On Sun, May 08, 2005 at 04:13:23PM +0100, Dave Turner wrote:
> Firstly, I'm not running off battery power.

So counting power line ticks is a possibility.

>  After much fiddling with
> config bits I have discovered that with the PIC running on XT mode, it
> runs a lot faster than it should if it is using the 32.768KHz clock. 
> Also, on INTRC mode it runs too fast.  On EXTRC, LP or HS mode it
> doesn't run at all.

There's no need for you to run the system clock from the 32 Khz. Run it
from the 8 Mhz INTRC and use the 32 Khz to clock Timer 1.

> The reason I'm trying to use the 32.768KHz clock as the system clock
> is that I don't have a clue how to make a delay by checking a clock -
> The only method I know is many embedded loops.

My sunrise/sunset contoller implements a full 365 day calendar using a
2 second timer 1 heartbeat. Check it out here:

http://www.finitesite.com/d3jsys/clock.asm

> 
> Any pointers to good tutorials / examples about using a non-system
> clock for a 1 second delay would be extremely welcome.

It's a two second delay but the idea is sound.

You implement it with a simple state machine. In a single big loop you
increment the smallest value. When that overflows, you reset that value
and increment the next one higher up. 

Check out the code for more details.

BAJ
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