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Figure 17: RTC supply from non-chargeable battery
z
Rechargeable battery backup
Figure 18: RTC supply from rechargeable battery
4.5.
Serial Port and USB Interface
SIM800H 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 8: Serial port and USB pin definition
Pin name
Pin number
Function
UART_DTR
69
Data terminal ready
UART_RI
68
Ring indicator
UART_DCD
70
Data carrier detect
CTS
34
Request to send
RTS
33
Clear to send
TXD
32
Transmit data
Serial port
RXD
31
Receive data
VBUS
7
USB power supply
USB_DP
59
Debug port
USB_DM
19
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
SIM800H_Hardware_Design_V1.01
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2013-08-20
