Enable Register 4000202h 2 R/W IF Interrupt Request Flags / IRQ Acknowledge 4000204h 2 R/W WAITCNT Game Pak Waitstate Control 4000206h - - Not used 4000208h 2 R/W IME Interrupt Master Enable Register 400020Ah - - Not used 4000300h 1 R/W POSTFLG Undocumented - Post Boot Flag 4000301h 1 W HALTCNT Undocumented - Power Down Control 4000302h - - Not used 4000410h ? ? ? Undocumented - Purpose Unknown / Bug ??? 0FFh 4000411h - - Not used 4000800h 4 R/W ? Undocumented - Internal Memory Control (R/W) 4000804h - - Not used 4xx0800h 4 R/W ? Mirrors of 4000800h (repeated each 64K)