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SIM800H _Hardware Design_V2.03
28
2016-10-10
Note: The clock error becomes larger when VBAT is turned off and RTC circuit was supplied from the backup battery or the
external capacitor.
4.5.
Serial Port and USB Interface
SIM800H default provides one unbalanced asynchronous serial ports. The module is designed as a DCE (Data
Communication Equipment). The following figure shows the connection between module and client (DTE).
Table 9: Serial port and USB pin definition
Note: Hardware flow control is disable by default. AT command “AT+IFC=2,2”can enable hardware flow control. AT command
“AT+IFC=0,0”can disable hardware flow control. For more details please refer to document [1].
Table 10: Serial port characteristics
Symbol
Min
Typ
Max
Unit
V
IL
-0.3
-
0.7
V
V
IH
2.1
-
3.1
V
V
OL
-
-
0.4
V
V
OH
2.4
2.8
-
V
SIM800H module can support dual serial port function, that need execute AT command "AT+CMNRP=1"first.
Dual serial port including one full modem serial port and one three-wire serial port, pin definition is different with
standard definition of the Figure 2: Pin assignment (Top view) and Table 5: Pin description. For more details
please refer to
Document [2]
.
Note: Only B05 and later version support dual serial port function.
4.5.1
Function of Serial Port
Serial port:
Full mode device.
Contains data lines TXD and RXD, hardware flow control lines RTS and CTS, status lines DTR, DCD and
Pin name
Pin number Function
Serial port
DTR
69
Data terminal ready
RI
68
Ring indicator
DCD
70
Data carrier detect
CTS
34
Request to send
RTS
33
Clear to send
TXD
32
Transmit data
RXD
31
Receive data
Debug port
VBUS
7
USB power supply
USB_DP
59
USB data line positive
USB_DN
19
USB data line
negative
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