User's Manual

GE865 Hardware User Guide

1vv0300799 Rev.6 - 04/06/09

8 Serial Ports

The serial port on the Telit GE865-QUAD is the core of the interface between the module and OEM

hardware.

2 serial ports are available on the module:

• MODEM SERIAL PORT 1 (MAIN)

• MODEM SERIAL PORT 2 (AUX)

8.1 MODEM SERIAL PORT

Several configurations can be designed for the serial port on the OEM hardware, but the most

common are:

• RS232 PC com port

• microcontroller UART @ 2.8V - 3V (Universal Asynchronous Receive Transmit)

• microcontroller UART@ 5V or other voltages different from 2.8V

Depending from 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 doesn't need a level translation is the 2.8V

UART.

The serial port on the GE865 is a +2.8V UART with all the 7 RS232 signals. It differs from the PC-

RS232 in the signal polarity (RS232 is reversed) and levels. The levels for the GE865 UART are the

CMOS levels:

Absolute Maximum Ratings -Not Functional

Parameter

Min

Max

Input level on any

digital pad when on

-0.3V +3.1V

Input voltage on

analog pads when on

-0.3V +3.1V

Operating Range - Interface levels (2.8V CMOS)

Level

Min

Max

Input high level V

2.1V 3.0 V

Input low level V

0V 0.5V

Output high level V

2.2V 3.0V

Output low level V

0V 0.35V