Vocoder Subsystem - LG -P500 Service Manual

3.9.4. 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.
3.9.5. Single-wire serial bus interface (SSBI)
The MSM7227 device's SSBI is designed specifically to be a quick, low pin count control protocol for
QUALCOMM's RTR6285 and PM7540 ASICs. Using the SSBI, the RTR6285 and PM7540 devices can be
configured for different operating modes and for minimum power consumption, extending battery life in
Standby mode. The SBI also controls DC baseband offset errors.
3.9.6. Audio function
MSM7227 audio functions include the analog Rx and Tx paths (or stereo wideband codec), audio digital
signal processing (DSP) that provides adjustable gains and filtering, PCM circuits for interfacing with external
devices, and additional audio DSP that actually implements encoding and decoding. Other key features
include:
-The wideband codec supports stereo music/ringer melody applications in addition to the 8 kHz voice
band applications on the forward link.
-A PCM interface allows an external codec to be used instead of the internal codec; this supports inter-IC
Sound (I2S) modes that allow an external stereo DAC or SADC to be used.
-Currently in AMSS baseline only I2S output mode is supported (SDAC-only, no SADC support).
-Audio decoder summing and headset switch detection are included.
-Audio DSP includes the Rx and Tx filters needed to meet ITU-T G.712 requirements.
-A programmable sidetone path provides for summing part of the Tx audio into the Rx path.
-Many codec parameters are configurable via SBI registers.
-The audio processing is configured through QDSP5 command types and is not directly controlled by the
microprocessor.

3.9.7. Vocoder Subsystem

The MSM7227 device's QDSP4000 supports AMR,FR,EFR and HR. In addition, the QDSP4000 has modules to
support the following audio functions: DTMF tone generation, DTMF tone detection, Tx/Rx volume controls,
Tx/Rx automatic gain control (AGC), Rx Automatic Volume Control (AVC), EarSeal Echo Canceller (ESEC),
Acoustic Echo Canceller (AEC), Noise Suppression (NS), and programmable, 13-tap, Type-I, FIR, Tx/Rx
compensation filters. The MSM7227 device's integrated ARM9TDMI processor downloads the firmware into
the QDSP4000 and configures QDSP4000 to support the desired functionality.
Copyright © 2010 LG Electronics. Inc. All right reserved.
Only for training and service purposes
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3. TECHNICAL BRIEF
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