User's Manual

UE866 HARDWARE USER GUIDE 1vv0301157 Rev.7 • 2015-04-17 36 of 68
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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
The input line ON_OFF and HW_SHDN state can be treated as in picture below
NOTE:
According to V.24, some signal names are referred to the application side,
therefore on the UE866 side these signal are on the opposite direction:
TXD on the application side will be connected to the receive line (here named
C103/TXD)
RXD on the application side will be connected to the transmit line (here named
C104/RXD)
For a minimum implementation, only the TXD, RXD lines can be connected,
the other lines can be left open provided a software flow control is
implemented.
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 UE866 when the
module is powered off or during an ON/OFF transition.