Rainbow Electronics GE863-PY - Manual (Page 37)

GE863 Hardware User Guide
1vv0300783 Rev.0 - 10/06/08
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved page 37 of 80
6.3 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 GE863 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 GE863 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