User's Guide

HE863 Family Hardware User Guide
1vv0300891 Rev.5
- 2011-03-18
Reproduction forbidden without Telit Communications S.p.A’s. written authorization - All Rights
Reserved. Page 61 of 89
9. Serial Ports
The serial port on the Telit HE863 Family is the interface
between the module and OEM hardware.
2 serial ports are available on the module:
 MODEM SERIAL PORT;
 MODEM SERIAL PORT 2 (DEBUG).
9.1. Modem Serial Port
Several configurations can be designed for the serial port on
the OEM hardware. The most common are:
 RS232 PC com port;
 microcontroller UART @ 1.8V – 2.0V (Universal
Asynchronous Receive Transmit) ;
Depending on the type of serial port on the OEM hardware, a
level translator circuit may be needed to make the system work.
The only configuration that does not need a level translation
is the 1.8V – 2.0V UART.
The serial port on HE863 Family is a +1.8V UART with all the 7
RS232 signals. It differs from the PC-RS232 in signal polarity
(RS232 is reversed) and levels. The levels for HE863 Family
UART are the CMOS levels:
Absolute Maximum Ratings -Not Functional
Parameter Min Max
Input level on any
digital pin when on
-0.3V +3.6V
Input voltage on
analog pins when on
-0.15V +3.0 V
Operating Range - Interface levels
Level Min Max
Input high level 1.26V 2.0 V
Input low level -0.2V 0.36V
Output high level 1.6V 1.8V
Output low level 0V 0.2V