6
The serial port protection module is mainly to fulfill the function of serial-port
ESD protection.
The R_UIM card interface circuit is mainly to contribute to the communication
between CPU and R_UIM card and provide and protect the power for the R_UIM
card.
1) Audio channel 1 fulfills the function of driving microphone and receiver in the
telephone handle.
2) Audio channel 2 fulfills the function of driving hands-free microphone and
speaker. The speaker has ringing function.
3) The environmental variable monitoring module fulfills the battery temperature
sampling function.
4) The power and power management module contains primary power interface
protection module, battery charging/discharging module, DC/DC power module,
and startup/shutdown control module.
5) The primary power interface protection module fulfills the antistatic function.
6) The battery charging/discharging module fulfills charging management
function for the battery.
7) The DC/DC power module fulfills second-time DC power conversion within
the board, and provides functions like voltage stabilizing, and constant current to
cooperate with the charging/discharging circuit.
8) The startup/shutdown control module fulfills startup/shutdown control
function of the external touching switch and control function of primary power
startup and software shutdown.
Besides the above modules, the following interface components are also included:
Connecting pad between PIPU board and TCPU board, DB9 connector of the serial
port, line for connecting the LCD module, line for connecting KPAD, 4-line crystal
header for connecting the handle, and inserting spring and slide switch.
1.3 Detailed Description of the FWT Main-Board
Functional Module
1.3.1 Subscriber Interface Sub-system
1. Asynchronous Serial Port Drive Circuit
We put the drive of the serial port onto the serial port line. The output power level
of the serial port drive does not match the MSM6000 power level---The high
power level of MSM6000 is 2.8V, while the high power level of the serial port
drive is 4.4V. Thus, what is needed is to make a power-level conversion and
protection circuit for the transistor to convert the power level of the serial port
