Samsung SCH-470 Service Manual page 16

Circuit Description
5-1-3 Baseband Part
MOBILE SYSTEM MODEM (MSM)
The MSM equipped with the INTEL 80C186 CPU
core is an important component of the CDMA
cellular phone. The MSM comes in a 176 pins
TQFP package.
MICROPROCESSOR INTERFACE
The interface circuitry consists of reset circuit,
address bus (A0-A19), data bus (AD0-AD15), and
memory controls (ALE, DT_R, HWR/, LWR/,
RAM_CS/, ROM_CS).
INPUT CLOCK
¶UCPU clock: 27 MHz
¶UTXCO/4 (pin 34): 4.92 MHz. This clock signal
from the BBA is the reference clock for the MSM
except in CDMA mode.
¶UCHIPX8 : 9.8304 MHz. The reference clock used
during the CDMA mode.
BBA INTERFACE
CDMA, FM Data Interface
¶UTXIQDATA0-7 (pins 24-32) : TX data bus used
during both CDMA and FM mode but it is used
only for CDMA mode at this phone.
Clock
¶UTC_CLK (pin 22), TX_CLK/(pin 23) : Analog to
Digital Converter (ADC) reference clock used in
TX mode.
¶UCHIPX8 : ADC reference clock used in CDMA
RX mode.
¶UFMCLK: TXclock used in FM mode.
5-2
ADC Interface
ADC_CLK (pin 3), ADC_ENABLE (pin 1) and
ADC_DATA (pin 2) are required to control the
internal ADC in the BBA.
Data Port Interface
Includes the UART. Also, supports Diagnostic
Monitor (DM), HP equipment interface, down
loading, and data service.
CODEC Interface
The MSM outputs 2.048 MHz PCM_CLK (pin 19)
and 8 KHz CODEC_SYNC (pin 16, 20) to the
CODEC (U117). The voice PCM data from the
MSM (U101) PCM_DIN (pin 135) is compressed
into 8 KHz, by QCELP algorithm in the CDMA
mode.
RF Interface
TX : TX_AGC_ADJ (pin 35) port is used to control
the TX power level and PA_ON (pin 44) signal is
used to control the power amplifier. This signal
depends on the TX vocoder rate.
RX : AGC_REF (pin 36) port is used to control the
RX gain and TRK_LO_ADJ (pin 45) is used to
compensate the TCXO clock.
General Purpose I/O Register Pins
Input/output ports to control external devices.
Power Down Control
When the IDLE/ signal turns LOW, only the TX
sections will be disabled. If both the IDLE/ and
SLEEP/ change to LOW, all the pins except for the
TCXO and 27MHz clock are disabled.
Samsung Electronics