User's Guide

LE920A4 HW User Guide Hardware Interfaces
Doc#: 1VV0301261 Serial Ports
Rev. 4.7.1 Page 73 of 124 2019-11-21
NOTE:
To avoid a back-powering effect, it is recommended to avoid any HIGH logic
level signal applied to the digital pins of the module when it is powered OFF
or during an ON/OFF transition.
NOTE:
For minimum implementations, only the TXD and RXD lines must be
connected. The other lines can be left open provided a software flow control
is implemented.
NOTE:
According to V.24, Rx/Tx signal names refer to the application side;
therefore, on the module side, these signals are in the opposite direction:
TXD on the application side will be connected to the receive line (here
named TXD / RX_UART) of the module serial port and vice versa for Rx.
NOTE:
Asserting the DTR pin low will prevent the UART and the entire module from
entering low power mode.
NOTE:
DTR pin can be left floating if not in use.