L
LE920 Hardware User Guide
1vv0301026 Rev.0 - draft4 – 2013-05-
Reproduction forbidden without written authorization from Telit Communications S.p.A. - All Rights Reserved.
Page 51 of 76
9.1.
Modem Serial Port 1
Serial port 1 on the LE920 is a +1.8V UART with all 7 RS232 signals.
It differs from the PC-RS232 in the signal polarity (RS232 is reversed) and levels.
RS232
Pin
Number
Signal
LE920
Pad Number
Name
Usage
1
DCD -
dcd_uart
AE18
Data Carrier
Detect
Output from the LE920 that indicates the carrier
presence
2
RXD -
Tx_uart
AF19
Transmit line
*see Note
Output transmit line of the LE920 UART
3
TXD -
Rx_uart
AH19
Receive line
*see Note
Input receive of the LE920 UART
4
DTR -
dtr_uart
AC18
Data Terminal
Ready
Input to the LE920 that controls the DTE READY
condition
5
GND
A6, A12, B13, B15…. Ground
ground
6
DSR -
dsr_uart
AG18
Data Set Ready
Output from the LE920 that indicates the module is
ready
7
RTS -
rts_uart
AA18
Request to Send
Input to the LE920 that controls the Hardware flow
control
8
CTS -
cts_uart
AK19
Clear to Send
Output from the LE920 that controls the Hardware flow
control
9
RI -
ri_uart
AJ18
Ring Indicator
Output from the LE920 that indicates the Incoming call
condition
NOTE:
In order 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 is powered OFF or during an
ON/OFF transition.
TIP:
For minimum implementation, only the TXD and RXD lines can 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 are referred to the application side, therefore on the
LE920 side these signal are on the opposite direction: TXD on the application side will be
connected to the receive line (here named TXD/ rx_uart ) of the LE920 serial port and vice
versa for RX.
