User's Manual
CE910-DUAL Hardware User Guide
1vv0301010 Rev .0 – 2012-07-10
Reproduction forbidden without written authorization from Telit Communications S.p.A. - All Rights Reserved. Page 37 of 63
It differs from the PC-RS232 in the signal polarity (RS232 is reversed) and levels.
Pin Signal I/O Function Type
N14
DCD - dcd_uart O Data Carrier Detect B-PU, 1.8V
M15
RXD - Tx_uart O Transmit line *see Note B-PU, 1.8V
N15
TXD - Rx_uart I Receive line *see Note B-PD, 1.8V
M14
DTR - dtr_uart I Data Terminal Ready B-PU, 1.8V
P14
DSR - dsr_uart O Data Set Ready B-PD, 1.8V
L14
RTS - rts_uart I Request to Send B-PD, 1.8V
P15
CTS - cts_uart O Clear to Send B-PD, 1.8V
R14
RI - ri_uart O Ring Indicator B-PU, 1.8V
The following table shows the typical input value of internal pull-up resistors for input lines
and in all module states:
Signal / State OFF RESET ON Powersaving Pull up tied to
TXD unknown Pd
(21K ~ 210K)
Pd
(21K ~ 210K)
Pd
(21K ~ 210K)
RTS unknown Pd
(21K ~ 210K)
Pd
(21K ~ 210K)
Pd
(21K ~ 210K)
CTS unknown Pu
(39K ~ 390K)
Pu
(39K ~ 390K)
Pu
(39K ~ 390K)
1V8
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 CE910-DUAL when the module is powered off
or during an ON/OFF transition.
NOTE:
According to V.24, RX/TX signal names are referred to the application side. Therefore, on the
CE910-DUAL side these signals are in the opposite direction: TXD on the application side
will be connected to the receive line (here named TXD/ rx_uart) of the CE910-DUAL serial
port and vice versa for RX.