GBA file format: I/O registers

The registers live at 0x04000000 and up; each address below is that base plus the offset. The names are GBATEK’s (“GBA I/O Map”), checked against the register table of the gbajs emulator. The viewer puts a name on a branch target or a referenced address when it is one of these. The meaning of each bit is not described here.

Display

Address	Name	Size	Meaning
`0x04000000`	DISPCNT	2	LCD control
`0x04000004`	DISPSTAT	2	General LCD status
`0x04000006`	VCOUNT	2	Vertical counter (the line being drawn)
`0x04000008`	BG0CNT	2	Background 0 control
`0x0400000A`	BG1CNT	2	Background 1 control
`0x0400000C`	BG2CNT	2	Background 2 control
`0x0400000E`	BG3CNT	2	Background 3 control
`0x04000010`	BG0HOFS	2	Background 0 horizontal offset
`0x04000012`	BG0VOFS	2	Background 0 vertical offset
`0x04000014`	BG1HOFS	2	Background 1 horizontal offset
`0x04000016`	BG1VOFS	2	Background 1 vertical offset
`0x04000018`	BG2HOFS	2	Background 2 horizontal offset
`0x0400001A`	BG2VOFS	2	Background 2 vertical offset
`0x0400001C`	BG3HOFS	2	Background 3 horizontal offset
`0x0400001E`	BG3VOFS	2	Background 3 vertical offset
`0x04000020`	BG2PA	2	Background 2 rotation and scaling parameter A
`0x04000022`	BG2PB	2	Background 2 parameter B
`0x04000024`	BG2PC	2	Background 2 parameter C
`0x04000026`	BG2PD	2	Background 2 parameter D
`0x04000028`	BG2X	4	Background 2 reference point X
`0x0400002C`	BG2Y	4	Background 2 reference point Y
`0x04000030`	BG3PA	2	Background 3 rotation and scaling parameter A
`0x04000032`	BG3PB	2	Background 3 parameter B
`0x04000034`	BG3PC	2	Background 3 parameter C
`0x04000036`	BG3PD	2	Background 3 parameter D
`0x04000038`	BG3X	4	Background 3 reference point X
`0x0400003C`	BG3Y	4	Background 3 reference point Y
`0x04000040`	WIN0H	2	Window 0 horizontal dimensions
`0x04000042`	WIN1H	2	Window 1 horizontal dimensions
`0x04000044`	WIN0V	2	Window 0 vertical dimensions
`0x04000046`	WIN1V	2	Window 1 vertical dimensions
`0x04000048`	WININ	2	Inside of window 0 and 1
`0x0400004A`	WINOUT	2	Inside of the object window and outside of windows
`0x0400004C`	MOSAIC	2	Mosaic size
`0x04000050`	BLDCNT	2	Colour special effects selection
`0x04000052`	BLDALPHA	2	Alpha blending coefficients
`0x04000054`	BLDY	2	Brightness (fade in/out) coefficient

Sound

Address	Name	Size	Meaning
`0x04000060`	SOUND1CNT_L	2	Channel 1 sweep
`0x04000062`	SOUND1CNT_H	2	Channel 1 duty, length, envelope
`0x04000064`	SOUND1CNT_X	2	Channel 1 frequency, control
`0x04000068`	SOUND2CNT_L	2	Channel 2 duty, length, envelope
`0x0400006C`	SOUND2CNT_H	2	Channel 2 frequency, control
`0x04000070`	SOUND3CNT_L	2	Channel 3 stop and wave RAM select
`0x04000072`	SOUND3CNT_H	2	Channel 3 length, volume
`0x04000074`	SOUND3CNT_X	2	Channel 3 frequency, control
`0x04000078`	SOUND4CNT_L	2	Channel 4 length, envelope
`0x0400007C`	SOUND4CNT_H	2	Channel 4 frequency, control
`0x04000080`	SOUNDCNT_L	2	Control of channels 1-4 (volume, enables)
`0x04000082`	SOUNDCNT_H	2	Control of direct sound A and B and mixing
`0x04000084`	SOUNDCNT_X	2	Sound on/off
`0x04000088`	SOUNDBIAS	2	PWM control and bias
`0x04000090`	WAVE_RAM	16	Channel 3 wave pattern RAM (16 bytes)
`0x040000A0`	FIFO_A	4	Direct sound channel A FIFO
`0x040000A4`	FIFO_B	4	Direct sound channel B FIFO

DMA

Address	Name	Size	Meaning
`0x040000B0`	DMA0SAD	4	DMA 0 source address
`0x040000B4`	DMA0DAD	4	DMA 0 destination address
`0x040000B8`	DMA0CNT_L	2	DMA 0 word count
`0x040000BA`	DMA0CNT_H	2	DMA 0 control
`0x040000BC`	DMA1SAD	4	DMA 1 source address
`0x040000C0`	DMA1DAD	4	DMA 1 destination address
`0x040000C4`	DMA1CNT_L	2	DMA 1 word count
`0x040000C6`	DMA1CNT_H	2	DMA 1 control
`0x040000C8`	DMA2SAD	4	DMA 2 source address
`0x040000CC`	DMA2DAD	4	DMA 2 destination address
`0x040000D0`	DMA2CNT_L	2	DMA 2 word count
`0x040000D2`	DMA2CNT_H	2	DMA 2 control
`0x040000D4`	DMA3SAD	4	DMA 3 source address
`0x040000D8`	DMA3DAD	4	DMA 3 destination address
`0x040000DC`	DMA3CNT_L	2	DMA 3 word count
`0x040000DE`	DMA3CNT_H	2	DMA 3 control

Timers

Address	Name	Size	Meaning
`0x04000100`	TM0CNT_L	2	Timer 0 counter and reload
`0x04000102`	TM0CNT_H	2	Timer 0 control
`0x04000104`	TM1CNT_L	2	Timer 1 counter and reload
`0x04000106`	TM1CNT_H	2	Timer 1 control
`0x04000108`	TM2CNT_L	2	Timer 2 counter and reload
`0x0400010A`	TM2CNT_H	2	Timer 2 control
`0x0400010C`	TM3CNT_L	2	Timer 3 counter and reload
`0x0400010E`	TM3CNT_H	2	Timer 3 control

Serial, keypad and interrupts

Address	Name	Size	Meaning
`0x04000120`	SIODATA32	4	Serial data (normal mode, 32-bit); also SIOMULTI0 and SIOMULTI1
`0x04000122`	SIOMULTI1	2	Serial data 1 (multi-player mode)
`0x04000124`	SIOMULTI2	2	Serial data 2 (multi-player mode)
`0x04000126`	SIOMULTI3	2	Serial data 3 (multi-player mode)
`0x04000128`	SIOCNT	2	Serial control
`0x0400012A`	SIOMLT_SEND	2	Serial send data (multi-player); also SIODATA8
`0x04000130`	KEYINPUT	2	Key status (0 = pressed)
`0x04000132`	KEYCNT	2	Key interrupt control
`0x04000134`	RCNT	2	Serial mode selection (R)
`0x04000140`	JOYCNT	2	Joy bus control
`0x04000150`	JOY_RECV	4	Joy bus receive data
`0x04000154`	JOY_TRANS	4	Joy bus transmit data
`0x04000158`	JOYSTAT	2	Joy bus receive status
`0x04000200`	IE	2	Interrupt enable
`0x04000202`	IF	2	Interrupt request flags, write 1 to acknowledge
`0x04000204`	WAITCNT	2	Game Pak wait-state control
`0x04000208`	IME	2	Interrupt master enable
`0x04000300`	POSTFLG	1	Post boot flag
`0x04000301`	HALTCNT	1	Power-down control

.GBA File Format – I/O registers

Display

Sound

DMA

Timers

Serial, keypad and interrupts