Gsm Subsystem - LG -E730 Service Manual

3.8.7 GSM Subsystem

The MSM8255 IC includes a GSM core that performs the data conversions and signal processing necessary to
maintain the GSM air interface, including PA gain control for GPRS support. In GSM mode, the power profile
ramps up before the burst and ramps down afterward. In GPRS mode, transmit bursts can occur in as many as
four sequential slots and the PA must be ramped up and down smoothly between each slot, holding the desired
output power level during each burst. GSM support includes:
-GSM release '99 (circuit switching)
-GPRS (packet switching)
-EDGE E2 power class for 8 PSK
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.
3.8.5 Single-wire serial bus interface (SSBI)
The MSM8255 device's SSBI is designed specifically to be a quick, low pin count control protocol for
QUALCOMM's QTR8200 and PM8058 ASICs. Using the SSBI, the QTR8200 and PM8058 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.
3.8.6 Audio function
The audio core in the MSM8x55 device includes four I2S interfaces and a PCM interface to connect to an
external device. The blocks are summarized below and shown in Figure 6-20. The audio core also includes an
internal low power audio and MIDI hardware accelerator. Both interfaces will be added to a future revision of
this document.
Independent Tx and Rx I2S interfaces (MI2S_CODEC) dedicated for a stereo wideband codec
Multiple I2S (MI2S) interface to support up to 8 channels of audio
AUX_CODEC that contains:
I2S interface to connect to a stereo ADC or stereo DAC I2S capable.
AUX_PCM interface to connect to an external mono codec.
Low power audio core to enable very low power for multimedia playback.
MIDI hardware accelerator core to support CMX 5.x features.
LGE Internal Use Only - 45 - Copyright © 011 LG Electronics. Inc. All right reserved.
3. TECHNICAL BRIEF
Only for training and service purposes