LG GB175, Service Manual, Page: 17 / 158

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3.1.1 System overview
The MT6225 is a highly integrated single chip solution for GSM/GPRS phone. Based on 32-bit
ARM7EJ-STM RISC processor, MT6225 features not only high performance GPRS Class 12
MODEM but is also designed with support for the wireless multi-media applications, such as
advanced display engine, synthesis audio with 64-tone polyphony, digital audio playback, Java
acceleration, MMS and etc. Additionally, MT6225 provides varieties of advanced interfaces for
functionality extensions, like 3-port external memory interface, 3-port 8/16-bit parallel interface,
NAND Flash, IrDA, USB and MMC/SD/MS/MS Pro.
Platform
MT6225 is capable of running the ARM7EJ-STM RISC processor at up to 104 MHz, thus
providing fast data processing capabilities. In addition to the high clock frequency, a separate
CODE cache is also added to further improve the overall system efficiency. For large amounts of
data transfer, high performance DMA (Direct Memory Access) with hardware flow control is
implemented, which greatly enhances the data movement speed while reducing MCU processing
load.
External Memory Interface
To provide the greatest capacity for expansion and maximum bandwidth for data intensive
applications such as multimedia features, MT6225 supports up to 3 external state-of-the-art
devices through its 16-bit host interface. High performance devices such as Mobile RAM and
Cellular RAM are supported for maximum bandwidth. Traditional devices such as burst/page
mode flash, page mode SRAM, and Pseudo SRAM are also supported. For greatest compatibility,
the memory interface can also be used to connect to legacy devices such as Color/Parallel LCD,
and multi-media companion chips 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 the 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 a turn over.
Multi-media Subsystem
In order to provide more flexibility and bandwidth for multi-media products, an additional 8/16
bit parallel interface is incorporated. This interface is designed specially for support with Camera
companion chip as well as LCD panel. In addition, MT6225 has camera YUV interface that can
connect to CMOS sensor of resolution up to VGA. Moreover, it can connect NAND flash device to
provide a solution for multi-media data storage. For running multi-media application faster,
MT6225 integrates also several hardware-based engines. With hardware based Resizer and
advanced display engine, it can display and combine arbitrary size of images with up to 4
blending layers.
User Interface
For user interactions, the MT6225 brings together all necessary peripheral blocks for
multi-media GSM/GPRS phone. It comprises the Keypad Scanner with capability of
multiple key pressing, SIM Controller, Alerter, Real Time Clock, PWM, Serial LCD Controller and
General Purpose Programmable I/Os. For connectivity and data storage, the
MT6225 consists of UART, IrDA, USB 1.1 Slave, SDIO and MMC/SD/MS/MS Pro.
Audio Interface
Using a highly integrated mixed-signal Audio Front-End,the MT6225 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, MT6225 also provides Stereo
Input and Analog Mux.
MT6225 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.