LG -MC2670 Service Manual page 10

LG-MC2670
Receptacle(CON301) exchanges audio signals and data with external sources and then, receives
power from the battery or external batteries.
2.3.2 MSM Part
MSM6000 is the core element of a CDMA mobile station. Subsystems within the MSM6000 include a
CDMA processor, an EVRC(Enhanced Variable Rate Codec) vocoder, an ARM7TDMI
microprocessor ,and assorted peripheral interfaces that are used to support other functions.
MSM6000, when operated in the CDMA mode, utilizes CHIP × 8 (9.8304MHz) as the reference clock
primarily for CDMA and vocoder processing.MSM6000 also uses TCXO/4 (4.92MHz).
The CPU controls total operations of the subscriber unit. Digital voice data, that have been inputted,
are encoded using the EVRC algorithm. Then, they are convolutionally encoded so that error
detection and correction are possible. Coded symbols are interleaved in order to avoid a burst error.
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.
The MSM6000 also supports Enhanced Variable Rate Coder (EVRC) operation in addition to the
standard 8k.
2.3.2.1 Audio Processing Part
MIC signals are inputted into the audio codec, and amplified with programmable gain, and converted
into digital signals(PCM). Then, they are inputted into MSM6000.
In addition, digital audio signals(PCM) outputted from MSM6000 are converted into analog signals
after going through the audio codec. These signals are amplified with programmable gain on codec's
internal AMP and external Audio AMP and then transferred to the ear piece. The signals is generated
in MSM6000 using SW MIDI.
2.3.3 Memory Part
The memory part consists of a 32Mbits Flash Memory and a 16Mbits SRAM. In the Flash Memory,
there are programs used for the operation of a mobile station. The programs can be changed through
down loading after the assembling of mobile stations. The Flash memory is also emulated as an
EEPROM to store ESN(Electronic Serial Number), Calibration Data, etc. On the SRAM, data
generated during the operation of a mobile station are stored temporarily.
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