User Guide

LE866 Hardware Design Guide
1VV0301355 Rev. 5 Page 46 of 91 2019-04-05
5.6.2. 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.
5.6.2.1. 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
B2
Data Carrier Detect
Output from the LE866 that indicates
the carrier presence
2
C104/RXD
A5
Transmit line *see Note
Output transmit line of LE866 UART
3
C103/TXD
A4
Receive line *see Note
Input receive of the LE866 UART
4
C108/DTR
A2
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
A2
Data Set Ready
Output from the LE866 that indicates
the module is ready
7
C106/CTS
A1
Clear to Send
Output from the LE866 that controls
the Hardware flow control