LG CU500 - Cell Phone, Service Manual

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3.8 Subsystem(MSM6275)
3.8.1 ARM Microprocessor Subsystem
The MSM6275 device uses an embedded ARM926EJ-S microprocessor. This microprocessor,
through the system software, controls most of the functionality for the MSM, including control of the
external peripherals such as the keypad, LCD, SDRAM, and NAND-Flash devices. Through a
QUALCOMM proprietary serial bus interface (SBI) the ARM926EJ-S configures and controls the
functionality of the RTR6250, RFR6202, RFL6202, and PM6650 devices.
3.8.2 UMTS Subsystem
The UMTS Subsystem performs the digital UMTS signal processing. Its components include:
• Searcher engine
• Demodulating fingers
• Combining block
• Frame deinterleaver
• Viterbi decoder
• Up-link subsystem
• Turbo decoder
On the down-link channel the UMTS subsystem searches, demodulates, and decodes incoming
CPICH, CCPCH, SCH, and Traffic Channel information. It extracts packet data from the downlink
traffic channel and prepares the packet data for processing. For the up-link, the WCDMA subsystem
processes the packet data and modulates the up-link traffic channel (DCH).
3.8.3 GSM Subsystem
The GSM/GPRS/EGPRS subsystem reuses the MSM6250 GSM core. It performs the digital GSM
signal processing and PA gain controls for GPRS support. The PA output level is controlled by an
analog signal generated on the MSM. In GSM mode, the power profile ramps up before the burst and
ramps down after the burst. In GPRS mode, at the beginning of each burst (up to four active transmit
slots), PA must be smoothly ramped up to some desired output power level, held at that level for the
current slot, smoothly ramped down/up during the transition period and held to the new level for the
next slot until the last slot. Then it must be smoothly ramped down to near-zero level. The MSM6275
support differential GSM PA power control output. The RF interface communicates with the mobile
station external RF circuits. Signals to these circuits control signal gain in the Rx and Tx signal path,
control DC offset errors, and maintain the system frequency reference.
3.8.4 RF Interface
The RF interface communicates with the mobile station’s external RF and analog baseband circuits.
Signals to these circuits control signal gain in the Rx and Tx signal path and maintain The system’s
frequency reference.
3. TECHNICAL BRIEF
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