Nintendo 1504166 Programming Manual - Page 30

AGB Programming Manual

Image System

©1999 - 2001 Nintendo of America Inc.

30

D.C.N. AGB-06-0001-002B4

DISPCNT [d07]

Forced Blank

Setting this bit causes the CPU to forcibly halt operation of the image

processing circuit, allowing access to VRAM, color palette RAM, OAM, and

the internal registers.

The LCD screen displays white during a forced

blank.

However, the internal HV synchronous counter continues to operate

even during a forced blank.

When the internal HV synchronous counter

cancels a forced blank during a display period, the display begins from the

beginning, following the display of three vertical lines.

DISPCNT [d06]

OBJ Character VRAM Mapping Format

Specifies the VRAM mapping format for an OBJ character.

A setting of 0 causes the OBJ character to be handled in memory mapped

2-dimensional.

A setting of 1 causes the OBJ character to be handled in

memory mapped 1-dimensional.

For information on OBJ character VRAM mapping formats, see section

6.3.2, Character Data Mapping.

DISPCNT [d05]

H-Blank Interval OBJ Processing Flag

A setting of 0 executes OBJ Render Processing with all H-Line

intervals(including H-Blank intervals).

A setting of 1 executes OBJ Render Processing with the display intervals

only and not for H-Blank intervals.

Thus, when the user accesses OAM or

OBJ VRAM during an H-Blank interval, this bit needs to be set.

However,

also in this situation, maximum OBJ display performance cannot be

obtained.

DISPCNT [d04]

Display Frame Selection

When rendering in bitmap format in a mode in which there are 2 frame

buffers (BG modes 4 and 5), this bit allows selection of one of the frame

buffers for rendering.

A setting of 0 selects the contents of frame buffer 0

for rendering; a setting of 1 selects the contents of frame buffer 1 for

rendering.

DISPCNT [d03]

(CGB Mode)

AGB is equipped with 2 CPUs.

In AGB mode, a 32-bit RISC CPU starts,

and in CGB mode, an 8-bit CISC CPU starts.

Because this bit is

controlled by the system, it cannot be accessed by the user.

DISPCNT [d02-00]

BG Mode

Selects the BG mode from a range of 0-5.

For more information on BG modes, see the following section.

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

Nintendo 1504166 Programming Manual - Page 30

OBJ Character VRAM Mapping Format, H-Blank Interval OBJ Processing Flag

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