LG KG70c Service Manual page 17

KG70C
6.2.2 Circuit Description
6.2.2.1 Keypad / LCD and Receptacle Part
This is used to transmit keypad signals to MSM6100. It is made up of a keypad backlight part that
illuminates the keypad, LCD part that displays the operation status on to the screen, and a receptacle
that receives and sends out voice and data with external sources.
6.2.2.2 Voice Processing Part
The voice processing part is made up of an audio codec in MSM6100 used to convert MIC signals into
digital voice signals and other external MIDI Synthesizer used to convert digital voice signals into
analog voice signals, amplifying parts for amplifying the voice signals and MIC signals are on external
MIDI Synthesizer and Codec in MSM6100.
6.2.2.3 MSM6100 (Mobile Station Modem) Part
The MSM6100 chipset integrates functions that support both tri-mode CDMA/FM and cellular-only
handset operation. Subsystems within the MSM6100 baseband processor device include a CDMA
processor, digital FM (DFM) processor, QCT's latest generation of DSP, the QDSP4000™ core, for
voice compression and applications support, PLL and an ARM® ARM926EEJ-S microprocessor. Also
integrated in the MSM6100 device are analog functions such as a wideband mono codec and analog
interfaces for the radioOne RF ASICs. Controllers for a universal serial bus (USB), device controller
for an R-UIM (CDMA SIM), GPIOs, and peripheral interfaces complete the system integration. And the
MSM6100 chipset and system software are designed to support IS95A/95B and Release 0 of
CDMA2000 standards.
In MSM, coded symbols are interleaved in order to cope with multi-path fading. Each data channel is
scrambled by the long code PN sequence of the user in order to ensure the confidentiality of calls.
Moreover, binary quadrature codes are used based on walsh functions in order to discern each
channel. Data created thus are 4-phase modulated by one pair of Pilot PN code and they are used to
create I and Q data.
When received, I and Q data are demodulated into symbols by the demodulator, and then
de-interleaved in reverse to the case of transmission. Then, the errors of data received from viterbi
decoder are detected and corrected. They are voice-decoded at the vocoder in order to output digital
voice data.
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