SIM Tech SimCom SIM340 Hardware Design page 38

SIM340 Hardware Design
Figure 19: Connection of software upgrade
Note: The RTS PIN must be connected to the GND in the customer circuit when only the TXD
and RXD are used in the Serial Port communication.
MODULE(DCE)
Debug port
DBG_TXD
DBG_RXD
The serial port and the debug port doesn't support the RS_232 level, it only supports the CMOS
level. Please refer to the table 10 for details about the voltage level. You should add the level
converter IC between the DCE and DTE if you connect it to the computer. Please refer to the
following figure.
SIM340_HD_V3.09
GND
Figure 20: Connection of software debug
Figure 21: RS232 level converter circuit
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CUSTOMER(DTE)
TXD
RXD
GND
18.03.2009