SIM802 Hardware Design
3.9 Serial interfaces
SIM802 provides two unbalanced asynchronous serial ports. One is the main serial port and the
other is the debug serial 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 figure 19 shows).
Autobauding supports bit rates from 1200 bps to 115200bps.
Main serial port
z
TXD: Send data to the RXD signal line of the DTE
z
RXD: Receive data from the TXD signal line of the DTE
Debug serial port
z
DBG_TXD: Send data to the /RXD signal line of the DTE
z
DBG_RXD: Receive data from the /TXD signal line of the DTE
NOTE: All pins of both serial ports have 8mA driver, the logic levels are described in following
table
Table 13: Logic levels of serial ports pins
Parameter
Min
Max
Unit
Logic low input
0
0.87V
V
Logic high input
2.05V
3.23V
V
Logic low output
GND
0.2
V
Logic high output
2.73V
2.93V
V
SIM802_HD_V2.01
12.01.2010
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