GBA Service Manual
Page 2
2. Theory of Operation
2.1 Description
The Game Boy Advance (GBA) is a portable and compact video game system. It is
composed of a Central Processing Unit (CPU), Film Transistors, a Liquid Crystal Display
(LCD) and related circuits. The device can be used with the 128 Bit Video Game, Game
Cube, as a discrete control, as well as being compatible with the Game Boy and Game Boy
Color games. Inputs from control are parallel and are read directly by the CPU. The L and R
buttons are new to the systems Nintendo's portable video games and have been added to
provide a wide variety of operations and gameplay.
2.2 Power
When the Power switch is set to the ON position, the 3 VDC voltage supplied by the 2 AA
batteries or through the AC adapter arrive at the device circuit. The input voltage is
converted by the U4 power IC to supply the system with 5 voltage operation that feed
various components, such as: CPU, LCD, Cartridge, Sound Amplifier and WRAM.
POWER VOLTAGE GBA MODE GBC MODE
CPU 3.3 VDC 5.0VDC
CPU PERIPHERAL CIRCUITS 2.5 VDC 2.5VDC
SOUND AMPLIFIER 3.0 VDC (VCC) 3.0 VDC (VCC)
REGULATOR 3.0 VDC (VCC) 3.0 VDC (VCC)
EXTERNAL WRAM 2.5 VDC 2.5 VDC
EXPANSION CONNECTOR 3.3 VDC 5.0 VDC
LCD 13.6 VDC, -15 VDC 13.6 VDC, -15 VDC
CARTRIDGE 3.3 VDC 5 VDC
The GBA has a bicolor LED that indicates the battery life. The green LED indicates that the
battery charge it is fine, but when the battery voltage drops below 2.35 VDC, the red LED is
activated. The GBA also has a shutdown function that is triggered when the battery voltage
is below 1.7 VDC.
2.3 CPU
The GBA CPU is basically composed of 2 processors in 1: A 32-bit RISC CPU, which
processes all GBA game functions and an 8-bit CISC CPU that processes the functions GB
and GBC games. The CPU searches and decodes the instructions recorded in the ROM,
reads the entries controls, generates priorities and controls the entire graph, decodes the
audio data and sends it to the audio amplifier.
2.4 System Timer
The system's timer section includes an oscillator and discrete components that provide a
4.194MHz master clock signal to the CPU. The CPU multiplies this signal by 4 to operate on
the GBA mode (16,776MHz), or multiplies by 2 for GB / GBC mode (8,388MHz).
2.5 Display section
The display section consists of a 2.9 inch (240x160 pixels) reflective LCD display, segments
that are mounted internally to the LCD and a regulating IC. Each pixel in the GBA can show
1 of the 32 levels of red, green or blue, making a total of 32,768 colors. The number total
colors that can be shown, depends on the number of objects and the screen background.
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