User's Manual

UL865-N3G Hardware User Guide

1VV0301177 Rev 2– 2015-04-20

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Mod. 0805 2011-07 Rev.2

11. Serial Ports

The serial port on the UL865-N3G V2 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)

11.1. MODEM SERIAL PORT 1

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

common are:

 RS232 PC com port

 microcontroller UART

1.8V (Universal Asynchronous Receive Transmit)

 microcontroller UART

3V or other voltages different from 1.8V

 microcontroller UART

5V or other voltages different from 1.8V

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 1.8V UART.

The serial port on the UL865-N3G V2 is a +1.8V UART with all the 8 RS232 signals. It

differs from the PC-RS232 in the signal polarity (RS232 is reversed) and levels. The levels

for the UL865-N3G V2 UART are the CMOS levels:

Absolute Maximum Ratings -Not Functional

Parameter Min Max

Input level on any digital

pad when on

-0.3V +2.1V

Operating Range - Interface levels (1.8V CMOS)

Level Min Max

Input high level V

1.5V 1.9V

Input low level V

0V 0.35V

Output high level V

1.6V 1.9V

Output low level V

0V 0.2V