> Depending upon CPU speed and power requirements, you may be able to get
> by without an external RTC chip.  There are three approaches you may
> wish to consider:
>
> [1] Use any PIC with a normal-speed oscillator and keep it powered; since
>     the PIC will use about 1-4mA, you will probably want to have it wall
>     supplied.

What kind of accuracy can one expect from a PIC with a X MHz crystal?
If you assume that the crystal is off by 25ppm, you would be off by
0.000025 seconds per second.  This would mean gaining (or losing)
0.000025*3600*24=2.16 seconds in a 24 hour period.  This does not
seem very accurate.

>
> [2] Use any PIC with a 32768Hz clock.  This will drop power consumption

Is the 32768KHz crystals used for RTC's more accurate than the 'normal'
crystals?  Or do you get the same kind of accuracy from them?

Just wondering...

Niki