U8655
Maintenance Manual
9 Principles and Failure Analysis
Issue 1.0 (2012-02-23)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
22
Providing analog multi-channel switch, real-time clock circuit, TCXO clock circuit, motor
driver circuit, and speaker driver circuit.
The RTR6285A is the RF signal processing chip, responsible for converting UMTS/GSM
uplink/downlink RF signals and using I/Q signals to exchange data with the baseband chip.
9.1.1 Function Description of the PCBA
The PCBA can be divided into four sub-systems: baseband, RF, power supply, and user
interfaces. The following table describes the subsystems' modules and units, as well as their
functions.
Table 9-1
PCBA subsystems' modules, units, and functions
Subsystem Module
Unit
Function
Baseband
subsystem
MSM7225A
Modem subsystem
The modem subsystem includes the ARM11
processor, modem DSP, modem AHB bus,
interruption controller, and sleep controller.
The ARM9 is a 400 MHz modem processor,
responsible for modulation and demodulation of
WCDMA, GPS, and GSM signals.
Application
subsystem
The subsystem includes ARM A5 processor,
application DSP, and dedicated data mover.
The A5 processor has a clock rate of 800 MHz,
supporting function modules such as the microSD
card, EBI2, UART/USIM, I2C, GPIO, and clock
modules.
User interface
processing unit
Provides camera, PCM, broadband codec, vocoder,
RF, HKADC, LCD, SD card, USB, UART, USIM
card, SBI, GPIO, JTAG/ETM, and keypad
interfaces.
Multimedia and
game engine
The multimedia and game engine is an MPEG/JPEG
hardware engine providing Java acceleration and
MP3/MMS/MIDI/VR processing functions.
PM8029
Power supply voltage
monitoring
Lists objects being monitored, such as the external
power supply input, Li-ion battery, and charger.
Temperature
monitoring
Monitors the battery temperature.
NAND flash
memory
File system support
Stores applications and NV items. Capacity: 4 GB.
DDR1 RAM
Random access
memory
Provide storage space for running applications.
Capacity: 2 GB.
RF
subsystem
WCDMA, and
GSM/DCS
signal
transmission and
reception
AFC circuit, APC
circuit, AGC circuit
Performs the RF function of WCDMA signal
reception and transmission.
Mainly includes the RTR6285A RF chip and the
peripheral circuit.
