User's Manual

HE910 Hardware User Guide
1vv0300925 Rev.9 – 07-02-2012
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10.2 MODEM SERIAL PORT 2 (USIF1)
The secondary serial port on the HE910 is a CMOS1.8V with only the RX and TX
signals.
The signals of the HE910 serial port are:
PAD
Signal
I/O
Function
Type
COMMENT
D15
TX_AUX
O
Auxiliary UART (TX Data to DTE)
CMOS 1.8V
SHARED WITH
SPI_MTSR
E15
RX_AUX
I
Auxiliary UART (RX Data from
DTE)
CMOS 1.8V
SHARED WITH
SPI_MRST
The signal VIO1_1V8 must be connected to the VDD_IO1 input pin to properly
supply this digital section.
NOTE:
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 HE910 when the module is powered
off or during an ON/OFF transition.
NOTE:
Due to the shared pins, when the Modem Serial port is used, it is not possible to use the
SPI functions.