Sony Ericsson GT47 Technical Description page 20

Note!
Note!
3.2.6 Second RS232 Serial Interface
Note!
3.2.7 Relationship between GT47 and GR47 signals
LZT 123 7607 R1B
3. ELECTRICAL DESCRIPTION
low side switches return to open circuit when deactivated. This allows the
external application hardware to determine the desired logic voltage levels
with the appropriate pull-up.
The output drivers are low side switches which short the pin to GND if
they are activated.
As an alternative configuration signals OUT-3 and OUT-4 can be used to
support a second RS232 serial interface as CTS-2 and RD-2. Further
information is given below.
There is a voltage regulator implemented inside the module that is capable
of supplying an external voltage source of +4.8V with a maximum current
of 75 mA.
The voltage source can be switched on/off with the DAC signal of the
internal GR47 GSM engine.
By default the voltage source is switched on. A high level of 2.75V at the
DAC output of the GR47 GSM engine will switch the voltage source off.
The +4.8V source may be switched on/off via an embedded or external
application and so may be used as an optional digital output with levels of
+4.8V and open circuit.
IN-3 and OUT-3 can be automatically reconfigured as signals TD-2 and
RD-2, of a second serial interface, by enabling UART3 of the internal
GR47. UART 3 may be enabled using AT command or intrinsic function.
In addition, IN-2 and OUT-4 can be automatically reconfigured as signals
CTS-2 and RTS-2 of the second serial interface by enabling hardware flow
control for UART3 on the internal GR47. Hardware flow control can be
enabled using intrinsic function only.
The signal level thresholds for each of the digital inputs of the second serial
interface are: 3V<V <32V and V
,+
An external RS232 transceiver component may be used to convert the serial
interface to standard RS232 electrical levels. The GT47's +4.8 V output
can be used to provide power for the transceiver.
When reconfiguring a GT47 signal, via AT command or intrinsic
function, the corresponding GR47 signal name must be used, see the
GT47-GR47 signal cross reference tables overleaf.
< 2.8V.
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