SIM340 Hardware Design
3.8 Serial interfaces
Table 9: Pin definition of the serial interfaces
Name
Pin
Function
DCD
28
Data carrier detection
DTR
38
Data terminal ready
RXD
40
Receive data
TXD
42
Transmit data
RTS
44
Request to send
CTS
46
Clear to send
Serial port
RI
48
Ring indicator
DBG_RXD
47
Receive data
Debug port
DBG_TXD
49
Transmit data
SIM340 provides two unbalanced asynchronous serial ports. One is the serial port and another is
the debug port. The GSM module is designed as a DCE (Data Communication Equipment),
following the traditional DCE-DTE (Data Terminal Equipment) connection.The module and the
client (DTE) are connected through the following signal (as following figure shows).
Autobauding
supports baud rate from 4800bps to 115200bps.
Serial port
TXD: Send data to the RXD signal line of the DTE
RXD: Receive data from the TXD signal line of the DTE
Debug port
DBG_TXD: Send data to the /RXD signal line of the DTE
DBG_RXD: Receive data from the /TXD signal line of the DTE
The logic levels are described in following table
Table
10
: Logic levels of the serial port and debug port
Parameter
Min
Max
Unit
V
IL
0
0.3*VDD_EXT
V
V
IH
0.7 *VDD_EXT
V0.3
V
V
OL
GND
0.2
V
V
OH
VDD_EXT -0.2
VDD_EXT
V
SIM340_HD_V3.09
18.03.2009
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