LG GS205, Service Manual

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3.1.1 System overview
The revolutionary MT6226M is a leading edge single-chip solution for GSM/GPRS mobile
phones targeting the emerging applications in digital audio and video. Based on 32-bit
ARM7EJ-STM RISC processor, MT6226M not only features high performance GPRS Class 12
MODEM, but also provides comprehensive and advanced solutions for handheld multi-media.
Typical application is shown in Figure 3-1-1.
Multi-Media Subsystem
The MT6226M multi-media subsystem provides connection to CMOS/CCD image sensor
and supports resolution up to 1.3M Pixel. With its advanced image signal and data processing
technology, MT6226M allows efficient processing of image and video data. It also has built-in
JPEG CODEC and MPEG-4/H.263 CODEC, thus enabling real-time creation and playback of
high-quality images and video. In addition to advanced image and video features, MT6226M
also utilizes high resolution DAC, digital audio, and audio synthesis technology to provide
superior audio features for all future multi-media needs.
In order to provide more flexibility and bandwidth for multi-media products, an additional
18-bit parallel interface is incorporated. This interface enables connection to LCD modules as
well as connection to NAND flash devices to allow for multi-media data storage capabilities.
External Memory Interface
Providing the greatest capacity for expansion, MT6226M supports up to 8 state-of-the-art
devices through its 16-bit host interface. Devices such as burst/page mode Flash, page mode
SRAM, Pseudo SRAM, Color/Parallel LCD, and multi-media companion chip are all supported
through this interface. To minimize power consumption and ensure low noise, this interface is
designed for flexible I/O voltage and allows lowering of supply voltage down to 1.8V. The driving
strength is configurable for signal integrity adjustment. The data bus also employs retention
technology to prevent the bus from floating during turn over.
User Interface
To provide complete user interface, MT6226M brings together all the necessary peripheral
blocks for multi-media GSM/GPRS phone. The peripheral blocks consists of the Keypad
Scanner with the capability to detect multiple key presses, SIM Controller, Alerter, Real Time
Clock, PWM, Serial LCD Controller, and General Purpose Programmable I/Os. For connectivity
and data storage, the MT6226M supports UART, IrDA, USB 1.1 Slave and MMC/SD/MS/MS
Pro. Furthermore, for large amount of data transfer, high performance DMA(Direct Memory
Access) and hardware flow control are implemented, which greatly enhances the performance
and reduces MCU processing load.
Audio Interface
Using a highly integrated mixed-signal Audio Front-End, the MT6226M architecture allows
for easy audio interfacing with direct connection to the audio transducers. The audio interface
integrates D/A and A/D Converters for Voice band, as well as high resolution Stereo D/A
Converters for Audio band. In addition, MT6226M also provides Stereo Input and Analog Mux.
MT6226M supports AMR codec to adaptively optimize speech and audio quality. Moreover,
HE-AAC codec is implemented to deliver CD-quality audio at low bit rates.
Overall, MT6226M’s audio features provide a rich platform for multi-media applications.
Radio Interface
MT6226M integrates a mixed-signal Baseband front-end in order to provide a well-organized
radio interface with flexibility for efficient customization. It contains gain and offset calibration
mechanisms, and filters with programmable coefficients for comprehensive compatibility control
on RF modules. This approach also allows the usage of a high resolution D/A Converter for