User's Manual

GSM/GPRS Module Series
M26 Hardware Design
M26_Hardware_Design Confidential / Released 34 / 80
3.7.1. UART Port
3.7.1.1. The Feature of UART Port
 Seven lines on UART interface
 Contain data lines TXD and RXD, hardware flow control lines RTS and CTS, other control lines DTR,
DCD and RI.
 Used for AT command, GPRS data, etc. Multiplexing function is supported on the UART Port. So far
only the basic mode of multiplexing is available.
 Support the communication baud rates as the following:
300, 600, 1200, 2400, 4800, 9600, 14400, 19200, 28800, 38400, 57600, 115200.
 The default setting is autobauding mode. Support the following baud rates for Autobauding function:
4800, 9600, 19200, 38400, 57600, 115200.
 The module disables hardware flow control by default. AT command AT+IFC=2,2 is used to enable
hardware flow control.
After setting a fixed baud rate or autobauding, please send ―AT‖ string at that rate. The UART port is
ready when it responds ―OK‖.
Autobauding allows the module to detect the baud rate by receiving the string ―AT‖ or ―at‖ from the host or
PC automatically, which gives module flexibility without considering which baud rate is used by the host
controller. Autobauding is enabled by default. To take advantage of the autobauding mode, special
attention should be paid according to the following requirements:
Synchronization between DTE and DCE:
When DCE (the module) 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.
DCD
21
Data carrier detection
CTS
22
Clear to send
RTS
23
Request to send
Debug Port
DBG_RXD
38
Receive data
DBG_TXD
39
Transmit data
Auxiliary UART Port
RXD_AUX
28
Receive data
TXD_AUX
29
Transmit data