User's Manual

LE920A4 HW User Guide Hardware Interfaces
Doc#: 1VV0301261 Serial Ports
Rev. 4.3 Page 74 of 123 2017-12-07
NOTE:
According to V.24, Rx/Tx signal names refer to the application side;
therefore, on the module side, these signal 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.
8.4.2. Modem Serial Port 2
Serial Port 2 is a +1.8V UART with Rx and Tx signals only.
Table 28 lists the signals of Serial Port 2.
Table 28: Modem Serial Port 2 Signals
PAD Signal I/O Function Type Comment
AB19 TXD_AUX O Auxiliary UART (Tx Data to DTE) 1.8V
AD19 RXD_AUX I Auxiliary UART (Rx Data to DTE) 1.8V
NOTE:
To avoid a back-powering effect, it is recommended to avoid having any
HIGH logic level signal applied to the digital pins of the module when it is
powered OFF or during an ON/OFF transition.