User's Manual

LE920A4 HW User Guide Hardware Interfaces
Doc#: 1VV0301261 Serial Ports
Rev. 4.3 Page 73 of 123 2017-12-07
RS232
Pin
Number
Signal
Pad
Number
Name Usage
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.
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.