SIM340 Hardware Design
Figure 18: Connection
of the serial interfaces
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
3.8.1 Function of serial port & debug port supporting
Serial port
Seven lines on serial port.
Contains data lines TXD and RXD, State lines RTS and CTS, Control lines DTR, DCD and RI.
Serial port can be used for CSD FAX, GPRS service and send AT command of controlling module.
Also serial port can be used for multiplexing function.
Serial port supports the communication rates as following:
300, 1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200 Default as 115200bps.
Autobauding supports baud rates as following:
4800, 9600, 19200, 38400, 57600 and 115200bps.
Autobauding allows the GSM engine to automatically detect the baud rate configured in the host
application. The serial port of the GSM engine supports autobauding for the following baud rates:
4800, 9600, 19200, 38400, 57600, 115200bps. Factory setting is autobauding enabled. This gives
you the flexibility to put the GSM engine into operation no matter what baud rate your host
application is configured to. To take advantage of autobauding mode, specific attention should be
paid to the following requirements:
Synchronization between DTE and DCE
When DCE powers on with the autobauding enabled, it is recommended to wait 2 to 3 seconds
before sending the first AT character. After receiving the “OK” response, DTE and DCE are
correctly synchronized.
SIM340_HD_V3.09
18.03.2009
36
