User's Manual

HE910 Hardware User Guide
1vv0300925 Rev.28 – 2015-06-24
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved page 66 of 66
12.1 MODEM SERIAL PORT 1 (USIF0)
The serial port 1 on the HE910 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 HE910
Pad Number
Name Usage
1 C109/DCD
N14
Data Carrier Detect Output from the HE910 that indicates the carrier presence
2 C104/RXD
M15
Transmit line *see
Note
Output transmit line of HE910 UART
3 C103/TXD
N15
Receive line *see
Note
Input receive of the HE910 UART
4 C108/DTR
M14
Data Terminal Ready Input to the HE910 that controls the DTE READY condition
5 GND
M12, B13, P13,
E14 …
Ground Ground
6 C107/DSR
P14
Data Set Ready Output from the HE910 that indicates the module is ready
7 C106/CTS
P15
Clear to Send
Output from the HE910 that controls the Hardware flow
control
8 C105/RTS
L14
Request to Send Input to the HE910 that controls the Hardware flow control
9 C125/RING
R14
Ring Indicator
Output from the HE910 that indicates the incoming call
condition
The following table shows the typical input value of internal pull-up resistors for RTS DTR
and TXD input lines and in all module states:
STATE
RTS DTR TXD
Pull up tied to
ON
5K to 12K 1V8
OFF
Schottky diode
RESET
Schottky diode
POWER
SAVING
5K to 12K 1V8