User's Manual

LE910 Hardware User Guide
1vv0301089 Rev.7 – 25-10-2015
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved page 56 of 88
11.1 MODEM SERIAL PORT 1
The serial port 1 on the LE910 is a +1.8V UART with all the 7 RS232 signals.
It differs from the PC-RS232 in the signal polarity (RS232 is reversed) and levels.
RS232
Pin #
Signal
LE910
Pad Number
Name
Usage
1
C109/DCD
N14
Data Carrier Detect
Output from the LE910 that indicates the carrier presence
2
C104/RXD
M15
Transmit line *see
Note
Output transmit line of LE910 UART
3
C103/TXD
N15
Receive line *see
Note
Input receive of the LE910 UART
4
C108/DTR
M14
Data Terminal Ready
Input to the LE910 that controls the DTE READY condition
5
GND
M12, B13, P13,
E14 …
Ground
Ground
6
C107/DSR
P14
Data Set Ready
Output from the LE910 that indicates the module is ready
7
C106/CTS
P15
Clear to Send
Output from the LE910 that controls the Hardware flow
control
8
C105/RTS
L14
Request to Send
Input to the LE910 that controls the Hardware flow control
9
C125/RING
R14
Ring Indicator
Output from the LE910 that indicates the incoming call
condition
NOTE:
According to V.24, some signal names are referred to the application side, therefore on the
LE910 side these signal are on the opposite direction:
TXD on the application side will be connected to the receive line (here named C103/TXD)
RXD on the application side will be connected to the transmit line (here named C104/RXD)
NOTE:
For a minimum implementation, only the TXD, RXD lines can be connected, the other lines can
be left open provided a software flow control is implemented.
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 LE910 when the module is powered off or during
an ON/OFF transition.