User's Manual

GSM/GPRS Module Series
M85 Hardware Design
M85_Hardware_Design Confidential / Released 38 / 88
3.7.1. UART Port
3.7.1.1. The Features of UART Port
 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 and 115200.
 The default setting is autobauding mode. Support the following baud rates for autobauding function:
4800, 9600, 19200, 38400, 57600 and 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 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:
1. Synchronization between DTE and DCE
When DCE (the module) powers on with the autobauding enabled, it is recommended to wait 4 or 5
seconds before sending the first AT character. After receiving the OK response, DTE and DCE are
correctly synchronized.
DTR
47
Data terminal ready
CTS
48
Clear to send
TXD
49
Transmit data
RXD
50
Receive data
RTS
51
Request to send
Auxiliary UART Port
TXD_AUX
40
Transmit data
RXD_AUX
41
Receive data