Real Time Clock - Eurotech Titan User Manual

Real time clock

The TITAN uses an external real time clock (RTC) (Intersil ISL1208) to store the date and
time and provide power management events. The RTC is connected to the I
PXA270 processor and is accessible through I
backed for the TITAN, but is not battery backed for the TITAN-Lite.
The accuracy of the internal RTC is based on the operation of the 32.768KHz watch
crystal. Its calibration tolerance is ±20ppm, which provides an accuracy of +/-1 minute
per month when the board is operated at an ambient temperature of +25°C (+77°F).
When the board is operated outside this temperature the accuracy may be degraded by -
0.035ppm/°C² ±10% typical. The watch crystal's accuracy will age by ±3ppm max in the
first year, then ±1ppm max in the year after, and logarithmically decreasing in subsequent
years.
The Intersil ISL1208 RTC provides the following basic functions:
•
Real time clock/calendar:
- Tracks time in hours, minutes and seconds.
- Day of the week, day, month and year.
•
Single alarm:
- Settable to the second, minute, hour, day of the week, day or month.
- Single event or pulse interrupt mode.
•
2 bytes battery-backed user SRAM.
2
•
I C interface.
PXA270 has an internal real time clock, which doesn't keep time after hardware reset
and should only be used as a wake-up source from deep-sleep.
Issue D
Detailed hardware description
2
C bus address 0x6F. The RTC is battery
2
C bus of the
25