User guide

UC864-E/G/WD/WDU Hardware User Guide
1vv0300766a Rev.4
- 03/02/09
Reproduction forbidden without Telit Communications S.p.A’s. written authorization - All Rights Reserved. Page 39 of 78
8. Serial Ports
The serial port on the Telit UC864-E/G/WD/WDU is 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. The
most common are:
• RS232 PC com port;
• microcontroller UART @ 2.6V – 2.9V (Universal Asynchronous Receive
Transmit) ;
• microcontroller UART @ 5V or other voltages different from 2.6V .
Depending on 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 does not need
a level translation is the 2.6V UART.
The serial port on UC864-E/G/WD/WDU is a +2.6V UART with all the 7 RS232
signals. It differs from the PC-RS232 in signal polarity (RS232 is reversed) and levels.
The levels for UC864-E/G/WD/WDU UART are the CMOS levels:
Absolute Maximum Ratings - Not Functional
UC864-E/G/WD/WDU
Parameter
Min Max
Input level on any
digital pin when on
-0.3V +3.0V
Input voltage on
analog pins when on
-0.3V +3.0 V
Operating Range - Interface Levels
UC864-E/G/WD/WDU
Level
Min Max
Input high level 2.0V 2.9 V
Input low level -0.3V 0.6V
Output high level 2.2V 2.6V
Output low level 0V 0.35V