User's Manual

HE910 Hardware User Guide
1vv0300925 Rev.9 – 07-02-2012
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10.1 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,
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
Line in OFF and RESET state can be treated as in picture below