User Guide

HE910 Hardware User Guide
1vv0300925 Rev.18 – 15-06-2012
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved page 62 of 91
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