Rev 1.0
1/27/14
40
40
Reference Guide
Signals and Indicators
*
The Flash LED can be disabled by the user when in Sleep mode in order to save power consumption. Refer to
the AT Commands Interface Guide at
http://www.usr.com/support/3500
for more information on how to disable the Flash
LED using an AT command.
4.4. Real Time Clock (RTC)
The USR3500 has implemented Real Time Clock for saving date and time when the
USR3500 is unplugged from the DC power supply through the DC power cable.
Table 29. Real Time Clock Specifications
Item
Minimum
Typical
Maximum
Charging Time start from fully discharged to fully charged
15 Hours
RTC Time Period*
Guaranteed
30 Hours
Not guaranteed
60 Hours
*
This RTC time period is measured when the RTC battery is fully charged before the modem is unplugged from
the DC power source.
*
This RTC time period is for temperature from -20
°
C to +60
°
C. Once the operating/storage temperature is
beyond this range, this time period is not guaranteed.
Caution:
When the modem is shipped out, the charging voltage of the RTC battery is not guaranteed. Once
the modem is on power, the RTC battery will start charging and the RTC feature can then be
resumed.
4.5. Interrupt
An interrupt pin, INT1, is multiplexed with GPIO25 on pin 1 of the Microfit connector.
Additional interrupt pins are also available via the expansion card connector. Refer to
the following table for the list of available interrupt pins in the modem.
Table 30. Available Interrupt Pins on the USR3500
Interface Location
Pin Number
Signal Name
Multiplex
Notes
Microfit connector
1
INT1
GPIO25
Expansion connector
32
INT0
GPIO3