User's Guide

LE920A4 HW User Guide Hardware Interfaces
Doc#: 1VV0301261 Serial Ports
Rev. 4.7.1 Page 72 of 124 2019-11-21
8.4.1. Modem Serial Port 1
Serial Port 1 is a +1.8V UART with all 8 RS232 signals.
It differs from the PC-RS232 in the signal polarity (RS232 is reversed) and levels.
Table 27 Serial Port 1 Signals
RS232
Pin
Number
Signal
Pad
Number
Name Usage
1
DCD -
DCD_UART
AE18
Data Carrier
Detect
Output from the module that
indicates carrier presence
2
RXD -
TX_UART
AF19
Transmit line
*see Note
Output transmit line of the
module UART
3
TXD -
RX_UART
AH19
Receive line *see
Note
Input receive line of the
module UART
4
DTR -
DTR_UART
AC18
Data Terminal
Ready
Input to the module that
controls the DTE READY
condition
5 GND
A6, A12,
B13, 15...
Ground Ground
6
DSR -
DSR_UART
AG18 Data Set Ready
Output from the module that
indicates the module is ready
7
RTS -
RTS_UART
AA18 Request to Send
Input to the module that
controls the Hardware flow
control
8
CTS -
CTS_UART
AK19 Clear to Send
Output from the module that
controls the Hardware flow
control
9 RI - RI_UART AJ18 Ring Indicator
Output from the module that
indicates the Incoming Call
condition
NOTE:
DCD, DTR, DSR, RI signals that are not used for UART functions can be
configured as GPIO using AT commands.