Users Manual

GSM/GPRS Module Series
M66 Hardware Design
M66_Hardware_Design Confidential / Released 37 / 82
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:
RXD 18 Receive data
DTR 19 Data terminal ready
RI 20 Ring indication
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