Flash ROM is used to store the terminal’s program. Using the down-loading program, the program can be changed
even after the terminal is fully assembled.
SRAM is used to store the internal flag information, call processing data, and timer data.
4. Level Translator Part
4.1 L/T supply power to Modem(4.2V).
DC/Jack
(small)
DC/Jack
(large)
Adjustable LDO
VEXT_DC
+4.2V
Fixed
LDO
+5V
max(207)
[Fig 4-1] The Block Diagram of Source (in brief)
4.2 UART Interface
The Universal Asynchronous Receiver Transmitter (UART) communicates with serial data that
conforms the RS-232 Interface protocol. The modem provides 3.0V CMOS level outputs and
3.0V CMOS switching input level. And all inputs have 5.0V tolerance but 3.0V or 3.3V CMOS
logic compatible signals are highly recommended.
All the control signals of the RS-232 signals are active low, but data signals of RXD, and TXD
are active high.
The UART has a 64byte transmit (TX) FIFO and a 64byte receive (RX) FIFO. The UART
Features hardware handshaking, programmable data sizes, programmable stop bits, and odd,
even, no parity. The UART operates at a 115.2kbps maximum bit rate.
4.2.1 UART Inter Pinouts
NAME
DESCRIPTION
CHARACTERISTIC
DP_DCD/
Data Carrier Detect
Network connected from the modem
DP_RI/
Ring Indicator
Output to host indicating coming call
DP_RTS/
Request to Send
Ready for receive from host
DP_TXD
Transmit Data
Output data from the modem
