Sony Ericsson GM28, Integrator'S Manual

Page: 35 / 268

2. ELECTRICAL DESCRIPTION
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LZT 123 7468 R1A
Data Terminal Ready (DTR)
DTR indicates that the DTE is ready to transmit and receive data. It also
acts as a hardware ‘hang-up’, terminating calls when switched high.
The signal is active low. You can define the exact behaviour of DTR
with an AT command.
The DTR line can also be used to switch on the modem when activated
for 0.2 seconds. The DTR line must be deactivated prior to switching
off the modem to ensure it switches off (powers down) correctly.
Data Set Ready (DSR)
An active DSR signal is sent from the modem to the application (DTE)
to confirm that a communications path has been established. DSR has
two modes of operation, which can be set using the AT command
AT&S.
Data Carrier Detect (DCD)
DCD indicates that the DCE is receiving a valid carrier (data signal)
when low. You can define the exact behaviour of DCD with an AT
command.
Ring Indicator (RI)
RI indicates that a ringing signal is being received by the DCE when
low. You can define the exact behaviour or RI with an AT command.
2.6 Real Time Clock
The GM28 contains a real time clock (RTC) to maintain accurate
timekeeping and to enable “timestamping” of messages.
The RTC is powered when d.c. power is connected to the modem AND
the modem is switched on. If the d.c. supply fails, a stored energy device
within the GM28 provides back-up power to maintain the RTC for at
least 12 hours.
2.7 Software Updates
It is possible and sometimes necessary to update the GM28 software.
Updates must be carried out by a Sony Ericsson approved technician.
Please contact your supplier for details (see “Service and Support”,
page 20).