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Interrupt Operation, 15.2.1 Normal Interrupt, In Monitor ROM, save each register R0~R3, R12

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AGB Programming Manual Interrupt Control 15.2 Interrupt Operation The user can arbitrarily define the Interrupt Processing Routine, but as a general rule, the Monitor ROM handles this processing. For further details on each register, please refer to "ARM7TDMI Data Sheet". 15.2.1 Normal Interrupt 1) If an interrupt occurs, the CPU enters IRQ mode and control shifts to the Monitor ROM. In Monitor ROM, save each register (R0~R3, R12, LR_irq (former PC)) to the Interrupt Stack. The total is 6 words. Next, call the user interrupt processing set up in 03007FFCh. Commands called from the monitor directly must be in 32bit code format. 03007F00 USR Stack 03007FA0 SP_usr IRQ Stack 6 WORDS SP_irq 03007FE0 SVC Stack SP_svc 03007F00 03007FA0 2) User interrupt processing is done (you can reference the cause of the interrupt with the IF Register). Also solve* problems with a stack, if necessary. 3) Restore the registers (total of 6 words) saved to the Interrupt Stack and return to user main processing. 03007F00 USR Stack 03007FA0 SP_usr IRQ Stack SP_irq 03007FE0 SVC Stack SP_svc 03007F00 03007FA0 *Note Only the interrupt stack is used for normal interrupt processing. Therefore, there is a possibility of stack overflow in some cases. To solve this problem, you can either allocate a larger interrupt stack by moving SP_usr in advance or use user stack for both, by switching the CPU mode to the user mode in user interrupt processing. For the latter method, see the explanation of multiple interrupts that is discussed on the following page. ©1999 - 2001 Nintendo of America Inc. 160 D.C.N. AGB-06-0001-002B4

Section	Page
Introduction	3
Revision History	4
Table of Contents	9
Using This Manual	12
1 AGB System	13
1.1 System Overview	13
2 System Configuration	15
2.1 CPU Block Diagram	15
2.2 Complete Block Diagram	16
2.3 Memory Configuration and Access Width	17
2.4 Little-Endian	17
3 AGB Memory	18
3.1 Overall Memory Map	18
3.2 Memory Configuration	19
3.2.1 AGB Internal Memory	19
3.2.2 Game Pak Memory	20
3.3 Game Pak Memory Wait Control	21
3.3.1 Access Timing	23
3.3.2 Game Pak Bus	24
4 LCD	25
4.1 LCD Status	26
4.1.1 V Counter	26
4.1.2 General LCD Status	27
5 Image System	29
5.1 BG Modes	31
5.1.1 Details of BG Modes	31
5.1.2 VRAM Memory Map	32
6 Rendering Functions	33
6.1 Character Mode BG (BG Modes 0-2)	33
6.1.1 BG Control	33
6.1.2 Mosaic Size	39
6.1.3 VRAM Address Mapping of BG Data	40
6.1.4 Character Data Format	42
6.1.5 BG Screen Data Format	43
6.1.6 BG Screen Data Address Mapping for the LCD Screen	45
6.1.7 BG Rotation and Scaling Features	49
6.1.8 BG Scrolling	52
6.2 Bitmap Mode BGs (BG Modes 3-5)	53
6.2.1 BG Control	53
6.2.2 BG Rotation/Scaling	54
6.2.3 Pixel Data	54
6.2.4 Pixel Data Address Mapping for the LCD Screen	55
6.2.4.1 BG Mode 3 (32,768 colors,240x160 dots,1 frame buffer)	55
6.2.4.2 BG Mode 4 (256 colors,240x160 dots,2 frame buffers)	56
6.2.4.3 BG Mode 5 (32,768 colors,160x128 dots,2 frame buffers)	57
6.3 OBJ (Object)	58
6.3.1 OBJ Function Overview	58
6.3.2 Character Data Mapping	60
6.3.3 OAM	62
6.3.4 OBJ Rotation/Scaling Feature	70
6.4 Display Priority of OBJ and BG	72
7 Color Palettes	73
7.1 Color Palette Overview	73
7.2 Color Palette RAM	74
7.3 Color Data Format	76
8 Window Feature	77
8.1 Window Position Setting	77
8.2 Window Control	78
9 Color Special Effects	80
9.1 Selection of Color Special Effects	80
9.2 Color Special Effects Processing	82
10 Sound	84
10.1 Sound Block Diagram	84
10.2 Direct Sounds A and B	85
10.3 Sound 1	87
10.4 Sound 2	91
10.5 Sound 3	93
10.6 Sound 4	97
10.7 Sound Control	100
10.8 Sound PWM Control	104
11 Timer	106
12 DMA Transfer	108
12.1 DMA 0	109
12.2 DMA 1 and 2	113
12.3 DMA 3	117
12.4 DMA Problems: How to avoid them	122
13 Communication Functions	125
13.1 8-Bit/32-Bit Normal Serial Communication	128
13.2 16-Bit Multi-player Communication	134
13.3 UART Communication Functions	142
13.4 General Purpose Communication	148
13.5 JOY Bus Communication	150
13.6 AGB Game Link Cable	154
14 Key Input	155
14.1 Key Status	155
14.2 Key Interrupt Control	155
14.2.1 Interrupt Conditions	156
15 Interrupt Control	157
15.1 System-Allocated Area in Work RAM	159
15.2 Interrupt Operation	160
15.2.1 Normal Interrupt	160
15.2.2 Multiple Interrupts	161
16 Power-Down Functions	163
16.1 Stop Function	163
16.2 Halt Function	164
17 AGB System Calls	165
17.1 System Call Operation	165
17.1.1 Normal Calls	165
17.1.2 Multiple Calls	167