NL865B1 HW Design Guide
1VV0301450 Rev. 1
Page
39
of
72
2017-11-20
Communication ports
5.5.1.
Serial Ports
The NL865B1 module is provided with by 2 Asynchronous serial ports:
•
MODEM SERIAL PORT 1 (Main)
•
MODEM SERIAL PORT 2 (TX Only, used for logging)
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 NL865B1 the ports are CMOS 1.8.
5.5.1.1.
MODEM SERIAL PORT 1
The serial port 1 on the NL865B1 is a +1.8V UART with only 2 RS232 signals.
It differs from the PC-RS232 in the signal polarity (RS232 is reversed) and levels.
Serial port 1 is considered a “low power UART” and is avalable during LPM and PSM
such that any activity in the TXD pin (NE866B1 input) will wakeup the system.
The following table lists the signals of Serial port 1:
RS232
Pin
Signal
Pad
Name
Usage
2
RXD
8
Transmit line *see
Note
Output transmit line of NL865B1
UART
3
TXD
7
Receive line *see
Note
Input receive of the NL865B1
UART
This pin also serves as a sleep
wakeup source.
5
GND
23, 32, 33, 35,
36, 46
Ground
Ground
