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SIM800L(MT6261)_Hardware Design_V1.01
28
2016-07-07
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
SIM800L 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
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
RI.
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
.
Serial port supports the following baud rates:
1200, 2400, 4800, 9600, 19200, 38400, 57600,115200,230400 and 460800bps
Autobauding only supports the following baud rates:
1200, 2400, 4800, 9600, 19200, 38400, 57600 and 115200bps
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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