Samsung SCH-1900, Service Manual, Page: 12 / 112

Circuit Description
4-2 Samsung Electronics
4-1-3 Base Band
MOBILE SYSTEM MODEM (MSM)
The MSM equipped with the INTEL 80186 CPU
core is an important component of the CDMA
cellular phone. The MSM comes in a 176 pins
TQFP package. The interface block diagram is
shown on page4-3.
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
°§
CPU clock : 27 MHz
°§
TXCO/4 (pin34) : 4.92 MHz. This clock signal
from the BBA is the reference clock for the MSM
except in CDMA mode.
°§
CHIPX8 : 9.8304 MHz.The reference clock used
during the CDMA mode.
BBA INTERFACE
CDMA,Data Interface
°§
TX_IQDATA0-7 (pin24-32) : TX data bus used
during both CDMA.
°§
C_RX_IDATA0-3 (pins16-20) and
C_RX_QDATA0-3(pins 12-15) : RX data bus
used during CDMA mode.
Clock
°§
TX_CLK(pin 22), TX_CLK/(pin23) : Digital to
Analog Converter(DAC) reference clock used in
TX mode.
°§
CHIPX8 : ADC reference clock used in CDMA
RX mode.
ADC Interface
ADC_CLK (pin3), ADC_ENABLE (pin1) and
ADC_DATA (pin2) are required to control the
internal ADC in the BBA.
Data Port Interface
Includes the UART. Also, supports Diagnostic
Monitor (DM) and HP equipment Interface.
CODEC Interface
The MSM outputs 2.048MHz PCM_CLK (pin19)
and 8KHz CODEC_SYNC (pin16,20) to the
CODEC (U102). The voice PCM data from the
MSM (U101)PCM_DIN (pin135) is compressed
into 13KHz by PureVoice algorithm in the CDMA
mode.
RF Interface
TX : TX_AGC_ADJ (pin35) port is used to control
the TX power level and PA_ON (pin44) signal is
used to control the power amplifier.
RX : AGC_REF (pin36) port is used to control the
RX gain and TRK_LO_ADJ (pin45) 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/ are changed to LOW, all the pins except
for the TXCO are disabled.