>> I need to make a clock that is accurate. It will be powered by the
>> mains, and I thought of using this as a time base as it is a fairly
>> stable waveform.
>>
>> Does anyone else know of a way which will be more accurate?

> i don't think using the mains for refrence frequency will give
> you a stable clock.  PIC being driven by a crystal oscillator
> will give much more stable clock.

In the USA, I'd have to disagree.  Mains here is 60Hz with
extremely good long term stability (second or so in several
months).  Short term, the frequency may vary more than a
crystal would.  For long term, power companies compensate.

                                                Lee Jones