DE910 Series Hardware User Guide
1vv0300951 Rev.9 – 2015-05-11
Reproduction forbidden without written authorization from Telit Communications S.p.A. - All Rights
Reserved. Page 47 of 77
8.1.
Modem Serial Port 1
Serial port 1 on the DE910 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.
Pin
Signal
I/O
Function
Type
N14
DCD
O
Data Carrier Detect
1.8V
M15
RXD
O
Transmit line *see Note
1.8V
N15
TXD
I
Receive line *see Note
1.8V
M14
DTR
I
Data Terminal Ready
1.8V
P14
DSR
O
Data Set Ready
1.8V
L14
RTS
I
Request to Send
1.8V
P15
CTS
O
Clear to Send
1.8V
R14
RI
O
Ring Indicator
1.8V
The following table shows the typical input value(pulled inside the baseband chipset) and
status for input lines all module states:
Signal/State
OFF
RESET
ON
Powersaving PU tied to
TXD
unknown
PD:
21K~210K
PU:
39K~390K
PU:
39K~390K
1.8V
RTS
PD:
21K~210K
DTR
PU:
39K~390K
NOTE:
For minimum implementation, only the TXD and RXD lines must 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 DE910 when the module is powered off or during
an ON/OFF transition.
