Smart Machine Smart Decision
SIM800H_Hardware_Design_V1.01
30
2013-08-20
document [1]
Table 9: Serial port characteristics
Symbol
Min
Max
Unit
V
IL
0
0.3
V
V
IH
2.5
2.8
V
V
OL
0
0.1
V
V
OH
2.7
2.8
V
4.5.1
Function of Serial Port
Serial port:
z
Full mode device.
z
Contains data lines TXD and RXD, hardware flow control lines RTS and CTS, status lines DTR, DCD and
RI.
z
Serial port can be used for CSD FAX, GPRS service and AT communication. It can also be used for
multiplexing function. For details about multiplexing function, please refer to
table 11
.
z
Serial port supports the following baud rates:
1200, 2400, 4800, 9600, 19200, 38400, 57600 and 115200bps
z
Autobauding only supports the following baud rates:
1200, 2400, 4800, 9600, 19200, 38400 and 57600bps
z
The default setting is autobauding.
Autobauding allows SIM800H to automatically detect the baud rate of the host device. Pay more attention to the
following requirements:
z
Synchronization between DTE and DCE:
When DCE powers on with autobauding enabled, it is recommended to send "AT" or "at" or "aT" or "At"
to synchronize the baud rate, until DTE receives the "OK" response, which means DTE and DCE are
correctly synchronized. For more information please refer to AT command "AT+IPR".
z
Restrictions of autobauding operation:
The DTE serial port must be set at 8 data bits, no parity and 1 stop bit.
The URC such as "RDY", "+CFUN: 1" and "+CPIN: READY” will not be reported.
Note: User can use AT command “AT+IPR=x” to set a fixed baud rate and the setting will be saved to
non-volatile flash memory automatically. After the configuration is set as fixed baud rate, the URC such as
"RDY", "+CFUN: 1" and "+CPIN: READY” will be reported when SIM800H is powered on.
4.5.2
Serial Interfaces
The following figure shows the connection between module and client (DTE).
