User's Manual

UE910 3G HARDWARE USER GUIDE 1vv0301171 Rev.3 • 2015-04-17 44 of 78
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MODEM SERIAL PORT 2 (USIF1)
The secondary serial port on the UE910 is a CMOS1.8V with only the RX and TX signals.
The signals of the UE910 serial port are:
PAD
Signal
I/O
Function
Type
NOTE
D15
TX_AUX
O
Auxiliary UART (TX Data to
DTE)
CMOS 1.8V
Shared with SPI_MOSI
E15
RX_AUX
I
Auxiliary UART (RX Data
from DTE)
CMOS 1.8V
Shared with SPI_MISO
NOTE:
Due to the shared pins, when the Modem Serial port is used, it is not possible
to use the SPI functions.
In order to avoid a back powering effect it is recommended to avoid having any
HIGH logic level signal applied to the digital pins of the UE910 when the
module is powered off or during an ON/OFF transition.