User's Manual

9. Serial Ports

The serial port on the GE865 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, ASC0)

 MODEM SERIAL PORT 2 (Auxiliary, ASC1)

9.1. 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

3.1 V

Input low level V

0.5V

Output high level V

2.2V

3.1V

Output low level V

0.35V