User's Guide
LE866 HARDWARE USER GUIDE 1vv0301210 Rev.0 – Preliminary • 2015-09-02 34 of 68
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Serial Ports
The LE866 module is provided with by 2 Asynchronous serial ports:
MODEM SERIAL PORT 1 (Main)
MODEM SERIAL PORT 2 (Auxiliary)
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 @ 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.
On the LE866 the ports are CMOS 1.8.
5.5.2.1 MODEM SERIAL PORT 1 (USIF0)
The serial port 1 on the LE866 is a +1.8V UART with all the 7 RS232 signals.
It differs from the PC-RS232 in the signal polarity (RS232 is reversed) and levels.
The following table is listing the available signals:
RS232
Pin
Signal
Pad
Name
Usage
1
C109/DCD
Data Carrier Detect
Output from the LE866 that indicates the
carrier presence
2
C104/RXD
Transmit line *see
Note
Output transmit line of LE866 UART
3
C103/TXD
Receive line *see
Note
Input receive of the LE866 UART
4
C108/DTR
Data Terminal Ready
Input to the LE866 that controls the DTE
READY condition
5
GND
D1, F1, G1,
D2, F2, C3,
E3, F3, G3,
F6, A8, G8,
A11, G11
Ground
Ground
6
C107/DSR
Data Set Ready
Output from the LE866 that indicates the
module is ready
7
C106/CTS
Clear to Send
Output from the LE866 that controls the
Hardware flow control
8
C105/RTS
Request to Send
Input to the LE866 that controls the
Hardware flow control
9
C125/RING
Ring Indicator
Output from the LE866 that indicates the
incoming call condition