User's Manual

HE910 Hardware User Guide

1vv0300925 Rev.28 – 2015-06-24

12.2 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 1V8_SEL must be connected to the VDD_IO1 input pin in order to use this port.

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.