User's Manual

UE866 HARDWARE USER GUIDE 1vv0301157 Rev.7 • 2015-04-17 37 of 68
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MODEM SERIAL PORT 2 (USIF1)
The secondary serial port on the UE866 is a CMOS1.8V with only the RX and TX signals.
The signals of the UE866 serial port are:
PAD
Signal
I/O
Function
Type
NOTE
C1
TX_AUX
O
Auxiliary UART (TX Data to
DTE)
CMOS 1.8V
Shared with SPI_MOSI
C2
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 UE866 when the
module is powered off or during an ON/OFF transition.