User's Manual

HE910 Hardware User Guide
1vv0300925 Rev.28 – 2015-06-24
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved page 65 of 65
12 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 2.1V
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