User's Manual

HE910 Hardware User Guide
1vv0300925 Rev.9 – 07-02-2012
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10 Serial Ports
The HE910 module is provided with by 2 Asynchronous serial ports:
MODEM SERIAL PORT 1 (Main)
MODEM SERIAL PORT 2 (Auxiliary)
Several configurations can be designed for the serial port on the OEM hardware, but
the most common are:
RS232 PC com port
microcontroller UART @ 1.8V (Universal Asynchronous Receive Transmit)
microcontroller UART @ 5V or other voltages different from 1.8V
Depending from the type of serial port on the OEM hardware a level translator circuit
may be needed to make the system work.
On the HE910 the ports are CMOS 1.8..
The electrical characteristics of the Serial ports are explained in the following tables:
Absolute Maximum Ratings -Not Functional
Parameter
Min
Max
Input level on any digital pin (CMOS 1.8) with
respect to ground
-0.3V
3.1V
Operating Range - Interface levels (1.8V CMOS)
Level
Min
Max
Input high level
1.5V
1.9V
Input low level
0V
0.35V
Output high level
1.6V
1.9
Output low level
0V
0.2V