SimCom SIM900D EVB, Проектирование аппаратного обеспечения

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SIM900D Hardware Design
Figure17: Seiko XH414H-IV01E Charge Characteristics
3.9 Serial Interfaces
Table11: Pin definition of the serial interfaces
Name Pin Function
DTR 43 Data terminal ready
RI 11 Ring indicator
DCD 42 Data carrier detection
CTS 45 Clear to send
RTS 44 Request to send
TXD 4 Transmit data
Serial port
RXD 3 Receive data
DBG_RXD 1 Receive data
Debug port
DBG_TXD 2 Transmit data
SIM900D provides two unbalanced asynchronous serial ports. One is the serial port and the other 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 1200bps to 57600bps.
When the RXD, TXD, DBG_RXD, DBU_TXD are used, it should be pull up 10k to 3V.
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 port
z DBG_TXD: Send data to the RXD signal line of the DTE
SIM900D_Hardware Design_V1.04 2010.10.09
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