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GE864 Hardware User Guide
1vv0300694 Rev.10 - 10/06/08
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved page 33 of 69
8 Serial Ports
The serial port on the Telit GE864-QUAD/PY is the core of the interface between the module and
OEM hardware.
2 serial ports are available on the module:
• MODEM SERIAL PORT
• MODEM SERIAL PORT 2 (DEBUG)
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
• Micro controller UART @ 2.8V – 3V (Universal Asynchronous Receive Transmit)
• Micro controller 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 GE864-QUAD/PY 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 GE864-
QUAD/PY UART are the CMOS levels:
Absolute Maximum Ratings –Not Functional
Parameter Min Max
Input level on any
digital pad when on
-0.3V +3.6V
Input voltage on
analog pads when on
-0.3V +3.0 V
Operating Range – Interface levels (2.8V CMOS)
Level Min Max
Input high level V
IH
2.1V 3.3V
Input low level V
IL
0V 0.5V
Output high level V
OH
2.2V 3.0V
Output low level V
OL
0V 0.35V